CEC/ICMC 2025 Abstracts & Technical Program

18 May 2025, 07:30 → 22 May 2025, 13:00 US/Pacific

Peppermill Reno

CEC Conference & Program Co-Chair: Srinivas Vanapalli, CEC Program Chair: Robert Duckworth, ICMC Conference Chair: Sonja Schlachter, ICMC Program Co-Chair: Shreyas Balachandran, ICMC Program Co-Chair: Ignacio Aviles Santillana

The Technical Program can be accessed via the Timetable tabs on the left. Please be sure to set the Timezone to US/Pacific time (see upper right corner).

If you have a presentation, you can view your session assignment details via the Speaker List tab on the left or login (see upper right corner) and then select the My Contributions tab on the left.

All Poster sessions will take place during the CRYO EXPO in the Tuscany Ballrooom on the 2nd floor of the Peppermill Resort. All Oral and Plenary Sessions will take place on the 2nd and 4th floors of the Peppermill Resort.

Any individual presenting at and/or attending CEC/ICMC 2025 must be a registered participant. Registration information can be viewed on the  CEC/ICMC 2025 website.

ALL PRESENTERS are requested to upload an electronic copy of their talk or poster in PDF format prior to their presentation at the scheduled CEC/ICMC 2025 session. By participating at CEC/ICMC 2025 and submitting your presentation, you implicitly agree to publish the content of your presentation on the public Indico site.

Session ID & Presentation ID Explanation

• The first character of the session ID (C or M) represents the conference designation, C for the CRYOGENIC Engineering Conference (CEC) and M for the International Cryogenic MATERIALS Conference (ICMC).
• The second character (1, 2, 3 or 4) indicates the day of the conference: 1 for Monday, 2 for Tuesday, 3 for Wednesday, and 4 for Thursday.
• The third and fourth characters (Or or Po) indicate whether the presentation is in an oral or poster session.
• The fifth character represents the time slot on that specific day (e.g., the first, second, third, or fourth time slot).
• The last character (A-F) differentiates between sessions held on the same day and time slot.
• Session ID examples are: C1Po1A or M1Po3A (CEC and ICMC posters on Monday); M3Or1A or C3Or2A (ICMC and CEC Orals on Wednesday)

Each abstract included in the technical program will be assigned a final Presentation ID which consists of the session ID plus the order within the session.

• Presentation ID examples are: M1Or1A-01, M1Or1A-02, etc.; C3Or2A-01, C3Or2A-02, etc.

 

All other conference information can be found on the CEC/ICMC 2025 website.

Sunday 18 May

08:00 Cryogenic Society of America (CSA) Short Courses

https://www.cryogenicsociety.org/2025-short-courses

09:00 ICMC Short Course

https://www.cec-icmc.org/2025/icmc-short-course/

12:00 Exhibitor Registration and Setup

13:00 ICMC Short Course

https://www.cec-icmc.org/2025/icmc-short-course/

15:00 Attendee Registration

18:30 Welcome & Exhibitor Reception

Monday 19 May

Opening | Plenary: John Davis [Novel Sub-Kelvin Cryogen-free Refrigeration at Zero Point Cryogenics] & CEC Awards

1 C1PL1-01: Novel Sub-Kelvin Cryogen-free Refrigeration at Zero Point Cryogenics

Abstract pending.

Speaker: John Davis (University of Alberta)

09:00 Cryo Expo Open

C1Po1A - Hydrogen Cooling and Test Facilities

2 C1Po1A-01: Numerical simulation of active magnetic regenerative refrigeration for hydrogen liquefaction

In the coming hydrogen society, the development of hydrogen infrastructure is an urgent task. Hydrogen infrastructure can be broadly categorized into “production,” “transportation and storage,” and “utilization.” Among these, it is desirable to use liquid hydrogen for storage and transportation from the viewpoint of energy density. On the other hand, since the liquefaction temperature of hydrogen is 20 K at 1 atm, the production of liquefied hydrogen requires a large amount of energy. To realize a hydrogen society, it is essential to reduce the price of hydrogen, and for this purpose, it is desirable to improve the liquefaction efficiency of hydrogen as much as possible. The liquefaction efficiency of conventionally used so-called gas refrigeration systems, which use compression and expansion of gas, is typically about 25%, and it is difficult to dramatically improve it further.
Magnetic refrigeration is a cooling method that utilizes the magnetocaloric effect of magnetic materials and is known to have a theoretical efficiency of over 50%. Among various magnetic refrigeration methods, the AMR is the most practical because it can operate over a much wider temperature range than ordinary magnetic refrigeration methods. On the other hand, since AMR uses heat exchange gas, the dynamic heat transfer characteristics of the heat fluid as well as the thermophysical properties of the magnetic material are important to understand the characteristics of AMR. Therefore, many parameters exist in AMR, making optimization difficult. In this study, a calculation model of AMR was constructed using ANSYS, and temperature distribution, freezing capacity, etc. were calculated and compared with experiments.

Speaker: Dr Koji Kamiya (National Institute for Materials Science)

3 C1Po1A-02: Active Magnetic Regenerative Refrigerator (AMR) with rotating permanent magnet for liquid hydrogen

Liquid hydrogen is attracting attention as an energy carrier derived from decarbonized power generation. Magnetic refrigeration is an application of the magnetocaloric effect, which is the reversible heating and cooling of magnetic materials by applying the external magnetic field. Active Magnetic Regenerative Refrigeration (AMR), which is one of the magnetic refrigeration methods, has been studied for hydrogen liquefaction to improve the cooling efficiency. In our device, eight magnetic material containers installed in a horizontal plane were in a radially with 45 degrees each other. Rotating permanent magnets for applying the magnetic field are similarly arranged four at 90 degrees each and can repeatedly magnetize and demagnetize the magnetic materials at each 45-degree rotation. Atomized particle of magnetic materials for AMR are used not only for their magnetocaloric effect, but also for their regenerative effect by enclosing them in containers that allows heat exchange gases to flow through the spaces between the particles. A temperature gradient can be created in the magnetic material container by flowing the heat exchange gas in opposite directions after the magnetic material is magnetized and demagnetized, respectively. The AMR was designed to recondense the boil-off hydrogen gas from the liquid storage tank, and the operating temperature was set close to 20 K. A 20 K-class single-stage GM refrigerator was used to absorb exhausted heat from the AMR at about 30 K. The magnetic field applied to magnetic materials is up to 1 T. Refrigeration operation has been performed using HoAl2 or HoB2 as magnetic materials and reached to 20 K and create the temperature gradient along to the magnetic material container about 10 K. To improve the cooling capacity, we are developing the new permanent magnet using novel materials invented by X. Tang et al. In the presentation, experiments result of the new magnet will be also reported.

Speaker: Kyohei Natsume (National Institute for Materials Science)

4 C1Po1A-03: Effect of helium-neon composition in Brayton refrigeration cycle for hydrogen liquefaction

A thermodynamic study is carried out to investigate how the composition of helium-neon mixture in Brayton refrigeration cycle affect the liquefaction performance of hydrogen. Two-stage expansion Brayton cycle is proposed for pre-cooling of a Linde-Hampson hydrogen liquefaction system, because the operating pressure of hydrogen can be significantly reduced. As refrigerant of the Brayton cycle, a gas mixture of helium and neon is considered as well as pure helium in order to take advantage of neon in both centrifugal compression and turbo expansion. Based on selected practical simulation basis, a rigorous thermodynamic cycle analysis is performed with process simulator (Aspen HYSYS) and the real-gas properties of mixed refrigerant and hydrogen. The specific energy consumption (SEC) for liquefaction is estimated for a variety of design parameters, such as the pre-cooling temperature, the flow rate, the pressure level, and the composition of mixed refrigerant. It is verified that the helium-neon composition can be optimally determined, taking into consideration the operation of turbo-machinery and the constraint of freezing temperature of neon. Details of design issues are presented and discussed towards the practical development of a prototype liquefier.

Speaker: Prof. Ho-Myung Chang (Hong Ik University)

5 C1Po1A-04: Design calculation and analysis of a coiled-tube heat exchanger and a condenser for a cryocooler-cooled LH2 target cooling system

A LH2 target cell and a vertex tracking detector system will be specifically optimized to fit inside the spherical target region of the Gamma-Ray Energy Tracking Array (GRETA) and are expected to operate at the Facility for Rare Isotope Beams (FRIB). The LH2 target-cell and windows will be made of thin Mylar of order 100um. The target thickness is in the range of 10~15 cm with an effective diameter of order 50~60 mm. A cryocooler-based hydrogen cooling system is under design and development at the Lawrence Berkeley National Lab (LBL) to cool down the target, liquefy gas hydrogen, deliver and maintain liquid hydrogen in the target while operating, and recover and store gas hydrogen. The whole cooling system consists of a cryocooler-based cooling cryostat, a subsystem equipped with safety devices to handle and store gas hydrogen and gas nitrogen, and instrument rack and PLC control system. The warm gas hydrogen is cooled through a coiled-tube heat exchanger attached to cold heads of a two-stage GM cryocooler and then liquefied in a condenser mounted to the second-stage cold head in the cryostat. The vaporized hydrogen is re-liquefied in the condenser and the liquefied hydrogen flows into the target through its gravity-driven thermos-syphon cooling circuit. A thermal radiation shield at around 30-40 K is mounted on the first stage of the cold head to reduce the radiation heat. A cryogenic control valve mounted on the cryostat is used to manipulate the hydrogen cooling circuit at different operating modes including cool‑down, liquefaction and re-liquefaction, physics operation, background measurement and warm‑up. The paper primarily presents the design calculation and analysis of the coiled-tube heat exchanger and the condenser in the LH2 target cooling cryostat.

Speakers: Li Wang (Lawrence Berkeley National Lab), Lianrong Xu (Lawrence Berkeley National Laboratory)

6 C1Po1A-05: Spallation Neutron Source Upgrade Status and Operational Success of the Cryogenic Moderator System

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) utilizes the Cryogenic Moderator System (CMS) to provide supercritical hydrogen cooling at 20 K to three neutron moderators. As part of the Proton Power Upgrade (PPU) project, two significant enhancements were made to the CMS: the integration of ortho-hydrogen into para-hydrogen catalyst beds and an expansion of hydrogen supply capacity through a new Hydrogen Refill System (HRS). This paper will detail the design, installation, and commissioning of these subsystems. PPU increased SNS beam power on the First Target Station (FTS) from 1.4 MW to 1.7 MW. Implementation of new controls for the CMS helium cryogenic cold box for this higher beam power will be discussed. Future work to ensure successful operation at a 2.0 MW beam power will also be outlined.

Speaker: Mr Brian DeGraff (Oak Ridge National Laboratory)

7 C1Po1A-06: Updated design of the ESS cryogenic moderator system

In 2024, ESS installed two hydrogen moderators, designed and optimized to achieve maximum neutron brightness while maintaining a parahydrogen fraction exceeding 99.5%. The cryogenic moderator system (CMS) was designed to meet two critical requirements: (1) a temperature rise of less than 3 K across each moderator, and (2) a parahydrogen fraction exceeding 99.5%. Subcooled liquid hydrogen at 17 K and 1.0 MPa is circulated at a flow rate of 1 kg/s using two centrifugal pumps arranged in series. The distribution lines to each moderator are configured in a parallel arrangement to ensure consistent inlet temperatures across all moderators. To achieve a parahydrogen fraction of 99.5%, an ortho-to-parahydrogen catalyst is incorporated within a bypass line. This configuration minimizes pressure drop, as the catalyst bed presents significant flow resistance. A 65-liter buffer tank stabilizes pressure and mitigates pressure fluctuations induced by changing the stepwise heat input at the proton beam injection or trip. The static and dynamic heat loads are removed via a heat exchanger connected to a 20 K large-scale helium refrigerator, Target Moderator CryoPlant (TMCP), with a cooling capacity of 30.3 kW at 15 K. Dynamic heat loads are compensated using a valve box adjacent to the CMS cold box, which adjusts the feed helium flow rate to the heat exchanger, and a developed fast-response heater that address thermal disturbance within the CMS loop. In 2020, the fabrication of the CMS cold box was completed by the ESS in-kind partner, Forschungszentrum Jülich GmbH (FZJ). The cold box underwent acceptance cryogenic tests using gaseous and liquid nitrogen until September 2021, and was subsequently installed at the ESS site in November 2021. Meanwhile, we designed and manufactured additional components, including hydrogen transfer lines connected from the cold box to the moderators, a hydrogen vent line, an in-situ ortho-to-parahydrogen measurement system using Raman spectroscopy, the fast-response heater to compensate for the nuclear heating, and a hydrogen filling station. Additionally, heaters wrapped around the buffer tank were redesigned, as the acceptance testing revealed that the initial design did not meet the required specifications. All installations were completed in May 2024. This paper presents the updated design status of the ESS CMS.

Speaker: Dr Hideki Tatsumoto (European Spallation Source ERIC (ESS))

8 C1Po1A-07: Design of a Laboratory-Scale Hydrogen Liquefier Cold Box for Low-Altitude Economy and Modular Deployment

The rapid development of the low-altitude economy, including hydrogen-powered unmanned aerial vehicles (UAVs) and decentralized hydrogen infrastructure, calls for compact and efficient hydrogen liquefaction systems. This study presents the design of a laboratory-scale hydrogen liquefier capable of producing 50 liters of liquid hydrogen per day (LPD) with a 10% capacity margin. The liquefaction process integrates liquid nitrogen pre-cooling and Gifford-McMahon (GM) cryocoolers, achieving high system reliability within a compact footprint of approximately 1.5m × 1.8m for the core cold box. Additionally, the cold box includes a 150L liquid hydrogen storage tank for holding the liquefied hydrogen produced.
The system's unique advantage of compactness will allow it to be integrated into standard containers in the future, enabling rapid, modular, and expandable liquid hydrogen plant deployments through reserved standard interfaces. This containerized configuration includes a core cold box and auxiliary components making it ideal for laboratory research and field applications. Furthermore, a continuous supply of liquefied hydrogen is possible with the existence of the 150L storage tank, ensuring efficient refueling of UAVs and other applications requiring liquid hydrogen as a fuel source.
The Efficient layout makes it particularly attractive for mobile applications in remote or temporary locations. The system is designed with Expandability in mind, enabling future expansion to meet the increasing demand for hydrogen in various sectors, such as transportation, energy storage, and aerospace. A large proportion of standard components, together with a small number of custom non-standard parts, is incorporated into the design, offering significant potential for cost reduction and scalability in mass production.
This paper represents a potential for flexible and compact hydrogen liquefaction of a small-scale hydrogen liquefier cold box, with promising applications in laboratory and low-altitude economy sectors. Future work will focus on experimental design validation, optimization of key parameters, and scalability for broader adoption in low-temperature hydrogen systems. The compact and space-efficient design, with its storage and rapid deployment capabilities, positions this system as a promising solution for the growing hydrogen economy.

Speaker: Jihao Wu

9 C1Po1A-08: Study on Zero Boil-Off of Liquid Hydrogen using a Single Stage GM cryocooler

Hydrogen is expected to become a one of the major energy sources as an environment-friendly fuel because it emits no carbon dioxide when used. Rather than as a gas, hydrogen will be transported and stored as liquid hydrogen (LH2) owing to its higher density, which enables more efficient utilization of container capacity. However, LH2 has a very low boiling point of 20 K, so a small amount of heat produces boil-off gas. For long-term storage of LH2, a system for cooling and recondensation the boil-off is required. Therefore, we demonstrated zero boil-off of LH2 by cooling and recondensing boil-off gas using a single stage Gifford-McMahon (GM) cryocooler and a heat exchanger. In this paper, we report on the results of the demonstration experiment for zero boil-off gas.

Speaker: Yutaro Koike (Sumitomo Heavy Industries, Ltd. - Technology Research Center)

10 C1Po1A-09: Impact of wave breaking on heat and mass transfer in a horizontal circular tank under non-isothermal sloshing conditions.

Liquid sloshing in next generation sub-cooled liquid hydrogen aircraft fuel tanks can induce rapid pressure drops in the ullage space when wave breaking is present. Significant pressure drops can result in problems such as cavitation in cryogenic pumping systems, thrust oscillations in the combustion chamber and structural instabilities on the tank walls. In flight, civilian aircraft are subjected to horizontal and vertical gusts which can induce large accelerations, leading to highly non-linear wave breaking conditions. Consequently, quantifying the pressure drop under different wave breaking conditions is essential to inform remedial measures such as active pressurisation and tank baffles.
This study explores wave breaking at resonance conditions for a range of vertical and horizontal excitations at a constant ullage pressure. A simplified horizontal circular tank has been manufactured for physical modelling, the tank has transparent faces allowing a high-speed camera to capture images of the sloshing dynamics. Two pressure sensors in the ullage space measure the pressure evolution for each test case and a vertical array of temperature sensors quantifies the thermal stratification between the vapour and liquid phases. The fluid HFE 7000 is used as a surrogate working fluid in the liquid and ullage space of the sloshing tank. This experimental research further investigates the effect of breaking waves on the ullage pressure, contributing valuable insights into the sloshing induced pressure drop for aircraft fuel tanks.

Speaker: Mr Stuart Colville (University of Plymouth)

11 C1Po1A-10: Hydrogen permeability of fiber-reinforced thermoplastics under cryogenic conditions

Developments toward future liquid hydrogen mobility require lightweight cryogenic engineering, favoring the use of composite materials over stainless steel. Fiber-reinforced thermoplastic (FRT) composites are considered for cryogenic applications, such as tanks and transfer systems. However, the permeation of hydrogen molecules through composite materials represents a significant challenge, as even small amounts can critically impair the insulation vacuum. Therefore, it is essential to evaluate the hydrogen permeability of these FRTs. This contribution presents a concept for measuring the long-term permeability rate of an FRT pipe section exposed to either liquid hydrogen or cryogenic gaseous hydrogen.

Speaker: Maximilian Grabowski

12 C1Po1A-11: Mega-Scale Liquid Hydrogen (LH2) Storage for Energy Storage & Transportation

Hydrogen is rapidly gaining recognition as a pivotal energy carrier capable of driving the transition to net-zero emissions by replacing conventional fossil fuels. When produced using renewable energy sources, hydrogen can achieve a completely net-zero lifecycle. Moreover, it provides an effective solution for addressing the intermittency of renewable energy by serving as a reliable storage medium. Among the various hydrogen storage technologies, liquid hydrogen (LH2) stands out as the most promising for large-scale storage and transportation. LH2 offers the highest volumetric density of hydrogen storage without requiring chemical conversion to other substances. While hydrogen liquefaction is energy-intensive, this process can be conducted in regions with abundant renewable energy. Consequently, in the hydrogen supply chain, energy-importing regions with limited renewable energy resources are relieved of the need for dehydrogenation processes. This characteristic makes liquid hydrogen particularly advantageous compared to other large-scale storage options, such as ammonia.
The primary challenge to the widespread adoption of LH2 is the current lack of infrastructure for its storage and transportation. As a cryogenic liquid, LH2 shares similarities with liquefied natural gas (LNG), suggesting that the development of LH2 infrastructure can draw valuable insights from the LNG industry. While the largest existing LH2 storage tank has a capacity of 4,732m³, LNG storage tanks have already reached scales of 200,000m³. This comparison highlights the future need for mega-scale LH2 storage infrastructure, leveraging lessons from the LNG market to support the mainstream adoption of LH2 as a global energy carrier.
A key challenge in developing LH2 storage tanks lies in accommodating hydrogen’s extremely low boiling point of 20K in an unpressurized state. Designing storage systems to maintain such cryogenic temperatures at a mega-scale requires precise thermal and structural considerations. This study focuses on the design and analysis of a mega-scale LH2 storage tank through finite element methods, addressing these challenges comprehensively.
The typical configuration of LH2 tanks includes an inner tank and an outer tank, with a vacuum-insulated space in between. The vacuum minimizes convective heat transfer, while insulation materials placed around the inner tank reduce radiative heat transfer. Spherical tanks are preferred due to their low surface-to-volume ratio, which helps limit heat ingress. A crucial component in this system is the internal support structure, which connects the inner tank to the outer tank. This structure not only transfers mechanical loads but also plays a significant role in minimizing conductive heat transfer, which is one of the primary heat transfer mechanisms in the system. By optimizing the internal support structure and insulation system, the tank design aims to reduce boil-off rates and ensure thermal efficiency. These elements work together to address the dual challenges of maintaining cryogenic temperatures and ensuring structural integrity at a scale required for mainstream LH2 applications.
The analysis revealed that the internal support structure contributes significantly to the heat transfer into the liquid hydrogen, even at the mega-scale. This finding underscores the critical need for optimizing the internal support structure to minimize thermal conduction. Such optimization can be achieved through strategic adjustments to the geometry and material selection of the supports, as demonstrated in this study. Additionally, the incorporation of thermal intercepts was shown to effectively remove part of the heat load, further reducing overall heat transfer into the tank.
Additionally, the analysis concluded that the boil-off rate of LH2 decreases as the tank capacity increases, offering an inherent thermal efficiency advantage for larger tanks. However, the practical challenges of constructing mega-scale spherical tanks prompted a comparative evaluation of cylindrical designs. A cylindrical mega-scale storage tank was designed, and its thermal and structural performance was analysed against that of spherical tanks, addressing both feasibility and efficiency.
This study provides valuable insights into the design of mega-scale LH2 storage tanks, highlighting key considerations for thermal management, structural integrity, and practical constructability. These findings contribute to the advancement of LH2 infrastructure, enabling its role as a scalable and sustainable energy carrier in the global energy transition.

Speaker: Shanaka Kristombu Baduge (The University of Melbourne)

C1Po1B - Aerospace Cryocoolers I: Pulse Tube and Stirling I

13 C1Po1B-01: In-line and coaxial configuration performances of Stirling pulse tube cryocoolers for spaceflight

Cryocoolers are critical components in space missions, providing the necessary cooling to maintain the functionality of sensitive instruments operating at cryogenic temperatures, such as superconducting devices and infrared detectors. This paper explores the design and application of Stirling and Stirling pulse tube cryocoolers (SPTCs) for spaceflight, emphasizing the trade-offs between different configurations and their suitability for specific mission requirements. Two primary configurations are analyzed: in-line and coaxial. The in-line design offers more simplicity and reduced fluid mechanical complexity but poses challenges in integration due to its linear geometry and lack of access to the cold head for detector integration. In contrast, the coaxial design is more compact, making it advantageous for detector coupling, although it introduces turbulence that can impact thermodynamic efficiency and cooling power. The study highlights critical design considerations, including minimizing vibrations, enhancing thermodynamic efficiency, and ensuring reliability over extended mission durations. Examples of these configurations utilized in space-based instruments are analyzed and underscore the importance of design innovations, such as dual-opposed compressors and advanced thermal linking, in addressing challenges like thermal noise and reliability. Future cryocooler development must focus on reducing mass, improving integration into space instruments, and enhancing energy efficiency, which are demonstrated to be achievable through configuration modifications. Addressing these challenges will enable the next generation of cryogenic systems to meet the stringent requirements of long-duration space missions.

Speaker: Alyssa Wang (Center for Astrophysics | Harvard & Smithsonian)

14 C1Po1B-02: 1 W@28.2 K micro single-stage coaxial pulse tube cryocooler operating at 52 Hz using precooling

With the advancement of deep cryogenic detection technology, spacecraft are required to operate at a background temperature of 100 K or lower, necessitating the use of pulse tube cryocooler as a critical support component. Traditionally, the compressor and hot-end heat exchanger of pulse tube cryocooler function at an ambient temperature of 300 K. Multi-stage pulse tube cryocooler typically require precooling to a temperature range of 80 K to 100 K before the second stage can commence operation. The transient regenerator serves as the thermal buffer between the ambient temperature compressor and the secondary pulse, leading to significant PV power losses and reduced cryocooler efficiency. Additionally, two-stage pulse tube cryocooler often exhibit low operating frequencies, large volumes and weights, and high launch costs. This paper presents the design of a micro single-stage coaxial pulse tube cryocooler capable of direct operation in the 80 K temperature zone. The cryocooler is powered by liquid nitrogen precooling and a linear compressor, with a total mass of 2 kg. It employs inertial tube and gas reservoir as phase shifters. The cold finger has a diameter of 14 mm and a fill length of 55 mm. Preliminary experiments yielded the following results: at a working frequency of 60 Hz, an input power of 20 W, a hot-end temperature of 80 K, and a working pressure of 1.5 MPa, the minimum no-load temperature achieved was 13 K, and a cooling capacity of 1 W at 28.2 K was obtained at 52 Hz.
Keywords: pulse tube cryocooler · liquid nitrogen · 80 K · micro · 52 Hz

Speaker: Dr Chenglong Liu (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China)

15 C1Po1B-03: Influence of the structure of multi-bypass configuration regenerator on the performance of Pulse Tube Cryocooler

As the fundamental component of the pulse tube cryocooler, the functionality of the regenerator exerts a direct influence on the overall performance of the cryocooler. In the design of a pulse tube cryocooler, two principal structural options for the regenerator are available, contingent on the specific requirements. One option is a non-variable cross-section structure, while the other is a variable cross-section structure. The advantage of the variable cross-section structure is that it allows the pulse tube cryocooler to increase the cold end heat exchanger at the variable cross-section for cooling, thereby enabling the cryocooler to operate in different temperature zones. Furthermore, the structure of the variable cross-section must incorporate a multi-bypass configuration at the variable cross-section region of the regenerator, with the objective of enhancing the phase modulation capacity of the inertial tube. Consequently, the mass of gas entering the cold end heat exchanger is reduced, which in turn diminishes the cooling capacity. The variable section structure presented in this paper is based on the design and processing experience of the single-stage pulse tube cryocooler. The design parameters are as follows: the diameter of the primary regenerator is 16 mm, with a filling length of 40 mm; the diameter of the secondary regenerator is 10 mm, with a length of 30 mm; and the packing of the regenerator is comprised of #500 and #635 stainless steel screens. The cryocooler was subjected to testing under varying charge pressures. At an input power of 100 W, a charge pressure of 4.2 MPa, a hot end temperature of 300 K and an operating frequency of 92 Hz, a minimum temperature of 32.16 K and a cooling capacity of 1 W at 44.44 K can be achieved.

Keywords: multi-bypass · regenerator · cold end heat exchanger · 4.2 MPa · 92 Hz

Speaker: Dr Chenglong Liu (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

16 C1Po1B-04: A high frequency lightweight coaxial pulse tube cryocooler operating at 70 K

An infrared detector represents a crucial instrument for human exploration of the universe. The pulse tube cryocooler is a widely utilized technology for the cooling of various types of infrared detectors. At present, the development of pulse tube cryocoolers, which can operate at lower temperatures and have higher cooling capacity, has become an important development direction in this field. In order to achieve this objective, a pulse tube cryocooler with a substantial cooling capacity in the lower temperature zone has been developed, in this study, a high-frequency pulse tube cryocooler operating at 70 K with a total weight of 4.7 kg, a cold finger diameter of 25.6 mm, and a length of 51 mm. The regenerator is filled with #600 and #500 stainless steel screens. Under the conditions of input power 200 W, hot end temperature 300 K, operating frequency 106 Hz, and charge pressure 6MPa, the minimum temperature is 32.4 K, and the cooling capacity of 10 W can be obtained at 70.75 K, the relative Carnot efficiency is 16.35%.

Keywords: pulse tube cryocooler·10 W@70.75 K·106 Hz·lightweight

Speaker: Bo Tian (1 Key Laboratory of Technology on Space Energy Conversion, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

17 C1Po1B-05: Numerical and experimental investigation of the compressor coupling characteristic of a 20K thermal-coupled two-stage high-frequency pulse tube cryocooler

With the rapid development of space technology, the demand for 20K thermal-coupled two-stage pulse tube cryocoolers (PTC) for space infrared detection equipment is increasing. The entire machine is composed of two parts: compressor and cryocooler, so the coupling characteristics of compressor and cryocooler have a serious impact on the performance of the entire machine. In this paper, the efficiency of the 2nd-stage of the thermal-coupled two-stage PTC is theoretically analyzed. Based on Sage, the model of the 2nd-stage of the PTC was established. After simulation calculation, the piston displacement, pressure wave, mass flow and phase angle of PTC coupling with different compressors were studied, and the performance of the entire machine was compared. The experimental results are highly consistent with the simulation results, which verifies the accuracy of the Sage model. Through experiments, the power factor, optimal frequency, no-load cooling temperature, and cooling capacity at 20K of PTC coupled with different compressors were compared and studied. By comparing the force balance diagram of the compressor and the phasor diagram of the PTC, the coupling characteristics of the entire machine are compared. With a total electrical power consumption of 490W, the maximum cooling capacity of a 1135mW@20K was obtained. When the total electrical power consumption was reduced to 185W, a cooling capacity of 647mW@20K was obtained, resulting in a maximum relative Carnot efficiency (rCOP) of 4.9%.

Speaker: Jia Quan (Technical Institute of Physics and Chemistry, Chinese Academy of Science)

18 C1Po1B-06: Performance simulation and model verification for a 20K thermal-coupled two-stage high-frequency pulse tube cryocooler

Currently, most high-precision infrared detectors used in space operate in the liquid hydrogen temperature range and require a two-stage pulse tube cryocooler (PTC) to provide a cryogenic environment. However, the existing two-stage thermal-coupled PTC suffer from low cooling capacity and efficiency. Therefore, in this study, the 2nd-stage of the PTC is considered as a whole system and a Sage model is established. The model is coupled with different inertance tube combinations to comprehensively simulate the performance. The simulation results are compared with the experimental results from the published article “Experimental optimization of phase and compressor of a 20K thermal-coupled two-stage high-frequency pulse tube cryocooler”. The accuracy of the model simulation for the no-load optimal frequency and the cooling capacity at 20K is verified. 70% of the simulated values for the no-load optimal frequency deviate from the experimental values by 0-1Hz. 84% of the simulated values for the cooling capacity at 20K deviate from the experimental values within a range of ±20%. It is observed that all experimental values for the optimal frequency at 20K is consistently 2-4Hz higher than the simulated values. The reasons for this phenomenon are revealed from the perspective of the phase angle between the mass flow and pressure wave inside the 2nd-stage regenerator, using the enthalpy flow phase-shifting theory. The research results provide a foundation for the application of Sage software in the study of overall performance of two-stage thermal-coupled PTC.

Speaker: Jia Quan (Technical Institute of Physics and Chemistry, Chinese Academy of Science)

19 C1Po1B-07: Investigation on a thermal-coupled two-stage pulse tube cryocooler with multi-bypass working at 8 K

The Stirling type pulse tube cryocooler (SPTC) eliminates moving parts at the cold end and is driven by a linear compressor at the hot end, thus offering the advantages of low vibration at both ends, high reliability, and long service life, which makes it attractive for various special fields, such as the space field.In practice, there is an increasing interest in providing cooling power at different temperature levels.This paper presents an experimental investigation of a thermal-coupled two-stage pulse tube cryocooler with multi-bypass structures.The experiments firstly investigated the effect of pre-cooling stage temperature on the temperature of the second-stage cold finger and multi-way bypass, and then focused on the effect of the second-stage operating frequency and charging pressure on the second-stage cold finger, multi-bypass as well as the pre-cooling stage, and experimental testing of cooling performance.The experimental results show that through the thermal coupling pre-cooling and the design of multi-bypass structure, the second-stage cold finger can realize the lowest temperature of 5.4K, and can simultaneously provide 40mw cooling capacity at 8K in the second-stage cold head and 60mw cooling capacity at 34K in the multi-bypass, respectively.

Speaker: Mingtao Pan (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

20 C1Po1B-08: Theoretical and experimental investigation of the effect of the phase shifter on the compressor of pulse tube cryocoolers

Phase shifters (inertance tubes and reservoirs) can perform the function of maintaining a proper phase relationship between pressure and mass flow rate. Although many theoretical models of phase shifters have been proposed in previous studies, it is not clear how the parameters of the phase shifters affect the compressor characteristics of pulse tube cryocoolers. How the inertance tubes and the gas reservoir volume affect the compressor displacement and the output PV power are yet to be further investigated.In this paper, the theoretical analysis of inertance tube and gas reservoir volume on compressor displacement and output PV power characteristics is presented, and a miniature pulse tube cryocoolers is numerically simulated by building a Sage model.The theoretical and simulation results were experimentally verified by adjusting different combinations of inertance tubes and gas reservoirs.

Speaker: Mingtao Pan (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

21 C1Po1B-09: Simulation and experimental of phase shifter in high frequency pulse tube cryocooler

The development of the 3rd generation infrared technology enables the pulse tube cryocoolers to become lighter, smaller and more efficient. The phase shifter has a significant effect on the performance of the cryocooler. Moreover, as the weight of the compressor and the cold finger decreases, the phase shifter, especially the reservoir increases its weight ratio in the whole pulse tube cryocooler. In this paper, a pulse tube cryocooler model is established to investigate the pressure wave, mass flow and the phase shift between them along the inertance tubes and discuss the possibility of eliminating the reservoir when the cryocooler works at high frequency. The effect of the diameter and length of the inertance tubes and the volume of reservoir are investigated by experiments.

Speaker: Geyang Li (Technical Institute of Physics and Chemistry CAS)

C1Po1C - Non-Aerospace Cryocoolers I

22 C1Po1C-01: Experimental demonstration on a bellows-sealed displacer for two-stage Stirling cooler

The displacer in a two-stage Stirling cooler should prevent gas leakage between the compression space at room temperature, the first stage expansion space, and the second stage expansion space. To achieve this, clearance seals are usually required at two locations between the displacer and the cylinder. Through the geometric analysis, we discovered that if the displacer operates with a very small angular tilting, undesirable sliding with friction between the displacer and the cylinder occurs at the cryogenic temperature region. In a simple single-stage Stirling cooler, clearance seals can be installed only at the room-temperature side of the displacer, and an appendix gap with a relatively large clearance is placed on the cryogenic part of the displacer to prevent friction at the cold end even if the friction occurs at the room-temperature side. However, in the two-stage Stirling cooler with a stepped displacer, an additional clearance seal is required at the cryogenic part to prevent leakage between the first and the second stage expansion spaces, making it impossible to structurally avoid friction at the cryogenic part. To address this problem, we introduced a bellows sealing method to the stepped displacer configuration. The clearance seal is installed at the ambient part of the displacer and the appendix gaps are installed at the first and the second stage cold ends of the displacer so that it can avoid the friction at the cryogenic part. In addition, the bellows sealing whose one end is stationary and the other end is oscillating together with the displacer is installed at the first stage expansion space. This sealing prevents the leakage between the first and the second stage expansion spaces. The present study experimentally verifies the performance of the displacer with the bellows sealing, suggesting its potential for practical application. Specifically, we discuss the design and fabrication methods of the two-stage Stirling cooler as well as its cooling performance.

Speaker: Bokeum Kim (KAIST)

23 C1Po1C-02: A new approach for low input and high capacity 4 K Gifford-McMahon cryocooler

Regenerative 4 K cryocoolers, such as Gifford-McMahon (G-M) and G-M type pulse tube cryocoolers, have been required for superconducting applications. A problem with these cryocoolers is the low efficiency to achieve the attainable temperature of 4 K. An electrical input of 6-7 kW is required to achieve a cooling capacity of one watt level at 4 K. To solve this problem, a new operating method, a two-stage G-M cold head driven by two 2 kW compressors connected in parallel, has been carried out. This is because we found that the specific mass flow, mass flow divided by electrical input, (g/s)/kW, of the low input compressor, such as the 2-kW class, is larger than that of the high input compressor, such as the 7-kW class. The comparison of the experimental results of the cooling capacity at 4.2 K was 1.7 W at 4.2 kW input (two 2 kW compressors) and 2.1 W at 7.0 kW input (single 7 kW compressor). The calculated relative Carnot efficiency at 4.2 K of the G-M cryocooler driven by two 2 kW compressors was 2.8%, compared to 1.4 times that of the single 7 kW compressor. From these results, this method is considered to be a new approach to achieve the low input and high capacity 4 K G-M cryocoolers.

Speaker: Prof. Shinji Masuyama (NIT, Oshima College)

24 C1Po1C-03: Parametric thermal characterization of Sumitomo RDE-418D4 two-stage Gifford-McMahon cryocooler

Cryocoolers are an excellent go-to solutions when cryogen-free dry cooling is essential. The existing cryocoolers in the market are certified with the cooling capacity specified only at generic points (such as 4.2 K, 10 K and 20 K). However, if the cryorefrigeration is to be obtained in any other cryogenic temperature range, the cryocooler capacity is not readily available. It is indeed possible to get a rough estimate from the capacity map supplied with the cryocoolers. Nevertheless, this is a generalized data based on tests conducted on numerous cryocoolers and not specific to the cryocooler unboxed. Our application seeks cryorefrigeration in liquid neon temperature range. For this purpose, the highest capacity 4K cryocooler manufactured by Sumitomo RDE-418D4 has been employed. At second-stage temperature of 4.2 K, the cold head has capacity specifications of 1.8 W @ 50 Hz and 2.0 W @ 60 Hz with first-stage load of 42 W and 50 W respectively. It operates with F-50SH water-cooled helium compressor. This work presents the thermal characterization of the cryocooler second-stage at varying heat loads from 100 mW to 25 W. Different data sets are obtained while maintaining the first stage at no load (0 W) or under constant load conditions (25 W, 50 W, 75 W). Additionally, the cooling capacity is recorded at different compressor frequency of 40 Hz, 50 Hz, 60 Hz and 70 Hz.

Acknowledgement: We thank Sumitomo for letting us publish this data.

Speaker: Gilles Authelet (CEA Paris-Saclay)

25 C1Po1C-04: Development of a 4 K pulse-tube refrigerator (PTR) for quantum device cooling

The rapid advances in quantum technologies have significantly increased the demand for reliable cryogenic refrigeration systems capable of cooling quantum devices. Quantum device requires a temperature level of 10-20 mK and quiet environment, because the entanglement of the superconducting qubit may not be sustained due to thermal fluctuations and mechanical vibration. This phenomenon is referred to as decoherence, and it makes a computation error. Conventional dilution refrigerators (DR), so called wet DR, are precooled by liquid helium, but a more cost-effective and easy precooling method can be achieved by using a mechanical refrigerator. This research aims to develop a pulse-tube refrigerator (PTR) capable of providing a cooling capacity of 1.5 W at 4 K. This research primarily focuses on the design and optimization of the regenerator, a key component in achieving high thermal efficiency. Based on the regenerator design, the PTR was fabricated and experimentally tested. The experimental results demonstrated that the system successfully achieved a minimum temperature of 4 K. Although the cooling capacity fell short of the 1.5 W target, this discrepancy was primarily due to the suboptimal performance of the orifice valve and the double inlet valve, which regulate phase adjustment and flow distribution within the pulse tube. The developed PTR marks a significant step in localizing cryogenic refrigeration systems for the quantum industry. It is expected to serve as the pre-cooling stage for the dry DR, which can achieve temperatures below 10 mK. Additionally, it will complement the magnetic refrigerator (MR), designed to reach temperatures below 100 mK, both of which are under development within the same consortium. This integration is expected to drive the localization of quantum technology infrastructure forward.

Speaker: Jiho Park (Korea Institute of Machinery and Materials)

26 C1Po1C-05: Study on the multiple cooling output characteristics of a gas-coupled high-frequency pulse tube cryocooler

Gas-coupled type multi-stage high-frequency pulse tube cryocoolers (HPTCs) whose different stages are coupled directly through mass flow offer unique advantages in terms of compact structure and small volume and weight, leading to significant application prospects in special fields such as deep space exploration. However, limited by the subtle intrinsic interaction of gas proportion and energy flow among different stages, few studies have been carried out on the mass-energy transfer mechanism of such cryocooler at cryogenic temperatures below liquid hydrogen, where the cooling capacities can be inevitably small compared to low-frequency cryocoolers. Furthermore, the cooling output is usually feasible only at the cold end of each stage. In order to optimize the refrigeration process of the gas-coupled type HPTCs and to improve the utilization efficiency of the cooling capacities in the higher temperature zone along the cryocooler, a pre-cooling type two-stage gas-coupled HPTC working at liquid-helium temperatures was designed to achieve stepped cooling output. The interstage multiple cooling output characteristics and the intra-stage cooling extraction mechanism were investigated. The research results can provide a useful reference for the practical application of a single HPTC with simultaneous multiple cooling output at different cryogenic temperatures.

Speaker: Dr Biao Yang (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

C1Po1D - Sub K Helium Cycle Cryocoolers

27 C1Po1D-01: Research on an efficient Joule-Thomson throttling refrigeration system based on cold compression cycle

2K-class or 4K-class mechanical Joule-Thomson (JT) throttling refrigeration system is crucial to cool far infrared detector or extremely high sensitivity and resolution detector，such as SQUID（Superconducting quantum interference device）, SNSPD（superconducting nanowire single photon detector）
A novel efficient precooled JT throttling refrigeration system is currently under development. In this system, JT cooler is pre-cooled by a GM refrigerator or a pulse tube refrigerator.The compression unit of JT cooler which drives the circulating mass helium, is at low temperature and directly coupled to the cold head of the pre-cooling cooler. Compared to traditional throttling refrigeration system, this design eliminates the need for multi-stage heat exchangers, simplifies the system architecture, and enhances the efficiency.
The linear motor components driving the compression unit is arranged in an environment of ambient temperature and pressure. The heat generated by the linear motor during operation is dissipated through air cooling or water cooling methods. The linear motor is connected to the compression unit by a connecting rod made of materials with low thermal conductivity and high strength, reducing heat loss.
The operating mass helium is isolated from the linear motor through a bellows, preventing the low-temperature operating mass from shuttling between the ambient-temperature motor, which would lead to heat loss.
Compared to traditional throttling refrigeration systems, this innovative system can still achieve rapid cooling without the need for a bypass valve. simplifying the structure and enhancing reliability.
A mathematical model is established in this work to reveal the cooling capacity characteristic based on thermodynamic analysis method. At present, the JT system experimental platform has been built and the corresponding performance tests are being carried out.

Speaker: Yuefeng Niu (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China)

28 C1Po1D-02: Design and experiments of 1 K superfluid 4He system for precooling the ultra-low temperature refrigerators

With the development of the frontier domains such as quantum computing, condensed matter physics and space exploration, there is an urgent need for the multi-stage ultra-low temperature refrigerators to reduce the internal thermal noise and external thermal interference. The superfluid 4He system is a key component at the 1 K stage of ultra-low temperature refrigerators. The cooling capacity of the superfluid 4He system depends on the throttling, liquefaction and evaporation process which were affected by the impedance. In this paper, the influences of the impedance parameters, the flow rates and the heat exchange means on the performance of the superfluid 4He system are tested. Based on the above researches, a superfluid 4He system with the minimum temperature of 1.1 K is constructed, which can meet the precooling requirement of the ultra-low temperature refrigerators.

Speakers: Zijie Pan (Key Laboratory of Cryogenic Science and Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Science, Beijing 100190, China), Lingjiao Wei (Technical Institute of Physics and Chemistry, CAS), Jiarun Zou (Key Laboratory of Cryogenic Science and Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Science, Beijing 100190, China)

29 C1Po1D-03: Simulation and experimental study of ultra-low temperature heat transfer characteristics of continuous heat exchangers in the dilution refrigerator

Dilution refrigerators, as the key instruments of quantum research, greatly contribute to the development of quantum computing. Continuous heat exchanger is an indispensable core component in the dilution refrigerator, which precools the incoming concentrated phase by exchanging heat with the return diluted phase. In this study, we propose a thermodynamic model of a continuous heat exchanger considering the factors of flow heat transfer and viscous heat conduction, and analyze the effects of its heat exchanger length, flow rate and inlet pressure on its performance. It is successfully applied to a dilution refrigerator and reaches an outlet temperature of 50 mK，and its system achieved a performance of 380 μW at 100 mk cooling capacity. The model proposed in this study can provide a reference for the subsequent research and design of dilution refrigerator and effectively improve its performance.

Speaker: Zijie Pan (Technical Institute of Physics and Chemistry, CAS)

30 C1Po1D-04: Design and performance evaluation of a closed-cycle ³He sorption cooler

Cryogenic technology plays a significant role in ground experiments and space exploration. ³He sorption refrigeration is one of the few methods capable of achieving temperatures below 500 mK, and due to its advantages such as small size, light weight, no vibration, no electromagnetic interference, and simple operation, it has considerable competitiveness in the field of space ultra-low temperature refrigeration. We demonstrate the design and performance evaluation of a closed-cycle single-shot ³He sorption cooler, which integrates a cryopump filled with activated carbon granules, and analyze the heat and mass transfer characteristics of different adsorption bed structures. The ³He sorption cooler, pre-cooled by a two-stage GM pulse tube refrigerator and a superfluid helium bath, achieves a minimum temperature of 394 mK and provides a net cooling power of 200 µW at 486 mK. The performance of the ³He sorption cooler needs further optimization and will be used for pre-cooling of adiabatic demagnetization refrigerators in the future.

Speakers: Juan Wang (Technical Institute of Physics and Chemistry, CAS), Xiang Fan (Technical Institute of Physics and Chemistry, CAS)

31 C1Po1D-05: Design and analysis of sub-K continuous heat exchanger for dilution refrigerators

A continuous tube-in-tube heat exchanger (TTHx) is used to pre-cool the concentrated stream (99.9% He-3) from 700 to 100 mK (or below) using a dilute stream (6.4% He-3 and 93.6% He-4) in a dilution refrigerator (DR). In commercially available DRs, the inner tube carrying the concentrated stream in TTHx is helically wound (H-TTHx) to increase the compactness and improve the effectiveness. However, in literature, a helically wound inner tube is rarely modeled, and instead, a linear one-dimensional (1D) tube-in-tube (L-TTHx) geometry is used. Since both streams' enthalpy and thermal properties depend strongly on temperature, modeling of H-TTHx as L-TTHx will lead to deviations from the actual temperature profile along the length of H-TTHx. Consequently, the temperature profile of both streams and the effectiveness of TTHx remains to be determined.

In this study, we present the three-dimensional (3D) numerical analysis of a compact footprint (diameter < 5 cm and length < 10 cm, fixed by the space availability in DR) L-TTHx and H-TTHx manufactured using 70/30 Cu-Ni alloy under the constraint that the outlet temperature of the concentrated stream (Tco) remains less than 100 mK. Under the above geometry and temperature constraints, the maximum concentrated stream flow rate is limited to 200 and 400 μmol/sec for L-TTHx and H-TTHx. The 400 μmol/sec flow rate in the H-TTHx will lead to a base temperature of 10 mK in the mixing chamber and a cooling power of 15 μW or higher at 20 mK. We further explicitly determine the contribution of viscous heating, Kapitza resistance, and axial and radial conduction on the temperature profile along L- and H-TTHx and identify their relative contribution in controlling the effectiveness of TTHx. Contrary to the modeling assumption in the literature, if we maintain the same molar flow rate of the concentrated stream for L- and H-TTHx, the temperature profile along the length differs significantly in both decay rates along the length and the outlet temperatures. Our study highlights the need to go beyond the standard 1D modeling of H-TTHx used in DR as L-TTHx to precisely capture the temperature profile along the length and cross-section and determine the effectiveness of TTHx.

Speaker: Prof. Dipanshu Bansal (Indian Institute of Technology Bombay)

32 C1Po1D-06: Development of a heat exchanger with distributed Joule–Thomson effect for a closed-cycle cryocooler

In this study, a counterflow heat exchanger for a Joule–Thomson (JT) cryocooler was developed and integrated into a closed-cycle cryocooler. The cryocooler uses a two-stage Gifford–McMahon refrigerator as the precooler and helium-4 as the working fluid for the JT cooling circuit. The cryocooler achieved temperature below 2 K, with the cooling power dependent on its operational settings. A typical cooling power of 0.2 mW was measured at 2.3 K with a circulation rate of 57 micromol/s. The developed heat exchanger has a helical-in-tube-type construction, consisting of a helically coiled capillary tube installed inside a straight outer tube. High-temperature and heigh-pressure fluid flowed through the helically coiled capillary, while low-temperature and low-pressure fluid flowed through the space between the outer surface of the capillary and the inner wall of the outer tube. The current in the high temperature side is cooled by that in the low temperature side. The flow impedance on the high-temperature side of the heat exchanger was designed to be significantly higher than that of conventional counterflow heat exchangers. This high impedance induced a substantial frictional pressure drop and a continuous temperature reduction in the fluid along the capillary in the flow condition of the present study. That is called distributed Joule–Thomson effect.
The distributed JT effect has been studied theoretically, numerically and experimentally by many researchers. Previous research has demonstrated that a counterflow heat exchanger incorporating the distributed JT effect can eliminate the need for flow restriction components, such as an orifice and needle valves, at the outlet of the high-temperature side of the heat exchanger. The flow restriction is one of the main components of a conventional JT cryocooler. Eliminating the independent flow restriction simplifies the JT cryocooler structure. However, experimental investigations into the characteristics of the distributed JT effect remain limited, especially at the liquid helium temperature range. Most prior studies used mixed refrigerants or operated above liquid helium temperatures, often involving experiments within a liquid helium dewar.
In this study, an experiment was conducted with helium-4 as a single-component working fluid and mechanical refrigerator as a precooler for the JT cooling circuit.
Estimating the pressure drops in a helically coiled capillary is crucial for designing a heat exchanger leveraging the distributed JT effect. To this end, pressure drops in helically coiled capillaries of varying inner diameters were measured at room temperature and liquid nitrogen temperature of 77 K prior to designing the heat exchanger. This study presents a detailed discussion of the characteristics of the developed counterflow heat exchanger and closed-cycle cryocooler.

Acknowledgement
This work was partly supported by JSPS KAKENHI Grant Numbers JP20K04319 and JP24K07368.

Speaker: Dr Takeshi Shimazaki (NMIJ, AIST)

C1Po1E - Large Scale Refrigeration I: Helium

33 C1Po1E-01: Evaluation of helium loss for a closed-loop cryogenic system

Notification of remarkable helium loss in early stage is crucial, especially in the shortage period of helium supply market, for operating a cryogenic plant with its downstream cryostats of superconducting devices. This paper proposes an indicator representing the amount of helium gas remained in the cryogenic plant and associate cryostats during their normal operation period. The indicator is based on normal operation status of the cryogenic system and intakes the effect from outdoors temperature and cryostat geometry. Applying the indicator to look back on helium loss from the archived data of an operating cryogenic system shows that the indicator provides an uncertainty close to 1% total amount of helium circulated in the system. This indicator is suitable for monitoring the helium loss of a closed-loop cryogenic system being in operation.

Speakers: Feng-Zone Hsiao (National Synchrotron Radiation Research Center), Mr Hsing-Chieh Li (National Synchrotron Radiation Research Center)

34 C1Po1E-02: Assessment of the existing cryogenic central plant for the Electron Ion Collider cryogenic loads at Brookhaven National Laboratory

The Electron Ion Collider (EIC) at Brookhaven National Laboratory consists of one existing hadron ring and new electron accelerator. The EIC incorporates beamline and detector elements that require superconductivity, which is achieved by cooling these elements to cryogenic temperatures. The EIC cryogenic systems are designed to provide cooling for various components, including heat shield circuits, current leads, power couplers, thermal intercepts, and superconducting devices operating at or below 4.5 K. The existing central plant used for cooling Relativistic Heavy Ion Collider (RHIC)’s magnet rings will also be used for EIC. There are Superconducting magnets that require operation at 1.92 K, and Superconducting Radio Frequency (SRF) cavities that require operation at 2.0 K. These are located at distinct locations around the Collider ring. Satellite systems located locally will be installed to produce the 1.92K and the 2.0K cooling capability. These systems will not be fully independent standalone plants, rather they will use the existing central plant for capacity assistance. The existing cryogenic distribution in the hadron magnet ring will also be used to supply the satellite systems.
This paper examines the different types of loads imposed on the existing central plant and evaluates where the plant is expected to operate. Due to modifications made to the plant for the RHIC program, the existing equipment will be evaluated to assess whether changes are needed to the cold end of the plant: expander(s), exchangers and return piping configuration to return the satellite return streams. The finding will provide valuable insights into upgrade/modification requirements, optimizing the cryogenic plant, and ensuring reliable support for EIC's advanced scientific objectives.

Speaker: Pratik Kumar Manubhai Patel

35 C1Po1E-03: A backup compressor system for the ESS accelerator cryoplant

The European Spallation Source ERIC (ESS) is a neutron-scattering facility being built with extensive international collaboration in Lund, Sweden. An essential part of the project is the linear 2.0 GeV proton accelerator (linac). Its superconducting part is cooled by means of a dedicated 2K refrigerator, the Accelerator Cryoplant (ACCP). 2K are achieved with three serial turbo compressors and a warm sub-atmospheric screw compressor. The ACCP operates in a four-pressure process with three warm oil-flooded screw compressors providing these pressures, one of them with sub-atmospheric suction pressure. Every one of these three compressors is a single point of failure for the entire ESS facility. Even worse, periodic maintenance on the high pressure (HP) machine would not be possible without warming up the plant and with it the superconducting linac. It has therefore been decided to implement a backup compressor that can replace any of the existing warm compressors.
The paper summarizes all project phases from initial decision to conceptual design, specification, procurement, execution, installation, commissioning and acceptance testing. Particularly mechanical and controls integration challenges are described in more detail as well as lessons learnt and planned improvements.

Speaker: Philipp Arnold (European Spallation Source ERIC)

36 C1Po1E-04: LCLS-II Cryoplant Cooling Water System: Challenges and Remediation

The SLAC National Accelerator Laboratory houses LCLS-II, a superconducting linear accelerator (LINAC) that began operations in October 2023. Central to this advanced accelerator technology are two 4 kW @ 2.0 K Cryoplants. Supporting their operation is a dedicated Cooling Water System (CWS) with a total capacity of 2,000 m³/h. Most of the water is directed to the Warm Helium Compressor (WHC) stations, which deliver a combined mechanical power of approximately 9.0 MW. Additionally, the CWS supplies a secondary water loop with finer filtration to serve smaller components such as recovery compressors, expansion turbines, cold compressors, and vacuum pumps. This paper describes the SLAC CWS and reviews the challenges encountered with cooling water chemistry during the first year of operation, focusing on their potential impact on cryoplant availability and the remediation strategies employed.

Speaker: Saee Vyawahare (Stanford National Accelerator Laboratory)

37 C1Po1E-05: Commissioning Results of The ESR 2 Compressors at JLab

The future operation of the 4 kW 15 Kelvin MOLLER experiment at Jefferson lab necessitates an increase of cryogenic capacity at the End Station Refrigerator. The current plant is the former 1.5 kW (4.5 K) ESCAR plant that has been operating at Jefferson Lab since 1995. The existing 1.5 kW plant is not able to support the load for MOLLER and will be replaced with a refurbished plant comprised of the cold box and compressors of the 4 kW ASST-A plant from the Superconducting Super Collider in Texas. This paper reports the commissioning results of the warm compressor system and compares the current performance with past commissioning performance for these compressors when they were part of the ASST-A plant.

Speaker: Christopher Perry (Thomas Jefferson National Accelerator Facility)

38 C1Po1E-06: Upgraded shield refrigerator for Jefferson Lab’s Cryogenic Test Facility

The Cryogenic Test Facility (CTF) at Jefferson Lab provides cryogens to support production and testing of accelerator cryomodules. Within the CTF, a standalone shield refrigerator produces nominally 35 K helium to cool heat shields in the cryomodules and cryogenic distribution system. It consists of four heat exchangers packaged into a cold box and a separate reciprocating expander pod. After 35 years of service, the shield refrigerator was unable to keep up with modern operations due to undersized heat exchangers, process and vacuum leaks, and expander wear and tear. A replacement shield refrigerator cold box has been designed and constructed by Jefferson Lab. The new heat exchangers were sized to meet thermal and hydraulic performance requirements during all operating modes, including a new bypass mode which allows shield flow to be supplied at 80 K while the expander is offline for maintenance. The expander pod itself was also refurbished and upgraded by a third-party contractor. This paper will discuss the design of the upgraded shield refrigerator and its performance during commissioning. Helium and nitrogen usage rates and expander rotational speeds under all operating modes have been reduced, and mean time between maintenance for the reciprocating expander has increased. The upgraded system improves CTF resource consumption and shield flow availability, benefitting cryomodule production and testing throughput.

Speaker: Brian Mastracci (Thomas Jefferson National Accelerator Facility)

C1Po1F - Large Scale Refrigeration II

39 C1Po1F-01: Performance Investigation of Gas-Solid Heat Transfer from Room to Cryogenic Temperatures in Moving Solid-Phase Cold Storage

Liquid Air Energy Storage (LAES) is an emerging energy storage technology characterized by its high energy density and non-polluting nature. It stores surplus electricity through the processes of compression, cooling, and liquefaction of air, and releases electricity to compensate grid loads through the pressurization, gasification, and expansion of liquid air. The core process involves the storage of cold energy from air liquefaction and gasification. Due to the inherent safety and low material costs, solid-phase cold storage technology has been widely studied. Among these technologies, the fixed particle packed bed cold storage technology is most extensively researched, but it suffers from dynamic effects due to thermocline development during heat transfer, limiting efficiency improvements. Based on this research status, we propose a moving solid-phase cold storage process where the cold storage particles exchange heat with the carrier gas in a countercurrent flow and store the cold and heat particles separately. The movement of particles can mitigate the adverse effects of the thermocline, thereby enhancing heat transfer efficiency. In this study, we construct a model of the heat transfer process and investigate the matching characteristics of gas-solid phase velocities as well as the establishment of a steady-state heat transfer process.

Speaker: Yihong Li (Technical Institute of Physics and Chemistry, CAS)

40 C1Po1F-02: “Keep it simple, stupid”: Redesigning a chaotic low pressure LN2 delivery system to NMR instrument

“Keep it simple, stupid” is an engineering design principle that is, sometimes, silently drifted away from when system modifications are implemented to rectify a problem; where, ironically, complexity is increased to achieve a simple objective. This project introduces a tumultuous low pressure (5psi) liquid nitrogen delivery system feeding an NMR instrumentation lab, with a current system stability analogous to a spinning top in a hailstorm. Over time, additional modifications have been added to this LN2 delivery system, increasing the complexity, albeit without enhancing stability. Our goal in presenting this system is to ultimately redesign its implementation aiming for improvement in efficiency and stability. Presently, the system requires near daily user input via adjustment of relief valves to maintain a stable flow rate, where its current state has a propensity towards chaos, reaching a point of constant filling and venting to maintain 5psi flow rate. The original system design, located on the roof above the NMR instrumentation lab, utilizes a VJ LN2 supply line entering a two-phase tank, with upper and lower fluid volume regulated via a pneumatically operated controller fill valve, where 5psi output flows from the bottom of the tank via VJ line to NMR instrumentation. The two-phase tank is equipped with a pressure relief valve set to 22psi. Overhead gas volume is maintained with an outlet vent to atmosphere, regulated with a pressure regulator valve set to 7psi and a solenoid valve set to 14psi. Ineffectual post modifications involved installation of an additional gas phase buffer pot placed above the two-phase tank and connected upstream from the original pressure regulator (7psi) and solenoid valves (14psi) to increase overhead gas volume with an intent for increased stability.

Speakers: Benjamin Arline (Florida State University - NHMFL), Zhiyi Jiang (Florida State University - NHMFL)

41 C1Po1F-03: Heat load characterization: a cross-facility comparative study

Static heat load (radiation, conduction, and convection) characterization in cryogenic systems can account for a significant portion of the total heat load, directly influencing the sizing and specifications of cryogenic refrigeration capacity. Currently, there is no established industry standard for calculating static heat loads; these are often determined using proprietary formulas supplemented with safety factors to address potential design and manufacturing flaws and inefficiencies during operation. This paper compares heat load calculation methods from various institutions and evaluates the discrepancies between calculated and observed static heat loads in the SLAC LCLS-II cryogenic system. Key challenges and lessons learned are summarized to provide guidance for the design phase of large-scale cryogenic facilities.

Speaker: Akanksha Apte (Stanford University)

42 C1Po1F-04: HL-LHC RF dipole crab cavities validation at TRIUMF

The High Luminosity (HL-LHC) upgrade of the Large Hadron Collider at CERN is an example of large-scale international scientific cooperation which spans multiple international partners. Canada through TRIUMF is making an in-kind contribution to the project with the delivery of five crab cavity cryomodules. The cryomodules will be delivered to CERN by 2026 for installation in the LHC. TRIUMF will receive the RF dipole (RFD) crab cavities from a consortium of US DOE labs. The cavity validation procedure at TRIUMF prior to cryomodule installation and our initial results are discussed in this paper.

Speaker: Alexey Koveshnikov

43 C1Po1F-05: Design of a new 12x150A helium-cooled current lead for EIC

Following the failure that ended the RHIC run 23, a review of the original 12x150A RHIC current leads has uncovered a series of design issues that granted a replacement of these leads before the EIC operation begins. Taking advantage of the lesson learned from 24 years of operation, significant design improvement to the old design have been studied. Going back to thermal and electrical conductivity measurement, we have derived suitable materials and conductor geometry. The new current lead design was optimized with its operational lifecycle in mind.
This paper will describe the lesson learned from the original lead operation, the principles driving this new current lead design, the lifecycle design optimization and the expected operational performances of the proposed design.

Speaker: Frederic Micolon (Brookhaven national laboratory)

09:15 Morning Coffee Break -- supported by Sumitomo (SHI) Cryogenics of America, Inc.

M1Or1A - Low Temperature Properties of Non-Ferrous Metals and Alloys

44 M1Or1A-01: Microstructure and 77K mechanical properties of electron beam welded Cu101- Inconel 625 joints

In developing large-scale next-generation superconducting radio frequency (SRF) linear accelerators using superconducting films on Cu, the design and development of dissimilar welding and joining metals, such as Cu to Inconel, stainless steel, and Nb, are essential. In this talk, we present the development of procedures for electron-beam welding of Cu-Inconel 625 and evaluation of the microstructure and 77K mechanical properties of the weld and base material in the welded condition and heat treatments in the 750°C- 950°C heat treatment range. The results will be presented in the context of developing joining techniques for low-temperature applications where high conductivity and strength, vacuum hygiene, and magnetic properties of the material need consideration. The methods presented here are being deployed to thin film SRF Cu cavities at Jefferson Lab.

Speaker: Shreyas Balachandran (Thomas Jefferson National Accelerator Facility)

45 M1Or1A-02: Multiscale Modeling of Polycrystalline Niobium Sheets to Capture Anisotropic Evolution

An integrated computational model based on a multiscale modeling approach was developed to utilize niobium sheets in forming processes required for high-performance superconducting radio frequency (SRF) cavities. The effects of microstructural features, such as crystalline texture and grain morphology in polycrystalline niobium, on mechanical properties were evaluated based on crystal plasticity. In particular, the influence of microstructural heterogeneity on anisotropy and formability was analyzed. Additionally, the effects of cold rolling and subsequent heat treatment processes on the mechanical properties, including plastic anisotropy, of niobium sheets were investigated. For phenomenological modeling applicable to continuum-scale stamping analysis, a two-yield surface plasticity based combined isotropic-kinematic hardening law was employed to account for the evolution of plastic anisotropy in non-proportional loading conditions.

Speaker: Dr Taejoon Park (The Ohio State University)

46 M1Or1A-03: Comparative Analysis on Recrystallization and Recovery of High and Low RRR Niobium

Transition niobium (Nb) metal has been widely accepted in superconducting technology due to its strong isotropic superconductivity. Its high mechanical formability allows the application of the radio frequency (RF) resonator (cavity) by fabricating a complex device form. The residual resistivity ratio (RRR: 300K/10K) is used to define the purity of superconducting Nb. To date, high RRR Nb (> 250) is known to exhibit ultimate low electrical surface resistance in the RF regime, which enables obtaining a high-quality factor, defined as the stored energy in terms of power dissipation. A high RRR Nb cavity significantly expels magnetic flux with post-treatment at 900°C for 3 hours, which promises acceptable RF performance. However, the flux expulsion ratio of a low RRR Nb cavity remains unsatisfactory even with 1000°C treatment. We suppose that a lack of understanding of the engineering process for the grain growth and recovery of the strained structure likely abandons the feasibility of lower RRR Nb application. In this study, we compare recrystallization and recovery between low and high RRR Nb regarding abnormal and normal grain growth in terms of annealing temperature and time. The comparison is based on evaluating grains and sub-grains coarsening and dislocation annihilation. Dislocation propagation associated with deformation is also investigated by nano-indentation. The same fashion of annealing is applied to both low and high RRR Nb materials in a high vacuum environment to minimize foreign element effects on the pinning of the grain boundary. Based on the evaluated trend on the recovery and recrystallization of high RRR Nb, we estimate the thermal treatment threshold for low RRR Nb, in which an optimal RF performance with sufficient magnetic flux expulsion can be achieved.

Speaker: Zu Hawn Sung

47 M1Or1A-04: Development of thermal joints for conduction-cooling applications

Adequate heat transfer is essential for components and systems that operate in cryogenic environments. In conduction-cooling applications, bolted joints are commonly employed to facilitate the heat transfer between the devices and cryocoolers. The performance of these joints is dependent on a multitude of factors such as material properties, surface topography, pressure distribution, and the use of interfacial materials. In support of the development of conduction-cooled superconducting radio-frequency (SRF) niobium cavities for use in continuous-wave linear accelerators, an experimental study of thermal contact conductance was performed on bolted joints using high-purity niobium, high-purity aluminum, and OFHC copper. The study investigates the relative performance of various combinations of these materials as well as two cryogenic thermal interface materials, Apiezon N grease and indium foil, by measuring the thermal resistance across each joint interface as well as the thermal conductivity of each material in the temperature range 3 - 8 K. The geometry of the joints investigated aims at replicating the design parameters of a 915 MHz conduction-cooled SRF Nb cavity currently under development at Jefferson Lab. This consisted of a single 3-bolt joint utilizing a Nb to Al plate contact as well as two 4-bolt joints, one comprised of a Cu to Al plate contact and one Cu to Nb. Prior to cold-testing, the interfacial contact pressure of each joint was determined using Fujifilm Prescale pressure-measuring film, providing characterization of the pressure distribution within the joint. The specimens were mounted to the second stage of a Sumitomo RDE-418D4 4 K cryocooler and tested in a high-vacuum dewar using the "two-heater" method. Additionally, the thermal conductivity of Al and Nb bar samples was measured using a simple setup holding one end in contact with a liquid helium bath through a "cold-finger" and with a heater mounted at the opposite end. The thermal conductivity of the Al was also measured with a strained sample. A finite-element analysis of the experimental joint setup was carried out using ANSYS to further investigate the results.

Speaker: Jacob Lewis (Old Dominion University)

C1Or2A - Large Scale Cryogenic Systems I: Operation & Design I

48 C1Or2A-01: Maintenance of SCL3 cryogenic helium plant for Korean heavy ion accelerator after 3 years operation

The cryogenic helium plant for SCL3 section of Korean heavy ion accelerator (RAON) has been successfully operated in approximately 16,000 hours during past 3 years. Therefore, several maintenance activities are necessary to prevent any failures and keep the performance of the cryogenic helium plant. The maintenance items are divided with two parts according to its characteristics. The first part consists of the preventive items which are suggested by the manufacturer of the cryogenic helium plant. The other items are defined by us during our own operation experience to repair several failed components and improve any inconvenience on the normal operation. The maintenance items, our promotion direction of the maintenance and the maintenance result will be introduced in this paper with spent budget.

Speaker: Junghyun Yoo (Institute for Basic Science)

49 C1Or2A-02: LCLS-II Cryoplant Operational Availability: 3 Years of Operation

The LCLS-II X-ray light source, powered by a 700-meter superconducting LINAC, is supported by two 4 kW @ 2.0 K cryoplants. The first cryoplant, commissioned in 2021, successfully cooled the LINAC in March 2022. This paper provides a detailed analysis of the cryoplant's operational performance and reliability over the subsequent three years of continued operation. Key metrics, including Mean Time Between Failures (MTBF) and Mean Time to Recovery (MTTR), are evaluated. The paper also highlights operational challenges, and the strategies implemented to enhance system availability and reduce downtime. These insights aim to guide the design and operation of future large-scale cryogenic systems, with a focus on improving availability and reliability.

Speaker: Saee Vyawahare (Stanford National Accelerator Laboratory)

50 C1Or2A-03: Cold compressor performance and energy consumption improvements at Jefferson Lab’s Central Helium Liquefiers

Jefferson Lab operates two large (18 kW at 4.2 K equivalent) central helium liquefiers (CHLs) in support of its upgraded 12 GeV electron beam accelerator. Both machines utilize full cold compression from the saturation pressure at operating temperature (approximately 2.1 K) to just over atmospheric pressure. The original plant, CHL1, was recently outfitted with a replacement subatmospheric cold box (SC1R) containing state-of-the-art cold compressor technology. The 12 GeV upgrade plant, CHL2, uses older cold compressors that were originally installed to provide redundancy for CHL1. In both cases, the heat of compression is absorbed at low temperature at the expense of electrical power consumed by the warm compressors. Due to the superior efficiency and turndown capabilities of SC1R, a new operating mode has been identified for CHL1 in which the required number of operating warm compressors is reduced by one. A cost-based method for optimizing cold compressor stability and efficiency has been developed and applied to CHL2, improving its turndown and lowering the warm compressor discharge pressure. As a result of these efforts, power consumption of the combined CHLs during normal 12 GeV operations has been reduced by 10%, or a total of 690 kW. The observed performance of CHL1 with SC1R, as well as the cold compressor optimization method, leading to this improved energy consumption rate will be discussed in detail. Though many installations already utilize the more efficient modern cold compressors, the optimization could still be applied to other large-scale subatmospheric helium liquefiers to improve turndown and efficiency and ultimately reduce operating costs.

Speaker: Brian Mastracci (Thomas Jefferson National Accelerator Facility)

51 C1Or2A-04: TurboBrayton systems for low and high temperatures

In the context of the energy transition, numerous cryogenic applications - both historical and emerging - such as the long-distance transport of electricity from offshore wind generation or hydrogen mobility, require the use of compact, flexible and efficient cryogenic systems.
The TurboBrayton technologies proposed by Air Liquide advanced Technologies for more than fifteen years have met with resounding success in the field of Boil-Off Gas recondensation on board LNG carriers in particular, but also via high-temperature superconductivity applications.
This technology, widely referenced with over two hundred cryogenic systems sold, is based on the thermodynamic concept of reverse Brayton cycles, providing a low-temperature refrigeration and/or liquefaction solution with a wide and high-efficiency flexibility range.
Very low-temperature applications call for the use of light molecules in processes. Conventional compression technologies are generally based on single- or multi-stage volumetric compression, which is mostly oil lubricated and a source of operating and start-up problems. As centrifugal compression technology is mastered within Air Liquide via TurboBrayton technologies, among others, the presentation will address the prospect of integrating the major advantages of AL-aT's TurboBrayton technologies down to very low temperatures, as well as an assessment of centrifugal compression for cycles handling low molar mass fluids.

Speaker: Mr Pierre Barjhoux (Air Liquide)

C1Or2B - Non-Aerospace Cryocoolers II

52 C1Or2B-01: A dynamic simulation model for gas guided pistons in Stirling machines

Superconducting motors offer high power-to-weight or -to-volume ratios and are the natural choice for applications such as the electrification of heavy transport. A particular challenge is the cooling of the superconducting rotor coils. While one option is to use a stationary cryocooler and to provide the cooling via a gas circuit on the rotating side – which introduces other technical challenges such as the sealing of the coolant on the rotating side – an alternative is to install the cryocooler on the rotor. In order to make this approach feasible and to eliminate problems that arise from rubbing seals, gas-guided pistons are proposed as are commonly used in free-piston Stirling machines. In combination with the reduction of side loads, the reliability of free-piston Stirling machines can be significantly improved. In contrast to conventional static gas bearings, no external pressure supply is required. This is made possible by using check valves for buffering parts of the compression pressure in a piston cavity and release it via tiny throttles into the gap between piston and cylinder. Due to the resulting fluctuations in the supply pressure, the properties of the gas-lubricated guide are highly dynamic and also affect the Stirling process. Therefore, calculating the load capacity required a new approach for which the dynamic modelling software Simulink was chosen. This paper presents the resulting model in the form of a fluidic network in which clearance gaps and throttles between volumes are considered as resistances. The model outputs enable the determination of the load capacity and static stiffness of the gas-lubricated guide as a function of the piston eccentricity and the phase angle of the piston movement.

Speaker: Bruce Fischer (Auckland University of Technology)

53 C1Or2B-02: Improving energy efficiency and cryocooling performance through independent speed control of cryocoolers and compressors

Energy efficiency and reduced power consumption are critical for modern cryogenic systems. Gifford-McMahon (GM) cryocoolers provide an economical, cryogen-free solution across a broad range of temperatures, offering high energy efficiency, reliable long-term performance, and easy maintenance thanks to their simple mechanical design. Compact size and low vibration levels make them especially suitable for precision applications, ranging from analytical instrumentation to large-scale astronomy arrays.

This work showcases optimization of GM cryocooler operation by dynamically adjusting performance of the coldheads’ and compressors. Precise cryogenic cooling is achieved, ensuring temperature stability over extended operation periods. Unlike traditional methods that rely on heating adjustments and often compromise efficiency, our approach matches heat lift to application demands while minimizing energy losses. Additionally, variable-speed control of the helium compressor further enhances energy efficiency by synchronizing its operation with the GM cryocooler, reducing excess cooling and the need for controlled heat dissipation.

We present a proof-of-concept performance analysis of an adjustable GM cryocooler system, demonstrating how tailored speed modulation enables optimized performance, reduces energy consumption, and lowers the operational costs of cryogenic systems. This strategy is particularly advantageous for long-term applications, offering a sustainable solution with reduced environmental impact.

High-speed coldhead operation is essential for handling high thermal loads or achieving rapid cooldowns. In this case study, Oxford Cryosystems Ltd (OCS) Coolstar 6/30 coldhead is operated at variable speeds. Increasing operational speed from 60 rpm to 90 rpm reduces the cooldown time by 34 % and provides cooldown rates up to 12.85 K/min. The OCS GMi controller dynamically optimizes coldhead speed to match system load, ensuring efficient performance. In addition, the OCS helium compressor maintains a constant differential pressure regardless of the gas demand from attached coldheads. When cooling demand is low, it results in substantial power savings. Conversely, during high cooling demand, such as when multiple coldheads are attached or the lowest temperatures are required, the compressor adjusts its speed to maintain system performance. The GMi controller fine-tunes the differential pressure to match system requirements, enabling significant energy optimization.

Performance data show operational potential of the coldhead across speeds ranging from 40 rpm to 90 rpm, as well as the dependency on differential pressure. By optimizing the differential pressure, compressor power consumption can be significantly reduced, which is especially critical for long-term operations. When operating al low cooling demand, it is possible to save up to 46 % of energy when compared to a standard fixed speed system, increase the coldhead lifetime by up to 50 %. Furthermore, at high cooling demand, it is possible to significantly reduce the cooldown times and still save up to 20 % of energy.
Moreover, we demonstrate benefits of running two different cold heads using one compressor, which allows for greater energy savings and offers operational flexibility.

This solution ensures cryogenic operations can be adjusted matching the cooling requirements, which is especially useful when heat load changed during the operation.

Keywords: Cryocoolers, Coldheads, Gifford-McMahon Cycle, Adjustable Speed Compressors, Energy Efficiency, Cryogenic Systems, Precision Applications

Speaker: Dr Amy Kennedy (Oxford Cryosystems Ltd)

54 C1Or2B-03: Exergy measurements between a 4 K pulse tube refrigerator and its compressor

At only about 1% of Carnot, the overall efficiency of 4 K, Gifford-McMahon cryocoolers and Gifford-McMahon type pulse tube refrigerators is not impressive. These refrigerators are most often studied from the perspective of minimizing losses in their regenerators and/or thermal buffer tubes, which are important topics, especially in the real-fluid regime where regenerator losses are very large. However, there are also significant inefficiencies that occur between the compressor and the refrigerator during the generation and delivery of acoustic power. These losses have rarely been considered in detail. In this study, we highly instrumented the flow paths between a commercial 4 K, two-stage pulse tube refrigerator and its compressor with high-speed mass flow meters, pressure transducers, and thermometers. With these measurements, we calculate and track the evolution of exergy between the outlet of the compressor and the inlet to the refrigerator, so that the efficiency of each process can be determined. Measurements show that a large amount of exergy is destroyed at the rotary valve, as the work of compression is not recovered in these systems. We also measure the efficiency of the commercial scroll compressor, and the exergy destroyed in the helium hoses between compressor and refrigerator. Measurements are presented for a variety of operating frequencies and cold-end temperatures. These results demonstrate that state-of-the-art pulse tube refrigerators generate acoustic power with low efficiency.

Speaker: Dr Ryan Snodgrass (National Institute of Standards and Technology)

55 C1Or2B-04: Parasitic Heat Load Reduction of Cryocoolers

With the further advance of cryogenic technology and high helium cost, more cryogenic environments are designed to be hermetically “sealed”, requiring a detailed understanding and analysis of parasitic heat fluxes crossing into a cryogenic environment. A thermal balance sheet therefore includes operational states but also needs to cover outages.
One of the frequently underestimated heat sources crossing the cryogenic boundary is a non-operating cryocooler attached to a cold mass. Once a cryocooler turns into a non-operating state, the cryocooler housing consisting of several stainless-steel tubes with internally stacked regenerator material creates a small, but steady parasitic heat conduction path to the cold mass.
Inclined, non-operating cryocoolers, however, follow the theory of inclined cryogenic tubes and operating inclined pulse tube coolers, delivering an excess heat flux to the cold mass that by a far exceeds any conductive thermal loads.
In this research paper we exemplary determine the dominating parasitic convective heat flux created by non-operating GM-type cryocoolers. Moreover, we propose a simple process for shutting down this convective flow that is applicable for all types of non-operating cryocoolers, based on experimental results.

Speaker: Mr Wolfgang Stautner (GE HealthCare – Technology & Innovation Center (HTIC))

C1Or2C - Cryogenics for Quantum Applications

56 C1Or2C-01: Development of cryogenic infrastructures for quantum computing

Quantum computing has recently gained interest from industry, opening new fields of applications. Air Liquide Advanced Technologies, thanks to its experiences on ultra-low temperature systems (CryoConcept, subsidiary has been commercializing Dilution Fridges for 20 years for scientific labs) and on Helium Refrigeration and Liquefaction systems for Physics and Industry, is actively developing solutions to address the many emerging challenges associated with Quantum Data Centers.
Recently, the challenges of scaling up various quantum computing technologies have been highlighted through the roadmaps of several major players. One key area of development is the need for increased cryogenic cooling power, which could be provided by helium refrigerators similar to those used to cool particle accelerator equipment or fusion reactors.
This presentation will address the adaptation of solutions developed by Air Liquide Advanced Technologies over several years for industrial and scientific helium cryogenics applications. It will focus on the upcoming needs of quantum computing, particularly in terms of energy efficiency, distribution, reliability, and operability leading to proposals of new cryogenic architectures.
By exploring these aspects, the presentation aims to contribute to the ongoing discourse surrounding the future of quantum computing and its integration into large-scale data centers, offering insights into the intricate challenges and innovative solutions within this burgeoning field.

Speaker: Jean-Marc Bernhardt (Air Liquide Advanced Technologies)

57 C1Or2C-02: Quantum Computer Test Facility at SLAC using existing Cryogenic Infrastructure

SLAC National Accelerator Laboratory hosts the LCLS-II, a 700-meter LINAC supported by two large 4 kW @ 2.0 K cryoplants. Located in Menlo Park, on the Stanford University campus in the heart of Silicon Valley, a hub for groundbreaking advancements in quantum technologies, which often rely on cryogenic temperatures. PsiQuantum, headquartered in Palo Alto just a few miles from SLAC, employs a unique photonics-based quantum computing technology that operates at cryogenic temperatures. Through a Cooperative Research and Development Agreement (CRADA), SLAC and PsiQuantum have partnered to integrate PsiQuantum’s test facility with SLAC’s advanced cryogenic infrastructure. The CRADA includes providing cryogenic capabilities ranging from 100 W to 300 W at 2.4 K. This collaboration enabled PsiQuantum to establish a fully operational cryogenic facility in just one year — a timeline that would have otherwise exceeded two years. This paper provides an overview of the partnership, focusing on the integration process, commissioning efforts, and challenges encountered.

Speaker: Swapnil Shrishrimal (SLAC National Accelerator Laboratory)

58 C1Or2C-03: Ultra Compact Rack Cryostat System for Quantum applications

In this talk, we present the development and implementation of the world's smallest fully automated cryostat system designed to operate below 3K, achieving a base temperature of 2.3K. This ultra-compact system is specifically engineered for seamless integration with Superconducting Nanowire Single-Photon Detectors (SNSPDs) and deterministic single-photon sources (SPS), making it an ideal solution for quantum computing and quantum communication applications in data centers.

The cryostat system is using a bellows driven Helium compressor combined with a commercial GM coldhead. An integrated control and pumping system is ensuring ease of use and reliability. It is designed with a strong focus on high efficiency in both energy consumption and space utilization, making it a highly practical solution for modern applications with a space requirement of only 10U in a server rack. Additionally, the system is mobile and prepared for deployment in research facilities, offering flexibility for various applications. We will discuss the technical challenges overcome in the design and the innovative solutions implemented to achieve such low temperatures in a compact form factor. Furthermore, we will provide examples of practical applications and recent deployments of this system in data centers, highlighting its impact on enhancing quantum computing and communication capabilities.

Speaker: Dr Sebastian Schaile (attocube systems AG)

59 C1Or2C-04: Conceptual Design and Initial Operation of a Single-Shot Dilution Refrigerator with a Small Helium-3 Inventory

A single-shot dilution refrigerator (SDR) features a compact and lightweight design without the need for heat exchangers, allowing it to achieve approximately 0.1 K with a small amount of Helium-3. This study conducts a conceptual design of the key components of the SDR, including mixing chamber, still, and thermal shield, to achieve the target temperature. To utilize the auxiliary cooling from an ADR capable of providing 1 J of cooling at 0.8 K, a unidirectional heat transfer structure is applied to the mixing chamber and still. To reduce the weight and minimize the heat capacity, the shield is constructed with thin sheets of copper, while 1 mm thick copper plates are added only to the thermal transfer pathways to account for initial cooling of the mixing chamber by the ADR. To overcome Kapitza resistance at cryogenic temperatures, the mixing chamber is sintered with silver powder to increase the effective collision surface area. Additionally, to minimize the cooling loss from the mixing chamber to the still, the stainless-steel capillary tube having diameter of 0.7 mm is coiled to extend its length to 50 cm, ensuring that the cooling loss remains below 1% under the steady-state conditions at 0.1 K. During the initial operation test, it is verified whether each component operates properly according to the intended physical design. This paper validates the conceptual design of the SDR’s key components and provides foundational data for equipment development and future SDR experiments.

Speaker: Byeungcheol An (Korea Advanced Institute of Science and Technolog)

C1Po3A - Cryogenic Components I

60 C1Po3A-01: Optimization design of the brake impeller for cryogenic hydrogen turbine expanders

In recent years, with the widespread adoption of hydrogen as a clean energy source, low-temperature hydrogen turbine expanders have played a crucial role in the production of liquid hydrogen. Currently, there is limited focus on the brake side, despite the interdependence and mutual influence between the brake impeller and the turbine impeller. To improve the efficiency and reliability of turbine systems, this paper proposes an optimization design method for brake impellers in hydrogen low-temperature turbine expanders based on artificial neural networks (ANN). The optimization process is divided into four steps: parameterizing the impeller model, building an automated CFD computation platform, generating a sample library, and model parameterization. During the optimization process, the meridional plane and blade shape are optimized sequentially. Comparative analysis of the optimization results shows that the efficiency of the optimized impeller increased by 10.61%, while leakage loss, recirculation loss, and wake mixing were significantly reduced. This method provides an efficient and reliable optimization tool for the design of hydrogen low-temperature turbine systems, with broad engineering application prospects.

Keywords: hydrogen turbine expanders; brake impeller; artificial neural networks; optimization design

Speaker: Mr Changlei Ke (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China,)

61 C1Po3A-02: Experiment research of intermittent flow cold storage surface heat exchanger

Pulse tube (or piston) expansion cryogenic refrigerators are a type of refrigeration equipment capable of highly reliable operation in low-temperature environments and are particularly suitable for medium-sized cooling requirements. In this type of refrigerator, intermittent flow cold storage surface heat exchanger is required to improve the refrigeration efficiency. In this research, we designed and constructed a test platform for the heat transfer performance of intermittent flow cold storage surface heat exchanger and revealed that, when the heat exchanger structure is fixed, the commutation frequency and the inlet mass flow rate are two important factors affecting the heat transfer efficiency of intermittent flow cold storage surface heat exchanger, as well as the qualitative relationship between them. It provides an important reference for further research, design, and operation of intermittent flow cold storage surface heat exchanger.

Speaker: Wenhui Cui (Technical Institute of Physics and Chemistry,CAS)

62 C1Po3A-03: Numerical simulation of active refrigeration for liquid helium storage

The storage and transportation of liquid helium inevitably lead to overpressure and leakage due to its extremely low boiling point and high evaporation rate, resulting in helium loss. By introducing cooling through a cryocooler, the thermal losses can be effectively reduced, potentially achieving ZBO(zero-boil-off). However, research on liquid helium lossless technology is still limited. This paper presents a numerical simulation study on the pressure evolution process during the active cooling of a liquid helium dewar. The study focuses on the 500L liquid helium storage platform at the Institute of Physics, under the condition of a 7.5W heat leakage. The numerical simulation of the self-pressurization process of the liquid helium dewar indicates that the pressure evolution follows a generally linear growth trend. Under overpressure conditions, the introduction of cooling results in a decrease in pressure, exhibiting a three-stage depressurization process. After a certain period, the pressure stabilizes. The results demonstrate that active cooling can effectively suppress the overpressure phenomenon during the storage and transportation of liquid helium, reducing helium loss, which holds significant importance for the storage and transportation of liquid helium.

Speaker: Xiujuan Xie (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

63 C1Po3A-04: Investigations on anti-surge control of cold compressors using bypass valve in superfluid helium refrigeration system

Throughout the progression of particle accelerator technology, there has been a significant upsurge in the demand for cooling capabilities within the superfluid helium temperature range. The integration of cold compressors not only minimizes the size of heat exchangers but also optimizes the utilization of cold exergy. In the context of multi-stage serial centrifugal cold compressors, the operation in pumping down, along with dynamic load conditions, is prone to surge phenomena due to the substantial fluctuation in flow rates. To reduce the expenses of manual control, this paper presents the dynamic model for the superfluid helium system and associated components, validations are also carried out by comparison of the model’s calculated results with the test results through a cold compressor experimental platform. Further to this work, the study delves into the control mechanisms governing the rotational velocities of the cold compressor series and the bypass valve. It also introduces the MPC controller for anti-surge control, aiming to enhance the operational efficiency and stability of the superfluid helium refrigeration systems.

Speakers: Baohua Chao (Technical Institute of Physics and Chemistry;University of Chinese Academy of Sciences), Huaiyu Chen (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences), Jihao Wu, Jin Shang, Dr Jin Zhen Wang (Technical Institute of Physics and Chemistry, CAS), Mr Lei Yi (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

64 C1Po3A-05: Experimental study of two thermally-connected hydraulically- independent 20-tube neon pulsating heat pipes working in parallel

In view of cryocooler-dependent dry cooling of superconducting magnets and systems, efficient heat transfer devices that can function independent of the gravity effect are in high demand. One of the recent candidates gaining popularity are cryogenic pulsating heat pipes (PHP), synonymously called as oscillating heat pipes. These wickless heat pipes, made by simply meandering capillary tubes, have illustrated the potential to function in different orientations not only in space but in earth-bound applications as well.
Cryogenic PHPs are still devoid of their first practical application. PHPs are largely dependent on multiple geometric and operational parameters. The precise impact of each of these parameters on the PHP thermal performance is not entirely understood owing to the complexities in experimental measurement at low temperatures and absence of fully-developed numerical prediction tools. So as to favour implementation of cryogenic PHPs is a real application, our laboratory has been involved in creating large experimental data set while investigating different study aspects.
One such study presented here is the thermal performance of two neon PHPs having the same cold source. Same cold source implies that the two PHP condensers are thermally connected to a single cryocooler. The two PHPs are geometrically identical having an inner tube diameter of 1.0 mm and 20 number of parallel tubes with a projected length of 0.4 m. The PHP tubes are made of stainless steel and the evaporator and condenser part are made of copper. Heat load on each of the PHP evaporator can be separately controlled. Moreover, the gas supply system for both PHPs is also separate thereby making the two PHPs hydraulically independent. Temperature and pressure time evolution plots for two neon PHPs working in parallel has been presented for a filling ratio of 40% in each of the PHPs. Thermal performance comparison with that of a single neon PHP under same working conditions is also reported in terms of thermal resistance.

Speaker: Tisha Dixit (CEA Paris-Saclay)

65 C1Po3A-06: Design and optimization of return gaseous helium heater for 2 K cryogenic test bench

Superconducting radio frequency (SRF) cavity technology is typically operated at 2 K temperature to minimize the RF surface loss by reducing the BCS resistance, thereby achieving a high-quality factor (Q0). To maintain a 2 K environment, LHe(liquid helium) is normally converted to saturated HeII by using a sub-atmospheric vacuum pumping system to pump down the pressure of the helium chamber to 31 mbar. To ensure the safe and high efficiency operation of the pump system, the inlet temperature of the vacuum pump and the pressure drop from the helium chamber to the inlet of the pump system are strictly controlled. For this purpose, a return gaseous helium heater using electrical heater rods and aluminum alloy fins has been designed to raise the temperature of the helium gas from 3 K to 300 K. The fin structure is dedicated designed and optimized to balance the total size, heating efficiency, and pressure drop budget. A 3D model has been simulated using CFD methods, demonstrating that the pressure drop remains within 100 Pa for a helium flow rate of 15g/s. Based on the design and CFD results, the 2 K heater has been manufactured and subsequently installed on-site. This paper gives an overview on the wide range of design considerations, CFD optimization, manufactory process, and commissioning result of the installed 2 K heater.

Speakers: Huikun Su (Institute of Advanced Science Facilities ,Shenzhen), Mr Haining Li (Institute of Advanced Science Facilities(IASF))

66 C1Po3A-07: Lumped Modeling of Cooling and Electric Devices in Aircraft

In this work, we focused on a lumped parameter model to compare a liquid ammonia-based as well as a liquid hydrogen-based cooling system for power electronics in aircraft motors using Open Modelica. The liquid ammonia in the cooling system has a relatively high volumetric energy density and is low zero carbon. Liquid hydrogen is also of interest. It is essential for power electronics to have high-performance cooling in electric aircraft. The lumped model was designed to simulate the thermal behavior of the power electronics with respect to the cooling system under different scenarios. This model, including thermal components, describes the heat transfer between power electronics and cooling system to determine how much heat can be removed. The heat is removed using liquid ammonia, eventually dissipating in ambient air, or liquid hydrogen, eventually rejected to the bath. In our model, an individual power electronic module generates 2 kW. There are 18 power modules needed to operate one electric motor with an accumulated total of 36 kW. Then, we considered the effect of adding transmission lines and a motor in this thermal balance model.

Speaker: Xianhao Zhang

67 C1Po3A-08: Dynamic Analysis and Optimization of Aerostatic Bearing-Rotor Systems in Cryogenic Turbo Expanders

High speed turbo expanders for hydrogen and helium serve as critical components in large-scale cryogenic systems. Their efficient and stable operation directly determines overall system performance. Due to the low density and high enthalpy drop of hydrogen and helium, turbo expanders must operate at extremely high rotational speeds, to achieve high thermodynamic efficiency. Aerostatic bearings are commonly employed to support the rotor; however, the inherent properties of gases make the system prone to vibration and instability, limiting further performance improvements. This study employs an improved polynomial transfer matrix method to develop a discrete mass model for the bearing-rotor system. By incorporating the damping characteristics of bearings, the method enables rapid and accurate calculation of the natural frequencies, critical speeds, and mode shapes. Comparisons with results from commercial software show acceptable deviations, validating the proposed approach. Furthermore, the effects of various parameters—including length, diameter, thrust disk position, and bearing stiffness and damping—on the dynamic characteristics of the system are investigated. These insights contribute to enhancing critical speeds and mitigating vibrations, providing valuable guidance for the optimization of high-speed cryogenic turbo expanders.

Speaker: Shun Qiu (Technical institute of physics and Chemistry,CAS)

C1Po3B - LH2 and LNG I: Safety

68 C1Po3B-01: A comparison of the toxicity and asphyxiation risk during bunkering of LH2, LNG and NH3 by means of a quantitative risk assessment

To achieve the GHG reduction goals, hydrogen, Natural Gas and ammonia are considered as marine fuel in their liquefied form. Hydrogen and Natural Gas need to be liquified at cryogenic temperatures, whereas ammonia can be liquefied through the application of moderate pressure, approximately 10 bar, or through the reduction of temperature to approximately -33 °C. LNG is already employed in maritime transportation in accordance with established safety protocols. In contrast, the utilization of liquid hydrogen (LH2) and ammonia is currently limited to pilot projects. Both liquid hydrogen and ammonia have the potential to be climate-neutral fuels, depending on the respective production pathway. However, concerns regarding their safety have been raised. Thus, the overarching aim of this investigation is it to addresses these concerns by conducting a comparative analysis of the safety of bunkering these fuels, with a particular focus on toxicity and asphyxiation hazards.
Risk is defined as the “combination of the probability of occurrence of harm and the severity of that harm”. A quantitative risk assessment is thus conducted in two steps: first, to identify the probability through a frequency analysis and second, to identify the severity through a consequence analysis. For this study, an event tree is introduced to combine reliability data for the occurrence of a leak with a model for the ignition probability. The second step of a quantitative risk assessment is the consequence analysis, which quantifies the severity of the harms identified through the event tree. This study will use the necessary safety distance as the threshold for the severity.
The approach outlined above for such a quantitative risk assessment is conducted to compare the toxicity risk of bunkering ammonia and the asphyxiation risk of bunkering liquid hydrogen and liquified natural gas. In the initial phase, a frequency analysis is undertaken. The results are employed to identify the events with the highest frequency of occurrence. In the second step, the events not resulting in an ignition are further investigated. The hazard arising from these events is usually the toxicity of ammonia or the asphyxiation, due to the displacement of oxygen by hydrogen or natural gas (i.e., both substances are not toxic). A Gaussian dispersion model is employed to calculate the safety distance necessary for the different fuels. Subsequently, both the necessary safety distance and the frequency of harmful events of all three fuels are then compared.
Result of the study will be the comparison of the safety distances and the frequencies. A fuel that requires smaller safety distances and the harmful event occurs less frequent can be considered safer.

Speaker: Jorgen Depken (Institute for Maritime Energy Systems, German Aerospace Center (DLR), Dünebergerstraße 108, Geesthacht, 21502, Schleswig-Holstein, Germany)

69 C1Po3B-02: Impacts of temperature on nitrogen adsorption of common cryogenic purification materials

As hydrogen continues to gain adoption as a global energy carrier, a renewed focus on hydrogen liquefaction technologies has emerged. The hydrogen liquefaction process requires extremely pure hydrogen feed gas to prevent the freeze out of impurities which can damage equipment. This study investigates the impact of temperature on the nitrogen adsorption performance of three widely used materials: Silica Gel, activated carbon, and 5A zeolite. The aim is to examine the thermal dependence of nitrogen uptake in these materials, providing insights into their efficiency and suitability for cryogenic purification of hydrogen. Comparative results for equilibrium capacity at temperatures between 80K and 110K are presented.

Speaker: Dr Ian Richardson (Plug Power)

70 C1Po3B-03: Numerical Simulation of the Protective Effectiveness of Bund Walls and the Impact of Key Parameters in Accidental Liquid Hydrogen Releases

Hydrogen is widely regarded as an ideal clean and renewable energy source. Liquid hydrogen (LH2) is often used for storage due to its high energy density and suitability for various applications. However, in the event of an accidental LH2 release, the liquid rapidly and extensively evaporates into gaseous hydrogen, posing significant safety risks. To address these concerns, a study utilizing open-source computational fluid dynamics code, OpenFOAM, was undertaken. The objective was to analyze the behavior of LH2 during accidental releases and to propose strategies for mitigating associated hazards. The validity of the numerical model employed has been demonstrated in previous publications.
Bund walls are a commonly implemented safety measure around LH2 storage facilities to limit the spread of released hydrogen. This study systematically evaluates the protective performance of bund walls, using a prototype LH2 storage facility as the reference scenario. The analysis focuses on the influence of bund wall dimensions, including height and radius, as well as the impact of varying wind speeds on their effectiveness.
The results indicate that at low wind speeds, bund walls significantly reduce the horizontal dispersion of gaseous hydrogen, mitigating potential risks. Increasing the height and radius of the bund wall further enhances safety; however, the improvements are relatively marginal. In contrast, wind speed exerts a dominant influence on the outcomes. When wind speeds exceed 7 m/s, the effectiveness of bund walls diminishes substantially. Additionally, after the cessation of LH2 release, larger bund walls impede the dilution of hydrogen, prolonging the presence of flammable concentrations.
These findings highlight the complex interplay between bund wall geometry and environmental factors, emphasizing the importance of considering site-specific conditions in designing safety measures for LH2 storage facilities.

Speaker: Mr Yanwei Liang (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

71 C1Po3B-04: Development of the Cool Fuel School: a comprehensive hands-on cryogenic hydrogen design and safety program

Investments in the hydrogen economy, including the 7-billion USD Hydrogen Hub initiative, are poised to greatly expand employment in the hydrogen sector. Training and education at all levels will be essential for ensuring hydrogen fuel maintains an excellent safety record amid expanding use. However, few cryogenic hydrogen safety programs are available and little to no data on program effectiveness are available in the open literature. To address this need, the HYPER Center aggregated existing hands-on trainings into a week-long program called the “Cool Fuel School.” Participants in the week-long program experience workshops on 1: Introductory cryogenic and hydrogen safety, 2: Elements of design and safety plans, 3: Fluid control, including manual valving and automatic pressure relief, 4: Cryogenic-compatible instrumentation, 5: Cryogenic fittings and sealing surfaces, 6: Thermal contraction and material selection, 7: Insulation and vacuum, 8: Leak checking and purging, 9: Procedural and operational safety analysis, and 10: Liquid hydrogen operation and safe system shutdown. Participants in the first session of this course held in May of 2025 completed pre- and post-activity knowledge assessments and surveyed on general improvements to the course. Recommendations for future versions of the course are made, and the implementation of these recommendations is discussed.

Speaker: Zachary Beadle (Washington State University)

72 C1Po3B-05: Simulation experiment of vacuum insulation deterioration in liquid hydrogen tank due to minute air leaks

Liquid hydrogen tanks and transfer tubes have vacuum layer for thermal insulation which is usually enclosed by a sealing-off valve with rubber O-ring. The rubber O-ring must degrade with age and then air leak from the outside should be considered for long term operation over several years. However, most of the air content could be condensed by cryo-pumping effect and vacuum pressure may be maintained due to low temperature on the outside of liquid hydrogen vessel. Thus, the scenario can be predicted that vacuum loss suddenly could occur when cryo-pumping speed decline because of rather large leak or thick ice layer composition, and the condensed ice evaporate in a chain reaction. This study aimed to reveal the process of vacuum insulation degradation in liquid hydrogen tanks.
This kind of problem may be predicted by past experimental studies for the development of cryo-pump or the sudden vacuum loss of super conducting cavities. However, the condensation speed on minute air leak to vacuum layer due to aging degradation of rubber must be small so that the pressure growth may be slow since the cryo-surface is stainless steel. Thus, a compact experimental setup has been developed to perform accelerating tests. The time constant should be proportional to the ratio between vacuum volume and cryo-surface area. In this experiment, the vacuum vessel of 38 mm in diameter equipped with temperature-controlled tube of 6 mm inside 20 layers MLI to leak air was immersed in liquid hydrogen. The vacuum vessel is made of stainless steel. The buffer tank of air about 100 torr and two tiny valves in series have been used to realize minutes leak rate on the order of 10-4 m3Pa/s. The condensation speeds were much lower than that of knowledge of cryopumps. It is indicated that degradation process of vacuum insulation strongly was related to heat transfer through the rarefied gas in the region between free molecular flow and continuous flow.
Since the number of experiments using liquid hydrogen was limited, the present experimental results have been compared with the results using liquid nitrogen and carbon dioxide in our previous experimental study. Liquid hydrogen test had been carried out at Noshiro Rocket Testing Center in JAXA where provides support for safe experiments related to hydrogen. Understanding physics of condensation and predicting results with wide parameters were examined.

Speaker: Suguru Takada

73 C1Po3B-06: CFD simulation of cryogenic LH2 external releases: a multicomponent-multiphase approach

The present work presents the computational fluid dynamics (CFD) modeling of the complex phenomena occurring during a cryogenic liquid hydrogen release into quiescent air at standard ambient conditions. The RANS simulated case is a 2D axisymmetric domain presenting the pressurised LH2 reservoir and a large ambient domain. The thermodynamic properties are calculated using the NIST database for the required range of temperatures, pressures and compositions found during this release scenario. Air is modelled as a three-component mixture of nitrogen, oxygen, and argon at their standard compositions. Therefore, it allows the capture of their individual condensation as a result of their mixing with the cold hydrogen jet. Then, these are tabulated and implemented through user-defined functions within the ANSYS Fluent software. As the thermodynamic properties of both hydrogen, air, and their mixtures are pre-calculated, they are thus accessed in real-time, accurately predicting the phase changes associated to this scenario. As well, the NIST database modelling allows for the accurate prediction of all components at LH2 cryogenic temperatures, as low as 20K, for which traditionally used equations of state are known to be insufficient. To the best of the authors' knowledge, this work is the first implementation of such a multicomponent-multiphase approach for cryogenic hydrogen releases. This methodology can then allow an improved foundation of safety analysis for both abnormal or nominal venting scenarios in hydrogen infrastructure applications.

Speaker: Alvaro Vidal

C1Po3C - Liquid Air, CO2, Ar Liquefaction and Storage

74 C1Po3C-01: A study of the whole life cycle carbon emission of liquid air energy storage system

Liquid air energy storage (LAES) is a cryogenic energy storage technology that stores electricity in the form of liquid air, with operating temperatures as low as 80 K. Currently, LAES is still in the stage of critical technological development and exploratory demonstration applications. Its quantified environmental impacts remain unclear, and research on the carbon accounting of LAES throughout its life cycle is significantly lacking, requiring further investigation. This study focuses on a 60 MW LAES system, developing a carbon emission accounting model that covers its entire life cycle, including production, construction, operation, maintenance, and decommissioning. A comparative analysis of system carbon emissions was conducted for the core cryogenic storage unit, considering both liquid-phase and solid-phase cold energy storage methods. Additionally, the research was conducted on the impact of key parameters such as the lifespan of the LAES system and the expander efficiency of the power generation unit on the carbon emissions of the system. Based on the carbon emission distribution of each unit in the system, the carbon reduction potential of each stage in the LAES system can be identified, which is essential for promoting the iterative optimization of the LAES system.

Speaker: Dr Zhaozhao Gao (Technical Institute of Physics and Chemistry)

75 C1Po3C-02: Ensuring High-Purity Liquid Argon for the LBNF FDC: Collaborative Cryogenics Research Between UNICAMP and Fermilab

The Long-Baseline Neutrino Facility (LBNF) located at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, hosts the Deep Underground Neutrino Experiment (DUNE). This experiment employs cryostats containing nearly 70,000 metric tons of high-purity liquid argon (LAr). Ensuring LAr purity is critical for achieving the required electron lifetime, which directly impacts the experiment’s signal-to-noise ratio. The Horizontal Drift (HD) detector demands an electron lifetime exceeding 3 ms within its 3.5 m drift, equivalent to less than 100 parts-per-trillion (ppt) Oxygen contamination, while the Vertical Drift (VD) detector requires over 6 ms electron lifetime within its 6.0 m drift, corresponding to less than 50 ppt Oxygen contamination. To mitigate Nitrogen (N2) quenching of scintillation light, N2 contamination must remain below 1 ppm, as higher levels can result in up to a 20 % loss of light.
The Brazil State University of Campinas (UNICAMP) significantly contributes to LBNF FDC through the development of argon purification and regeneration systems for HD and VD cryostats.
UNICAMP designed and constructed the Purification Liquid Argon Cryostat (PuLArC), a small-scale test facility holding approximately 90 liters of LAr. Tests using PuLArC demonstrated that 1 kg of Li-FAU zeolite could reduce N₂ contamination from 20-50 ppm to 0.1-1.0 ppm within 1-2 hours. Tests at Fermilab’s Iceberg cryostat (2,625 liters) confirmed scalability, with 3 kg of Li-FAU reducing N₂ contamination from ~5 ppm to <1 ppm over 96 hours without active circulation.
This presentation will detail the research methods, test setups, and results, showcasing the potential of Li-FAU as an alternative to Molecular Sieve 4A for large-scale LAr systems. This advancement enhances DUNE's precision and demonstrates the impact of international collaboration on cryogenic research.

Speaker: Roza Doubnik (Fermilab)

76 C1Po3C-03: Detector prototyping experience and design updates for the LBNF Near Site Liquid Argon proximity cryogenics

The Deep Underground Neutrino Experiment (DUNE) near site located at Fermilab will host the neutrino beam complex. It includes a high voltage liquid argon time projection chamber located 60-meter underground used as beamline instrumentation. The cryogenic system provided by the Long-Baseline Neutrino Facility (LBNF) will regulate the thermohydraulic conditions of the ND LAr detector composed of 35 detector modules, each measuring 1 meter wide, 1 meter long and 3 meter tall. The 35 modules will be arranged in a 7x5 horizontal grid sitting inside a membrane cryostat filled with 310 Ton purified liquid argon. The detector collaboration has cryogenically tested detector a full-scale prototype and a 4-cell scaled version. Experimental results, requirement changes and design updates originated in this test campaign are reported in this paper.

Speaker: Joaquim Creus Prats

77 C1Po3C-04: Development of a 10 ton/day air liquefaction system for liquid air energy storage

To achieve carbon neutrality, the contribution of renewable energy to electricity generation is steadily increasing. However, renewable energy sources often experience significant output fluctuations due to varying weather conditions. Consequently, the demand for high-capacity energy storage systems is gradually rising to ensure grid stability. The Liquid Air Energy Storage (LAES) system liquefies air using surplus electricity for energy storage. When electricity is needed, the system pressurizes and vaporizes the liquid air to generate power through turbines. The energy storage using liquid air at ambient pressure is safe and eco-friendly. It also allows for the storage of large amounts of energy. In this study, a 10 ton/day air liquefaction system was developed as a pilot plant for liquid air energy storage. The system consists of two compressors in series, an air pre-treatment system, an air cooler, a liquefaction cold box, and a liquid air storage tank. The air is pressurized and pre-treated by removing water and CO2, then liquefied in the cold box through a modified Kapitza cycle. To enhance the process, a cold nitrogen stream is introduced into the cold box to simulate the recycling of cold thermal energy recovered during the power generation process. The cold stream is divided into two branches to improve cycle efficiency. Experiments were performed under various conditions, including different mass flow rates, split flow ratios to cryogenic expanders, and flow rates to the cold stream branches. The experimental results are presented and discussed in detail in this study.

Speaker: Dr Sehwan In (Korea Institute of Machinery and Materials)

78 C1Po3C-05: Investigation of cold energy transfer characteristics in the liquefaction unit of the liquid air energy storage system

In the global pursuit of energy transition, energy storage technologies play a pivotal role in integrating renewable energy into the grid, maintaining grid stability, and ensuring energy security. Liquid air energy storage (LAES) technology offers a scalable, cost-effective, and geographically unconstrained solution for large-scale, long-duration energy storage, making it a promising solution for the future energy storage market. The liquefaction unit serves as the core part of the LAES system, which includes components such as the large-scale cold energy storage equipment and heat exchanges, responsible for recovering, storing, and utilizing the cold energy of liquid air. However, existing research on the LAES system predominantly focuses on system-level analysis, with limited attention given to the mechanisms of cold energy transfer within the liquefaction unit. To address this, the study investigates the cold energy transfer characteristics within the liquefaction unit of the LAES system, with a specific emphasis on the exergy destruction during the cold energy transfer process. The thermodynamic model and heat exchanger model for the liquefaction unit are established and validated. Subsequently, the cold energy transfer characteristics are analyzed, and sensitivity analyses are conducted on the key design parameter.The results reveal the asymmetric characteristics of the cold energy transfer process and identify the primary components contributing to cold exergy destruction, providing a unique perspective on the design of the liquefaction unit. The research provides a fundamental understanding of cold energy transfer in the LAES system, paving the way for the further optimization and broader application of the LAES technology.

Speaker: Xiaoyu Fan (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

79 C1Po3C-06: Experimental investigation of CO2 desublimation characteristics in flue gas on horizontal copper plate influenced by surface temperature and CO2 concentration

Cryogenic desublimation carbon capture (CDCC) has attracted widespread attention due to its high capture efficiency, environmental compatibility, and the production of high-purity CO2. However, limitations in cryogenic visualization technology have hindered a comprehensive understanding of CO2 desublimation characteristics in mixed gases, confining the application of CDCC to small-scale experimental stages. To reveal the detailed frosting mechanism, a cryogenic visualization experimental system was developed, integrating a GM cryocooler and heaters for precise temperature control. Frosting experiments were performed on post-combustion flue gases with CO2 concentrations of 5%, 10%, and 15% under surface temperatures ranging from 150 K to 180 K, representing the typical carbon capture scenarios. Frost point data were obtained for pressures ranging from 0.1 to 1 MPa, distributed approximately between 166.3 K and 199.7 K, while the entire frosting process (0-20 minutes) was visually recorded. Image processing techniques were employed to extract the dynamic growth patterns of the frost layer, and sensitivity analyses were conducted to evaluate the effects of CO2 concentration and surface temperature on key indicators, including frost height, growth rate, and roughness. Particular emphasis was placed on the nucleation process (within the initial 0-2 minutes) and the fully developed growth process (over 8 minutes), where the frost crystal morphology transitioned from needle-like structures to plate-like formations. This study elucidates the mechanisms and morphological variations of CO2 frost crystal formation under cryogenic conditions, offering quantitative insights for system design and heat transfer analysis in practical desublimation capture applications.

Speaker: Bo Zhao (Institution of Refrigeration and Cryogenics, Zhejiang University, Hangzhou 310027, China)

80 C1Po3C-07: Thermodynamic Analysis of Cold Energy Replenishment in Liquid Air Energy Storage System

Liquid air energy storage (LAES), as a promising large-scale energy storage technology, offers significant advantages due to its geographical independence and the ability to store energy at ambient pressure. It holds great potential for future applications. The cold storage unit is the core component of the LAES. During the energy storage phase, the unit supplies cold energy to compress the air, while in the energy release phase, it recovers cold energy from the liquid air. However, as the cold storage unit operates in a cryogenic environment, cold energy inevitably leaks from the unit into the surrounding environment. If this cold energy is not replenished in time, the temperature of the cold storage fluid will rise, eventually preventing the compressed air from liquefying and causing the LAES to fail. Therefore, this paper calculates the cold energy leakage from the cold storage unit under different configurations and analyzes its impact on system performance. Additionally, a method is proposed to replenish the cold energy to the cold storage unit by reducing the pressurization of the liquid air. The study also explores the effects of different configurations on the pressure drop of the liquid air and the overall performance of the system. Through these analyses, the paper aims to provide optimized solutions to mitigate cold energy leakage and ensure the efficient operation of the LAES, offering theoretical support and practical guidance for its actual application.

Speaker: Dr Liubiao Chen

C1Po3D - Thermophysical Properties and Transport Processes I

81 C1Po3D-01: Design and performance analysis: characteristics of multi-dimension helium turbine brake wheels based on CFX simulation

Helium turbine expanders are widely used in low-temperature refrigeration applications, and the efficiency and performance of their brake impellers directly impact the overall equipment efficiency and stability. This study employs the computational fluid dynamics (CFD) software ANSYS CFX to analyze the performance characteristics of ten brake impellers of varying sizes in helium turbine expanders at different rotational speeds. It examines how the impeller outlet diameter and the number of impellers affect the pressure ratio, isentropic efficiency, and brake power within the stable operating range of the brake impeller. The results indicate that increasing the outlet diameter significantly enhances both the stable operating range and brake power of the brake impeller, while the efficiency remains relatively unchanged. Additionally, increasing the number of impellers expands the stable operating range without significantly affecting efficiency, although the impact on brake power is less pronounced compared to changes in outlet diameter. Through the analysis of brake impellers of multiple sizes, this study provides a method to optimize brake impeller performance without altering the impeller design.

Keywords: brake impeller, multiple sizes, CFD simulation, performance analysis

Speaker: Mr Changlei Ke (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China,)

82 C1Po3D-02: Study on Helium Adsorption Properties of Carbon Nanotubes in the Liquid Helium Temperature Range Based on the Monte Carlo Method

The sorption pump is a critical component of helium sorption cryocoolers operating in the liquid helium temperature range. Current research on porous materials for sorption pumps predominantly focuses on activated carbon, with limited exploration of alternative porous materials such as carbon nanotubes. Due to differences in elemental composition and molecular structure, the helium adsorption capacity of these materials remains unclear. In this study, a molecular model of carbon nanotubes was established based on the Monte Carlo method to numerically calculate the adsorption capacity of helium-4 over a pressure range of 10-200 kPa and a temperature range of 4-70 K. Additionally, an experimental setup was developed to measure the cryogenic adsorption capacity of porous materials, and corresponding experiments were conducted. The findings of this research provide valuable insights for optimizing sorption pump materials.

Speaker: Zhijian Zhang (Key Laboratory of Cryogenic Science and Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

83 C1Po3D-03: Measurement of Apparent Thermal Conductivity of Insulation Materials at Cryogenic Temperatures

The efficient and long-term storage of cryogenic liquids, such as liquid oxygen and liquefied natural gas, relies heavily on the use of various insulation materials. However, the apparent thermal conductivity data for many insulation materials, including foam glass slabs, high-density polyisocyanurate, and aerogel, under cryogenic and atmospheric pressure conditions remain insufficiently documented. In this study, a testing apparatus was designed and constructed to measure the apparent thermal conductivity of insulation materials under these conditions. Apparent thermal conductivity tests were conducted on foam glass slabs, high-density polyisocyanurate, aerogel blankets, and nitrile rubber curved panels at liquid nitrogen temperatures and above. The results indicate that aerogel blankets exhibit superior insulation performance, with an apparent thermal conductivity of 0.0063 W/(m·K) at 110 K. These findings provide valuable references for the selection and application of insulation materials in cryogenic storage tanks.

Speaker: Zhijian Zhang (Key Laboratory of Cryogenic Science and Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

84 C1Po3D-04: Transient Heat Transfer in Superfluid Helium from Localized Heating Spots on Spherical Surfaces

The transient heat transfer in superfluid helium (He II) from curved surfaces presents unique features that differ significantly from planar geometries. We numerically investigate this process by solving the two-fluid model coupled with Vinen's equation for vortex-line density, focusing on how surface curvature affects the propagation of the second sound wave. The numerical model is first validated against experimental data through comparisons with previous planar heater results, showing good agreement in temperature profiles and second sound behaviors. Analyzing cases of curved surfaces reveals distinct wave propagation patterns. When a heat pulse is applied, a second sound wave emerges and propagates away from the curved surface, accompanied by a rarefaction tail. The counterflow between superfluid and normal fluid components shows direction-dependent characteristics, with the wave's relatively velocity distribution, which provides insights into the energy transport mechanism. Our results demonstrate that curvature significantly influences both the magnitude and direction of energy transport. By analyzing different characteristic regions (10%, 50%, and 90% Energy Region), we identified different impacts of curvature on wave propagation angles. To quantify these effects, we establish dimensionless parameters using flat surface cases as a reference, enabling systematic analysis of curvature-dependent phenomena. These findings provide fundamental insights into the heat transfer of He II from curved surfaces, which also offer valuable guidance for optimizing the heat transfer process in curved geometries cooled by He II.
Keywords: Superfluid helium, Heat transfer, Second sound wave, Curved surface.

Speaker: Yingxuan Hu (Zhejiang University, Institute of Refrigeration and Cryogenics)

85 C1Po3D-05: Simulation Research on the Transient Characteristics of the Helium Turbine Expander

The helium turbine expander is one of the core components of a helium cryogenic system. The operation of the helium turbine expander varies during variable load adjustments in a helium cryogenic system, and has significant time-varying characteristics. In this paper, numerical simulations are conducted to investigate the time-varying flow field characteristics of the helium turbine during inlet load variations and to obtain the time-varying pattern of turbine efficiency. This paper is intended to provide a reference for the design of helium turbine expanders and the regulation of helium cryogenic systems.

Speaker: Chenghao Dai (Institute of Plasma Physics, Hefei)

86 C1Po3D-06: Streamlined Heat Leak Estimation for Vacuum Jacketed Cryogenic Pump Assemblies

Notable cost is invested in the liquification of cryogenic fluids such as liquid Nitrogen, Helium, Hydrogen, and Argon. End users have an interest in knowing the level of heat leak cryogenic systems experience, and convenient methods of heat leak calculations. End-users value pump designs that minimize heat leak in cryogenic systems to improve system efficiency and reduce operating costs. At the engineering and design phase, heat leak calculations assist in establishing the efficacy and confirmation of designs for vacuum jacketed, cryogenic, extended shaft pump assemblies as well as gaseous cryogenic compressors and blowers. When compared to more sophisticated finite element (FEA) analysis methodologies provided by engineering analysis programs such as ANSYS, this relatively straight forward, one dimensional heat leak analysis method provides reliable first-pass estimates that assist in design optimization by achieving similar accuracy while being faster and easier to implement, making the method an ideal tool for early design evaluation.

Speaker: Mr Chris Rista (Barber-Nichols LLC)

87 C1Po3D-07: Design considerations for valve dynamics of a positive displacement cryogenic pump

Operation of a cryogenic pump near saturated conditions proves challenging to maintain fluid quality throughout the intake process of the pump. Design considerations for minimizing the phase change of fluid across the pump are explored, highlighting the goal of maximizing mass flow throughput of the positive displacement pump. CFD studies were conducted to predict state change performance across the inlet valve of the pump in saturated liquid nitrogen conditions. High-speed video of the designed valve operating in liquid nitrogen on an optically accessible cryogenic setup were captured to validate the CFD predictions. Experimental results indicate good agreement with qualitative CFD analysis regarding state change performance, and demonstrate the underlying dynamics of designing dynamic cryogenic valves.

Speaker: Brandon Demski

88 C1Po3D-08: A review of the technology practice and future opportunities of liquid hydrogen centrifugal pumps

Liquid hydrogen centrifugal pumps play a crucial role in the large-scale transport and utilization of liquid hydrogen as a kind of energy-transporting device with a wide range of application prospects. However, the liquid’s motion within the pump is quite complex, making it challenging to fully determine the properties of the pump and the parameters of the fluid using only analytical methods. Consequently, the ongoing advancement of pump design methodologies and experimental testing techniques is imperative with the consideration of the intrinsic properties of the working mass, as well as the phenomenon of liquid vaporization, to facilitate the effective utilization of liquid hydrogen pumps in practical applications. This paper reviews the current state of development for liquid hydrogen centrifugal pumps and their technological approaches based on the parameter considerations and optimization. The difficulties associated with cavitation and lubrication during the design, simulation, testing, and application of liquid hydrogen pumps are highlighted. In addition, corresponding recommendations for addressing these issues are discussed. By utilizing high-temperature superconductor coils and superconducting magnetic levitation bearings as examples, the research also reflects the potential creation of liquid hydrogen pumps in conjunction with this technology.

Speaker: Prof. Jihao Wu

89 C1Po3D-09: Design and optimization of a Single-Phase heat exchanger for GM cryocooler coupled with parahydrogen conversion catalyst

Ortho-para hydrogen conversion is a pivotal step in the hydrogen liquefaction process. This study introduces a novel single-fluid conduction-type GM cryocooler heat exchanger designed specifically for hydrogen liquefaction, with its performance enhanced through systematic optimization. The heat exchanger utilizes oxygen-free copper as the conductive material and incorporates ortho-para hydrogen conversion catalysts, enabling simultaneous conversion and liquefaction of hydrogen during cooling. To streamline the design and improve overall system efficiency, a parameter adjustment strategy based on fluid dynamics and heat transfer optimization is proposed. An optimization model is developed to maximize the heat exchanger’s volumetric performance, thus improving heat transfer efficiency and the hydrogen liquefaction process. Using the NLopt-based COBYLA algorithm, key design parameters, such as channel diameter, the number of flow channels, and the heat exchanger length, are optimized. Numerical simulations reveal the coupled process of ortho-para hydrogen conversion and convective heat transfer within the temperature range of 20 K to 81 K, offering an efficient and practical solution for hydrogen liquefaction and energy storage systems.
Keywords；Hydrogen liquefaction； GM cryocooler (Gifford-McMahon cryocooler)； Ortho-para hydrogen conversion； Heat exchanger design； Optimized design

Speaker: Jihao Wu

M1Po3A - Materials Aspects of HTS

90 M1Po3A-01: Measurements of composite Bi-2212 Rutherford cable's mechanical properties.

The U.S. Magnet Development Program (US-MDP) explores high-field accelerator magnets that require operating conditions beyond the limits of Nb$_3$Sn technology. The ongoing R&D process for High-Temperature Superconductor (HTS) characteristics enhancement suggests using Bi$_2$Sr$_2$CaCu$_2$O$_{8-x}$ (Bi-2212) as a superconductor element. Coils made of Bi-2212 Rutherford cable maintain high critical current (Ic) when submerged in high external magnetic fields. The Nb$_3$Sn mechanical properties are well described and can be found in the literature. Concerning the Bi-2212 superconductor, the sources are limited. In this paper, a set of Bi-2212 Rutherford cables was obtained from a previously realized racetrack coil and used to perform a post-mortem mechanical properties analysis of the superconductor. The samples studied are described and characterized geometrically and mechanically. Results are discussed and collected in tables highlighting the measurements performed at room and cryogenic temperatures in liquid Nitrogen. The empirical data were then inserted into the APDL code to characterize the 3D Bi-2212 Rutherford cable model realized for modeling analysis.

Speaker: Alessio D'Agliano (FNAL)

91 M1Po3A-02: Investigation of Leakage in Bi-2212 Rutherford Cables

Bi-2212 round wire is the only viable HTS superconductor to produce high-field magnets. It can be fabricated in a variety of multifilamentary architectures, and it can be fabricated into Rutherford and six-on-one cables. Rutherford cabling degrades JE of the round Bi-2212 wire, and the isostatic overpressure heat treatment (OPHT) used for Bi-2212 distorts the shape of the wires. Single strands of Bi-2212 have been rolled and OPHTed simulating the deformation that occurs during Rutherford cabling plus OPHT. The JE decreased up to ~18 % in rolled wire with this decrease saturating at about ~20% thickness reduction. The layers in a Rutherford cable coil must be insulated from one another so the wires do not bond together during OPHT at 890 C, and this same insulation must prevent the layers of Rutherford cable from shorting together at cryogenic temperature. In the past, braided alumino-silicate fiber was used for the insulation, but it often chemically reacted with the Bi-2212 wire during OPHT causing the wire to leak, further degrading JE. Recently, the alumino-silicate has been replaced with braided pure alumina fiber that does not chemically react with the Bi-2212. Surprisingly some Rutherford cable coils with pure alumina braid leaked after OPHT. The reason why these Rutherford cables leaked is being investigated. The presentation will report our finding on the causes of the Rutherford cable leakage and how to eliminate this leakage.

This work is supported by US DOE Accelerator R&D and Production (ARDAP). Work at NHMFL is also supported by US DOE OHEP under Grant DE-SC0010421, by NSF under Award DMR-2128556, and by the State of Florida. Work at LBNL is supported by US DOE, Office of Science under contract No. DE-AC02-05CH11231.

Speaker: Eric Hellstrom (Applied Superconductivity Center - NHMFL)

92 M1Po3A-03: The Effect of Calcium Doped Y-Ba-Cu-O (CaY123) Layer Thickness on the Flux Pinning in (CaY123 / BaZrO3 Doped Y-Ba-Cu-O) Multilayer Composite Films at a Wide Range of Temperatures and Applied Fields

Past research has shown the significant impact of utilizing a calcium doped YBa2Cu3O7-x (YBCO) layer that separates three individual layers of 6 vol.% BaZrO3 (BZO) +YBCO multilayer composite films. Experimental evidence illustrated the ability of the calcium to diffuse and repair the defective interface existing between the BZO nanorods and the YBCO matrix. The composite films consisted of five total layers: three individual 50 nm layers of BZO doped YBCO interspersed by a 10 nm thick layer of calcium doped YBCO, Ca0.3Y0.7Ba2Cu3O7-x (CaY123). This research investigates any limits that may exist on the thickness of the calcium containing layers and the efficiency of the resulting interface repair, resulting in an increased flux pinning for the films. Films were produced via pulsed laser deposition with the CaY123 layer thickness varied from 1 nm, 2 nm, 5 nm, 10 nm, and 15 nm, while maintaining the BZO/YBCO individual layer thickness of 50 nm. Resulting magnetic current densities at 5 K–77 K and with field parallel to the c-direction at 0–9 T will be presented, along with microstructure analysis.

Speaker: Timothy Haugan

93 M1Po3A-04: Self-consistent solution of Eliashberg equations for metal hydride superconductors

In the last years, the search for high critical-temperature superconductors has focused on metal and molecular hydrides, which may exhibit superconductivity at room temperature under very high pressures [1]. Actually, such behavior has been suggested by N. W. Ashcroft in 1968, since hydrogen-based materials possess elevated vibrational frequencies, as a consequence of the low atomic mass of hydrogen [2].

In this work, we present a self-consistent solution of the Eliashberg equations [3], in contrast to the widely used McMillan-Allen-Dynes parameterized one [4], where effects of the electron-phonon coupling, the density of states at the Fermi level and characteristic phonon frequencies are further analyzed. Finally, these two solutions are comparatively applied to several metal hydride superconductors, whose results are additionally contrasted with their measured critical temperatures.

This work was partially supported by research projects CONAHCYT-CF-2023-I-830, UNAM-IN110823 and LANCAD-UNAM-DGTIC-039. T.E. acknowledges the master’s fellowship from CONAHCYT of Mexico.

[1] A. P. Drozdov, M. I. Eremets, I. A. Troyan, V. Ksenofontov and S. I. Shylin, Conventional superconductivity at 203 Kelvin at high pressures in the sulfur hydride system, Nature 525, 73-76 (2015).

[2] N. W. Ashcroft, Metallic hydrogen: A high-temperature superconductor? Phys. Rev. Lett. 21 (26), 1748-1749 (1968).

[3] G. M. Eliashberg, Interactions between electrons and lattice vibrations in a superconductor, Soviet Phys. JEPT 11 (3), 696-702 (1960).

[4] P. B. Allen and R. C. Dynes, Transition temperature of strong-coupled superconductors reanalyzed, Phys. Rev. B 12 (3), 905-922 (1975).

Speaker: Mr Tomas Javier Escamilla Lara (Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico)

M1Po3B - Mechanical and Thermal Properties of Materials at Low Temperature

94 M1Po3B-01: Fatigue analysis of Stirling cryocooler flexure springs for long space mission lifetime

Cryocoolers are used in space instruments to cool detectors and superconducting devices to cryogenic temperatures. Inside a cryocooler, a flexure spring is used to ensure the cryocooler piston is axially free to move but is radially restricted, preventing off-axes forces that could cause piston contact with the sides of the cylinder, which is the primary cause for failure in a space cryocooler. Given that the flexure spring is mission-critical to the cryocooler operation yet prone to failure, its lifetime can, in effect, determine the lifetime of the space mission itself. By extending the life of the flexure spring, space missions can be extended and pose longer reliability. This study investigated various key spring design parameters to assess their impact on the operation of a spiral flexure spring built with AISI 1045 Steel, which consists of spring arms in a characteristic spiral shape. These parameters include the number of spiral spring arms, spring design, and spring thickness. Results show that the lowest maximum stress is observed at lower spring thickness values, moderate arm numbers, and teardrop sizes that vary for different arm numbers. Based on these results, an optimal design is proposed that maximizes flexure spring lifetime while operating at a resonant frequency in continuous oscillatory motion to reduce the input power requirements and increase the lifetime of flexure springs for long-lifetime space cryocoolers. In this design, the design parameters are adjusted for optimal flexibility as a proof of concept, with additional designs inspired by origami proposed. In the latter design, a longer lifetime is demonstrated, extending to the lifespan of space missions that rely on cryocooler operation.

Speaker: Raymond Feng (Center for Astrophysics | Harvard & Smithsonian)

95 M1Po3B-02: Characterizing niobium fatigue failure near 20 K

Niobium plays a critical role in a range of cryogenic applications, including superconducting magnets, superconducting radio frequency (SRF) cavities, and cryogenic electronics, owing to its superior superconducting properties, high strength, and excellent resistance to embrittlement. Although tension, compression, and the shear behavior of niobium has been studied at cryogenic temperatures, research on fatigue failure, particularly near 20 K has remained sparse. Furthermore, the underlying mechanisms of damage and failure under fatigue in niobium are not well understood. To address this gap, this study utilizes a Cryogenic Accelerated Fatigue Tester (CRAFT) setup to characterize limits of failure under cyclic tension-tension loading. Our experimental setup consists of a PT415 GM cryocooler mounted on a custom vacuum chamber housed between the uprights of an MTS Acumen load frame with a dynamic load capacity of 12 kN and 100 Hz. Heat transfer is mitigated by an actively cooled copper shield and a multi-layer insulation blanket as well as pulling vacuum inside the test chamber. We characterize the fatigue life of pure niobium at different temperatures and frequencies to develop the stress-life cycle (S-N) curves and use a Scanning Electron Microscope (SEM) to identify the mechanisms of crack initiation and propagation. Findings of this study provide insights into the fatigue behavior of niobium at cryogenic temperatures and help identify the safety limits of niobium components.

Speaker: Md Shakil Mahmood (Washington State University)

96 M1Po3B-03: Mechanical Properties of Stainless-Steel co-wind Tapes for REBCO magnets

REBCO high-temperature superconductor tapes offers remarkably high critical current density in high magnetic fields. It has been used successfully in ultra-high field superconducting magnets. To address the challenge of high mechanical stress in these magnets, co-winding REBCO tapes with insulated stainless-steel tapes has emerged as a promising technique to enhance their overall performance. In this paper, we present the mechanical properties of 316L stainless steel co-wind tapes of different tempers. In addition, we investigated the impact of heat treatment, a process simulating the curing of sol-gel insulation, on the mechanical properties of 316L stainless steel tapes. Quarter-hard (0.006") and half-hard (0.008") stainless steel tapes were subjected to heat treatment at 550°C for approximately one minute. Subsequent mechanical testing at 77 K revealed an increase of 6.5% in the modulus of elasticity for both tape thicknesses by heat treatment. Conversely, the yield strength decreased by 2%. These findings provide crucial insights into the mechanical behavior of heat-treated stainless-steel tapes and their suitability for co-winding with HTS tapes in high-field superconducting magnets. By understanding the effects of heat treatment on the mechanical properties, we can optimize the design and performance of future superconducting systems.

Acknowledgement
This work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1644779, DMR-1839796, DMR- 2131790, and the State of Florida.

Speaker: Dr Aniket Ingrole (National High Magnetic Field Laboratory (NHMFL), Florida State University)

97 M1Po3B-04: Effect of Cryogenic Treatment on the Strength Properties of Welded SS304 Joints

Stainless steel is a very popular material for cryogenic temperature applications since it does not exhibit ductile to brittle transition at low temperatures. In most of the cryogenic temperature equipments, welded joints of stainless steel are extensively used. The strength of the welded area will be less than the original material since the gap is filled by melting the welding rods. This is due to lower packing density of atoms of the filler metal as compared with the main material. In this experimental study, the welded joints made out of SS304 are subjected to cryogenic treatment for thirty six hours at 80K in a specially designed and developed cryogenic treatment system which uses LN2 as the cooling medium. The cryotreatment unit is made of a double walled stainless steel with polyurethane foam (PUF) insulation filling up the annular space. Test specimens housed within this unit is gradually cooled to cryogenic temperature by the closed loop circulation of cold nitrogen gas by forced convection. Test specimens of SS304 were prepared following the guidelines of ASTM standard E8 and their mechanical strength properties (yield strength, ultimate tensile strength and percentage elongation) were determined with the help of Universal Testing Machine (UTM) following the test procedure specified by ASTM A370-2022. Same tests were conducted on welded test specimens to determine their strength properties. Later, many specimens were prepared with the welded joints at the critical area and divided into two batches. One batch was subjected to cryotreatment alone and the other batch was tempered at 440 Celsius for one hour after cryotreatment. Strength tests were conducted on specimens of both these batches. Experiments have rendered encouraging results which are analysed and discussed.

Speaker: D.S. Nadig

98 M1Po3B-05: Exploring Cryogenic Properties of 3-D Printed Materials using FDM and SLA Techniques

In recent years, 3-D printing has gained widespread popularity as a cost-effective method for rapid prototyping across various fields. The emergence of new materials has broadened the potential applications of 3-D printing, such as opto-mechanical supports in cryogenic environments. However, many of these materials lack defined thermal and mechanical properties under cryogenic conditions. This paper addresses this gap by determining the thermal conductivity and stress of various 3-D printed materials fabricated using both Fused Deposition Modeling (FDM) and Stereolithography (SLA) techniques under cryogenic environments. The materials selected for this study exhibit a total mass loss (TML) lower than 1%, a critical criterion for cryogenic applications. Through analysis and experimentation, this study aims to provide valuable insights into the performance and suitability of select 3-D printed materials for cryogenic applications.

Speaker: Eveke Calixtro (IRLabs, Inc)

99 M1Po3B-06: Inconel 625 flange development for Cu-based superconducting radio frequency cavities

Depositions of superconducting Nb3Sn (Tc ~18K) layers on Cu is a promising approach to developing superconducting radio frequency (SRF) cavities comprising the next generation's high-efficiency linear accelerators operating at 4K. This technology can significantly reduce costs beyond the 2K state-of-the-art Nb-based technology. Developments in physical and chemical vapor depositions of Nb3Sn on Cu are underway and require high cavity processing temperatures between 750C- 950C for multiple hours to achieve high-quality superconducting Nb3Sn. Beyond the superconducting layer development, permanent fastening methods are needed to develop Cu-based SRF systems. Here, we present the development of electron beam welding of Inconel 625 flanges directly to copper that can withstand high deposition temperatures and thermal shock during cooling. Development tests with replica Inconel 625 blanks butt-welded to Cu indicate excellent weldability as observed by homogeneous mixing, no weld defects, and successful leak check tests. Progress on the final welding of Inconel 625 flanges to 1.3GHz hydroformed seamless Cu cavities will be presented.

Acknowledgment: This work was performed under the US- DOE- ACCELERATE- program. The authors would like to acknowledge the support of Jefferson Science Associates, LLC under U S DOE Contract No. DE-AC05-06OR23177.

Speaker: Adam O'Brien (The Thomas Jefferson National Accelerator Facility)

100 M1Po3B-07: Assessing the Adhesion of Nanofibrous PVDFHFP as Passive Thermal Control Coatings for the Extraterrestrial Storage of Cryogenic Propellants

Future space missions to distant frontiers could require significantly larger amounts of cryogenic propellants than typical missions. Such missions and esoteric applications, like space tourism, would benefit from propellant storage in space for refueling space vehicles. In this regard, advancements in cryogenic fluid management are necessary to achieve extraterrestrial storage. Specifically, passive cryogen management techniques in space, like radiative cooling, are necessary to reduce the burden on active thermal control methods, like cryocoolers. Particularly, materials with superior optical properties (high solar reflectance and infrared emittance) would be beneficial for passive thermal control to reject most of the incident solar radiation and enhance thermal emission from the storage tank, leading to self-cooling. We developed a nanofibrous passive thermal control material by electrospinning polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) co-polymer onto an aluminum foil substrate. The electrospun nanofibrous PVDF-HFP has a porous nanostructure, as observed by scanning electron microscopy. The material exhibits a very high solar reflectance (>99%) and infrared emittance (86%) when characterized in the ultraviolet-visible-near infrared and mid-infrared wavelengths using spectrophotometers interfaced with integrating spheres.
This study focuses on the adhesion of the electrospun PVDF-HFP to the aluminum foil substrate. We conduct adhesion peel strength testing using an Instron universal testing machine following the ASTM D3330 standard test method. First, we tested a pristine PVDFHFP-aluminum foil material at room temperature to assess the adhesive strength of the nanofibers to the substrate. Subsequent tests, performed at room temperature, incorporated in-lab fabricated and commercial adhesives between the nanofibers and the aluminum foil substrate to improve the adhesion between the nanofiber and the substrate. For extraterrestrial applications that would expose the materials to extreme temperature swings, we studied the effects of cycling between cryogenic and high temperatures on the adhesive strengths of the adhesives used in this study. Further characterization and testing in extreme environmental conditions would provide insights into its applicability for extraterrestrial long-term storage of cryogenic propellants in space depots.

Acknowledgments: The authors acknowledge the support of the National Aeronautics and Space Administration under Grant No. 80NSSC21K0072 issued through the Space Technology Research Grants.

Speaker: Chieloka Ibekwe

101 M1Po3B-08: Electrospun Polyvinylidene fluoride co-hexafluoropropylene (PVDF-HFP) for Passive Thermal Management in Space

Managing heat in space is essential for spacecraft to operate within acceptable thermal limits, and ensure the success of extended missions. Future applications, such as the storage of cryogenic propellants in space depots, impose strict requirements on thermal control, making it necessary to adopt efficient means to meet these requirements. Consequently, while both active and passive thermal control techniques are applied, passive thermal management is preferable to address the radiation-dominated heat transfer in space. This approach would require materials that exhibit exceptional optical properties like low solar absorptivity (or high solar reflectivity) and high infrared emissivity. Hence, the need to advance materials with superior optical properties for space applications is critical. We address this need by developing new materials consisting of nanofibers as the radiation-exposed exterior surfaces of space objects for passive temperature control.
This study uses electrospinning to fabricate the nanofibrous materials from polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) co-polymer. Scanning electron microscopy reveals its porous structure, which consists of randomly ordered nanoscale fibers. This porous structure imparts a strong light scattering ability, as evidenced by its very high solar reflectance (>99%), obtained from ultraviolet-visible and near-infrared spectroscopic characterization. The material also emits strongly in the mid-infrared wavelengths, which is desirable for self-cooling. Thermogravimetric analysis was also performed on the material to gain insight into its thermal stability.
The harsh environmental conditions in space affecting spacecraft materials make it necessary to assess the materials’ performance in similar conditions before they qualify for use in space. To this end, we exposed the nanofibrous PVDF-HFP material to (a) ultraviolet radiation, (b) a thermal vacuum environment to assess its outgassing characteristics, and (c) thermal cycling tests between cryogenic and high temperatures to understand the material’s resistance to extreme temperature swings. Subsequently, we characterized the optical properties to quantify the effects of exposure to these extreme conditions. We observed only marginal changes indicative of good extraterrestrial durability. The material’s thermal control performance was assessed in a vacuum chamber operated at 300K to emulate space-like conditions of a dark background, low pressure, and extraterrestrial solar illumination from a solar simulator providing 1367 W/m2 intensity. In addition, experimentally validated COMSOL thermal models were used to predict the material’s thermal control performance under different conditions. From these observations and with further optimization, the nanofibrous PVDF-HFP holds good promise as a passive thermal control material for space applications.

Acknowledgments: The authors acknowledge the support of the National Aeronautics and Space Administration under Grant No. 80NSSC21K0072 issued through the Space Technology Research Grants.

Speaker: Chieloka Ibekwe (Rensselaer Polytechnic Institute)

M1Po3C - Magnet Design and Applications I

102 M1Po3C-01: Design, fabrication, and testing of the quadrupole triplet magnet for the HRS project

The Facility for Rare Isotope Beams (FRIB) is a scientific user facility under the U.S. Department of Energy Office of Science (DOE-SC) and an independent scientific user organization of approximately 1,800 researchers. The High Rigidity Spectrometer (HRS) will be the centerpiece experimental tool of the FRIB fast-beam program, enabling experiments with the most exotic, neutron-rich nuclei available at FRIB. A discrete cosine theta quadrupole triplet was designed for the HRS project. This magnet, with a warm bore of 200 mm, 18.5 T/m quadrupole field gradient, and a total length exceeding 2 meters, lacks an iron yoke and thus weighs only one-third of a traditional iron-dominated quadrupole triplet, which can reduce cooldown time and reduce the helium requirement by a factor of 3-4. The newly designed magnet can improve mechanical behavior and operation efficiency by reducing secondary beam tuning time. A new protection circuit has also been designed to ensure the safe operation of superconducting magnets. This work will present the design, full-scale prototype fabrication, and testing of the quadrupole triplet magnet.

Speaker: Xiaoji Du (Michigan State University)

103 M1Po3C-02: Structural analysis and field mapping test setup of the quadrupole triplet magnet for HRS project

The Facility for Rare Isotope Beams (FRIB) at Michigan State University (MSU) stands as one of the world’s leading experimental facilities for research in rare isotope science. At FRIB, the High Rigidity Spectrometer (HRS) is a new system that combines a magnetic spectrometer with an associated analysis beamline. Designed for experiments utilizing fast beams (≳100 MeV/𝑢), the HRS accommodates magnetic rigidities of up to 8 Tm. As part of the high-transmission beamline (HTBL) within the HRS, a discrete cosine-theta superconducting quadrupole triplet has been designed. This triplet magnet has a nested coil structure that includes quadrupole and multipole corrector coils. This paper firstly analyzes the mechanical response of the magnet when nested coils operate at different polarities. Secondly, the reinforcement structure is developed to improve the structural stability of the magnet. Lastly, the fabrication process of the multipole coils and the field mapping test setup for the quadrupole magnet are presented. The field mapping test will validate the mechanical design and fabrication accuracy of the quadrupole magnet.

Speaker: Hengkang Zheng (Michigan State University)

104 M1Po3C-03: Thermal Modeling of CCT Dipole Magnets wound using Defected REBCO Cables

We analyzed numerically, using a Finite Element Method (FEM), the performance of REBCO CORC® cable containing various structural defects. We focused on defects of the defects on heating and thermal runaway of the magnets. Defects are possible in any HTS cable, originating from the tape manufacture, or during cabling, or in service. We considered a design based on real Canted Cosine Theta (CCT) dipole magnet, wound using CORC® cable, which was built and tested at the Lawrence Berkeley National Laboratory, USA as a stand-alone dipole magnet providing a magnetic field of 2.9 T in liquid He bath at 4.2 K. Because, thermally the turns of the CCT dipole magnet behave as parallel straight wires immersed half way in the grooves of the mandrel material with their outside surfaces in direct contact with pool boiling liquid He, in our FEM model we adopted a 3D straight geometry which significantly reduces the computational cost. To model the REBCO superconducting material we used its measured power law E-J curve.

Speaker: Milan Majoros

105 M1Po3C-04: Researches on Superconducting Magnetic Drivers

Magnetic drive is a technology that utilizes magnetic force to achieve non-contact driving, which has advantages such as high efficiency, reliability, and environmental protection. It can meet the needs of different working conditions and has important application prospects. In this presentation，we conduct researches on magnetic drivers based on superconducting materials, explain the principle and structure of the superconducting magnetic drivers, simulate and optimize its design, develop a prototype of the superconducting magnetic drivers. A testing platform for superconducting magnetic drivers is built, and the performance tests on the developed magnetic drivers are conducted.

Speaker: Guomin Zhang (Institute of Electrical Engineering，Chinese Academy of Sciences)

106 M1Po3C-05: Magnetic field and force calculation of the new SCU prototypes

New 0.5m long SCU prototypes were designed based on lessons learned from the previous full length (1.5 m) core experiences. The original monolithic cores have all steel poles. The new cores have plastic back poles to avoid electrical shorts of superconducting wires to cores. Magnetostatic calculation was made for one period model for each of two designs under consideration. Then, magnetostatic, and mechanical analysis was also conducted for the prototype SCUs with the lengths of 29.5 and 23.5 periods. The software used for this simulation is ANSYS Maxwell and Mechanical. Both the magnetostatic and the mechanical analyses confirm the validity of the new design.

Speaker: Dr Yuko Shiroyanagi (Argonne National Laboratory)

107 M1Po3C-06: Development of the CCT superconducting magnets for the STCF interaction region

In older to explore charm physics and tau physics in next decades, a third-generation circular electron-positron collider Super Tau-Charm Facility (STCF) with the energy range of 2-7 GeV is being developed and pre-studied in University of Science and Technology of China. As the last correction of the particles before the collision, the superconducting magnets in the interaction region (IR) play an important role in the whole device. The distance between the interaction point (IP) and first IR magnet (called QD0) is 900mm and the collision angle of IR magnet is only 60 mrad. The effective thickness of the QD0 magnet is very limited. The QD0 magnet need 50 T/m at the reference radius of 10 mm. The pre-design of the CCT QD0 magnets will be proposed in this study.This high order harmonics and cross-talk of the of the twin aperture CCT magnet will be studied and analyzed. The optimization method of the twin aperture CCT magnet will be proposed. Some ideas of CCT magnet and its analysis will be also introduced in this study.

Speaker: Dr Shaoqing Wei (Institute of Plasma Physics (IPP), Chinese Academy of Sciences (CAS))

108 M1Po3C-07: The Design and Manufacturing of Superconducting Undulator Magnets Utilizing Additive Manufacturing & Plastic Components.

The next generation of superconducting undulator (SCU) magnets are being design and manufactured for use in the Advanced Photon Source (APS). These Niobium Titanium (NbTi) superconducting magnets consist of cores fabricated from low carbon steel and are surrounded with isolating material that makes up the remainder of the magnet. These isolating structures are fabricated utilizing additive manufacturing techniques including 3D printing. Because the magnets for the SCUs cannot be shimmed once installed, they have very tight machining tolerances. This poses unique manufacturing and fabrication challenges, which are simplified using this new design. This paper will cover the design of the prototype magnets cores being fabricated for use in superconducting undulators at the APS, lessons learned from manufacturing, magnet training data, and potentially measurement data from full length magnets.

Speaker: Ethan Anliker

M1Po3D - Insulation, Impregnation, and Polymeric Materials

109 M1Po3D-01: Cryogenic properties of polyimide aerogel composites for thermal insulation

Polyimide (PI) aerogels have the advantages of low density, low thermal conductivity, excellent thermal stability and a wider range of working temperature than other organic aerogels, making them promising materials for cryogenic thermal insulation. The use of aerogel materials to replace the traditional porous perlite materials can further reduce the insulation cost, weight and space. Up to now, there has already been researchs on polyurethane foams as well as commercial aerogel blankets as substitute insulation material. However, the cryogenic characteristics of those materials such as mechanical properties, thermal insulating performance are normally the main limitations to their applications. In this work, attracted by the unique advantages of PI aerogels, we managed to validate their thermal insulation capabilities under cryogenic conditions (77K). A series of PI aerogel composites were prepared and characterized for the microstructure and cryogenic properties. This work provides a theoretical basis for the thermal insulation application of PI aerogel composites under cryogenic conditions.

Speaker: Shen Zhao (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

110 M1Po3D-02: Formation of thermal conductive hydrogel network in boron nitride/polyvinyl alcohol by directional freezing assisted salting-out method for cryogenic application

Polymers play a crucial role as packaging materials for flexible electronic devices. Along with the rising power of electronic components, enhancing the thermal conductivity of hydrogel materials can greatly improve the performance of flexible electronic components. Herein, we designed a hydrogel material composed of polyvinyl alcohol (PVA) doped with 500nm boron nitride nanosheets (BNNS), which was prepared by directional freezing assisted salting. The directional porous structure was confirmed via scanning electron microscopy, while the mechanical properties and thermal conductivity were validated by universal tensile test and steady-state thermal conductivity measurement respectively. The thermal conductivity of this material reaches 0.65 W/m·K at room temperature, and the tensile strength achieves 513.4 kPa. Besides, the thermal conductivity can still reach 0.32 W/m·K at the temperature of 77K. Therefore, the material is capable of enhancing heat dissipation in the packaging of flexible electronic devices, both in room and cryogenic environment. In addition to being an encapsulation material for flexible devices, the material is also able to form a three-dimensional BN skeleton, which can be subsequently injected into epoxy resin to prepare epoxy composite with enhanced thermal conductivity. The thermal conductivity of the epoxy composite is up to 0.82 W/m·K at room temperature and 0.38 W/m·K at the temperature of 77K respectively. Due to the heat conduction network constructed by the skeleton structure, the thermal conductivity of epoxy composite is improved. In our work, a flexible hydrogel with improved thermal conductivity was constructed by means of directional freezing assisted salting out. The hydrogel and its derivatives are expected to be applied in the field of low temperature electronic packaging in the future.

Speaker: Junting Zhao (1) Key Laboratory of Cryogenic Science and Technology, Technical Institute of Physics and Chemistry; 2) Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences)

111 M1Po3D-03: Assessing the Feasibility of Adopting Molecular Dynamics in Designing Cryogenic Polymers

Thermoplastics have long been a focal point in materials science, particularly in applications such as liquid hydrogen infrastructure and space fuel tanks. Their lightweight make them highly advantageous in such advanced technologies. However, the exploration of novel polymers for cryogenic applications has remained restricted to a limited subset of materials due to the high costs associated with experimental synthesis and testing. This limitation has hindered innovation, preventing the discovery of new monomers and the development of a molecular-level understanding of cryogenics-specific polymers. While computational approaches like Molecular Dynamics (MD) are well-established in fields such as drug design, their adoption in cryogenic polymer design remains underexplored, representing a missed opportunity for advancing cryogenic engineering.

MD offers a powerful method for simulating and characterizing the behavior of polymers at the atomic level. With the use of the Newtonian motion of atoms, MD provides critical insights into the mechanical, thermal, and permeability properties of materials, enabling the prediction of performance of polymers under cryogenic conditions. This study focuses on the simulation and analysis of polyetheretherketone (PEEK), a semi-crystalline polymer known for its exceptional mechanical and thermal properties as a case study to evaluate the adoptability of MD simulations in cryogenic polymer designing. MD simulations were used to examine key properties of PEEK at cryogenic temperatures, including tensile strength, Young’s modulus, Poisson’s ratio, coefficient of thermal expansion, and cryogenic hydrogen permeability, which are critical for cryogenic applications. Recognizing the semi-crystalline nature of PEEK, amorphous and crystalline phases were modelled separately. The simulations utilized two force fields: the Optimized Potentials for Liquid Simulations (OPLS) force field and the reactive force field (ReaxFF). For OPLS, CM5 charges were used as partial charges, derived from Density Functional Theory (DFT) calculations performed using the ORCA. This approach ensured high reliability in representing atomic interactions and charge distributions, thereby enhancing the accuracy of the MD results. MD simulations were run on Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). After equilibration, isothermal-isobaric ensemble (NPT) was used to examine the glass transition and melting temperature of the polymer which validates the ability of the MD simulations to capture polymer properties.
Also, this study presents the comparison of cryogenic experimental results of tensile strength, Young’s modulus, Poisson’s ratio, and coefficient of thermal expansion with the MD simulations providing insight on the possibility of using MD simulations in cryogenic polymer designing. Although molecular dynamics provide a significant amount of details at the atomic level, converting molecular scale results into macro-scale requires a multiscale modeling approach linking two distinct material levels. Therefore, finally, this study presents a comprehensive computational workflow that can be adopted in converting MD results for composite designing.

The findings of this research pave the way for broader adoption of computational chemistry techniques, especially MD in the field of cryogenic polymer composites. By integrating MD simulations and multiscale modeling, researchers can create a comprehensive toolkit for designing materials with unparalleled performance. As the demand for advanced materials in aerospace, energy storage, and hydrogen infrastructure continues to grow, molecular dynamics will enable revolutionizing the design and optimization of cryogenic polymers.

Speaker: Shanaka Kristombu Baduge (The University of Melbourne)

15:00 Afternoon Coffee Break -- supported by Sumitomo (SHI) Cryogenics of America, Inc.

C1Or4A - Thermophysical Properties and Transport Processes II

112 C1Or4A-01: Validating effective thermal conductivity of glass microspheres in cryogenic storage insulation via finite element analysis

In this work we consider multi-mode, multi-scale heat transfer within a cryogenic storage system and demonstrate the importance of using gaseous conduction functions derived from low pressure gas theory in converging to published experimental data. Through validation of modeling data against experimental cryostat data available in the academic literature, we develop the framework for extrapolating such an analysis to large scale cryogenic storage container systems. An accurate estimation of the effective thermal conductivity of these insulation materials is essential in the evaluation of heat leak and boil-off rate from liquid hydrogen storage tanks. Heat transfer through evacuated packed beds of microspheres for cryogenic storage applications is primarily driven by a combination of solid conduction, radiation, and gaseous molecular transport. In the practical range of interest of cold vacuum pressure between approximately 100 and 1000 mTorr for tank insulation conditions, this study finds that the intra-sphere gaseous molecular transport begins to deviate from the diffusive regime into quasi-ballistic behavior. We further corroborate a size effect fitting parameter through a Monte Carlo ray tracing analysis to calculate the ballistic transport length distribution.

Speaker: Dr Marc Dunham (3M)

113 C1Or4A-02: Development of a test apparatus for thermal conductivity measurements of insulation materials with adsorbed nitrogen between 20 and 77 K

With the growing interest in utilizing liquid hydrogen to decarbonize the aviation and transportation industries, understanding the effective thermal conductivity of insulations utilized in vacuum-jacketed liquid hydrogen vessels is critical to predicting heat leak and boil-off characteristics. Moreover, the ability to predict the transient heat flux during a loss of vacuum event is a critical metric that will impact the design of safety systems and hold time of these tanks. While these metrics have been characterized thoroughly with liquid nitrogen cold boundary temperatures (77 K and above), there is a lack of measurements at liquid hydrogen boundary temperatures. Boil-off calorimetry has been a typical method for measuring thermal conductivities but proves challenging for liquid hydrogen temperatures (20 K). In this study, a cryogenic refrigerator enables thermal conductivity measurements of three common insulations (glass microbubbles, aerogel, and multi-layer insulation) with an accuracy better than ± 1 mW/m-K at liquid hydrogen boundary temperatures. Additionally, the experiment is capable of uniformly introducing gas in the insulation space, simulating a catastrophic fail of vacuum. Transient heat fluxes can be determined from these experiments and utilized to design safety systems. Measurements are compared to a theoretical model for validation purposes, enabling the use of this data for development of liquid hydrogen storage vessels.

Speaker: Justin Jessop (Washington State University)

114 C1Or4A-03: Experimental study on the heat transfer coefficient in the vacuum degradation process

Process line rupture leading to pressurization of the vacuum enclosure with released gas is one of the failure cases that must to be analysed during the design of the cryogenic systems and devices. The selection of the number and size of the pressure relief devices (PRD) that protect the enclosure against excessive overpressure requires, among others, an assessment of heat transfer between enclosure and released gas. The theoretical value of the heat transfer coefficient can be estimated based on the natural convection equation including Grashof and Prandtl criteria numbers. However, in the literature there is a lack of experiments and research data presenting heat transfer processes during the loss of vacuum insulation. An experiment confirming theoretical considerations was proposed at the Wroclaw University of Science and Technology. The test stand enables measurement of the temperature profile along the enclosure pipe during vacuum degradation with liquid nitrogen, providing input data for the determination of the experimental heat transfer coefficient. This paper presents theoretical analysis, description of the test stand, procedure and preliminary results of the experiments.

Speaker: Prof. Jaroslaw Polinski (Wroclaw University of Science and Technology)

115 C1Or4A-04: Wicking dynamics of cryogenic liquids in superheated porous media

The ability of porous media to wick cryogenic liquids is critical for applications such as propellant management devices in space and so-called dry-shippers. A dry-shipper is a vacuum-insulated container lined internally with a porous material saturated with liquid nitrogen, as required by aviation safety regulations. Substantial evaporation during the absorption of cryogenic liquids significantly impacts wicking performance, necessitating a thorough understanding of this process to select suitable porous materials. Therefore, the impact of evaporation on the wicking performance of liquid nitrogen into superheated porous media is investigated, focusing on the influence of material properties, such as pore size, porosity, and specific heat capacity, as well as the thermodynamic state of the liquid.
The liquid nitrogen wicking properties of two porous samples commonly used in dry-shippers were investigated, one with relatively large pores (1–100 µm) and another with smaller pores (0.5 µm). The absorbed liquid mass was quantified by monitoring the sample weight during imbibition in a pure nitrogen environment. The experimental results closely adhered to the square root dependence predicted by the Lucas-Washburn framework. Furthermore, the liquid bath's mass was measured to determine the evaporation rate, enabling the calculation of its impact on the wicking process within the Lucas-Washburn framework. Additionally, the wicking performance of a fibrous porous material was examined. A theoretical model, incorporating the cross-sectional contact line length and a permeability model for fibrous media, provided reasonable predictions of the imbibition process, despite the absence of detailed material structure data. Notably, the material properties in the model were derived solely from fiber diameter and porosity.
Building on the experimental results and the authors' previous work, recommendations are proposed for selecting new dry-shipper materials and design considerations for cryogenic sorbents. The similarities in the influence of gravitational and viscous effects across different systems are highlighted, with particular emphasis on the analogous behavior of capillary tubes, porous media, and bonded fibrous media. These systems exhibit similar solution forms due to shared underlying physical principles. Key material properties, including porosity, wicking dynamics, equilibrium height, and residual vapor fraction, are identified as critical factors. These properties can be derived from parameters such as pore size distribution, porosity, and permeability. Furthermore, the impact of subcooling on these design considerations will be discussed.

Speaker: Rick Spijkers

116 C1Or4A-05: Lumped-element modeling of density wave oscillations in two-phase hydrogen flow

Density wave oscillations (DWO) are one of the most common instability types in flow boiling systems. In liquid hydrogen (LH2) pipe flow with heat ingress, DWO can cause large fluctuations of temperature, pressure, void fraction, and flow rate, which puts strain on the system and makes LH2 transfer processes unstable. Predicting the onset of these oscillations and the magnitudes is important for designing robust liquid hydrogen fuel lines. In this study, lumped-element modeling of density wave oscillations in two-phase hydrogen flow is undertaken to evaluate the instability threshold and limit-cycle oscillations in a single heated channel with different orientations. Nonlinear time-domain simulations and linearized stability analysis are employed. The variable parameters include initial liquid subcooling, flow rate, and heat supplied to the channel wall. Stability plots using non-dimensional groups relating these parameters and examples of stable and unstable behavior of the system will be presented. The present results can assist developers and operators of liquid hydrogen transfer systems.

Speaker: Trinity Templeton

117 C1Or4A-06: Development and validation of a vibrating-wire viscometer for liquid natural gas measurements down to 80 K

Viscosity data for natural gas mixtures in particular with helium components are insufficient in literature, which creates an obstacle to the development of a corresponding mixture viscosity model or correlation. Precise viscosity measurement of cryogenic fluids including methane, ethane and their mixtures with other rare components requires a viscometer capable of operating at high pressures up to 10 MPa and at temperatures down to 80 K. A cryogenic vibrating-wire viscometer has been designed and developed for such an application. Tungsten wire is used as the sensing element and is clamped at both ends instead of being fixed at one end but leaving the other end freely connecting to a suspended weight. Tungsten rods were chosen as the supporting structure to synergize the expansion of the Tungsten wire, which avoids creating a tension induced by a large variation of temperature. Thereby, it ensures that the resonant frequency of the wire remains nearly unchanged from 300 K to 80 K. By using nitrogen as a calibration fluid, the viscosity measurement is estimated to have an uncertainty of < 2 % in the range from 17 to 150 μPa·s. Some methane mixtures are tested in wide temperature and pressure range and their viscosity data will be reported.

Speaker: Yilun Yang (Shanghai Jiao Tong University)

C1Or4B - Large Scale Cryogenic Systems II: Operation & Design II

118 C1Or4B-01: LBNF/DUNE Liquid Argon Roadmap

The Deep Underground Neutrino Experiment (DUNE) is an international flagship venture to unlock the mysteries of neutrinos. Hosted at the Sanford Underground Research Facility (SURF) and supported by the Long-Baseline Neutrino Facility (LBNF), DUNE relies on nearly 70,000 tonnes of ultrapure liquid argon (LAr) housed in state-of-the-art cryostats. Transporting such vast quantities of LAr to its destination a mile underground in Lead, SD, is a logistical and engineering challenge. The process begins with securing large quantities of liquid argon from suppliers located far from the site, with major sources situated near Houston, TX and Chicago, IL. The receiving facility, located atop a mountain with steep, often snow-covered access roads, provides limited maneuverability for trucks and can only handle two deliveries simultaneously. The facility serves as an entry point for argon to the greater LBNF cryogenic system. It is furnished with truck unloading stations, limited buffer storage of some 260 tonnes capacity, and vaporizers. The last are crucial for converting liquid argon into gas for transfer down the Ross Shaft, eliminating the need for cryogens in the vertical pipeline. These constraints, along with other operational factors, cap the delivery rate at 70 tonnes per day. Once underground, the argon is purified and recondensed before filling the cryostats. This roadmap outlines the integrated supply chain and cryogenic systems that enable the delivery of LAr to support DUNE's groundbreaking physics research.

Speaker: Matt Maciazka (Fermi National Accelerator Lab. (US))

119 C1Or4B-02: Overview and status of the Long-Baseline Neutrino Facility Far Detectors cryogenics system

The Sanford Underground Research Facility (SURF) will host the Far Detectors of the Deep Underground Neutrino Experiment (DUNE), an international multi-kiloton Long-Baseline neutrino experiment that will be installed about a mile underground in Lead, SD. Detectors will be located inside four cryostats filled with almost 70,000 metric tons of ultrapure liquid argon, with a level of impurities lower than 100 parts per trillion of oxygen equivalent. The cryogenics infrastructure supporting this experiment is provided by the Long-Baseline Neutrino Facility (LBNF). An international engineering team is designing these systems and will manufacture, install, test, commission, and qualify them. This contribution presents the status of the design and procurement of the various systems, along with present and future functional and performance requirements to support the DUNE experiment. It also presents modes of operation, layout and main features of the LBNF Far Detectors cryogenics system, which is composed of the following subsystems: argon receiving facilities, nitrogen refrigeration system, argon distribution system, argon purification and regeneration systems, argon circulation system, argon condensers system, internal cryogenics, miscellaneous items, and process controls.

Speaker: David Montanari (Fermi National Accelerator Lab. (US))

120 C1Or4B-03: The Cryogenic System for the Mainz Energy-recovering Superconducting Accelerator (MESA)

The Mainz Energy-recovering Superconducting Accelerator (MESA) is an electron accelerator currently under construction at the Institute of Nuclear Physics, Johannes Gutenberg University Mainz, Germany. MESA is designed as a superconducting multi-turn energy recovery linac (ERL) to provide high-intensity, low-energy electron beams for precision electron scattering experiments testing the limits of the Standard Model of particle physics.

The accelerator incorporates several cryogenic components, each with specific cooling requirements. Particle acceleration is achieved through two superconducting radiofrequency (SRF) cryomodules, utilizing XFEL/TESLA-type cavities at 1.3 GHz, which must be cooled to 1.8 K. This requires up to 8 g/s of helium at 16 mbar. Additionally, the P2 experiment requires cooling a superconducting solenoid to 4 K and liquefying hydrogen in the target at 15 K, with 4 kW of cooling power supplied by the helium circuit. Both the solenoid and cryomodules are thermally shielded using liquid nitrogen. A cryogenic system was designed to provide and distribute helium and nitrogen throughout the accelerator.

The refrigerators are placed in a surface building, while the accelerator is placed in an underground area 10m below surface. Multiple (multi) transfer lines are connecting the surface equipment to the underground equipment. The cryogenic system consists further of three distribution valve boxes, a sub-atmospheric electric heater and an sub-atmospheric compressor to feed the 16mbar helium back into the compressor circuit of the liquefier.

To meet these demands, the existing helium liquefier was upgraded to provide the required liquid helium mass flow and manage potential impurities introduced through the 16 mbar pressure system. A refrigerator with 4 kW cooling power at 15 K was installed for the P2 target cooling.

Currently, the most complex components like the liquefier, the refrigerator and the cryomodules and parts of the transferlines are already installed and commissioned, while other components are still in manufacturing stage. The commissioning of the cryogenic system is planned in mid-2025.

This paper introduces shortly the MESA accelerator and discusses the design and current status of the MESA cryogenic system, focusing on key components such as the cryomodules, the P2 experiment, valve boxes, transfer lines, and the 16 mbar pumping system.

Speakers: Hendrie Derking (Cryoworld BV), Timo Stengler (Johannes Gutenberg-Universität Mainz)

121 C1Or4B-04: Design status of the second target station cryogenic moderator system

The Second Target Station (STS) at Oak Ridge National Laboratory will be a 700 kW pulsed spallation neutron source optimized to deliver 18 high brightness cold neutron beams. To supply the optimum neutron performance, two compact liquid hydrogen moderators are located in the peak neutron production zones, immediately above and below the rotating tungsten spallation target, resulting in a nuclear heat load of over 400 W in each moderator. To simplify the Cryogenic Moderator System (CMS), the hydrogen loop will supply the two moderators in series with less than 20 K and greater than 99.8% para hydrogen fraction hydrogen at a constant flowrate of 0.5 L/s. A total nuclear heat load of up to 850 W will be removed while providing required hydrogen temperature, density, and spin state to maximize neutron performance. The hydrogen loop consists of a hydrogen circulator, a helium hydrogen heat exchanger, ortho-para converter, accumulator, transfer lines, and the two moderators. The hydrogen loop will operate with a minimum pressure of 14 bara, just above the critical pressure, in order to reduce instabilities during system cool down and to provide margin against loss of density in recirculation zones in the moderators. The accumulator, which consists of a gaseous helium volume surrounded by the flowing hydrogen but separated by a bellows, allows thermal and pressure equilibrium between the hydrogen and helium volume. The coupling of the hydrogen and the helium volume allows the hydrogen loop to run in a constant pressure mode, where volumetric changes of the liquid hydrogen driven by beam transients are compensated by small changes to the hydrogen and corresponding helium volume temperature in the accumulator, providing system stability through beam transients which can rapidly vary the nuclear heat load. The ortho-para converter counteracts the radiation driven back-conversion of para to ortho hydrogen in the moderators by driving the moderator supply parahydrogen concentration to near equilibrium as required for optimal neutron performance. Both the required performance of the ortho-para converter and the ortho-para diagnostics, monitoring the parahydrogen fraction, have been demonstrated as part of the recent upgrades provided by the Proton Power Upgrade at the Spallation Neutron Source. The STS CMS design is maturing rapidly, and system requirements are being verified in order to demonstrate system performance.

Speaker: Jim Janney

122 C1Or4B-05: LCLS-II HE Cryogenic Distribution System Status

LCLS-II HE project will increase the energy of the CW-SCRF linac from 4 to 8 GeV, enabling the photon energy range to be extended to at least 13 keV and potentially up to 20 keV at 1 MHz repetition rates. HE’s Cryogenic Distribution System (CDS) will connect existing Cryoplant 1&2 to 23 new HE cryomodules. Reference designs have been completed for all components. Current status of the CDS will be discussed as well as challenges and lessons learned.

Speaker: Renzhuo Wang (SLAC National Accelerator Laboratory)

123 C1Or4B-06: Design, fabrication and installation of the refurbished K500 cyclotron cryogenic distribution system for MSU chip testing facility

Michigan State University (MSU) has refurbished the superconducting K500 cyclotron and installed it as the heart of a new semiconductor / electronic chip testing facility at the Facility for Rare Isotope Beams (FRIB). The K500 cyclotron used to be a part of the Coupled Cyclotron Facility (CCF) at MSU but was decommissioned in 2020 following the reconfiguration of the beamlines for the FRIB LINAC. The K500 cyclotron consists of a superconducting solenoid and several cryo-panels (independently maintained at 4.5 K and 80 K). The refurbishment of this cyclotron required a completely new cryogenic distribution system incorporating several different modes of operation for the solenoid and the cryo-panels to satisfy the testing requirements. The cryogenic distribution has been designed using the same operational concept used for the FRIB experimental system cryogenic distribution system – which has separate lines for cool-down and 4.5 K operation. This provides flexibility for commissioning, different modes of operation, and maintenance of the K500 cyclotron without affecting other cryogenic loads on the refrigerator. The refurbishment, associated additions and modifications of a legacy system to fit new requirements presented several design challenges which were resolved during the concept design phase. Design, fabrication, and installation of all the elements of the cryogenic distribution system were carried out in-house at FRIB. This paper presents an overview of the process design, analysis, fabrication, and installation of the refurbished K500 cyclotron cryogenic distribution system.

Speaker: Mathew Wright (Michigan State University)

124 C1Or4B-07: 2 Kelvin helium distribution system for the Electron Ion Collider’s 10 o’clock satellite refrigerator

The Electron-Ion Collider (EIC) at Brookhaven National Laboratory (BNL) will involve superfluid helium cooling of superconducting magnets and Superconducting Radio Frequency (SRF) cavities at several sites around the existing Relativistic Heavy Ion Collider (RHIC) accelerator tunnel. While the majority of the cooling power for these loads is provided by BNL’s central cryogenic plant, Jefferson Lab is designing satellite equipment which augments the central plant and enables 2 Kelvin operation. The 2K cryogenic distribution system for the collider’s 10 o’clock location (Interaction Region 10 or IR10) includes all necessary interfaces to the IR10 Satellite Refrigerator, to the overall EIC cryogenic distribution system, and to as many as 22 SRF cryomodules for the electron and hadron storage rings. In addition to providing the required cooling capacities in all operating modes, the IR10 2K cryogenic distribution system also stabilizes the supply temperature and enables safe connection and disconnection of individual IR10 cryomodules. Moreover, the layout of the IR10 2K cryogenic distribution system copes with challenging spatial constraints and adapts to the process configuration and routing of existing RHIC cryogenic distribution components which will be re-used for EIC. This paper gives a full overview of the IR10 satellite cryogenic distribution system design, and highlights some of the challenges encountered.

Speakers: A. Rizzato (Thomas Jefferson National accelerator facility), N. Laverdure (Thomas Jefferson National accelerator facility)

125 C1Or4B-08: Progress on design and construction of a new Helium liquefaction system at LBL

A new helium liquefaction system with high capacity is under design and will be built at the Lawrence Berkeley National Laboratory (LBL) in the next couple of years to replace a 43 years old liquefier. The new liquefaction system will provide at least a mixed 80 liter per hour liquefaction rate and 35 W refrigeration capacity at 4.5K without liquid nitrogen pre-cooling, or a mixed 140 liter per hour liquefaction rate and 35 W refrigeration capacity at 4.5 K with liquid nitrogen pre-cooling. As a core element, the new liquefaction system will significantly improve the capability and efficiency of the magnet testing system at LBL in developing and testing novel magnet configurations. The system is designed and built with the capability to be further expanded to 1.8 K to 2 K by adopting a warm pumping system, as well as to furthermore enable future integration of helium recovery and purification capability. It can be operated as a liquefier to produce liquid helium to the users at the LBL, UCB (University of California Berkeley), or other institutes and labs. It can be operated to provide both liquid helium and refrigeration for superconducting magnet testing. It can run at various operating modes. This paper describes the recent progress of design and construction of the new LBL’s liquefaction system.

Speaker: Dr Li Wang (Lawrence Berkeley National Lab)

C1Or4C - Liquid Hydrogen Storage

126 C1Or4C-01: Validating a thermodynamic model for self-pressurization in liquid hydrogen tanks using novel tank trailer data

To ensure the safe and efficient operation of the liquid hydrogen (LH2) infrastructure, it is crucial to understand the thermodynamic processes in LH2 tanks. All LH2 tanks, both stationary tanks and tank trailers, experience pressurization due to heat inleak through their thermal insulation. The self pressurization rate over time is important for safe operation, but the complex thermodynamic phenomena involved make it challenging to develop an accurate, universally applicable model. A variety of models for this phenomenon is proposed in the literature, but only a very limited amount of experimental data, mostly from stationary LH2 tanks, is published. So far, validated models for these stationary LH2 tanks are usually based on correlations or correction factors for the heat transfer or phase transition at both the liquid-gas interface and between the tank wall and the fluid.

In this work, novel experimental data of the self-pressurization of LH2 trailers in operation is presented. The unique benefit of this pressure data arises from the fact that the phases in the LH2 trailer can be either in equilibrium, when the trailer is on the road and the phases are mixed due to the dynamic movements, or in non-equilibrium, when the trailer is parked. This allows a direct calculation of the heat inleak through the insulation, limiting the need for approximations via correlations or correction factors solely to the heat transfer and phase transition at the liquid-gas interface.

A thermodynamic model is presented in this study, based on a lumped-element method. The thermodynamic model is then validated against the novel data of the self-pressurization of LH2 trailers. The resulting validated thermodynamic model targets to be universally applicable. Together with the presented novel data from LH2 trailers in operation, the results and insights of this work support the development of accurate models of the processes in LH2 tanks required for an efficient future LH2 infrastructure.

Speaker: Mr Christian Wolf (Technical University of Munich, TUM School of Engineering and Design, Department of Energy and Process Engineering, Institute of Plant and Process Technology, Garching/Germany; Linde GmbH, Clean Energy Technologies R&D, Pullach/Germany)

127 C1Or4C-02: Comparison of liquid hydrogen tank performance at different storage pressures and operational scenarios using a reduced-order model

Liquid hydrogen storage is accompanied by boil-off losses as heat leak penetrates the tank. However, these losses are also affected by tank operational scenarios which have been relatively unconsidered in the literature. To address this need, a reduced-order model capable of analyzing different operational scenarios was developed. Using this model, the present study investigates the effects of storage pressure in vertical and horizontal storage tanks on the average daily boil-off losses. Parametric studies are conducted using the dimensions of the Integrated Refrigeration and Storage (IRAS) system tank with varied venting pressure, fill level, and initial temperature of the liquid in the tank. The results indicate that storing saturated liquid hydrogen at lower pressures with no liquid extraction from the tank in steady-state cyclic venting results in lower daily losses. The initial temperature of the liquid in the tank also plays a key role in selecting a storage pressure for a tank. With no liquid subcooling, lower storage pressures are desirable but with 1K subcooled liquid higher storage pressures with larger fill levels result in lower losses. The resulting model is a useful tool for analyzing different liquid hydrogen tank operational scenarios.

Speaker: Kyle Appel (Washington State University)

128 C1Or4C-03: On the Thermodynamic Boundaries of Cryogenic Liquid Storage in Closed Containers

The self-pressurization behaviour of a cryogenic liquid due to the inevitable heat inleak into a closed cryogenic storage system is of great importance for the design of such a storage vessel. In recent years, the resurgence of cryogenic liquid hydrogen as a fuel in future sustainable transportation and logistics sparked new interest in this field of research. The cryogenic fuel tank represents the core of these liquid hydrogen applications. It is the goal to store as much total hydrogen mass for as long as possible and, most importantly, loss-free. Key design parameters of such a tank are therefore the so called dormancy time and the pressure increase rate. It is already known that the geometry and the heat inleak distribution play an important role in the self-pressurization behaviour of a closed cryogenic system. We want to expand on this idea and study the underlying thermodynamic changes of state resulting in two theoretical boundary cases: One process that gives a maximum dormancy time (minimum pressure increase rate) and another process that gives minimum dormancy time (maximum pressure increase rate). With this, we want to capture the notion of non-uniformly distributed heat being the most significant influencing factor on the self-pressurization behaviour of closed cryogenic liquid storage systems. These theoretical boundary cases give the opportunity to quantify the quality of actual cryogenic storage vessels and to consider the maldistribution of heat on a more abstract level. This theoretical analysis could support future design choices of cryogenic liquid storage systems.

Speaker: Thomas Just (Technische Universität Dresden)

129 C1Or4C-04: Towards Economic Zero Boil-Off Technology for Liquid Hydrogen Storage

Hydrogen is increasingly recognized as a cornerstone of the transition to sustainable energy systems. Storing hydrogen in liquefied form (LH₂) is particularly advantageous due to its relatively high energy density and scalability for storage and transport. However, managing boil-off rates (BOR) during storage and transportation remains a significant challenge. Hydrogen boil-off leads to safety concerns, environmental impacts, and economic losses, highlighting the critical need for zero boil-off (ZBO) systems. Depending on the size and application, the BOR ranges from 0.05–0.2% per day for large-scale, stationary, spherical storage tanks (>500 m³) to 0.3–1% per day for stationary cylindrical vessels (1–100 m³), and even up to 1.5% per day for 0.1 m³ tanks typically used in mobile applications.

Advances in passive insulation technologies, such as vacuum-insulated multi-layer insulation (MLI) and variable density MLI (VDMLI), have shown potential to reduce BOR further compared to conventional vacuum-perlite. However, passive measures alone are insufficient due to the high liquefaction energy costs (~30% of hydrogen’s energy capacity) of LH2. This underscores the need for active cooling systems to achieve ZBO in LH₂ storage and transport applications. While existing ZBO systems in aerospace demonstrate feasibility, their high energy requirements and costs limit large-scale industrial deployment.

An in-depth review of the current state of LH₂ storage technologies was conducted, focusing on BOR mitigation strategies and their limitations. A framework for the design and development of economic ZBO systems is proposed, with an emphasis on bridging the gap between laboratory-scale solutions and practical implementation. This work is part of the HyTROS program under the Dutch GroenvermogenNL initiative to advance hydrogen storage and transport technologies.

Speaker: Harro Beens

130 C1Or4C-05: Development of novel non-vacuum insulation system for large-scale liquid hydrogen storage applications

Developing advanced infrastructure components, including Liquid Hydrogen (LH2) storage tank, is crucial to LH2 supply chain pathway development for maritime & international trade applications. Because of extreme cryogenic temperatures of LH2 at 20 K, the storage tank needs to be well insulated to minimize the boil off rate (BOR). While high vacuum insulation technology is commonly used for LH2 storage systems today, it is non-practical for large tanks given the high CAPEX of the storage tank with double wall steel and excessive amounts of time required to draw the vacuum to the necessary level. Alternatively, for nonvacuum insulation systems, one of the major challenges is the runaway cryopumping effect. This phenomenon is developed as air gases such as O2 and N2 will condense and freeze at the cold boundary temperature. The low pressure created drives more gases to the cold face, while the liquified gases flows under gravity to the warm side of the insulation, where it re-vaporizes and flows back towards the cold side of the insulation. This phenomenon results in loss of insulation capabilities due to the involved heat transfer operation. In addition, the scale-up of the tank possess other technical challenges such as selection of right insulating material, determination of insulation properties at cryogenic conditions, long term mechanical integrity of the tank, which must be resolved for a technical and economically feasible design.
For our DOE sponsored project (DE-EE0009387), Shell partnered with CB&I, NASA Kennedy Space Center, GenH2 and the University of Houston to develop a low-cost, large-scale LH2 storage tank design for maritime & international trade applications. Target design is based on present day commercial LNG tanks from 20,000 m3 to 100,000 m3 with target BOR of 0.1%/day. Through 3-year R&D, the project team has developed a first-of-its-kind design using a non-vacuum insulation concept based on polymeric materials with significant cost savings compared to currently used vacuum insulation system. Though polymeric insulation was applied as a thin layer on the LH2 tanks of rockets for space application, Currently, no commercially available polymeric insulation material has been applied for long-term LH2 storage. During this presentation, we will provide an overview of the project with the focus on the development of insulation concept and the derisking process by modeling and experiments. The proof of concept will be demonstrated by the demo tank constructed at NASA MSFC (Marshall Space Flight Center). The significance and application of this project will be summarized at the end.

Speakers: Kun Zhang (Shell), Neeharika Rajagiri (Shell)

131 C1Or4C-06: Thermal and Structural Modification to Repurpose Existing Full Containment (FCT) Liquified Natural Gas (LNG) Tanks for Liquid Hydrogen (LH2) Storage

In 2023, the global LNG industry's operational mandate reached a record high of 404 Million Metric Tonnes (MMT). In contrast, the long-term sustainability of LNG as a primary fuel is declining, particularly in view of the carbon-neutral objectives established for 2050. The proposed decarbonisation objectives for 2050, would render many re-gasification and liquefaction facilities at numerous LNG terminals obsolete. The storage tanks are the most expensive component of these LNG terminals, accounting for approximately 50% of the terminal capital cost. These LNG terminals contain FCTs with capacities of up to 200,000 m3. The potential to adapt these LNG storages to accommodate liquid hydrogen (LH2) has been recognised as a viable alternative, as the hydrogen demand is anticipated to reach 550 MMT by 2050, where LH2 will constitute a substantial portion of the anticipated demand.

In this study two distinct aspects were analysed to evaluate the efficacy of the proposed solution: the structural evaluation, which evaluated the tank's performance in static and dynamic stress conditions, and the thermal evaluation, which assessed the potential for heat in leak due to inadequacy of existing insulation. For the structural evaluation, a comprehensive design of a typical 200,000 m3 LNG FCT was conducted, and its static and seismic performance was analysed using Finite Element Modelling (FEM) and numerical analyses for both LNG and LH2 fills. The performance of the inner chamber against liquid sloshing and buckling and both inner and outer chamber against lateral deformation and base shear were evaluated following the full containment design philosophy. Additionally, the evaluation included the introduction of a new inner containment stainless steel layer held in place by thermally intercepted supports, which serves as the LH2 container in the converted storage system, due to the fact that the current inner chamber materials in the LNG storage tanks are not capable of performing well below -200 C.

Considering the thermal analysis, preliminary finite element modelling showed that the exterior prestressed concrete section in the tank shell, bottom and dome is not exposed to significant thermal stress switching from LNG to LH2 filled cases. Hence, this analysis focused on improving insulation space between the inner tank and the outer concrete section for both the shell and the bottom, with two different insulation arrangements. In the initial arrangement, vacuum insulation was incorporated with an intermediate fill agent to achieve a rough vacuum (0.1 bar – 1 bar). The boiloff rate was considerably reduced as a result. However, the second insulation arrangement assessed the potential for achieving similar insulation effectiveness with passive insulation materials, given the challenge of establishing vacuum insulation for the 200,000 m3 storage scale. This assessment primarily included Glass wool, Perlite, Cellular glass, Aerogel, Glass bubbles, and Aerogel blankets and powders in three-layer, four-layer, and five-layer configurations. The most optimal configuration was determined by calculating the heat flux and associated boiloff rates using FEMs and a unique dynamic boiloff model based on a superheated vapour model between the boiloff gas and the liquid, which accounted for the temperature difference between the two mediums. Furthermore, the model evaluated and optimised the overall tank insulation performance as the material loss by regulating thermal inleak from the roof by placing different insulations on the suspended aluminium deck as well.

This analysis facilitated the development of a viable solution for establishing large-scale LH2 storage, wherein the suggested conversion costs would constitute a fraction of the capital expenditure required for new LH2 storage while fully leveraging the strategic positions of LNG terminals. Further, the recommended retrofitting components from this research enable the incorporation into new and continuing LNG tank builds, making future conversions more feasible.

Speakers: Shanaka Kristombu Baduge (The University of Melbourne), Amila Premakumara (Graduate researcher)

132 C1Or4C-07: Experimental Study on Thermodynamic Performance and Lossless Storage of a Vehicle-Mounted Horizontal LH2 Tank

Liquid hydrogen (LH2) storage offers significant advantages in storage density and operating pressure, showing promising prospects for mobile applications. However, experimental studies on tank internal thermodynamics typically involve smaller tank sizes and primarily focus on vertical tanks. Detailed studies of horizontal tanks, which are more suitable for vehicle applications, are limited, particularly regarding experimental data under actual operating conditions.

This study presents experimental results from a 500L vehicle-mounted horizontal liquid hydrogen storage tank equipped with a vapor-cooling-shield (VCS) and lossless storage capabilities.

Temperature and pressure measurements were conducted using calibrated Pt-1000 and Pt-100 sensors strategically placed throughout the tank. Results show that the average daily boil-off rate with VCS operation is approximately 5.62%, compared to 7.35% without VCS, indicating that the VCS improves efficiency by approximately 23.54%.  During steady-state evaporation, significant thermal stratification was observed in the vapor phase, while the liquid phase showed minimal stratification. Temperature sensors demonstrated potential for supplementary liquid level measurement, as they clearly detected stratification when liquid levels dropped below sensor positions.

The self-pressurization tests revealed that the lossless storage cycle durations gradually decreased before stabilizing, with four consecutive cycles lasting 16.23h, 13.18h, 10.83h, and 10.34h respectively. Liquid level and temperature sensor data indicate that during self-pressurization, the evaporation of liquid hydrogen may be suppressed. Therefore, thermal stratification in the vapor phase is likely a significant factor contributing to the increase in self-pressurization rates.

Liquid hydrogen storage's active cooling technology holds promise for addressing irreversible hydrogen evaporation and achieving true lossless storage. For lossless storage, the system employed two cryogenic refrigerators. The evaporated hydrogen gas was condensed in a cold box after passing through the vapor cooling screen, demonstrating an intermittent gravity-driven liquid hydrogen self-circulation process with a period of approximately 7.45 minutes. The pressure reduction from the rated pressure to atmospheric pressure demonstrated the successful implementation of lossless storage. This achievement provides valuable insights for long-term LH2 storage solutions by effectively minimizing evaporation while maintaining stable storage conditions.

These comprehensive findings not only provide essential experimental data for horizontal LH2 storage tanks and offer insights for optimizing pressure management strategies in vehicle applications, but also serve as valuable reference for the design of lossless storage systems intended for long-term storage applications.

Speaker: Chuancong Wan (Zhejiang University)

M1Or4A - [Special Session] Transportation I: Government Agencies & Industry Partners

133 M1Or4A-01: [Invited] 30 + years of Development of SC-cryo at ARPA-E

Speaker: TBD

134 M1Or4A-02: [Invited] Updates on DOE Hydrogen program

Speaker: TBD

135 M1Or4A-03: [Invited] An overview of the challenges and opportunities for liquid hydrogen aircraft development from a UK perspective

In 2022 the Aerospace Technology Institute (ATI) published the findings of the FlyZero project, which concluded that liquid hydrogen (LH2) is the most viable zero-carbon emission fuel with the potential to scale to larger aircraft. At the same time, the ATI published the UK aerospace technology strategy, Destination Zero, highlighting LH2 aircraft as one of the key pathways to enable the aircraft fleet to transition towards net zero.

Amongst the reports published, FlyZero identified several gaps and opportunities for LH2 aircraft development. The ATI Programme has funded many projects working to develop LH2 technologies to support the next generation of zero-carbon aircraft, however, there are still several unique underpinning gaps that are limiting the pace of this development.

The Hydrogen Capability Network (HCN) was launched in April 2023 with support from the UK Government's Department for Business and Trade, to progress key recommendations from FlyZero which will enable the aerospace sector to deliver liquid hydrogen research & development (R&D) at pace to meet net zero targets.

The HCN has worked with sector stakeholders across industry and research organisations, to identify the current critical gaps across the LH2 landscape. Three areas were identified; test and demonstration infrastructure, fundamental & basic research, and training & skills. The HCN have carried out studies to identify the global landscape in each of these areas to understand where there are opportunities for collaboration and which gaps are the priorities for further development.

This talk will highlight the critical gaps and steps the HCN is taking to try and drive collaboration to try and address them. Given the limited and dispersed existing expertise, it is important to bring the community together to share knowledge and tackle the priority research topics in an open and collaborative environment, reducing repetition and enabling fastest progress.

Speaker: Mr Huw Edwards (Aerospace Technology Institute)

136 M1Or4A-04: [Invited] Non-functional superconducting system requirements in a marine environment

The US Navy has been investing in superconducting and cryogenic technology since the 1940’s when the Navy Research Lab published its first scientific article on the subject. Since then the Office of Naval Research and the Naval Sea Systems Command have worked towards developing applications of the technology including motors, generators, cables, and magnets. When designing such complex systems, a set of specifications and requirements are the basis for meeting performance metrics. For example, a ship propulsion motor must provide a certain level of power to provide enough speed for the ship. Therefore, the motor must operate at the required torque and speed to generate this power. A motor design engineer is able to calculate these requirements, and a test engineer is able to measure these requirements. Quantifiable requirements may be considered as functional since they are necessary to meet a goal. Non-functional requirements are also important when designing superconducting systems for use in military applications, specifically in the marine environment. These non-functional requirements may include quality attributes of affordability, availability, reliability, sustainability, resiliency, and upgradeability to name a few. As the US Navy starts to adopt superconducting and cryogenic technology for use in the Fleet these non-functional requirements become more important to ensure safe and continuous operation of its ships and sailors. It is the responsibility of the engineers and researchers working on new applications to ensure these aspects of a system are considered along the way. Therefore, the goal of presenting these concepts is to make the superconducting and cryogenic community at large aware of these additional non-functional requirements that must be included for the US Navy to embrace the technology.

Speaker: Peter Ferrara (Naval Surface Warfare Center, Philadelphia Division)

137 M1Or4A-05: [Invited] Advanced Cryogenic Cooling Concepts for Superconducting Technologies on Electric Transport Platforms

There is growing interest in superconducting technologies for large electric transport platforms such as electric aircraft and ships to eliminate greenhouse gas emissions from the transportation sector. Superconducting technologies have high efficiency and power density, which are necessary to achieve the electrification of large transport platforms. Liquid hydrogen (LH2) fueled platforms offer the synergy to reduce the complexity of superconducting technologies by using the liquid fuel at 20 K as a cryogenic heat sink. Many government-funded research programs and the efforts by aircraft manufacturers are developing technology components necessary to realize the dream of zero-emission aircraft and ships. Significant investments are also being made to establish LH2 production, storage, and distribution infrastructure. High power density propulsion motors, generators, and power distribution systems are under development. It has been recognized that thermal management, electrical insulation, and safety are critical to success with LH2-fueled electric aircraft. Fuel cells and hydrogen-burning generators are options for electrical power generation using hydrogen. The low efficiency of fuel cells represents significant thermal loads that are difficult to manage on an aircraft or ship. The low volumetric energy density of LH2 coupled with limited space available for fuel storage requires that the thermal loads be curtailed to the levels supported by the mass of LH2 necessary for fuel needs.
The paper will briefly review various research and development efforts on electric ships and aircraft. It will discuss the absence of comprehensive research facilities required to develop the technologies, the need for broad collaborations and joint developments to quickly design and validate initial design options, and build and test prototype propulsion, power distribution, and cryogenic systems, and international efforts to establish such regional technology support centers.
The Center for Advanced Power Systems (CAPS) and the FAMU-FSU College of Engineering have established testbeds for high temperature superconducting (HTS) power distribution systems, cryogenic electrical insulation systems, cryogenic fluid circulation systems, advanced AC loss measurement systems at LH2 temperature relevant to developing electric aircraft and ships. The paper will describe the facilities and examples of collaborative development efforts. The paper will discuss the facilities, ongoing research, and opportunities for collaboration.
The paper will briefly discuss the R&D efforts of the NASA-funded University Leadership Initiative project, Integrated Zero-Emission Aviation (IZEA), in superconducting technologies and cryogenic thermal management.

Speaker: Sastry Pamidi (FAMU-FSU College of Engineering & The Center for Advanced Power Systems)

138 M1Or4A-06: [Invited] Impacts of Liquified-Petroleum-Gas (LPG) and Liquid-H2 Cryogenic Fuels to improve the Performance and Thermal Management of Aerospace Vehicles

Alternative families of propulsion fuels such as hydrogen, the liquified-petroleum-gas (LPG) family (methane, ethane, propane, butane, other), alcohols of hydrocarbons (methanol, ethanol, propanol, other), natural gas, biofuels, and other, are increasingly being considered for transportation industries and applications, including shipping, aerospace and rocket propulsion. And the cryo-cooled versions of these fuels are being studied for transportation, since their higher volume densities critically affect cost, viability and performance benefits. The use of liquified-natural-gas (LNG) or bio-LNG with (~ > 98% methane content) has strong benefits for transportation, including ~ 30 % higher energy-per-mass, greatly reducing thermal-management-system (TMS) hardware needed with direct cooling, lower average cost, very high domestic reserves, and broadly located production and distribution piping networks. However, LNG has the drawback of ~ 40 % lower volume density than petrol or kerosene fuels including JP8. The family of LPG gases other than methane (bio-LNG) have relatively unknown properties of similar benefits to methane of ~ 25-30 % higher energy density than JP8, however without the drawbacks of lower volume density that methane has.
This talk will be present about general properties of alternate families of cryogenic fuels, and the benefits for performance and thermal management focusing mostly on aerospace applications. Relatively unknown fuels and properties will be presented, such as liquid mixtures that have freezing points as low as ~ 63K, that can enable significantly higher power density and more efficient cryogenic power electronics using ultra-pure metals and superconductors. Cryogenic fuels also have important system benefits to provide much larger lift capacities even ~ 4-100 x than JP8, which will be important to address the increasingly larger and low-temperature thermal loads resulting from increasing electrification of propulsion.
Acknowledgments. Support by the Air Force Office of Scientific Research (AFOSR) awards LRIR # 18RQCOR100, LRIR #23RQCOR008, LRIR #24RQCOR004, the Aerospace Systems Directorate (AFRL/RQ), and ARPA-E ASCEND Award # DE-AR0001355.

Speaker: Timothy Haugan

M1Or4B - Insulation & Impregnation Materials: Polymeric Materials

139 M1Or4B-01: [Invited] Thermal Conductivity of Polymer Aerogels at Different Vacuum Levels for Cryogenic Insulation Applications

Effective management of the heat transfer into cryogenic piping and storage reservoirs is accomplished with low thermal conductivity insulation systems. Polymer aerogels are renowned for their low density, high mesoporosity, high internal surface area, low thermal conductivity, mechanically robust structural integrity, and high acoustic impedance. These unique properties present in one material envelope result in an advanced, multi-functional technology ideally suited for space applications. This study focuses on polymeric aerogels fabricated in various structural dimensions while maintaining low thermal conductivity over a wide temperature range, with a focus on cryogenic temperature environments. To measure the thermal conductivity, a NASA Cryostat-400 flat plate comparative boiloff calorimeter is used to measure the thermal conductivity of these materials at residual gas pressures ranging from high vacuum, soft vacuum, and atmospheric pressure. The calorimeter uses the boiloff of liquid nitrogen to measure the heat transfer through the insulation sample. Measurements of thermal conductivity will be between a cold boundary temperature maintained by the liquid nitrogen (80 K) and hot temperature boundary which was at room temperature (290 K). A pressure control system is used to maintain vacuum pressure in the cryostat at different levels using nitrogen as the residual gas. For better understanding of the heat transfer measurement, a numerical model of the system was developed in Python. This model is used to estimate heat flow across the sample to validate the one-dimensional heat flow used for determining thermal conductivity.

Speaker: Ryan Ehresman (LeTourneau University)

140 M1Or4B-02: Dynamic Thermal Conductivity of Polyimide Aerogels at Cryogenic Temperatures

Aerogels are suitable for use as a thermal insulation material in both evacuated and non-evacuated applications at cryogenic and room temperatures. Polymer aerogels, in particular, exhibit thermal insulation properties similar to other types of aerogels while offering polymer-based structural integrity and toughness, vital for cryogenic insulation requirements. Among all polymer aerogels, polyimide aerogels stand out due to their exceptional onset decomposition temperature and environmental resilience. Here in this study, various polyimide aerogels with distinct chemical compositions were investigated. Their dynamic thermal conductivities were measured using transient plane source method at room temperature. Finally, the optimized polyimide aerogel materials were characterized by measuring their dynamic thermal conductivities at liquid nitrogen cryogenic conditions. This investigation aims to identify the most suitable polyimide aerogels for critical cryogenic insulation applications, including those pertaining to cryogenic tank insulation.

Speaker: Sadeq Malakooti (NASA Glenn Research Center)

141 M1Or4B-03: [Invited] Quantifying the relation between strain energy release rate and heat generated in the CTD-101K epoxy resin magnet impregnant at cryogenic temperatures

Accelerator magnets based on Nb3Sn superconductor are often prone to severe training. Previous works in literature found that stored strain energy in the coil’s impregnant, usually epoxy resin, is released as heat during cracking, debonding and subsequent friction. This heat affects locally the temperature margin of Nb3Sn eventually leading to a quench, and it can contribute to elongated magnet training. However, the relation between the mechanical strain energy release rate of the magnet impregnant and thermal heat generation during cracking at cryogenic temperatures is not well known and it is investigated in this study.
To quantify this relation, a compact tension double cantilever beam (CT-DCB) type of experiment at 77 K was chosen. This type of mechanical experiment allows to measure the strain energy release rate from the load-displacement curve for a certain initial crack under cryogenic conditions. The CT-DCB sample is made of CTD-101K, a typical epoxy magnet impregnant these days often used in accelerator magnets. It is further prepared to mimic cracks in the impregnant near the Nb3Sn wire in the coil windings. Therefore, a copper tube insulated with S-2 fiberglass mimicking the Nb3Sn wire is embedded in the CT-DCB sample. After fracture, a deposited thermal energy of 100 +/- 10 J/m2 was measured with a thermocouple positioned inside the copper tube. This energy matches closely half the strain energy release rate measured to be at the level of 220 +/- 20 J/m2. The latter is a value reported in literature. This let us to believe that the mechanical strain energy is almost integrally converted into thermal energy on the two fracture surfaces.
In combination with a descriptive model for the minimum quench energy of the Nb3Sn superconductor, this experimental result can help to better understand and quantify the relation between the locally stored strain energy in the impregnant and causes of training in Nb3Sn magnets.

Speaker: Prof. Herman ten kate (University of Twente)

142 M1Or4B-04: Study on the Feasibility of Using TELENE® Resin for HTS Superconducting Magnets

By using TELENE® resin as superconducting magnet impregnation material, training and magnet retraining after a thermal cycle were nearly eliminated in Nb3Sn undulators and NbTi accelerator magnets. We herein perform a study on how effective TELENE is in preventing quenches also in HTS magnets, without damaging the superconductor. This study encompasses measurements of transport current, minimal quench energy (MQE) and mechanical properties of wires and cable stacks at nitrogen temperature. The critical current and the MQE of REBCO tapes was measured for bare samples, and samples impregnated with different TELENE resins and epoxies, including 2850 STYCAST and CTD-101K. The critical current of REBCO cables of various geometries was measured using a superconducting transformer. The mechanical properties were measured for both REBCO and Bi-2212 cable stacks impregnated with TELENE resins.

Speaker: Daniele Turrioni

143 M1Or4B-05: Elimination of Training in Nb3Sn and NbTi Superconducting Magnets

By using TELENE® resin as superconducting magnet impregnation material, training and magnet retraining after a thermal cycle were nearly eliminated in Nb3Sn undulators. This allows reducing operation margins in light sources, and increasing the on-axis magnetic field, thereby expanding energy range and brightness intensity. TELENE is Co-60 gamma radiation resistant up to 7-8 MGy, and therefore already applicable to impregnate planar, helical and universal devices operating in lower radiation environments than high energy colliders. Radiation resistance further increases in TELENE when mixed with high-Cp and/or high-thermal conductivity powders. We herein show that when combined with the ductility and toughness properties of TELENE, these resins display superior training performance with respect to CTD-101K in a variety of Nb3Sn magnet models. In addition, TELENE was proven to eliminate training also in NbTi accelerator magnets. Therefore, TELENE can be used in the Magnetic Resonance Imaging (MRI) industry to solve the NbTi solenoids training problem. The transfer of technology in using TELENE resin to the $40B+ MRI industry will have transformative societal impact on global health.

Speaker: Prof. Emanuela Barzi (Ohio State University)

144 M1Or4B-06: Composite cryogenic hydrogen insulated lightweight lined storage (C-CHILL)

The Composite Cryogenic Hydrogen Insulated Lined (C-CHILL) Storage System, developed by Dynovas, addresses the need for advanced reusable liquid hydrogen storage. The C-CHILL system is engineered to support spacecraft, surface systems, and hydrogen aircraft requiring long-duration cryogenic hydrogen storage. Leveraging a Type IV composite overwrapped pressure vessel (COPV) with a carbon fiber vacuum jacket, the C-CHILL system provides a 25%-60% weight reduction compared to traditional metallic tanks.

The design of the C-CHILL system focuses on material selection for the 3 main components of a Type IV COPV: composite overwrap, port boss, and permeation liner. The main technical challenges are the compatibility between these components at cryogenic temperatures, differences in thermal strain between unlike materials, tank permeability to LH2, and bond strength under cryogenic conditions between sealing surfaces. To address these issues, a carbon nano tube (CNT) resin has been selected to reduce the effects of microcracking in the carbon fiber filament wound overwrap. This additive is expected to increase the durability of the composite overwrap to the LH2 environment. The use of a carbon fiber overwrap necessitates careful material selection for the port boss and liner because the difference in thermal strain between components needs to be minimized. After evaluating more traditional tank metals like 300 series stainless steel and aluminum alloys, invar was selected as the boss material for its high dimensional stability because it negates any concerns of the port boss “shrinking” during temperature differentials. Liner material selection requires it to have a low CTE, low LH2 permeability, a high bond strength under cryogenic conditions, and it must be compatible with rotational molding, Dynovas’s liner manufacturing method of choice. Based on these requirements, polyetheretherketone (PEEK) was found to be the best suited liner material because it has the lowest CTE of the low hydrogen permeability, roto-moldable materials. It also has superior mechanical properties compared to similar inert plastics and has a legacy of use with cryogenic hydrogen. Dynovas has conducted permeability testing and lap shear tests to confirm viability of PEEK as a liner material. Dynovas’ next phase of prototyping focuses on manufacturing PEEK liners and winding prototype articles for the upcoming full-scale burst tests.

The C-CHILL system is currently at TRL 4, and Dynovas plans to demonstrate TRL 6 in 2025, with a goals that include:
1. Optimize Hydrogen Compatibility: Engineer a storage system specifically designed for liquid hydrogen compatibility, addressing all challenges presented from the LH2 environment.
2. Reduce Parasitic Permeation: Limit hydrogen permeation rates to less than 1x10⁻³ sccm/m², ensuring compliance with NASA's leakage requirements for long-duration missions.
3. Demonstrate Thermal and Pressure Cycle Durability: Demonstrate the system’s ability to survive over 10,000 thermal cycles between 20°K and 327°K and more than 5,000 pressure cycles at cryogenic temperatures under an operating range of 150-300 psi.
4. Validate Vacuum Insulation Stability: Develop a vacuum insulation layer capable of maintaining pressures below 10 millitorr for extended durations, with rapid re-evacuation in under 1 hour to ensure operational reliability.
5. Showcase Scalability: Provide a modular system for diverse cryogenic applications, supporting storage sizes from current 20 L prototypes to planned production models of 100 L, 700 L, and 1400 L tanks.

Speaker: Sascha Stevens (Dynovas)

Tuesday 20 May

Plenary: Laura Greene [The National MagLab and Unsolved Mysteries in Superconductors] & ICMC Awards

145 M2PL1-01: The National MagLab and Unsolved Mysteries in Superconductors

Unconventional superconductors differ from conventional superconductors in that they typically exhibit a ubiquitous phase diagram with intriguing, correlated electron phases that break the symmetry of the underlying lattice at temperatures well above Tc. These non-Fermi liquid phases remain some of the greatest unsolved problems in physics. After an introduction to the MagLab and an overview of unconventional superconductivity, I will present some of our planar tunneling revealing a possible new paring mechanism in the heavy-fermion superconductor CeCoIn5.

Speaker: Laura Greene (Florida State University)

09:00 Cryo Expo Open

C2Po1A - Cryogenic Components II

146 C2Po1A-01: Experimental Study on the Cavitation Characteristics of a Centrifugal Pump in Liquid Helium

In the past, a compact single-stage centrifugal pump for liquid helium was designed and successfully tested at TU Dresden University. The pump is an integral part of a dual-flow transfer system which reduces the decanting losses of liquid helium from 30% down to 4%. Since the pump transfers the liquid close to saturated conditions, the cavitation characteristics of the pump need to be further investigated. This article presents the latest experimental data on the cavitation performance of the pump.

Speaker: Johannes Doll (TU Dresden)

147 C2Po1A-02: Research on Optimization Strategies for Heat Switches Based on Helium Adsorption Models

Heat switches play a crucial role in cryogenic systems, regulating thermodynamic cycles or accelerating cooling processes. Among them, active gas-gap heat switches (AGGHS) are extensively employed, typically utilizing activated carbon and helium as the adsorbent-gas pair. Thermal conductance in AGGHS is controlled by driving gas adsorption or desorption through heating or cooling of the adsorbent. Due to significant variations among different activated carbons and other adsorbents, and the substantial variations in design requirements for AGGHS, systematic research on the performance optimization of AGGHS remains very challenging and is currently lacking. To address this, this study investigates optimization strategies for heat switches based on the cryogenic adsorption characteristics of helium. Specifically, parameters for evaluating the filling ratio are defined, and a suitable design range for AGGHS operation is determined. Further, targeted optimization directions for the filling ratio are provided to address diverse application needs, such as adjusting the switching temperature range of the adsorption pump or speeding up the response time of AGGHS.

Speaker: Mr Teng Pan (Technical Institute of Physics and Chemistry)

148 C2Po1A-03: Design and development of a control valve plug for precise control and measurement of cryogenic flow

Cryogenic control valves are one of the critical components of a cryogenic fluid distribution system. They are used for both control (process and safety) and isolation of the cryogens within the distribution system. In many cases, control of the cryogenic process flow needs to be directly or indirectly accompanied by accurate flow measurement. Fundamentally, cryogenic flow measurement can be accomplished by expensive instrumentation (e.g. venturi, Orifice, Coriolis meter, which intern require additional instruments like differential pressure measurement etc.). However, the implementation can be challenging due to the additional measurement device introducing heat in-leak, potential thermal hydraulic instability, design complexities and cost. In addition, designing the valve for a maximum Cv can also be use as the flow limiter for safety limits. A well calibrated control valve with precisely known stroke vs. flow coefficient profile has the potential to serve as a cryogenic flow measurement device. As an integral part of the cryogenic distribution system, it is immune to the issues of an added measurement device mentioned above. A valve flow test bench is developed for the calibration and characterization of cryogenic control valve plugs. The test bench incorporates accurate measurement of mass flow using a venturi and Coriolis meter, differential pressure, valve stroke using a digital caliper mounted to the valve stem, as well as pressure and temperature. For applications in helium cryogenic distribution systems, low flow (Cv < 1.0) control valve plugs with equal percent characteristics and high rangeability (≥10) are of particular interest. Several control valve plug profiles for a specific cryogenic control valve (available domestically) are designed using an analytical model. These include equal percent profiles with different rangeability, flow coefficient as well as hybrid profiles with variable rangeability. Flow characteristics of each of these control valve plugs are evaluated using the valve flow test bench, under ambient conditions. The variation of the flow coefficient with valve stroke is calculated from the measurements. The potential variability in the characterization from machining tolerance of the plugs is also studied. An error analysis of the collected data is performed, and the accuracy of the measurements is established. Moreover, a comparative analysis of the measurement accuracy of the proposed set-up against advertised accuracy of trivial flow measurement devices are presented.

Speaker: Mr Austin Grake (Michigan State University)

149 C2Po1A-04: Optimizing nozzle-impeller coupling to enhance efficiency in hydrogen Turbo-Expanders

Hydrogen energy, as a clean and efficient power source, plays a key role in the global energy transition. Hydrogen turbo-expanders, essential in liquid hydrogen production, significantly impact system performance. However, their efficiency is relatively low, primarily due to improper coupling between the nozzle and the impeller. This interaction greatly influences both efficiency and stability, and optimizing this coupling can lead to significant improvements. The study investigates the effects of nozzle-impeller coupling on turbo-expander efficiency, focusing on the flow characteristics between the nozzle outlet and impeller inlet, as well as the influence of the blade gap and attack angle. Results show that optimizing these factors reduces impact losses, minimizes vortex formation, and enhances energy conversion, leading to improved overall efficiency. The findings highlight the importance of nozzle-impeller coupling in enhancing hydrogen turbo-expander performance and provide valuable insights for future optimization efforts.

Speakers: Changlei Ke (Technical Institute of Physics and Chemistry), Mr Hongmin Liu (Technical institute of physics and Chemistry, CAS)

150 C2Po1A-05: Performance assessment of liquid hydrogen pump for the ESS cryogenic moderator system during initial commissioning using helium

At the European Spallation Source (ESS), the high-energy neutrons produced through spallation reaction are moderated to cold and thermal energies using a combination of hydrogen moderators and a light water premoderator, which are optimized to achieve a high cold neutron brightness. The ESS employs two hydrogen moderators positioned above the target wheel, with an estimated nuclear heating of 6.7 kW for a 5-MW proton beam power. A cryogenic hydrogen moderator was designed to circulate subcooled liquid hydrogen at 17 K and 1.0 MPa to the moderators. Each moderator requires a flow rate of 250 g/s to limit temperature rises at the moderators to below 3 K, resulting in a total circulation flow rate of 0.5 kg/s for the two-moderator configuration. The associated pressure drop for this flow rate is estimated to be 100 kPa. To overcome the significant pressure drop, the ESS incorporates two centrifugal pumps with ball-bearings arranged in series, providing the necessary pump head to sustain the required flow rate. The pump revolution speeds are adjustable, ranging from 1,000 to 14,000 rpm. The pump motor is cooled using a glycol-water system at a flow rate of 5.7 L/min. During cooldown, particularly at ambient temperatures where hydrogen density is significantly low, both pumps must operate at a high speed of 13,000 rpm to maintain adequate circulation.
During preliminary commissioning using nitrogen and helium prior to hydrogen operation, the pump performances were measured at 120 K and 17 K. The results demonstrated that, when expressed in terms of dimensionless expression of head and discharge coefficients, all measured data aligned on the same curve, regardless of working fluid (nitrogen or helium). Additionally, thermal properties, including adiabatic efficiencies, pump flange temperatures, and pump casing temperatures were also measured. The performance test identified an operational flow coefficients range of 0.027 to 0.034 as necessary to maintain the flange temperature above 10℃. However, deviations from the maximum efficiency point resulted in flange temperatures dropping as low as 4℃. To address this issue, a water-radiator jacket was designed and integrated onto the pump flange. This provides an effective solution to stabilize the flange temperature and ensure reliable sealing performance.

Speaker: Theodoros Vasilopoulos (European Spallation Source ERIC)

151 C2Po1A-06: Basic design of a 17 kW orifice type heater for the ESS cryogenic moderator system

At the European Spallation Source (ESS), a cryogenic moderator system (CMS) has been designed to circulate subcooled liquid hydrogen at 17 K with a parahydrogen fraction exceeding 99.5% and a flow rate of 0.25 kg/s for each hydrogen moderator. The nuclear heating for the 5-MW proton beam power is estimated to be 6.7 kW and is projected to increase to 17.2 kW for the four moderators in the future. The static and dynamic heat load is effectively dissipated through a plate-fin exchanger by a large-scale 20 K helium refrigeration system, known as the Target Moderator Cryoplant (TMCP) with a cooling capacity of 30.3 kW at 15 K. When the proton beams are injected, a stepwise heat load applied to the hydrogen moderators results in a 1.76 K temperature rise. This temperature fluctuation propagates toward the heat exchanger at a rate corresponding to the circulation flow rate. To compensate for the transient heat load, ESS employs two approaches: a valve box integrated with the TMCP, and an electrical heater installed within the CMS loop. This valve box adjacent to the CMS cold box regulates a cooling power by adjusting the feed helium flow rate to the CMS, without altering the operational conditions of the TMCP turbines. As proton beam powers increase, a fast-response and high-power heater is required to improve the stability of the CMS and TMCP, while maintaining a stable hydrogen supply temperature at 17 K within ±0.1 K during the proton beam injection or trip. The heater compensates for rapid nuclear heating without causing thermal disturbance, ensuring that heat loads transferred from the CMS to the TMCP remains constant. The heater was designed based on an orifice-type heater with a 5-kW capacity, originally developed at J-PARC by the author. Its geometry was optimized through CFD simulations using ANSYS FLUENT, ensuring that the heated surface temperature does not exceed 27 K, which is 4.26 K lower than its saturated temperature at an operational pressure of 1.0 MPa. The results confirmed that the designed heater met the required performance specifications. Furthermore, a straightforward method for determining the parameters of the orifice type heater using a conventional heat transfer correlation was also established.

Speaker: Dr Hideki Tatsumoto (European Spallation Source ERIC (ESS))

152 C2Po1A-07: Pre-design and efficiency analysis of electric generator brake cryogenic helium turbine expender

A high-speed cryogenic helium centrifugal turbine expander with an electric generator brake for experimental helium refrigerator is presented in this paper. This design differs from traditional compressor-braked cryogenic helium turbine expanders. The turbine expander is braked by a permanent magnet generator (PMG), and its shaft is coupled to the PMG to enhance operational stability. The designed power output of the turbine expander is 28.3 kW, and the pressure ratio is 2.85 under the design conditions. In comparison to compressor braking, generator braking can increase the braking power, which facilitates improvements in the power of individual turbines. The braking power and speed of the turbine can be rapidly adjusted through control of the brake generator, thereby enhancing the operational capability of the turbine under variable operating conditions. However, due to the limitation of generator, the rotational speed of the turbine is restricted to 10,000 rpm, which adversely affects its efficiency. To achieve high-speed operation of the generator, the shafting structure is supported by hydrostatic gas bearings. Additionally, part of the working substance is extracted from the impeller to dissipate heat from the generator rotor. The design rotational speed is established at 96,000 rpm. This paper introduces an overall design approach for the turbine expander and provides predictions regarding its efficiency.

Speaker: Mr Chenghao Dai (Hefei Institutes of Physical Science, Chinese Academy of Sciences, University of Science and Technology of China)

153 C2Po1A-08: Analysis of unbalance response of the rotor of a typical cryogenic turbine for helium refrigerator under thermal effect

As the core equipment of a helium cryogenic system, the safe and stable operation of a helium turbine is critical to the smooth operation of the entire system. During the processing and assembly of the rotor, it is inevitable to produce unbalance. The unbalance force generated by the unbalance measure may affect the stability of the turbine and even cause damage to the equipment. In order to study the unbalance response of the rotor in a low temperature environment, the finite element method is used in this paper to calculate the resonance amplitude of the rotor at critical speed under thermal effect. The results show that the thermal effect significantly increases the value of the first-order resonance amplitude of each part of the rotor, but the effect on the second-order resonance amplitude is relatively limited. In addition, the influence of the balance quality grade, bearing stiffness, and damping on the unbalance response are also studied when considering thermal effect.
KEYWORDS: Helium turbine, Unbalance response, Thermal effect, Resonance amplitude

Speaker: Chenghao Dai (Institute of Plasma Physics, HFIPS, Chinese Academy of Sciences)

154 C2Po1A-09: Development of the linear Compressor of 152Hz Micro Pulse Tube Cryocooler

Compressor is the key component of pulse tube cryocooler. It introduces the structure of a linear vibration compressors specifically designed for pulse tube cryocoolers. The paper delves deeply into the impact of compressors on four key aspects: support systems, control systems, compressor efficiency, and vibration and noise reduction. Based on the findings, a compressor weighing 160 grams has been developed, capable of delivering an output power of up to 30W. Furthermore, a micropulse tube cryocooler, coupled with this compressor, operates at a frequency of 152 Hz and provides a cooling capacity of 1.14W with a input power of 10W and a temperature of 150K. Leveraging the design of this compressor, various models have been built and have already undergone mass production for practical applications.

Speaker: Yuhong Zhang (中国科学院理化技术研究所)

C2Po1B - Large Scale Cryogenic Systems III: Operation & Design III

155 C2Po1B-01: LHC cryogenic system adaptation and recovery after a major insulation vacuum breakage in a final focusing superconducting magnet in 2023

On July 17, 2023, during the LHC (Large Hadron Collider) beam operation for Physics Run 3, one of the low-beta superconducting quadrupoles located on the left side of LHC Point 8 (ITL8) experienced a quench following an electrical network disturbance. This quench unfortunately caused a crack in one of the magnet interconnection bellows, resulting in a significant leak between the cryogenic helium vessel, maintained at 1.9 K, and its insulation vacuum. As a result, the magnet rapidly warmed up, necessitating immediate repairs to resume LHC operations.

To avoid a full warm-up and cooldown of the entire 3 km LHC sector, which would have significantly impacted the physics schedule, it was decided—after a thorough risk analysis prioritizing personnel safety—to repair the magnet interconnection bellow in situ. This approach involved locally warming the affected area to room temperature while allowing the rest of the LHC sector to drift in temperature, with an upper limit of 80 K. This limitation restricted the available repair time to 10 days.

This scenario, originally not foreseen in the cryogenic operation procedures, was swiftly studied and validated using cryogenic dynamic simulations. A repair plan for the damaged bellow was rapidly developed and executed thanks to an impressive collaborative effort from various CERN teams, minimizing LHC downtime.

This paper describes the exceptional procedure of partial, localized warm-up, the requalification of the helium circuits following the repair, and the subsequent recooling of the machine to its nominal operating temperature, enabling the LHC to resume physics operations.

Speaker: Benjamin Bradu (CERN)

156 C2Po1B-02: The SCL3 linac operation and improvements following RAON's 2nd beam commissioning

RAON (Rare Isotope Accelerator complex for ON-line experiments) is a heavy ion accelerator built under the Institute for Basic Science (IBS) in South Korea. The RAON facilities are composed of SCL3 linac (QWR cavity (81.25MHz, 4.5K) & HWR cavity (162.25MHz, 2K)) and SCL2 (SSR1 cavity (325MHz) & SSR2 cavity (325MHz), 2K). The total capacity of the cryo-plant is 17.7kW, divided between two accelerator lines (SCL3 linac: 4.2kW, SCL2 linac: 13.5kW). SCL3 was completed in Q4 2022, and two beam services were conducted from 2023 to 2024. It is currently undergoing regular maintenance after warming up. The cryo-plant for SCL2 is in progress, with pre-commissioning expected to be completed in the second half of 2025 (covering cryo-plant pre-commissioning & SCL2 linac valve boxes (49 units) to the IF separator (Quadrupole magnet’s cryostat (13 units)) valve boxes).
After the first beam test run of the SCL3 linac, the plug of the control valve for 4.2K of the QWR super-conducting cryomoduleg are canged from Kv=0.5 to Kv=0.1 to improve beam stability and liquid helium pressure stability. In addition, for the HWR super-conducting cryomodules, dampers were additionally installed in the 2K recovery line, and convection brakes were additionally installed in the 2K control valve to secure a thermal load margin of approximately 100 W along with prevention of TAO. Moreover, the SCL3 cryoplant has been operated stably without a single accident during two cool-down and warm-up processes, improvements are underway to improve beam operation time and stability, which will begin in Q2 2025.

Speaker: Dr MinKi Lee (Institute for Basic Science)

157 C2Po1B-03: Design of the Tunnel Transfer line of PIP-II Cryogenic Distribution System

The Cryogenic Distribution System (CDS) of PIP-II will distribute cryogenic helium from Cryoplant (CP) to the 23 SRF cryomodules for supporting various operating modes of the PIP-II accelerator. The CDS is being designed as a collaborative effort of Fermilab, USA and Wroclaw University of Science and Technology (WUST), Poland. The largest section of the CDS is the Tunnel Transfer Line (TTL) comprising a string of segment modules running parallel to the cryomodule string. Each TTL Module interfaces with the corresponding cryomodule and houses adequate control valves (cryogenic and room temperature), instrumentation, relief lines, and u-tubes for supply/recovery of cryogenic helium. The design of TTL is marked with unique challenges arising from space availability and installation constraints in the accelerator tunnel. The Fermilab and WUST teams have completed the technical design of the TTL while meeting these challenges. This contribution will highlight these challenges and present an overview of the process design, analysis, fabrication and installation plan of the Tunnel Transfer line.

Speaker: Vrushank Patel (Fermi National Accelerator Laboratory)

158 C2Po1B-04: PIP-II Cryogenic Distribution System – status and outlook

The Cryogenic Distribution System (CDS) is a key cryogenic sub-system of Fermilab’s upcoming Proton Improvement Plan II (PIP-II) accelerator, responsible for supplying cryogenic helium to support all of PIP-II operating modes and handling overpressure safety. The CDS is being designed and manufactured as a collaborative effort between Fermilab, USA and Wroclaw University of Science and Technology (WUST), Poland. The main components of the CDS are Distribution Valve Box (DVB), Intermediate Transfer Line (ITL), Tunnel Transfer Line (TTL), Cryogenic Controls System, and Warm Piping System. This contribution will delve into the collaborative R&D being done by Fermilab and WUST, highlighting the design and construction progress made to date. The contribution will also present an outlook of the upcoming activities leading to the final commissioning of the CDS.

Speaker: Dr Ram Dhuley (Fermi National Accelerator Laboratory)

159 C2Po1B-05: Operational experience of QWR cyromodules for RAON

Low energy linac(SCL3) of RAON (Rare isotope Accelertor comples for ON-line experiment) has been commissioned since 2023. SCL3 is composed of two types of superconducting cavity, which are QWR (Quarter wave resonator) and HWR (Half wave resonator). The stable operation of cavities was limited due to the imperfect performance of tuners in QWR cryomdules. Also, the various disturbances originated from the cryogenic system, utilities, and so on causes the failures of the superconducting cavities. Since QWRs are operated in 4.5 K, the main disturbances are related with the cryogenic system such as helium pressure, helium flow rate, valve movement and so on. The operational experience which is focused on the causes of cavity failures and source of disturbances of QWR cryomdoules of RAON will be introduced.

Speaker: Dr Youngkwon Kim (Institute for Basic Science)

160 C2Po1B-06: Introduction to the protection system for RAON cryogenic system

The cryogenic system for accelerator complex for ON-line experiments (RAON), is designed to maintain extremely low temperatures to support superconducting equipment, such as superconducting linear accelerators and low-temperature superconducting magnets. Proper operation of this system is essential for ensuring high efficiency, stability, and safety in the experimental processes. A robust protection system is crucial to safeguard the cryogenic equipment and infrastructure from potential failures or hazards. By integrating advanced monitoring, control, and emergency management technologies, it ensures the smooth functioning of RAON's sophisticated experimental setup while mitigating risks associated with cryogenic operations. This paper introduces the structure of the cryogenic system's protection system and discusses improvements made to the system, as well as insights into designing effective protection logic.

Speaker: Seojeong Kim (Institute for Basic Science)

C2Po1C - Helium Management and Processing

161 C2Po1C-01: Helium inventory and losses in DALS after several cooldowns

The Dalian Advanced Light Source (DALS) test facility has completed the com-missioning of the cold box in June 2024, and the first cooldown of the distribu-tion system began in September of that year. The whole cryogenic system re-quires helium inventory of 1.4 tons. For a more rational use of this helium, the helium distribution and the total inventory in the system are monitored, and a tool for monitoring the helium inventory is developed. With this tool, it is possible to understand the helium inventory changes intuitively and take effective measures to prevent the helium loss. In this paper, we analyze the changes in the helium in-ventory of the system after several cooldowns, and propose specific measures to reduce the helium loss.

Speaker: Mr He Sheng (Insititute of Advanced Science Facilities, Shenzhen)

162 C2Po1C-02: Development of a moisture removal device for helium cryogenic plants

Water contamination represents a critical challenge in helium cryogenic systems, presenting multifaceted operational risks for advanced industrial and scientific facilities. These water contaminants undergo complex phase transformations during system operations, crystallizing under extreme low-temperature conditions and posing significant threats to precision engineering infrastructure. Such crystallized particles can critically damage sensitive mechanical components, particularly turbines within Cold box assemblies, and accumulate within intricate heat exchanger networks, progressively compromising thermal transfer efficiency and overall system performance.
At National Synchrotron Radiation Research Center (NSRRC), we have developed an innovative moisture removal device capable of eliminating water contaminants both during offline maintenance and online system operation. Currently, four of these devices are deployed: one at the Taiwan Photon Source (TPS), two at the Taiwan Light Source, and one integrated with the purification system to enhance moisture contaminant removal capabilities. This paper will detail the device's design and present comprehensive testing results.

Speakers: Dr Feng-Zone Hsiao (National Synchrotron Radiation Research Center), Hsing-Chieh Li

163 C2Po1C-03: Changes in cooling strategies from 2005 to 2025 at temperatures from 3 K to 25 K using He or H2 as coolants

The strategy for cooling in the temperature range from 3 to 25 K is likely to change because of the working fluid cost (in the case of helium) and safety issues (in the case of hydrogen). In both cases this requires minimizing the inventory of the working fluid for the reasons stated above. These limitations may apply for systems using coolers and definitely apply for systems that involve central refrigeration. This paper covers a range of temperature of interest to superconducting devices that use LTS and HTS conductors. The methods for minimizing the gas inventory are similar for the two gasses. Hydrogen has many advantages for cooling above 15 K. Liquid hydrogen has a heat of vaporization that is over twenty times that of liquid helium. This paper will be show how one can reduce the amount of these liquids in cryostats. Hydrogen appears to be a better working fluid than helium for cooling down a device using natural convection. Hydrogen safety issues and other issues with hydrogen will be discussed

Speaker: Michael Green

164 C2Po1C-04: Cryogenic purification of low purity helium with temperature swing adsorption and membrane separation

Ability Engineering Technology (AET) has developed a system capable of receiving helium at very low concentrations (less than 10% by volume) and effectively separating out undesirable gases to yield high purity helium (5.0 – 6.0 grade) at high recovery rates (greater than 90%). This is accomplished with membrane separation and a subsequent cryogenic adsorption process. The operational advantages of utilizing this method for helium recovery will be discussed. The results of field testing this equipment and its implementation for scientific and industrial use cases will also be discussed.

Speaker: Mr Cody Wilson (Ability Engineering Technology)

165 C2Po1C-05: Integration and commissioning experience of Full Flow Purifier at Muon Campus

The Full Flow Purifier for Fermilab’s Muon Campus uses a charcoal bed surrounded by a liquid nitrogen jacket to purify up to 240 g/s of helium gas. Fabrication by Ability Engineering Technology Inc. has been completed and the purifier delivered to Fermilab. It is the largest purifier to be used at Fermilab based on both capacity and size. A previous paper discussed the design of purifier for various operational conditions and horizontal shipping. The purifier is designed to withstand 5g force in vertical and 2g force in lateral and longitudinal directions. Transportation experience from vendor to Fermilab and within site is discussed. Integration of the purifier involved design and fabrication of a liquid nitrogen transfer line, regeneration system, and helium piping to connect it to Muon Campus cryogenic system. It also involved establishing electrical, instrumentation and controls connections to the system. Integration of the purifier is discussed in detail. The purifier was commissioned using up to 4 Mycom helium compressors to supply helium and liquid nitrogen was supplied by a 15,000 gallons tank. Inlet and outlet temperature of each of the three streams in DATE heat exchanger was recorded during commissioning operation along with inlet and outlet temperature of helium across the adsorber vessel. Actual effectiveness of the 3-stream heat exchanger was estimated based on measured temperatures and flow rate. Impurity levels are monitored at inlet and outlet of the purifier. Theoretical adsorption capacity of the purifier is calculated based on the measured temperatures and flowrates and is compared to actual adsorption capacity over time. The effect of increasing adsorber diameter and length on charcoal bed temperature is measured during commissioning. LN2 jacket vessel covers around 90 % of charcoal adsorber bed surface. Effect of liquid nitrogen level in LN2 jacket on charcoal bed temperature and overall capacity of adsorber is also studied.

Speaker: Jeewan Subedi

166 C2Po1C-06: Helium recovery system at IB3a

The increasing need for optimal and sustainable use of cryogenic resources to support Fermilab’s scientific mission has highlighted the necessity of improving the Laboratory’s helium management practices. An assessment of cryogenic test facilities identified the Technical Division’s Industrial Building 3a (IB3A) as a key site requiring upgrades to integrate a helium recovery system. The IB3A facility is essential for characterizing and testing superconductors, cables, and coils for various R&D projects, including the US High-Luminosity LHC Accelerator Upgrade Project (AUP), Mu2e, and other external collaborations. Currently, the facility relies on 500 L helium Dewars and vents the vaporized helium directly into the atmosphere, leading to significant helium loss. Given the non-renewable nature of helium, recovering and reusing this resource is critical for the sustainability of Fermilab’s operations.
To address this challenge, a project has been initiated to connect IB3A to an existing helium purification station and refrigeration system located in another building via a dedicated pipeline pass over the roof of several buildings. This solution will enable the efficient capture of vented helium, its transfer to the purification station, and subsequent liquefaction for reuse in future operations. The project includes a detailed design phase, specifying the pipeline route, flow control mechanisms, and integration with the existing cryogenic infrastructure, followed by phased implementation and commissioning.
By implementing this pipeline connection and upgrading IB3A, Fermilab aims to significantly reduce helium waste, lower operational costs, and align with its commitment to sustainability. This initiative provides a model for resource-efficient cryogenic operations and reinforces the Laboratory’s capacity to support its science mission for the long term.

Speaker: Dominika Porwisiak (Fermi National Accelerator Laboratory)

C2Po1D - Ortho-Parahydrogen Conversion

167 C2Po1D-01: Magnetic field acceleration of catalyzed para- to orthohydrogen conversion for cooling superconducting motors

The cryogenic boil-off from liquid hydrogen can be utilized to harness the endothermic para- to orthohydrogen quantum state conversion, providing cooling, for example to superconducting motors, thereby enabling high efficiency sustainable transportation. Magnetic catalysts, such as Fe2O3, are used to accelerate the rate of parahydrogen conversion to achieve higher cooling rates. However, the large volume and mass requirements of these catalysts can be a barrier to the use of parahydrogen conversion for cooling superconducting motors. Externally applied magnetic fields can enhance catalyst activity to deliver larger cooling loads with smaller parahydrogen catalytic converter sizes. This approach offers a potential synergy with the magnetic field produced by superconducting motors. The degree of magnetic enhancement is highly dependent on the catalyst material and operating temperature and requires experimental measurements to assess its potential value for cooling superconducting motors.

This study experimentally investigated the influence of an externally applied magnetic field on the para-orthohydrogen conversion rate on a Fe2O3 based (Molecular Products Ionex OP) catalyst at temperatures relevant to superconductor motor cooling. Experiments revealed that a 0.2 kOe applied magnetic field accelerates the catalysis rate by 50 % at a temperature of 40 K, whereas slight magnetic deceleration of the catalysis rate was observed at a T = 90 K. A combined kinetic and heat transfer model suggests that the magnetic kinetic enhancement could reduce the required catalyst volume for cooling a superconducting motor by 50 %. Kinetic analysis and magnetic characterization of the catalyst indicate a potential dual mechanism underlying the magneto-catalytic effect, which could help support the development of high activity magnetic catalysts and advance fundamental theory on the para-orthohydrogen conversion mechanism.

Speaker: Thomas J Hughes (Monash University)

168 C2Po1D-02: Improving the activation of ortho-para hydrogen conversion catalysts for hydrogen liquefaction: Effects of pre-treatment on the performance of Ionex OP

The storage and handling of liquid hydrogen (LH₂) are critical components of cryogenic hydrogen engineering, particularly as LH₂ is poised to play a pivotal role in future energy systems. At ambient temperature, hydrogen gas consists of approximately 75 % ortho-hydrogen and 25 % para-hydrogen. However, at the normal boiling point of LH₂ (20.3 K), the equilibrium para-hydrogen concentration increases to 99.8 %. Efficient and stable LH₂ storage requires the catalytic conversion of ortho-hydrogen to para-hydrogen during liquefaction, as the exothermic nature of this conversion generates heat that can cause hydrogen boil-off. Ionex, a commercially available catalyst based on hydrous ferric oxide, is widely utilised for ortho-para conversion (OPC) in industrial liquefaction systems. However, the activation and pre-treatment of such catalysts are critical to achieving optimal performance under cryogenic conditions. Despite its importance, the mechanisms underlying pre-treatment methods and their effects on catalyst activity remain poorly understood.

This study investigates the influence of different catalyst pre-treatment methods - including hydrogen flow, vacuum pre-treatment, and helium flow - on the performance of Ionex catalysts. One gram of Ionex was loaded into a fixed-bed reactor and subjected to pre-treatment at temperatures of 140, 160, and 180 °C for varying durations (4 and 16 hours). The OPC performance was evaluated at 77 K (liquid nitrogen bath) using a thermal conductivity detector (TCD) to determine the para-hydrogen concentration. Results demonstrate that vacuum and helium flow pre-treatment yield higher catalyst activity. Advanced characterisation techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and superconducting quantum interference device (SQUID) magnetometry, were employed to investigate catalyst structure, composition, and magnetic properties with pre-treatment conditions and performance.

By identifying improved pre-treatment strategies, this study contributes to enhancing the efficiency of cryogenic hydrogen liquefaction systems. Furthermore, these findings may provide valuable insights into practical industrial activation procedures for next-generation catalysts, enabling more effective and sustainable LH₂ storage and transport.

Speaker: Dr Thomas J Hughes (Monash University)

169 C2Po1D-03: Screening of ortho-parahydrogen catalysts

The growing demand for liquefied hydrogen (LH2) results in an increased need for ortho-parahydrogen catalysts. Currently, the LH2 supply chain relies heavily on a single catalyst product: hydrous ferric oxide, commercially available as “Ionex-Type O-P Catalyst” (Ionex) from Molecular Products. On the one hand, this reliance poses a supply vulnerability for liquefaction plants under construction. On the other hand, previous research indicates the potential for catalysts with much higher conversion activity than Ionex. This holds promise for optimizing liquefaction plants thermodynamically and substantially reducing the size of the ortho-para converters.
To identify alternative catalyst options, a screening of several catalyst samples was conducted as part of the HyCat project. The samples were synthesized by external manufacturers and tested at 77.3 K and 2.5 bar(a) in the Ortho-Para Catalyst Test Facility at TU Dresden.
This work presents the results of the screening, including some promising candidates suitable for further development and potential use in large-scale LH₂ liquefaction.

Speaker: Sebastian Eisenhut

170 C2Po1D-04: Experimental Investigation and Performance Evaluation of Catalysts-Filled Plate-Fin Heat Exchangers for Hydrogen Liquefaction

Cryogenic hydrogen plate-fin heat exchangers (PFHXs) with continuous ortho-para hydrogen conversion are crucial for large-scale, efficient hydrogen liquefaction. However, most existing research relies on numerical methods, and detailed experimental data under cryogenic conditions remain scarce. To address this gap, experiments on catalysts-filled plate-fin heat exchangers (CPFHXs) were conducted within the temperature range of 40-80 K to obtain data on thermal-hydraulic-conversion performance. Based on these experimental results, correlations were derived and compared with numerical simulations. It was observed that when the space velocity is sufficiently low, the conversion efficiency approaches 100%, indicating that the outlet composition reaches equilibrium. However, the conversion efficiency decreases to 83.5% as the space velocity increases to 1.14 h⁻¹. Additionally, the inlet concentration and temperature significantly affect performance. Thermal performance improves under lower temperatures, with the j-factor reaching 0.070 when the inlet helium temperature is approximately 41.7 K. Notably, the numerical results for temperature and composition exhibited considerable deviations from the experimental data. More accurate correlations, derived from experimental data, were integrated into numerical simulations using CFD, improving the accuracy of performance predictions. These findings provide valuable insights for the design and optimization of CPFHXs.

Speaker: Junjie Teng (Zhejiang University)

171 C2Po1D-05: Enhancing Flow and Heat Transfer in Continuous Conversion Heat Exchangers with Honeycomb-Structured Catalysts

The continuous conversion heat exchanger is a critical component for scaling up hydrogen liquefaction plants while reducing energy consumption. However, existing continuous conversion heat exchangers utilize randomly packed catalyst structures, which suffer from uneven flow and heat transfer, leading to significant challenges such as high pressure drops and low heat transfer and conversion effectiveness. In this context, this paper proposes a novel continuous conversion heat exchanger featuring structured catalysts, where a honeycomb-matrix structure is integrated into the hot-side channels of the cryogenic heat exchanger. A multi-zone computational fluid dynamics model is developed by embedding a user-defined function for thin-layer heat and mass sources, capturing the interactions of flow, heat, and mass transfer across the refrigerant, hot hydrogen, metal walls, and catalysts. The effects of fluid inlet states and honeycomb matrix structural parameters are numerical analyzed. As a result, the optimal operating conditions and structural parameters are determined for various potential catalysts. Based on the ortho-para hydrogen conversion test platform, the novel structural catalytic unit demonstrates effective reductions in pressure drop and improvements in heat transfer and conversion effectiveness, compared to existing randomly packed structures. This work offers a new perspective for structural improvements in continuous conversion heat exchangers, contributing to the development of low-energy-consumption large-scale hydrogen liquefaction plants in the future.

Speakers: Dr Song Fang (Institute of Refrigeration and Cryogenics, Zhejiang University), Prof. Kai Wang (Institute of Refrigeration and Cryogenics, Zhejiang University)

172 C2Po1D-06: Design and Optimization of Efficient Catalyst-filled Spiral Wound Heat Exchangers for Large-Scale Hydrogen Liquefaction Systems

It seems to have become a consensus that spiral wound heat exchangers are more suitable for large-scale cryogenic liquefaction processes than plate-fin heat exchangers, based on the mature experience of LNG industry. In the hydrogen liquefaction systems, the most advanced continuous catalytic technology integrates the exothermic conversion process of orthohydrogen to parahydrogen within the heat exchanger unit. It is necessary to explore the design criteria of spiral wound heat exchangers for hydrogen liquefaction considering this distinct characteristic. This study establishes a comprehensive model, which couples the first-order reaction kinetics for ortho-para hydrogen conversion and the energy balance model for the flow and heat transfer of hydrogen in the spiral wound two-fluid heat exchanger. The performance of the component is evaluated from the fields of catalysis, flow, heat transfer, and economics. The variations in effectiveness with the design parameters of the heat exchanger in different temperature ranges, including 80-65 K, 65-50 K, 50-40 K, and 40-30 K, are determined. Furthermore, a Genetic algorithm is used for optimization, and the effects of optimization indicators such as minimum weight, pressure drop constraints, and cost on the design are analyzed. This paper aims to provide theoretical data and model references for the design of efficient spiral wound heat exchangers for hydrogen liquefaction, and to lay the foundation for the progressive large-scale development of hydrogen liquefaction plants.

Keywords: Hydrogen liquefaction; Spiral wound heat exchanger; First-order reaction kinetics; Energy and economic analysis; Genetic algorithm

Speaker: Hanwei Zhang

173 C2Po1D-07: Test platforms for ortho-para hydrogen conversion at cryogenic conditions

Large-scale, low-energy-consumption hydrogen liquefaction technologies are crucial for the widespread adoption of liquid hydrogen. However, fundamental data on continuous ortho-para hydrogen conversion at cryogenic temperatures remain limited. To address this, a series of test platforms has been established to investigate ortho-para hydrogen conversion under a wide range of cryogenic conditions, providing essential data that support the precise design of cryogenic hydrogen heat exchangers. These platforms range from small-sample catalyst tests at 77 K to intermediate-scale single-channel plate-fin heat exchanger tests, and finally to a large-scale prototype heat exchanger. At the smallest scale, catalyst performance is measured at 77 K to obtain conversion rates, pressure drops, and useful correlations. At the intermediate scale, a plate-fin heat exchanger configuration is used with a single hydrogen flow channel containing approximately 2 kg of catalyst, sandwiched between two helium coolant channels. This setup operates at 30 to 80 K, with mass flows from 0 to 1 g/s, pressures up to 3 MPa, and inlet ortho-para hydrogen concentrations of 25% to 50%. At the largest scale, a prototype facility operates at 80 to 300 K, supporting mass flows up to 3 g/s (about 0.26 tons per day) and pressures up to 3 MPa. These systematic experiments provide a comprehensive dataset covering a wide range of conditions. The resulting data enable the development of accurate models and correlations for flow, heat transfer, and conversion, ultimately guiding the optimization and improved performance of cryogenic hydrogen liquefaction systems.

Speakers: Xinyu Wei (zhejiang university), Mr Junjie Teng (Zhejiang University)

C2Po1E - Instrumentation, Visualization, and Controls I

174 C2Po1E-01: Combined Single and Two-Phase Cryogenic Flow Sensor: Experimental Results with Nitrogen

The increasing industrial use of cryogens for fuel, refrigeration, and energy storage demands the development of advanced metrology to effectively design systems and accurately meter fluid transfer operations. However, the storage and transport of cryogens near saturation conditions frequently results in multiphase flow, precluding the use of existing single phase only cryogenic flow meters. Furthermore, industry requirements of low pressure drop, and low heat-in-leak requirements make many intrusive designs infeasible for general applications as well. In this paper we present the results of a prototype combined single and two-phase cryogenic flow sensor that combines a capacitance-based multiphase flow measurement technique with a thermal mass-based single-phase measurement technique for both the liquid and vapor single-phase flow regimes. The combined prototype is tested in a cryogenic nitrogen flow loop through a variety of phase and flow rate conditions to assess the performance of the two sensing methods and determine the optimal switching method between them.

Speaker: Dr Qussai Marashdeh (Tech4Imaging LLC)

175 C2Po1E-02: Irradiation tests of 3/2-way piezo valves at CERN

Most cryogenic regulating valves used in CERN cryogenic facilities rely on the Siemens Sipart™ intelligent valve actuator and for future deployment in the Large Hadron Collider (LHC) High Luminosity (HL-LHC) upgrade it is necessary to better understand the effects of particle radiation on the operation of these control valve actuators. When used in radiation environments, the Siemens™ intelligent valve actuator is split into two parts: the control module containing electronic circuits which is located in a radiation-free area and the pneumatic unit with both the miniature valves and the feedback position potentiometer mounted on the control valve stem, which is exposed to particle radiation when installed in a high energy accelerator.
Concerning cryogenic ON/OFF valves, currently solenoid-pneumatic switch valves are being used in the LHC. For the HL-LHC upgrade, the use of Hoerbiger™ piezo-pneumatic switch valves, containing the same piezo ceramic bending element as Siemens Sipart™ intelligent valve actuator, was investigated. Piezo valves require very low current for activation, and no energy to maintain the active state. This minimizes power losses, eliminates voltage drops, and reduces the required cable cross-section. As for the process control equipment design, more channels are supported, providing enhanced flexibility. These features are particularly advantageous in systems where control equipment is located at a significant distance.
The HL-LHC cryogenic upgrade will expose the valve actuators and pneumatic switch, as well as all the LHC-tunnel instrumentation, to a high level of radiation that is expected to reach up to 100 kGy. To date, all reported radiation tests were performed by using gamma rays that may underestimate the effects if the devices are prone to radiation displacement damage.
To investigate the radiation effects, two campaigns were carried out. The first radiation test was performed in CERN’s IRRAD proton facility where the primary proton beam with a momentum of 24 GeV/c is extracted from the CERN PS accelerator ring. Such heavy particle irradiation, apart from radiation damage, provokes the activation of materials complicating the handling of irradiated components. The radiation test was performed on the components that had previously failed in tests, specifically the 3/2-way piezo miniature valves. The test set-up was made of ten piezo miniature valves mounted on a movable table that permits inserting the devices under test into the beam. The control equipment was located outside the irradiation area, and it was composed of a voltage generator opening and closing the micro valves, control valves and instrumentation to measure the inlet flow as well as the pressures at the inlet and control ports of the miniature valves. Signal cables, 20 meters in length, and flexible pipes with a 4-mm internal diameter were used to connect the control system to the devices under test.
The second campaign, for testing the Hoerbiger™ piezo-pneumatic switch for ON/OFF valves, was conducted at CERN's Cobalt-60 (CC60) gamma-ray facility to study accumulated radiation dose effects. The valves were exposed to a dose rate of 8 kGy per day for two weeks, reaching a total dose of 105 kGy. In total, six valves were tested, with four featuring 3D-printed cases: two made from Accura 25 and two from Ultem material. The remaining two valves retained the company's proprietary polyarylate material. The Hoerbiger™ electronics, including radiation sensitive microcontrollers and integrated circuits, were replaced with CERN developed electronics using only passive components and achieving the same functionality. All valves were disassembled and rebuilt, placing CERN electronics. 3D-printed cases were placed on four valves before testing. Like the IRRAD campaign, control equipment was located outside the irradiation area.
This paper presents the test setup and examines the effects of hadron radiation and gamma rays on the performance of 3/2-way valves under various operating conditions, providing insights into their reliability in radiation environments.

Speaker: Nikolaos Chatzipapas (CERN)

176 C2Po1E-03: Cernox® Cryogenic Temperature Sensor Performance after High Level Neutron Irradiation

The need for superconducting magnets in high energy physics investigations currently drives much of the research and development in cryogenics. With collider energies and fusion reactors continuing to reach new levels, it’s necessary to constantly push the operating limits of supporting technologies. A crucial component in these experiments is the cryogenic temperature sensor used to monitor both superconducting magnet temperatures and their accompanying cryogen support infrastructure. Gamma radiation and neutron radiation are often used as a predictor of both the survival and accuracy of sensors in the actual radiation environments. In this research, three models of cryogenic temperature sensors commercially available from Lake Shore Cryotronics, Inc. were neutron irradiated at the Ohio State University Nuclear Reactor Laboratory pool reactor. The tested devices consisted of Cernox® models CX-1010-SDs, CX-1050-SDs, and CX-1080-SDs. Separate test groups comprised of samples of each model were irradiated at room temperature to total fluences of 1E+12 n/cm2, 1E+13 n/cm2, 1E+14 n/cm2, 1E+15 n/cm2, 1E+16 n/cm2, 1E+17 n/cm2. and 1E+18 n/cm2. Temperature calibrations over each sensor’s respective operating temperature range were performed both before and after irradiation, with the neutron-induced shifts presented in terms of equivalent temperature. The Cernox® temperature sensors continued to operate with temperature offsets increasing with both increasing fluence and increasing temperature. This work details the resulting survivability and performance of each tested model as a function of temperature and total neutron fluence. A fit of the equivalent average temperature offset as a function of total neutron fluence and temperature is presented.

Speaker: Dr Scott Courts (Lake Shore Cryotronics, Inc.)

177 C2Po1E-04: Digital twin for the CRAFT helium cryogenic plant

The helium cryogenic plant of the Comprehensive Research Facility for Fusion Technology (CRAFT) is equipped with four helium refrigerators, to meet the demands of testing superconducting magnets, conductors, and materials. A digital twin platform, Cryo-DT, has been developed based on the cryogenic plant control system. Cryo-DT uses the Experimental Physics and Industrial Control System (EPICS), integrating the physical and virtual spaces in parallel. In the virtual space, dynamic models of the actual refrigerators in the physical space are developed using the EcosimPro software, enabling simulations to reproduce the real operational processes. This paper provides a detailed explanation of the components and connection architecture of Cryo-DT, the implementation of real-time data interaction and synchronization between actual and virtual processes, and presents the deployment and online simulation results on the CRAFT 1 kW@4.5 K refrigerator.

Speaker: Dr Qiang Yu (Institute of Plasma Physics, Chinese Academy of Sciences)

178 C2Po1E-05: Commissioning and Initial Operations of the ESS Linac Cryomodules Cryogenic Controls: Achievements and Future Prospect

The Cryomodules are critical components in the European Spallation Source (ESS) accelerator, playing a crucial role in connecting spoke cavities to high-beta elliptical cavities in the SRF Linac. These Cryomodules provide the necessary environment for operating, Spoke (Spk) cavities, Medium-Beta (MBL) and High-Beta (HBL) elliptical cavities, which are responsible for accelerating protons from 90 MeV to 2.0 GeV. The Cryomodule houses two double-spoke cavities per Spoke cryomodule and four elliptical cavity packages for MBL and HBL cryomodule, which need to be cooled to 2K to become superconductive and accelerate the beam. There are 13 SPK, 9 MBL and 21 HBL cryomodules to be installed and commissioned on the ESS accelerator.
An automation control system was developed to control and operate the cryogenic circuits, consisting of temperature, pressure, level, and flow sensors, heaters, and automatic valves connected to a control system based on a Programmable Logic Controller (PLC) integrated into EPICS through the Controls Network.
After the individual commissioning of the cryogenic control system for each cryomodule, a coordination of the entire system was needed using a Master PLC with overall safety functions and an Automatic Control Sequencer (ACS). The cryomodule controls were therefore integrated with the CMDS master control system, overseeing the simultaneous operation of all cryomodules and the distribution system.
The Control System was successfully commissioned leading to initial operations in December 2024, where the ESS Linac was cooled down to 2K.
This paper describes the last steps of the commissioning activities involving the coordination activities by the Master PLC, and the challenges and achievements when integrating the cryomodules controls into the CMDS. Furthermore, it describes the first operations of the control system during the cooldown until the Linac reached stable conditions at 2K, while preparing the next steps in the Accelerator Cryogenic Controls.

Speaker: Adalberto Ferreira Melo Fonotura (ESS ERIC)

179 C2Po1E-06: Helium Flow Meter for Measuring SRF Cavity Power Dissipation

We present a helium gas flow meter designed to measure power dissipation in Superconducting Radio Frequency (SRF) cavities by quantifying the evaporation rate of helium vapor. The meter operates in the 3–7 K temperature range, measuring helium flow rates with a resolution of 0.05 g/s (~1 W) and functioning at gas velocities from 1 to 14 m/s.
At the Thomas Jefferson National Accelerator Facility (JLab), the flow meter is installed in the return U-tube of an 8-cavity SRF cryomodule. It enables precise power dissipation measurements, identifying individual cavity losses (~30 W range) and total cryomodule heat loads (~200 W with beam on). This capability is critical for detecting contaminated cavities and optimizing cryogenic system performance.
The meter’s exceptional sensitivity stems from a niobium-titanium sensor element (critical temperature 9.2 K) paired with a resistive heater. In "hot-wire anemometer" mode, the heater current is dynamically adjusted to maintain a partially normal conducting state, maximizing sensitivity to helium flow changes. An alternative "sawtooth" mode averages heater current over cyclic operations, compensating for minor variations in helium supply conditions.
To ensure accuracy, each flow meter reading is calibrated using cryomodule heaters while the cavity is off. The meter’s control and data processing are managed via a Linux-based system and a LabJack T7 interface. This system has streamlined SRF cavity performance assessments, replacing labor-intensive methods previously used for LCLS-II-HE cryomodule qualification.
The flow meter is currently installed in 19 of 52 positions in CEBAF, with integration into operations underway. It enables real-time monitoring of cavity dissipation, optimizes cryogenic heat management, and supports long-term performance tracking, correlating cavity degradation with environmental or hardware factors.

Speaker: Mr Kevin Jordan (Jefferson Science Associates)

180 C2Po1E-07: More advancements with CCE pre-integration and automated PI tuning

The traditional integration of Cryocooler Control Electronics (CCE) into spacecraft is evolving. Iris Technology’s continual growth and development of pre-integration methods for CCEs with cryocoolers will further reduce the complexity from the larger spacecraft system integration. Enhancements have been made to the system integration process, including an automation feature for Proportional-Integral (PI) tuning, which optimizes temperature control settling time performance and extends the scope of pre-integration tests for CCE and cryocoolers.

This improved pre-integration service from Iris Technology allows for the establishment and verification of key sub-system conditions before they are included in the complete system. These conditions range from determining optimal power levels to confirming function over a specified temperature range (to be detailed). The established norm for CCE testing relies on an assortment of instruments and physically intensive set-ups, and when actual cryocoolers are absent, substitute static loads might not truly reflect real-life dynamic load scenarios. To overcome such limitations, Iris Technology is creating scripted testing tools designed to automate and refine the CCE testing procedures, providing an approximation of cryocooler performance as well.

In the upcoming presentation, Iris Technology intends to showcase how software automation serves to enhance the integration process of CCE. It will present findings from automated PI tuning and tests pertaining to in-rush current and temperature characterization.

Speaker: Ms Kristin Malenfant

181 C2Po1E-08: Real time heat load calculation software based on EPICS for Fermilab PIP-II CM tests

Fermilab has a project to improve the proton beam energy which is called PIP-II (the 2nd Proton Improvement Plan). There is a superconducting linear accelerator, LINAC, to improve the proton beam power and the LINAC consists of 5 types of cryomodules (CM), 1 HWR CM, 2 SSR1 CM, 4 SSR2 CM, LB650 CM, and HB650 CM. The prototypes of these cryomodules are being tested at Fermilab’s CryoModule Test Facility (CMTF). Heat load measurements are an important part of the prototype CM testing.
The CMTF cryogenic control system was developed based on the ACNET (Accelerator Control NETwork) for CM testing for other projects, but the PIP-II cryogenic control system will be implemented using the Experimental Physics and Industrial Control System (EPICS). As part of the prototype CM testing campaign an EPICS based control system has been implemented at CMTF. This EPICS cryogenic control system includes real time heat load calculation software utilizing the Fortran implementation of Hepak.
This paper details the real time heat load calculation software developed for the prototype CM testing including the first results from the HB 650 CM.

Speaker: Sungwoon Yoon (Fermilab)

182 C2Po1E-09: Design and Development of EPICS-based 6kW Helium Cryogenic Control System

CRAFT is a fusion reactor research facility initiated by the Institute of Plasma Physics, Chinese Academy of Sciences, as part of the national scientific strategy. CRAFT 6kW helium refrigerator is used to provide 4.5K cryogenic test environment for superconducting magents.The EPICS (Experimental Physics and Industry Control System) architecture allows direct access to the PLC controller via the S7 protocol. Both the IOC and the S7-1500R PLC are designed for master-slave redundancy. The entire system communicates with the EPICS Channel Access Bus (LAN) protocol. The control system of the 6kW helium refrigerator based on EPICS architecture is designed and developed, aiming at realizing the efficient and stable supervision operation for the helium refrigerator through automated control and real-time monitoring means. The system adopts EPICS distributed control architecture, combined with sensor data acquisition of key parameters such as temperature, pressure and flow rate, to adjust the operating status of the helium cryogenic system in real time, and is equipped with alarm functions to improve the reliability and safety of the system.During the system design process, this study combines the openness and flexibility of the EPICS platform to design a multi-level and modular control system architecture. In the research methodology, the IOC redundancy design ensures that when the main control unit fails, the standby unit can quickly take over to avoid a single point of failure affecting system operation. The data storage scheme utilizes an efficient database for real-time data acquisition and storage, supporting long-term data analysis. The supervisory control interface is developed using Phoebus software to display the operating parameters of the helium cryogenic system in real time through the graphical interface, which is convenient for the operator to monitor and adjust the control parameters, and at the same time, has a fault alarm function.

Speaker: Mr Xiaofei Lu (中国科学院等离子体物理研究所)

C2Po1F - Large Scale Cryogenic Systems IV: Operation & Design IV

183 C2Po1F-01: Dynamic simulation and automatic control strategy design for the compressor system of 6kW Helium refrigerator

Comprehensive Research Facility for Fusion Technology (CRAFT) is a large-scale scientific engineering project led by the Institute of Plasma Physics, Chinese Academy of Sciences. The cryogenic system of the project includes four helium refrigerators, among which 6 kW@4.5k after the completion of the helium refrigeration unit, it will be used as a magnetic performance research and testing platform for CRAFT. The compressor system is one of the key components of the helium cryogenic system, providing stable and pure high-pressure helium gas for the cold box. The performance of the compressor control system directly affects the refrigeration performance of the refrigerator. The automatic control system can monitor and adjust the working status of the compressor unit in real time, improve the efficiency of the entire cryogenic system operation, and ensure the stability of the system operation. In order to design an automatic control strategy for the compressor system in a 6 kW@4.5k helium refrigerator unit, this paper uses the process simulation software EcosimPro to simulate 6 kW@4.5k A compressor system model was established for the refrigeration unit, and experimental simulations were designed to simulate the start stop sequence and operation process of the compressor unit and the gas storage recovery and purification system. The dynamic response characteristics of the compressor station system were obtained. And analyze the control process of the compressor system based on this model.By analyzing the process flow of a 6 kW@4.5k helium refrigerator, the control flow in the compressor system was studied, including the control flow of the compressor unit and the gas storage and recovery system. Based on the compressor system model established by EcosimPro, complete the automatic control strategy design for the compressor unit and auxiliary system in a 6 kW@4.5k helium refrigeration unit. At present, a preliminary compressor system model has been constructed, and through theoretical verification, the model can provide key basis for subsequent research.

Speaker: Xiaofei Lu

184 C2Po1F-02: Modeling and Dynamic Simulation for the Cold Box of 6kW Helium Refrigerator

The CRAFT 6kW helium refrigerator is used for magnet performance testing and magnet performance research, and the project is designed to build a cryogenic control system adapted to the future direction of fusion reactor development. However, a detailed and accurate modeling and simulation of a specific 6 kW helium refrigerator cold box, especially considering its unique structural characteristics and operating conditions, is the focus of the research on how to model and simulate a helium refrigerator cold box using EcosimPro. The objective of this work is to model and simulate a 6 kW helium refrigerator cold box to understand its thermodynamic performance, flow characteristics and heat transfer process under different operating conditions, aiming to be a reference for optimizing the design and operation of the cold box as well as the design of the automatic control strategy. The main object studied is the 6 kW helium refrigerator cold box, which consists of various components such as Including 80K liquid nitrogen pre-cooling stage, 7-stage heat exchanger, 80K adsorber, turbine expander, throttle circuit, cryogenic valves and pipings.The helium gas enters the cold box and is first compressed by the compressor to raise the temperature and pressure, then cooled down by the heat exchanger, and finally cooled by adiabatic expansion in the turbine expander. The modeling approach is based on thermodynamic and fluid dynamic principles. The key variables considered include the inlet and outlet temperatures and pressures of helium at different points within the cold box, the mass flow rate, and the heat transfer coefficient. The helium refrigerator cold box was modeled and simulated using the specialized simulation software EcosimPro. At present, a model of the helium refrigerator cold box has been completed, and its structural rationality and logical rigor have been ensured through theoretical verification, laying a foundation for subsequent data input and simulation analysis. The dynamic simulation of the cool-down process from 300K to 4.5K will be presented in this paper, and the main control loops will be simulated and analyzed in the end.

Speaker: Xiaofei Lu

185 C2Po1F-03: RAMI analysis of 6kW helium refrigerator system

Helium refrigeration systems, as a critical low-temperature technology, are widely used in high-energy physics experiments, nuclear fusion devices, and cryogenic engineering. These systems serve as essential infrastructure to ensure the normal operation of superconducting magnets, cryogenic equipment, and other related systems. This study focuses on the periodic operation characteristics of a 6 kW helium refrigeration system, employing RAMI (Reliability, Availability, Maintainability, and Inspectability) analysis to investigate the functional decomposition and fault analysis of its critical subsystems. The study covers the functional identification of major subsystems (such as compressors, oil removal systems, and refrigerators), the synergistic interactions between subsystems, and a comprehensive analysis of potential fault modes. By establishing a functional fault mode list, the basic functions, common fault modes, main fault causes, and their impacts on overall system performance are systematically summarized.Building on this foundation, the study conducts a detailed evaluation of the fault modes and impacts of key components (such as turbo-expanders, heat exchangers, and compressors), offering optimization measures from the perspectives of equipment design, operating conditions, and maintenance strategies. By integrating operational data and typical fault cases, the research further evaluates and enhances existing maintenance models, proposing feasible solutions to improve system reliability and operational efficiency.The findings of this study are not only significant for enhancing the safety, reliability, and efficiency of 6 kW helium refrigeration systems but also provide theoretical support and technical references for the design optimization, operation, and performance improvement of similar refrigeration systems

Speaker: Mr Jialong Ye

186 C2Po1F-04: Numerical study of liquid medium based packed bed cold storage in liquid air energy storage system

Liquid air energy storage (LAES) is a promising large-scale energy storage technology that supports renewable electricity integration and reduces carbon emissions. The cold energy storage unit plays a critical role in determining the efficiency of the LAES system. Currently, solid-phase packed beds are commonly used as cold energy storage units in LAES due to their safety and ease of arrangement. However, the thermocline effect within packed beds significantly reduces cold energy storage efficiency. To address this issue, this study introduces an innovative cold storage device employing a liquid heat transfer fluid in a packed bed. This paper presents a numerical analysis based on the porous media model to compare and evaluate the effects of various parameters, such as particle diameter, bed length-to-diameter ratio, and operating temperature range, on the thermocline effect within the packed bed. The findings of this study enhance the development of packed-bed cold storage technology, thereby advancing the large-scale application of LAES systems.

Speaker: Junxian Li (Key Laboratory of Cryogenic Science and Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

187 C2Po1F-05: Conceptual design of a replacement 2.1 K cold box for the Spallation Neutron Source Central Helium Liquefier

The Central Helium Liquefier (CHL) for the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) supports a primary superconducting linear accelerator (LINAC) load up to 2.4 kW at 2.1 K. Sub-atmospheric saturation conditions in the LINAC are generated and maintained by a sub-atmospheric cold box (SCB) within the CHL. The SCB contains four magnetic bearing cold compressors with a nominal flow rate of 125 g/s and a demonstrated operating envelope of 90 – 140 g/s. After more than 20 years of operation the cold compressor technology is obsolete, and replacement parts and service are not available. SNS has partnered with Jefferson Lab to design and construct a replacement SCB using modern cold compressor technology. The general design follows from Jefferson Lab’s experience on other recent sub-atmospheric cold box projects. Design decisions are backed by thorough engineering analysis to ensure technical requirements are met in a cost-effective manner. Conceptual design of the replacement cold box has been completed, and will be summarized in this paper. It features five cold compressors with an expanded operating flow range of 110±30 g/s, and includes new piping and valving to support cold compressor maintenance without interrupting flow circulation to the load. The approach to thermal shielding, insulation, and integration of the upgraded cold compressor hardware into the existing SNS control system will also be addressed. In addition to the operability improvements, process modeling suggests that resource consumption at the CHL will be reduced due to the efficiency of the modern cold compressor system.

Speaker: Brian Mastracci (Thomas Jefferson National Accelerator Facility)

188 C2Po1F-06: Validation of a dynamic simulation model for SNS cryogenic system and its design study for a new 2K cold box

The process simulation model for the Spallation Neutron Source (SNS) cryogenic system consists of a Central Helium Liquefier (CHL) and LINear ACcelerator (LINAC): 30 cryomodule equipped with a dedicated JT valve and its heat exchanger (Vapor vs Supercritical Helium). Each cryomodule has embedded heaters to regulate the suction pressure of a cold compressor train. By adopting the operation setup of CHL, utilizing the floating high pressure of a warm compressor station, the model has been validated by implementing a heater sequence for each module. The paper describes the validation of the global model against the operation dataset. In addition, the paper discusses the new 2 K cold box conceptual design to assess its impact on the 4K cold box operation.

Speaker: Ryuji Maekawa (Oak Ridge National Laboratory)

189 C2Po1F-07: Simulation and optimization of reliquefication refrigerator for cryogenic liquid

Boil-off gas (BOG) in cryogenic vessels must be vented to keep the pressure below the limit and preserve the safety of the tank. Since liquefaction consumes a lot of energy, it is not economical to vent it directly. Undoubtedly, providing refrigeration power to reliquefy the evaporated gas or subcool the cryogenic fluid is a superior scheme. Therefore, an efficient cryogenic refrigerator is essential to provide sufficient refrigeration power, and the performance of the refrigeration system is determined by the composition of the refrigerant, the design of the refrigeration cycle, and the operating parameters. In this paper, we optimized the working fluid composition and process parameters of the turbine-Brayton cycle in the temperature range of LNG, liquid nitrogen, and liquid hydrogen. The refrigeration cycles are established in Aspen HYSYS, and the optimization is performed in MATLAB using the genetic algorithm. Reasonable constraint parameters and variables are given for the optimizations. The optimal process parameters were obtained by 3 independent optimizations. The performance of the three cycles in different temperature ranges was compared in detail. The results show that the new process has significant advantages over the turbine-Brayton cycle. The refrigeration system can be easily scaled and combined so that it can be arranged in scenarios with different refrigeration requirements. This paper will provide an important reference for zero-boil-off storage of large cryogenic tanks.

Speakers: Jihao Wu, Dr Jin Zhen Wang (Technical Institute of Physics and Chemistry, CAS)

190 C2Po1F-08: Model development and optimization of cryogenic mixed-refrigerant cycles with phase separators

Cryogenic mixed-refrigerant cycles (CMRCs) are a promising technology for providing cryogenic temperatures in several areas of research and technology, offering high power density and high efficiency combined with scalability and inexpensive process design.
In order to achieve high process efficiency, the ideal mixture composition and operating conditions for a specific application need to be identified. For this purpose, a simulation and optimization tool is being developed at the Karlsruhe Institute of Technology. The tool uses the Differential Evolution algorithm for optimization, taking advantage of parallel computation.
This contribution focuses on a subgroup of CMRCs known as auto-cascade refrigeration cycles (ARCs), which use one or more phase separators to split the initial mixture into a liquid phase enriched with the high-boiling components and a vapor phase with a higher concentration of low-boiling components. The developed ARC model covers a wide range of process configurations with up to three phase separators and five heat exchangers, optional subcooling of the separated liquid as well as multistage compression. The modeling approach and the optimization algorithm are introduced, and the benefit of phase separators is demonstrated by comparing the efficiency of optimized cycles with and without phase separators.

Speaker: Mr Jakob Reichert (Karlsruhe Institute of Technology (KIT))

09:15 Morning Coffee Break -- supported by Sumitomo (SHI) Cryogenics of America, Inc.

M2Or1A - Characterization of REBCO Conductors II

191 M2Or1A-01: [Invited] Detection of Local Obstacles in Long REBCO Coated Conductors with Introduction of Machine Learning Based Analysis in High-Speed Reel-to-Reel Magnetic Microscopy

Spatial homogeneity is one of the most important requirements of REBCO coated conductors (CCs) for practical applications. We demonstrated automatic detection of local obstacles in a PLD processed long length REBCO CC by introducing image classification based on machine learning into reel-to-reel scanning Hall-probe magnetic microscopy [1, 2]. This allows us to classify magnetic images including obstacles from thousands of images taken from long CC tape. In this study, we further explore this approach for detecting the obstacle more directly as an object, which enables us to analyze the features of the obstacles including size and position in the REBCO CCs. Influence of measurement conditions on the detection was also examined. We found that the spatial resolution is the most important conditions for the detection, and it should be selected the same or similar value between training data and input data so as to realize reliable detection. When we trained an object detection model by using data set from PLD processed REBCO CC from a company, the model can detect obstacles with similar performance even in the other PLD processed REBCO CC from different manufacture. We also studied the influence of these obstacles on the critical current fluctuation of the CCs from the viewpoint of statistics. This method allows us to analyze spatial homogeneity more in detail, which is hardly possible by the conventional methods, and can compare the quality of the CCs and/or clarify the influence of the process conditions. Namely, it can lead useful insights for both CC users and manufacturers.

Acknowledgements: This work was supported by Moonshot R&D - MILLENNIA Program Grant Number JPMJMS24A2 and JSPS KAKENHI Grant Number JP24H00320, JP23K13368.

[1] K. Higashikawa et al., SUST vol. 33, No. 6, June 2020, Art no. 064005, doi: 10.1088/1361-6668/ab89ef
[2] N. Somjaijaroen; T. Kiss; K. Imamura; K. Higashikawa, TEEE TAS, vol. 32, no. 6, pp. 1-4, Sept. 2022, Art no. 6601504, doi: 10.1109/TASC.2022.3156541

Speaker: Takanobu Kiss

192 M2Or1A-02: Critical transverse loading limits of REBCO CORC©-like cables for fusion

High magnetic fields of up to 20 T in tokamak-type fusion devices, such as in Central Solenoids of European DEMO and the Chinese BEST fusion reactors, require High-Temperature Superconductors (HTS). Among the potential candidates, ReBCO tape has emerged as a promising choice. However, the substantial Lorentz forces in these environments can lead to localized mechanical stress, which can irreversibly degrade the critical current of the superconductor.
In addressing this challenge, the Conductor On Round Core (CORC®) configuration appears as a viable solution to withstand these demanding operating conditions. The design of such cables requires comprehensive electromechanical characterization of ReBCO tapes, CORC® cables, and finite element analysis (FEA). This presentation outlines the work conducted at the University of Twente to investigate these three aspects.
For the mechanical characterization of ReBCO tapes, two experiments were performed to examine the strain sensitivity of the critical current under tensile and compressive strains. Tapes from three different manufacturers were tested, and the results are presented.
The transverse load response of two CORC® cables was also studied using an hydraulic press (Twente-Press). A specially designed sample holder was designed to resemble the loading conditions in real CORC®-CICC. Measurements of the critical currents of individual tapes and contact resistances between tapes as functions of applied load and load cycling are shown.
Finally, results from a 3D FEM model are discussed. After validation against experimental data, the model is used to replicate tests conducted at SULTAN for CORC®-like CICC samples. The model predictions are in agreement with the current-sharing temperature behavior, allowing for conductor optimizations.

Speaker: Dr Arend Nijhuis (University of Twente)

193 M2Or1A-03: Integrated Platform for 2D Reel-to-Reel Characterization of 2G-HTS Superconductor Combining Raman Spectroscopy, Color Machine Vision, and Curvature Profiling

Characterizing Second-Generation High-Temperature Superconductors (2G-HTS) or REBCO Coated Conductors (CC) (RE = Rare Earth, Barium, Copper Oxide) requires multi-modal approaches to evaluate critical current density (Jc), chemical and structural uniformity, and defect distribution. Laboratory-scale methods are often limited in speed and throughput, limiting their viability for quality control and emphasizing the need for fast non-destructive techniques. We present an advanced quality control and characterization platform integrating machine vision (MV), Scanning Raman Spectroscopy (SRS) and tape height profiling into a two-dimensional (2D) reel-to-reel (R2R) system. The platform achieves fast 2D scanning of REBCO tapes, providing spatially-resolved Raman spectra, visible surface images, and mechanical characteristics such as tape curvature. Utilizing high-resolution color MV, we detect and quantify precipitates, localized defects and cracks, as well as chemical variations caused during tape fabrication. These features are directly correlated with 2D Raman maps obtained simultaneously, as well as independently collected Scanning Hall Probe Microscopy (SHPM) measurements. This provides the potential to identify features that affect (Jc) performance. Furthermore, integrated optical profiling enables measurement of tape curvature induced by residual strain, which is generally proportional to the density of artificial pinning centers. The system demonstrates reliable and repeatable performance, operating at scan rates of 10 m/h in MV mode, and 1.5 m/h in SRS mode, with the possibility of selective tape rewinding for detailed high-resolution analysis of regions of interest identified via preliminary scans. The long-term goal of this platform is to correlate fast multi-modal scanning with industry-standard critical current density measurements (Jc), significantly increasing throughput for superconductor quality control.

Speaker: Nathaly Andrea Castaneda Quintero (University of Houston)

194 M2Or1A-04: FEM and Modelica Modelling of Current Sharing in Tape Stack Cables; Influence of ICR, ITR, Defect Number, Defect Patterns, and Thermal Boundary Conditions

Previous simulations have shown that the current sharing level decreases with increasing defect density in the middle layer of a three-layer stack cable. Earlier studies focused on a five-layer YBCO tape structure composed of copper, silver, YBCO, Hastelloy, and copper. However, in real-world applications, the buffer layer exists between YBCO and Hastelloy, which has not been accounted for in previous models.
Simulations were performed using Comsol for three-layer cable models with single-layer defects, and Modelica to address the complexity and computational inefficiency of Comsol for modeling five-layer cables with three-layer defects. Defect patterns such as column and tic-tac-toe configurations were tested. A buffer layer was added to the Comsol simulation, modeled as an insulating layer, to see the impact of the buffer layer on a single-side YBCO tape current sharing level. Also, the simulation will be run to see the performance of a double-sided YBCO tape structure under the same conditions.
The analysis revealed that the current sharing level varied significantly with defect patterns, with the column defect pattern demonstrating the worst performance. The simulation showed the buffer layer decreased the current sharing level. Additionally, the double-sided tape configuration exhibited a higher current sharing level compared to the single-sided tape.

Speaker: Minzheng Jiang

195 M2Or1A-05: Nuclear transmutation effect by thermal neutron on degradation in superconductivity of ReBCO tapes

GdBCO, EuBCO and YBCO tapes were irradiated at Japan Research Reactor #3. The samples were bundled and wrapped with cadmium foil with 25 m thick. The first bundle was wrapped with aluminum foil and no cadmium foil. The second bundle was wrapped with three turns (75 m) of cadmium foil and the third was wrapped with five turns (125 m) of cadmium foil. The maximum thermal neutron and the fast neutron were 8.29 x 1022 n/m2 and 1.46 x 1021 n/m2, respectively. The GdBCO tape showed heavy degradation in its superconductivity and the EuBCO tape showed less degradation than the GdBCO tape. The YBCO tape showed almost no degradation. The degradation behavior is strongly connected with the cross section of {n,} reaction of the rear earth elements. The coated layers of the irradiated samples were pealed and scratched out and the gamma ray spectrum was investigated by a Ge detector. The Ge detector analysis showed that the isotopes of Gd and Eu were detected but no isotopes of Y was measured. From these results, the degradation process and mechanisms were considered. The thermal neutron capture by Gd and Eu generated the radio isotopes of Gd and Eu, and the radio isotopes decay by electron capture or beta decay. During the decay process, the nuclear transmutation of Gd and Eu continues and the electron exchange on the nucleus will disturb the electron state on CuO2 planes which sandwich the rear earth element. The disturbance will perturb the superconducting current flow and the degradation behavior could be observed.

Speaker: Prof. Arata Nishimura (National Institute for Fusion Science)

C2Or2A - Large Scale Refrigeration III: 2K Systems

196 C2Or2A-01: Operation experience with a 1.8 K refrigeration unit during the 2024 LHC physics run at CERN

More than 6’000 hours of nominal cryogenic conditions were provided for the LHC (Large Hadron Collider) physics run during 2024, allowing to reach a record integrated luminosity of 124 inverse femtobarns. The cryogenic system availability during this year was of 96.5% (target 95% to 98%). Out of the total downtime, 80% came from a series of events that led to five trips of the same 1.8 K refrigeration unit. To ensure that a high level of availability is kept as the equipment ages and the luminosity of the machine increases, all failure cases as well as its effects have been thoroughly analyzed. The results together with new consolidation measures aiming at further increasing the reliability and availability to physics are presented.

Speaker: Boyan Naydenov (CERN)

197 C2Or2A-02: Performance of the 2K cryogenic refrigerators for SHINE

The Shanghai High repetition rate XFEL and Extreme light (SHINE) facility is a free electron laser facility that is located at the Zhangjiang High-tech Park of Shanghai Pudong. The major facility is installed in the tunnels at the depth of ~29m underground and with a maximum length of 3.1 km. It is composed of five shafts, one accelerator tunnel and three parallel undulator tunnels and the donwnstream three beamline tunnels, with each undulator tunnel capable of accommodating two undulator lines. In its initial phase, the SHINE consists of an 8 GeV continuous wave (CW) superconducting radiofrequency (SCRF) linac, three undulator lines, three downstream FEL beamlines, and ten experimental end-stations.
AL-AT (Air Liquide Advanced Technologies) takes part in the project by supplying three cryogenic refrigeration systems located at different places of the tunnel. Each of the three plants has an equivalent power of 13kW at 4.5K. Each plant is composed of a four pressure level Warm Compression Station, a 4K cold box composed of four turbines and a liquid Nitrogen pre-cooling and a deported 2K cold box including the cold compressors. The available power at 2K is 4000W for each plant in addition to other loads such as Thermal Shield, Cold Shield, liquefaction. The performance test of the refrigeration system has been demonstrated and will be presented here.

Speakers: Jean-Marc Bernhardt (Air Liquide Advanced Technologies), Nicolas Chantant, Noelle Besse (Air Liquide Advanced Technologies), Pascale Dauguet (Air Liquide), Yannick Fabre

198 C2Or2A-03: Performance of the 2K cryogenic refrigerators for HIAF

The iLinac of the Heavy ion Accelerator Facility (HiAF) project, undertaken by the institute of Modern Physics (IMP), Chinese Academy of Science (CAS), is located at Huizhou Guangdong Province, China. The HiAF iLinac adopts Superconducting Linear Accelerator (SLA) technology, includes thirteen cryomodules of three different types of cavity with about 100 meters length in total, using 2K super-fluid helium bath cooling. In order to meet the requirements of the project, it is necessary to build a new cryogenic system to provide cryogenic conditions for test and operation of the facility in IMP.
At this facility, AL-AT (Air Liquide Advanced Technologies) is the cryogenic supplier of the refrigeration system. The installed refrigeration system has an equivalent power of 6.5kW at 4.5K including 2150 W at 2K. The refrigeration system is composed of a warm compression station including oil flooded screw compressor and vacuum pumps, the cold box including four turbines and three cryogenic compressors and a large capacity dewar. The performance test of the refrigeration system will be presented here.

Speakers: Jean-Marc Bernhardt (Air Liquide Advanced Technologies), Nicolas Chantant, Pascale Dauguet (Air Liquide), Yannick Fabre

C2Or2B - [Special Session] Liquid Hydrogen Testing for Aircraft

199 C2Or2B-01: [Invited] Design and Development of a State-of-the-Art Cryogenic Testing Platform for Liquid Hydrogen Applications

Liquid hydrogen (LH₂) is emerging as a promising alternative to fossil-based fuels to reach net-zero targets by 2050 due to its purity, high volumetric density compared to compressed gas, and versatility. However, designing infrastructure to handle LH₂ presents significant challenges, necessitating rigorous testing at cryogenic temperatures (20 K) to evaluate the materials and systems involved. This study introduces a novel, state-of-the-art cryogenic testing platform comprising five newly designed equipment to evaluate cryogenic properties.

Cryogen-Free Mechanical Testing Cryostat (MTC): The MTC is precisely engineered to comply with industry standards, including ASTM E8/E8M, ASTM D638, and ASTM D3039/D3039M, to meet the specific requirements of tensile testing for a range of materials including metals, plastics and composites. The system features a tensile loading capacity of 50 kN and integrates a two-stage Gifford-McMahon (GM) cryocooler within a customized self-reacting tensile testing jig. In addition to the cryostat design, this study presents the novel gripper design adopted for this cryostat system and its performance in both room and cryogenic temperatures.

Composite Leak Testing Cryostat (CLTC): The CLT setup enables the quantification of cryogenic gas leakage under thermal stress and uniaxial loads applied to cylindrical composite specimens. Given the critical importance of cryogenic composite tanks in LH₂ and space applications, real-time measurement of gas leakage caused by failures such as microcrack generation and delamination is essential. The CLTC system measures the gas leakage due to 1 atm pressure difference while incrementally increasing loads. This equipment not only assures the serviceability of the composite but also allows the determination of the maximum stresses that can be tolerated by the material with specified leak rates.

Magnetic Refrigeration Testing Setup (MRTS): Magnetic refrigeration is a promising technology for reliquefying LH₂ boil-off from tanks to reach zero boil-off conditions. This lab-scale MRTS facilitates the testing and optimization of magnetocaloric materials, refrigerants, and magnetic systems enabling industrial-level upscaling. The equipment can accommodate both permanent and superconducting magnet systems up to 8T and uses supercritical helium as the working fluid, circulating at a flow rate of 0.2 g/s, extendable to 7 g/s. The design incorporates two GM cryocoolers, an actuator system, and four heat exchangers to replicate real-world conditions. The novel transient numerical modelling approach adopted in this design evaluates the regenerator bed's performance integrated with heat exchangers and an external magnetic field, quantifying the hydrogen liquefaction rate.

Cryogen-Free Thermal Conductivity Testing Cryostat (TCTC): Thermal conductivity is one of the critical properties in cryogenic infrastructure design for both structural and insulation materials. Comparative to traditional boil-off measuring techniques of thermal conductivity measurement, utilization of GM cryocoolers embedded cryostat allows more flexibility in measurements. However, designing the equipment with minimal thermal noise interfering with the readings is challenging. TCTC is designed based on the concept of C1774 and it can accommodate both cylindrical and flat samples. Finite element modelling used in TCTC design facilitates the precise analysis of thermal interferences during measurements and enables the development of effective strategies to mitigate potential failures.

Hydrogen Liquefier: The lab-scale hydrogen liquefier integrates a GM cryocooler with an ortho-para hydrogen catalytic bed, enabling efficient hydrogen liquefaction. Gaseous hydrogen will be taken in at a mass flow rate of 10 mg/s within a range of pressures of 35 – 50 bar in the equipment. A 100 L LH2 dewar is incorporated into the cryocooler system for the storage of liquid hydrogen with minimum boil-off.

Overall, this study presents the innovative designs and design methodologies adopted in developing this advanced cryogenic testing platform. Additionally, it delves into the insights gained and the challenges encountered throughout the equipment design and development process.

Speaker: Shanaka Kristombu Baduge (The University of Melbourne)

200 C2Or2B-02: [Invited] Airbus Structures Test - Cryogenic Test Capability Development

At Airbus, our ambition is to bring hydrogen commercial aircraft to market by 2035. Our ZEROe programme was launched in 2020 to explore different aspects of hydrogen aviation encompassing the technologies that need to be adapted and the hydrogen ecosystem required to make this ambition a reality. One of the main challenges that was identified early on in the project is the limited cryogenic testing capability in the aviation industry.

Within Airbus Structures Test, we're doing all we can to accelerate our journey towards certifying hydrogen aircraft, by up-skilling the team with the required knowledge, from the design of test rig suitable for cryogenic/hydrogen environment, through to the measures that need to be taken whilst testing in cryogenic conditions.

In this talk, I will give a brief overview of Airbus’ Structures Test cryogenic test strategy, spanning our cryogenic test facility development, our future vision and our current and future cryogenic tests taking place in Airbus.

Speaker: Dr Harina Amer Hamzah (Airbus Operations UK Ltd)

201 C2Or2B-03: [Invited] A vertically integrated cryogenic hydrogen testing laboratory

Over the last 15 years, the Hydrogen Properties for Energy Research (HYPER) laboratory has completed cryogenic hydrogen research in a university laboratory setting safely and sustainably. However, the current demand for cryogenic hydrogen research facilities is rapidly outpacing available testing capacity. Future growth of the nascent cryogenic hydrogen industry will be significantly hindered if the available testing capacity is not improved. In this presentation, the key tools enabling HYPER to conduct this research are presented, which have led to the development of multiple customizable cryostats. Scale of the facilities is continuing to increase. Last fall, the US Department of Energy selected the HYPER-Flow and HYPER-Fuel projects for funding which will add the world’s first continuous liquid hydrogen flow loop and a Medium/Heavy-Duty liquid hydrogen refueling station. The resulting combination of equipment spans Technology Readiness Levels 3-7, making HYPER a vertically integrated facility for the production of startup companies in the cryogenic hydrogen sector.

Speaker: Prof. Jacob Leachman

202 C2Or2B-04: [Invited] The Development of a Liquid Hydrogen Test Capability for Aviation and Beyond as a US National Asset

NASA has over 70 years of experience handling both gaseous and liquid hydrogen for space and aeronautical applications. As hydrogen comes back into the public sphere as a possible energy carrier, NASA can contribute in multiple ways to help US industry lead the way into these new ventures. Based on the results from workshops and discussions with US industry, academia, and other government agencies, one way for NASA to infuse their experience is through facilitating testing endeavors. Testing with hydrogen, especially liquid hydrogen, is an expensive endeavor requiring a specially trained workforce and significant infrastructure investments beyond the capability of many small and medium businesses. A multi-center NASA team is exploring the needs and requirements that might play into the development of a Liquid Hydrogen Test Area as a National capability supporting the implementation of new materials and technologies for aeronautical applications, allow the development of operational procedures for airport operations, and also support the needs for the development of technologies for other hydrogen transportation applications. These needs may include testing at a range of scales, from material development and component characterization to full sized aircraft.

This exploratory activity only gathers information to inform future plans; it offers no promise of future funding, or request for proposals for either execution or implementation of such a facility. However, the gathering of this information can be used to help NASA and others within the US Government understand how this might be best executed and the level of interest across the country for its implementation. As such, NASA has issued a Request for Information from US Industry and Academia and continues conversations with other US government agencies pursuing Hydrogen technology development, deployment, and commercialization.

Speaker: Wesley Johnson (NASA Glenn Research Center)

203 C2Or2B-05: Panel Discussion

C2Or2C - Large Scale Cryogenic Systems V: Analysis and Modeling

204 C2Or2C-01: Analysis of quench safety and cryogenic energy recovery for FRIB High Transmission Beam Line magnets

The High Rigidity Spectrometer (HRS) will be the centerpiece experimental tool of the Facility for Rare Isotope Beams (FRIB) fast-beam program. The HRS project is staged in two phases: the High Transmission Beam Line (HTBL) phase followed by the Spectrometer (SPS) phase. The HTBL will contain 24 superconducting quadrupole magnets (in 8 triplet cryostats), four superconducting dipole magnets, and three (non-superconducting) vertical corrector magnets. In general, these magnets will store a peak energy of 300-400 kJ and the cryogenic boil-off flow from a quench induced heat release will be primarily handled by the FRIB quench energy recovery system. The magnet cryostats will be also equipped with pressure safety devices as auxiliary protection. The FRIB quench energy recovery system has proven to be tremendously useful during the commissioning and operation of the FRIB target and pre-separator segment magnets. All these magnets were tested, commissioned with the aid of this quench energy recovery system, without losing any helium during a quench and a rather quick turn-around time from quench to normal operation of approximately 30 minutes. A thermodynamic model to estimate a magnet cryostat pressurization due to quench, and subsequent release of cryogenic helium flow to the FRIB quench energy recovery system has been developed and validated using test data. The HTBL magnet cryogenic system response (heat release, subsequent pressurization and boil-off flow) during a quench is simulated using this model. The results are utilized to predict the overall system response and address relevant design issues e.g. sizing of magnet cryostat pressure relief devices and relevant HTBL cryogenic system components. The model development, validation and the simulated results are discussed in this paper along with the sizing methodology for the relevant cryogenic components.

Speaker: Dr Nusair Hasan (Michigan State University)

205 C2Or2C-02: Protection of the SFRS Local cryogenic system against catastrophic pressure increase and sizing of safety valves

Super Fragment Separator (SFRS), currently under construction at FAIR GmbH, is a superconducting powerful in-flight facility which will provide spatially separated isotopic beams up to elements of the heaviest projectiles. The facility is divided into 8 functional sections, called branches, and ultimately will comprise 63 cryostats containing dipole and multiplet magnets. The magnets in the cryostats will be cryostated at 4.5 K by liquid helium. The cryostat cold masses will be thermally protected by a shield cooled by 50 K – 80 K gaseous helium. Helium is to be distributed along the SFRS separator by Local Cryogenics System (LCS), which is also sectorized into 8 branches. Each LCS branch consists of Feed Boxes supplying the cryostats with helium and interconnected by a 4-channel cryogenic line. The hydraulically coupled LCS branches connected via so called Common Cryogenic System with a dedicated helium plant and several distribution boxes, create a very complex hydraulic system. All process lines of the LCS system must be protected by safety valves against excessive pressure that may arise in the event of the system failure. The paper presents the details of the SFRS Local Cryogenics System construction and explains the concept of the process lines overpressure protection. Further it discusses the most critical scenario of the LCS failure and introduces the methodology of safety valves dimensioning, used by Wroclaw University of Science and Technology during the System design phase.

Speaker: Jaroslaw Polinski

206 C2Or2C-03: Modelling two-phase He II flow for heat load limits in EuXFEL cryomodules for CW operation

The European XFEL is under consideration for a High Duty Cycle (HDC) upgrade to enable Continuous Wave (CW) or Long Pulse (LP) operation, enhancing the user’s operational range. One of the key challenges for this upgrade is managing the increased heat load of the existing cryomodules while ensuring sufficient cryogenic capacity for stable operation. The two-phase pipe within the cryomodules plays a critical role in maintaining stable cryogenic conditions, preventing vibrations and microphonic effects.
To address these challenges, a simulation model has been developed to analyze the two-phase flow behavior of superfluid helium (He II) in EuXFEL-like cryomodules at the cryomodule test benches CMTB and AMTF. The model incorporates the Taitel-Dukler criterion to evaluate the transition from stratified smooth to stratified wavy flow under varying heat loads. Flow characteristics were systematically studied for different heat loads, helium temperatures, vapor qualities, and filling grades of the two-phase pipe.
The results highlight the maximum heat load that a EuXFEL-cryomodule can sustain before the transition to wavy flow in the two-phase pipe occurs and provide insights into optimizing operating conditions. These findings suggest potential pathways for increasing the heat load limits without requiring modifications to the cryomodule design.

Speaker: Dr Aman Kumar Dhillon (Deutsches Elektronen-Synchrotron DESY)

207 C2Or2C-04: System-scale dynamic simulation of the 400W@1.8 K Test facility at CEA Grenoble: experimental validation on steady state and transient configurations (towards new applications)

CEA Grenoble DSBT (Low Temperature System Department) commissioned in 2004 a test facility with a cooling capacity of 400W@1.8K (or 800W@4.5K). This system comprises a cold box with two centrifugal cold compressors, a cold turbine, a wet piston expander, counter flow heat exchangers and a phase separator at 4.5 K and a large Multi-Test Cryostat than can include a phase separator at 1.8 K. It has been designed to be modular in order to meet the needs of a wide range of studies: test of industrial components at 1.8 K, studies on thermal-hydraulics of two-phase superfluid helium, fundamental research on high Reynolds number turbulent flows. Recently, in the framework of the future High Luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN, the 400W@1.8K facility was used to characterize a specific compact heat exchanger between a He II pressurized bath and a He II saturated bath in order to cool the D2 magnet in different operating conditions at 1.8K and 2K.
At the same time, the Simcryogenics library was developed in the same CEA team to simulate and optimize cryoplant and its distribution to end-users. This homemade tool, based on Simscape, the modelling language extension of the Matlab/Simulink software, aims in particular to generate model-based control schemes for cryogenic plants that are subject to high disturbances (such as pulsed heat loads infusion reactors or particle accelerator). The library is validated on numerous experimental systems: warm compression station, cooling of superconducting magnets, cold boxes (JT-60SA Auxiliary cold box), RF cavities (SPIRAL 2 cryomodules), data from the 400W@1.8K test facility in the 800W@4.5K configuration.
Recently specific tests have been carried on the 400W@1.8K test facility to validate the simulation of systems including parts with superfluid Helium. The present paper aims to complete the Simcryogenics validation using these specific tests. The validation includes two parts: firstly, validation of each component and of the whole system based on steady-state tests with different flowrates and temperature between 1.8 K and 2 K; secondly, validation of the whole system model on transient configurations.
Anchoring the Simcryogenics library to the available data in superfluid helium will facilitate the running of the 400W@1.8K test facility (i.e. parameters optimization, model-based control tuning) and to explore new configurations. In particular, a System-modelling approach will be used to answer to the new challenges: to define the best architectures to provide several levels of cooling temperature at the same time or for managing load variations in the case of many end-users with varying cooling requirements for new applications such as the refrigeration of quantum cluster-like computer infrastructure.

Speaker: Dr Jérôme Pouvreau (Univ. Grenoble Alpes, CEA, IRIG, DSBT, 38000 Grenoble, France)

208 C2Or2C-05: Development of a simulation code for analyzing pressure and temperature fluctuations in the J-PARC cryogenic moderator system

At the Japan Proton Accelerator Research Complex (J-PARC), three hydrogen moderators operate using supercritical hydrogen at 1.5 MPa and 18 K. Nuclear heating induced in the hydrogen moderator during 1-MW proton beam operation is estimated to be 3.8 kW. A cryogenic moderator system (CMS) was designed to circulate the supercritical hydrogen at 162 g/s, effectively removing this transient heat load and limiting the temperature rise to below 3 K. Additionally, a parallel configuration was implemented to ensure consistent delivery of 18 K hydrogen to each moderator. The J-PARC CMS is cooled by a helium refrigerator with a cooling capacity of 6.4 kW at 16 K. An ortho-to-parahydrogen catalyst vessel is also integrated to maintain the parahydrogen fraction above 99%. To mitigate pressure fluctuations caused by transient temperature rises in the moderators due to nuclear heating, a pressure mitigation system was developed. This is system consists of a heater and a helium-filled bellows vessel, ensuring stable operation under varying thermal loads. A simplified simulation model was previously developed to study the cooldown process of the J-PARC CMS and optimize operational parameters. In this model, the parallel distribution lines to the moderators were treated as a single combined line, and the heat load was directly applied without modeling the heat exchanger. However, as the proton beam power increases, adjusting the flow distribution becomes essential to ensure the temperature rise across the moderators remains below 3 K. In this study, we developed a comprehensive simulation code that incorporates the parallel distribution lines and heat exchanger to estimate propagation of temperature fluctuation throughout the entire CMS loop and the resulting temperature fluctuations in the return helium flow to the refrigerator cold box. This code aims to optimize the J-PARC CMS operational conditions for not only the current 1-MW proton beam operation but also to study the future 1.5-MW proton beam operation planned for the upgrade target station. The simulation results demonstrated good agreement with experimental data, validating their ability to predict temperature propagations behavior across the CMS loop.

Speaker: Dr Hideki Tatsumoto (European Spallation Source ERIC (ESS))

209 C2Or2C-06: Advancing 1D thermo-hydraulic tools for large cryogenic facilities

The Cryogenic Division at Fermilab is dedicated to designing and fabricating large cryogenic facilities for particle accelerators, as well as test facilities for superconducting magnets and cavities. The development of these large-scale facilities necessitates innovative numerical tools to aid in the design of various components and to provide more accurate estimates of heat loads. Several years ago, the cryogenic team developed a Python-based code capable of calculating friction factors and pressure drops in various piping components, including manual, control, and relief valves. This initial version of the code has proven instrumental in better estimating pressure variations in large facilities during cooldown and across various operating modes.
This paper introduces new heat transfer functions that have been incorporated into the existing code, along with the enhanced design and diagnostic capabilities they bring. The theoretical foundation and assumptions underlying these heat transfer functions are described in the first section of this paper. The first example demonstrates a one-dimensional thermo-hydraulic calculation applied to various relief pipes of the Proton Improvement Plan-II (PIP-II) particle accelerator at Fermilab. The analysis of pressure and temperature evolution along these pipes informs optimal pipe sizing to minimize pressure drops, limit static heat conduction and prevent damage to relief valves during critical events.
The second example highlights the application of these functions to more accurately estimate heat load evolution and its impact on temperature sensors in a pipe filled with sub-atmospheric helium. This thermal analysis is crucial for accurately diagnosing the temperature evolution of sub-atmospheric gas returning to the cold compressor from cryomodules filled with saturated superfluid helium.
These advancements in the code significantly enhance its utility, offering robust tools for the design and diagnostic processes critical to the development and operation of large cryogenic facilities.

Speaker: Romain Bruce (Fermilab)

C2Or2D - Aerospace Cryocoolers II: JT Cryocoolers

210 C2Or2D-01: Northrop Grumman NewATHENA 4.5K Cryocooler DM Testing

The NewATHENA X-ray Integral Field Unit (X-IFU) requires a cryogenic precooler capable of providing significant heat lift at both 4.5 K and 20 K. To increase the design maturity and identify key technical risks of a candidate Engineering Model (EM) and Flight Model (FM) cryocooler, a Demonstration Model (DM) phase was awarded to Northrop Grumman. Northrop Grumman’s approach to providing the NewATHENA cryocooler is a modification of the Mid-InfraRed Instrument (MIRI) hybrid Pulse-Tube (PT) Joule-Thompson (JT) cryocooler design that is implemented on the James Webb Space Telescope (JWST). The Northrop Grumman cryocooler for the JWST MIRI instrument was designed for operation at 6 K with intercept loads at ~18 K and continues to operate nominally on orbit. By implementing minor modifications to the JT loop of the cryocooler, the cryocooler can achieve the required heat lift at both 4.5 K and 20 K while maximizing reuse of heritage hardware and hardware designs for reduced risk on NewATHENA. Modifications to the JT portion of the hybrid cryocooler are the focus of Northrop Grumman’s DM phase testing. This paper provides our approach to the NewATHENA cryocooler, the compressor level performance requirements consistent with the heat lift required at both 4.5 K and 20 K, and the results of to-date performance tests conducted at a range of rejection temperatures and input power levels. The results of these tests demonstrate that minor modifications to Northrop Grumman’s TRL-9 cryocooler yield system level performance consistent with NewATHENA cryocooler heat lift and operating temperature requirements.

Speaker: Nicholas Rich (Northrop Grumman)

211 C2Or2D-02: BAE Hybrid Cryocooler Solution for the ESA Athena Mission

Next generation Astrophysics Science Missions seek to interrogate the Far-IR and X-ray wavelengths requiring ADR cooled detectors to 100 mK or less. Operation of these ADR systems requires efficient thermal rejection at 4-5 K coupled with observatory cooling needs at 4-5 K and parasitic load interception at nominally 20 K. One example is the ESA Athena Mission that focuses on X-ray wavelengths. BAE has developed a high efficiency Hybrid Cryocooler Design capable of meeting the thermodynamic, EFT, mass, and power requirements for this mission. The BAE Hybrid Cooler consists of a Two-Stage Stirling Pre-cooler coupled to a J-T stage that provides remote cooling between 4-5 K and 18-20 K. Performance predictions for the BAE Hybrid cooler solution are presented in comparison to the Athena Mission requirements. Additionally, details of a custom BAE J-T cooler test facility used to validate performance predictions for the 4K/20K J-T cooling stages is discussed.

Speaker: Ryan Taylor (BAE Systems Inc.)

212 C2Or2D-03: Sorption Compressor Developments for Vibration-Free JT Cryocoolers

The ETpathfinder (ETPF) is a scaled prototype of the Einstein Telescope gravitational wave observatory, developed to validate and advance the technologies required for next-generation detection. It features two Fabry–Perot Michelson interferometer arms cooled by liquid nitrogen (LN₂), with one arm requiring additional cooling to approximately 10 K. Because third-generation laser-interferometry detectors demand minimal vibration for precise measurements, the University of Twente has proposed a modular “cryochain” design. This configuration combines sorption-based compressors and Joule–Thomson (J–T) cold stages in a parallel cascade at 40 K (neon), 15 K (hydrogen), and 8 K (helium), yielding cooling powers of 2.5 W, 0.5 W, and 0.05 W, respectively. A key factor in ensuring the cryocooler’s compactness and performance is the sorption compressor, which comprises multiple sorption cells and additional passive components. The design and operation of these sorption cells require thorough investigation and optimization to achieve the targeted cooling efficiency. Recent predictive models of the sorption process offer valuable insights into factors such as pressure dynamics and thermodynamic cycles, informing critical design decisions for improved efficiency and reduced vibration. Crucially, these optimizations can also be adapted for low-vibration cryocooling in space-based systems and satellite applications, where minimizing disturbance is equally vital. Collectively, these developments establish a pathway for implementing a robust, low-vibration sorption cryocooler, representing a significant stride toward meeting the stringent requirements of high-sensitivity measurement applications.

Speaker: Mr Arvi Xhahi (Nikhef / University of Twente)

213 C2Or2D-04: Closed Loop He3 JT Stage Performance Demonstration

To mature the cryocooling system for the Probe far-Infrared Mission for Astrophysics (PRIMA) mission concept, a closed-loop JT stage using flight-like residual hardware from the JWST program was assembled to assess its cooling capacity at 4.5 K. The performance of the JT stage over a range of heat sink temperatures and system pressures was characterized. The paper presents test results without using a DC current to maintain the piston dynamic center position. The maximum allowable piston stroke was determined experimentally to maintain adequate headroom at the piston fore end over the entire expected operating temperature and pressure range. The paper presents the JT stage performances and maximum allowable stroke length with two different passive piston back pressure controls. The measured performance is compared with predicted performance and PRIMA mission required capability.

Speaker: Dr Weibo Chen

M2Or2A - Low Temperature Properties of Austenitic and Maraging Steels

214 M2Or2A-01: Numerical and Experimental Investigation of Deformation Induced Martensitic Transformation in Fused Filament Fabricated Austenitic Stainless Steel for Cryogenic Applications

Cryogenic structural components, such as collars, bladders, keys for superconducting magnets, and elements of liquid hydrogen storage systems like hoses and valves, are frequently constructed from austenitic stainless steel due to its favorable properties. However, manufacturing these components using traditional methods is challenging due to their complex geometries. Additive manufacturing emerges as a promising solution, though a comprehensive understanding of the associated material behavior under extreme conditions is still developing.

This study aims to explore the deformation-induced martensitic transformation (DIMT) in fused filament fabricated (FFF) 316L stainless steel through both experimental testing and numerical simulation. The research focuses on predicting the material’s response under tensile stress at ambient, 77K, and 4K temperatures.
Numerical simulations employ a finite element approach to incorporate the constitutive model and its temperature-dependent phase transformation kinetics, enabling detailed investigation of stress and strain distributions at various cryogenic temperatures. These simulations are systematically calibrated and validated against corresponding experimental datasets, ensuring that the computational predictions mirror the observed microstructural evolution and macroscopic response under tensile loading. By comparing simulation results to experimental findings obtained at temperatures from room temperature down to 4K, the reliability of the model can be assessed, and its predictive capabilities can be refined.

Ultimately, the research seeks to expand the understanding of DIMT in additively manufactured 316L components, supporting the development of advanced, simulation-driven material models tailored for demanding cryogenic structural applications.

Speaker: Daniela Schob

215 M2Or2A-02: Electromagnetic properties of austenitic stainless steels in cryogenic, high magnetic field environments

Commonwealth Fusion Systems (CFS) is developing a high-field, compact tokamak, SPARC, enabled by REBCO-based high temperature superconducting (HTS) magnets. For the toroidal field magnetic coils, the REBCO tape is housed in austenitic stainless steel radial plates. The structural loads on the radial plates from Lorentz forces are extremely high during operation. Austenitic stainless steels are chosen for their high strength and low magnetization in SPARC operating conditions. Under extreme temperature and magnetic field, changes in electromagnetic properties can be profound if not accounted for when modeling the electric and magnetic performance of these components in cryogenic electromagnetic systems. While stress-induced martensitic transformation in austenitic stainless steels is well studied, the combined effects of cryogenic temperatures (<25 K), high magnetic field (>10 T), and mechanical stress alter the transformation kinetics. This research explores the effects of cryogenic temperature and high magnetic field cycling on key electromagnetic properties of the radial plate material. In this study, we have correlated electromagnetic properties at room temperature with in-situ measurements. We attribute the differences in room temperature electromagnetic properties and performance to potential phase transformations and dislocation build up in the material. The correlative models we have built from this data will be presented.

Speaker: Polina Ermoshkina (Commonwealth Fusion Systems)

216 M2Or2A-03: In-Situ and In-Operando Monitoring of Laser and Electron Beam Welding Processes for Austenitic Stainless Steels

Laser and electron beam welding processes are advanced manufacturing technologies that are critical for the high precision and complex geometries prevalent in cryogenic systems. Implementation of these technologies is currently reliant on high skilled labor. Furthermore, designs are pushing the process physics and the material properties to their limits. In-situ and in-operando monitoring is of high interest to control operation within these constricted process windows, to develop models and automation systems to minimize the reliance on skilled labor, and to advance the fundamental understanding of the process-structure relationships. The presentation will explore the in-situ and in-operando monitoring of laser and electron beam welding of austenitic stainless steels which are important materials for cryogenic systems.

Speaker: Boyd Panton (The Ohio State University)

217 M2Or2A-04: Low-Temperature Fatigue and Fracture Properties of Maraging C250 Steel

Maraging steels are attractive alloys for engineering applications requiring high strength, good fatigue, and fracture properties. Although Maraging steel is usually used in room temperature or elevated temperature applications, it has found a place in cryogenic applications. Cryogenic data for maraging steels in the literature is limited. Since it is a precipitate-hardened martensitic steel, fatigue and fracture properties at low temperatures are of concern. Preliminary examinations reveal that at 77K, this alloy can operate at a cyclic stress value of 1000 MPa (r=0.1), for greater than 106 cycles. Here, we report on tensile and fracture toughness properties, axial fatigue life data (S-n curves, R = 0.1), and fatigue crack growth rates on commercially available C-250 maraging steel at cryogenic temperatures. Metallographic evaluations of microstructure and fracture surfaces will be presented to correlate structure-property relationships.

Speaker: Mr Robert Walsh (Materials Reliability Inc.)

218 M2Or2A-05: First Approximation for Unified Fatigue Models for 316 Stainless Steel and IN718 Materials at 4K, 77K & 293K from Monotonic Material Properties

Fusion applications utilizing magnets require the use of materials that are capable of withstanding the cyclic electromagnetic forces during startup and shutdown at cryogenic temperatures. Because of the cyclic nature of loading, a fatigue model is essential to characterize the capability of these parts to determine operational life and prevent premature component failure. Thus, there is a need for test data at low temperatures, specifically at 77K and 4K, corresponding to the temperatures of liquid nitrogen and helium, respectively. However, testing at such conditions is very expensive, requiring proper containment, sufficient coolant supply, and load / strain monitoring throughout the life of the test. Thus, the initial approach to this effort is to conduct a literature search to establish a preliminary foundation of available fatigue data, then supplementing the database with additional testing as needed. At this time, the data from the literature search has been successfully fit at three temperatures (4K, 77K, and 293K) to a standard Manson-Coffin-Basquin model with a typical to min scatter under 7.0. Additional work has been done to apply this data to a hardness-based lifing approach, which proposes that fatigue behavior can be sufficiently characterized using monotonic properties, at least to a first approximation. Preliminary results for this approach have been successful for both 316 type stainless steel and Inconel 718, resulting in conservative but reasonable fatigue estimates for both room and cryogenic temperatures.

Speaker: Raymond Kersey (Advanced Fracture Mechanics Associates LLC)

219 M2Or2A-06: In-Situ Monitoring of Strain Field Evolution and Dissipative Effects at Cryogenic Temperatures (77K): Insights into Advanced Materials for Superconducting and Hydrogen Storage Applications

The in-situ monitoring of strain field evolution and dissipative effects in advanced materials at cryogenic temperatures represents a significant milestone in understanding thermo-mechanical behaviour under extreme conditions. This research focuses on conducting full-field strain measurements at liquid nitrogen (77K) temperatures using an innovative DIC-enhanced experimental platform. Two type materials are tested: (i) conventional austenitic stainless steels (ASS), and (ii) additively manufactured (AM) austenitic stainless steels.
Currently, no experimental framework exists for performing such detailed 2D strain measurements on macro-specimens and structural components at 77K, particularly when coupled with multi-detector identification of dissipative effects. To address this, a unique experimental setup will be developed, integrating the following components: (i) a 4-thermistor system for precise temperature distribution measurements, (ii) a force link system for direct force application monitoring, and (iii) an acoustic emission system for detecting micro-damage and dissipative effects. The specimen will be immersed in a glass cryostat equipped with active and passive insulation to maintain thermal stability during mechanical testing at 77K. Signals from this multi-detector array will be synchronized with strain field evolution data obtained via digital image correlation (DIC), enabling comprehensive real-time monitoring of material behavior during tensile, fracture, and fatigue tests.
The experiments conducted with this advanced platform aim to achieve the following objectives:

-Identification of Dissipative Effects: The origins of dissipative effects such as plastic flow instability, phase transformation, and micro-damage evolution will be experimentally recognized.

-Material Property Determination: Mechanical properties of advanced materials, including yield strength and fracture toughness, will be accurately measured at cryogenic temperatures.

-Correlations of Dissipative Effects with Plastic Strain: Key phenomena, such as damage-induced plastic flow or phase transformations, will be correlated with incremental plastic strain during deformation.
- Coupled Effects Analysis: Coupled effects, including damage-influenced discontinuous plastic flow, will be identified and analyzed.

-Constitutive Model Validation: The data will be used to validate constitutive models describing advanced materials deformed at 77K.

Speaker: Jakub Tabin (Institute of Fundamental Technological Research PAS)

C2Po3A - Magnet and Cryomodule Heat Load Management

220 C2Po3A-01: Heat load measurements for the PIP-II pHB650 cryomodule

This study presents a brief overview of the 1st and 2nd phases and an in-depth analysis of the 3rd phase heat load testing performed on the pHB650 (prototype High Beta 650 MHz) cryomodule at PIP2IT (PIP-II Injector Test Facility), with a focus on both the results and the methodological advancements that have improved testing efficiency and accuracy. A key challenge identified in the testing campaign is the higher-than-expected heat loads observed in the first PIP-II (Proton Improvement Plan II) prototype cryomodules (pSSR1 and pHB650) tested at PIP2IT. Elevated heat loads are concerning given the fixed capacity of the PIP-II cryoplant that is currently being installed at Fermilab. However, understanding the sources of these elevated heat loads offers a critical opportunity to implement effective heat load mitigations on upcoming PIP-II cryomodules to stay within the available capacity of the PIP-II cryoplant.
The study includes a summary of test results, descriptions of measurement procedures, and key observations on parameters directly and indirectly related to heat load measurements. Direct observations include measured heat loads and the effectiveness of JT heat exchanger under varying conditions, while indirect observation analyze factors such as the temperature distribution on the two-phase pipe and relief piping under varying conditions.
Thermal acoustic oscillations (TAO) were identified during testing, which was mitigated by replacing the original G10 stem with a stainless steel stem equipped with wipers for the cryomodule cooldown valve.
A major innovation during pHB650 Phase 3 testing was the development of an automated Python script to streamline data acquisition, analysis, and reporting of heat load results. This script automatically retrieved data from ACNET (Accelerator Control Network), performed heat load calculations, and generated detailed reports featuring plots and tables. This advancement significantly reduced manual labor and enhanced the thoroughness of data analysis compared to earlier campaigns. The heat load test reports were promptly uploaded to the electronic logbook shortly after each test, enabling rapid feedback and collaboration between the SRF and cryogenic teams.
The heat load measurements included various components: HTTS (high-temperature thermal shield), LTTS (low-temperature thermal shield), 2K isothermal and non-isothermal heat loads. Results were recorded both within the cryomodule and between the bayonet can supply and return. Measurements were conducted under different operating conditions such as "standard", "linac", and "simulated dynamic". Additionally, HTTS and LTTS heat loads were calculated in real time, allowing for the tracking of thermal stability and identification of changes during testing, both in steady-state and transient conditions. The results of this testing campaign not only provide valuable insights into the performance of the pHB650 cryomodule but also highlight best practices and lessons learned that will inform future cryomodule testing at PIP2IT. These include adopting automated tools for data analysis, refining real-time measurement capabilities, and emphasizing detailed pre-test planning. The framework established in this campaign aims to set an improved standard for cryomodule testing and heat load reporting in future cryomodule test campaigns.

Speaker: Dominika Porwisiak (Fermi National Accelerator Laboratory)

221 C2Po3A-02: Development of the zero liquid helium consumption cryostat for a superconducting undulator

Superconducting undulators have become a research hotspot of the insertion devices in the synchrotron radiation facility. However, the cryostat, which is used to create a liquid helium temperature environment, often causes the failure of the superconducting undulator. In this work, a cryostat with a new refrigeration distribution for a superconducting undulator is designed, fabricated and tested. For the cooling of the superconducting magnet, a liquid helium circulation loop based on the thermosiphon effect is designed with no moving component. The systematic thermal analysis and optimization are carried out to minimize the total heat load. The cooling capacity matches the heat load at different temperatures well and the theoretical excess cooling capacity is increased. In the experiment, the cryostat was tested with several superconducting magnets. There was no liquid helium consumption with excess cooling capacity in the test. Finally, the superconducting magnet reached a direct current of more than 450 A. This study can be a reference for the development of superconducting undulator cryostats.

Speaker: Xiangzhen Zhang (Institute of High Energy Physics，CAS)

222 C2Po3A-03: Thermal analysis of a HTS magnet with effects of magnet field

Conduction cooled HTS magnet have been developed due to their easy operation and compact size. REBCO coated conductors are widely used for the HTS power application, high magnetic field magnet application, and etc.. The thermal stability of the REBCO conductor is essential for the operation of HTS-based device, and thermal conductivities of the conductor are relevant parameters for modeling cryogenic heat transfer. At cryogenic temperature, thermal conductivity of copper and silver strongly depend on the purity of the material and the intensity of the magnetic field.
In this study, FEM analysis was performed to obtain the magnetic field distribution of the magnet. In heat transfer analysis, thermal conductivity of REBCO conductors and cooling structures were calculated using the obtained magnetic field and temperature. Thermal conductivities of the laminated composite structure of REBCO conductor are evaluated by using the thermal network model. As a result, the heat transfer characteristics of the demostration HTS magnet for the NMR were examined depending on the magnetic field.

ACKNOWLEDGMENT
This research was supported by National R&D Program through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT (2022M3I9A1072464)

Speaker: Dr Yong-Ju Hong (Korea Institute of Machinery & Materials)

223 C2Po3A-04: Thermal performance test of the cryogenic transfer line for SHINE cryogenic system

Thermal performance of the cryogenic transfer line with long distance and multi-channels is crucial to the efficiency of large helium cryogenic systems built for Shanghai high repetition rate x-ray free electron laser and extreme light facility (SHINE). We have performed several tests to measure the thermal performance of the cryogenic transfer lines developed and optimized for SHINE. The method of liquid helium evaporation rate was chosen to calculate the heat load. In order to fill liquid helium into different channels of the cryogenic lines ready for the test and also measures the corresponding mass flow rate of evaporating helium gas from each channel, respectively, an experiment test setup has been designed and built utilizing the cryogenic system for the SHINE test facility. In total, we have measured three types of cryogenic transfer lines, and the heat load of 0.2 W/m was achieved for the channel employed as the 2 K circle. These results verifies the modified design and are anticipated to improve the cooling power transfer efficiency of the SHINE cryogenic system.

Speaker: Lei Zhang

224 C2Po3A-05: Preliminary heat load measurements of DALS cryomodule

Dalian Advanced Light source (DALS) test facility project is primarily responsible for the performance test of DALS accelerator cryomodules and superconducting cavities. Accurate measurement of the Q0 of superconducting cavities relies on precise heat load measurements, including the static heat load of the cryomodule and the dynamic heat load during cavity operation. The DALS horizontal testbench (HTB) process design and sensor layout incorporates multiple common methods for measuring heat loads. This paper presents the HTB process design used for static and dynamic heat load measurements, along with the methods it enables. Preliminary experiments have been conducted using multiple measurement methods to test the cryomodule static heat loads, and the results were summarized and analyzed to determine the static heat load of the HTB feedcap and endcap, laying a foundation for the accurate measurement of the cryomodule performance.

Speaker: Zheng Sun (Dalian Institute of Chemical Physics)

225 C2Po3A-06: Thermal design of conductive superconducting magnet for MRI system with thermal buffer

MRI ( Magnetic Resonance Imaging) is a non-invasive medical imaging technique that uses strong magnetic fields to produce detailed images of the body's. which is generated by the superconducting magnet generates typical at low field, 1.5T, 3T, and 7T (typical for ultra-high field) in clinical practice. The traditional magnet is cooled by liquid helium, with safety features including gas evacuation and monitoring systems to prevent hazards.
The global helium shortage poses a significant challenge to hospitals reliant on MRI technology, as liquid helium is crucial for cooling the superconducting magnets in MRI systems, leading to increased costs and potential disruptions in MRI services and the quench emergency evacuation system limits the installation. It becomes more and more important to develop the conductive cooling superconducting magnet technology.
When examining the scenarios involving superconducting magnets in MRI systems, we must consider processes such as ramping up, quench recovery, scanning, and power down. It's important to note that the superconducting coil does not exist in an ideal adiabatic environment; rather, it is subject to heat leaks from the cryostat and heat induced by the gradient coil during scanning. The cooling capacity provided by a single cold head restricts the usability of the superconducting magnet, and the magnet's thermal vulnerability increases as the thermal buffer develops.
In this study, we will utilize high-pressure helium gas as a thermal buffer. The research will focus on the most widely used 1.5T superconducting magnet as the target. The cryocooler design will be grounded on a two-stage system with a capacity of 1.25W @ 4.2K. Furthermore, we will perform thermal calculations based on different scenarios to assess performance.
The results will be meticulously analyzed and compared against those of traditional liquid helium-based superconducting magnets. Specifically, our computational findings will be juxtaposed with the experimental outcomes of a purely conductive 1.5T system, highlighting the advantages of incorporating a thermal buffer. Additionally, the analysis will delve into the disparities between the conventional superconducting magnets and the 1.5T conductive superconducting magnet, offering insights and recommendations for improvement.

Speaker: Mr Jian Li (SIEMENS Shenzhen Magnetic Resonance Ltd.)

226 C2Po3A-07: Cryogenic Performance in Factory Acceptance Testing of the Material Plasma Exposure eXperiment (MPEX) Magnet System

To achieve the desired field profile to facilitate rf source and heating for the Material Plasma Exposure eXperiment (MPEX), a series of seven magnet subsystems have been designed and manufactured by Tesla Engineering. A crucial step in the manufacturing process especially for the six superconducting magnet subsystems is successful completion of the factory acceptance testing that involves validation of each subsystem performance with respect to the MPEX requirements. For these magnet subsystems, which have individual helium recondensing refrigeration cryocoolers, factory acceptance testing with respect to cryogenic requirements involve verifying the cooldown performance with respect to time and amount of liquid nitrogen and helium consumed before steady state operation is reached and the margins in the heat loads to available cryocooler cooling capacity. Initial results from factory acceptance testing for the Upstream and Downstream Helicon and Helicon Source subsystems including integrated testing will be presented and compared to the design values and the MPEX requirements. The factory acceptance testing results provide the baseline that will be utilized when site acceptance testing is completed at Oak Ridge National Laboratory in mid to late 2025 prior to installation on final MPEX assembly.

 This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan

Speaker: Robert Duckworth

227 C2Po3A-08: Cryogenic Cooldown Performance of the GE (HTIC) Compact 7 T MRI Magnet

A Compact 7 T ultra-high field and fully sealed low cryogen Magnetic Resonance Imaging (MRI) system has been developed at the GE HealthCare Technology & Innovation Center, Niskayuna, USA. The cold mass (magnet) has been cooled down to 4 K using only 12 liters of liquid helium liquified with three SHI GM type RDE-412 two-stage cryocoolers. A gas tank has been charged to 150 bar with pure helium at room temperature. Helium vapor is liquefied with several recondensing cups in contact with the cryocooler second stage. Recondensing liquid helium is collected in a liquid tank from where liquid helium flows into a closed loop thermosiphon system in thermal contact with the cold mass. The first stage of the cryocooler cools the thermal shield down to 40 K. Several pre-cooling lines are wrapped around the cold mass externally connected to an open-loop Bluefors/Cryomech MPC600 fast Cold Helium Circulation System (CHCS). All three cryocoolers and the CHCS operate in tandem to cool the cold mass down to 50 K within two weeks. Upon reaching 50 K, the CHCS is turned off and cooldown continues with all three system cryocoolers, reaching a base temperature of 4 K within 5 days. This research explains the cryogenic cooling technique adapted for a Compact 7 T MRI magnet. The cryogenic system performance during the magnet ramp to the designed magnetic field will be discussed as well.

Speaker: Dr Vijay Soni (GE HealthCare Technology and Innovation Center, Niskayuna, NY 12309, USA)

C2Po3B - Large Scale Cryogenic Systems VI: Operation & Design V

228 C2Po3B-01: CRMF Cryogenic System Overview

The SLAC National Accelerator Laboratory is currently in the design phase for the Cryomodule Repair and Maintenance Facility (CRMF), a new facility scheduled for commissioning in 2028. CRMF will feature a Superconducting Cryomodule Test Bench capable of testing LCLSII cryomodules, with provisions for a future addition of single cavity Vertical Test Stands. The cryogenic infrastructure will provide a cooling capacity of 250 W at 2.0 K for a minimum of 8 hours, enabling comprehensive performance testing of cryomodules. The system will include a stationary dewar, low-pressure helium pumps, and a helium distribution and recovery system, along with all necessary utilities. This paper presents an overview and detailed description of the cryogenic system and the cryomodule test bench at CRMF.

Speaker: Biren Rama

229 C2Po3B-02: Verification and optimization of cooldown operation mode for the ESS cryogenic moderator system during preliminary commissioning using helium

At the European Spallation Source (ESS), a cryogenic moderator system (CMS) was designed to continuously supply subcooled liquid hydrogen at 17 K with a parahydrogen fraction exceeding 99.5% to the two moderators. Heat loads are removed via a heat exchanger in the CMS cold box, which is cooled by a large-scale 20 K helium refrigeration system, the Target Moderator Cryoplant (TMCP), with a cooling capacity of 30.3 kW at 15 K. A temperature controller regulates a supply temperature by operating two bypass valves for two cold parallel turbines. A high-pressure helium stream at 15 K is transported to the CMS cold box via a 385-meter-long vacuum-insulated cryogenic transfer line (CTL) and a valve box adjacent to the CMS cold box. The valve box adjusts the feed flow rate and the supply temperature to the CMS cold box, as well as the return temperature to the TMCP cold box. Installation of the CMS began in 2022. Concurrently, TMCP commissioning without the CMS was conducted over five months, concluding in December 2022, confirming that the TMCP met the design requirements. By May 2024, the CMS installation was completed and subsequently the preliminary commissioning, cooled by the TMCP, was conducted without connecting the moderators using helium prior to hydrogen operation.

In this study, the cooldown process was investigated during the preliminary commissioning. These studies were guided by the results of the TMCP commissioning and simulations of the CMS cooldown process. The CMS operational pressure was set to 0.6 MPa, matching the helium density to that of gaseous hydrogen at the CMS cooldown operational pressure of 1.2 MPa. Operational parameters were optimized, and effective controllers were developed to complete the cooldown operation within 30 hours. It was demonstrated that the TMCP must operate its two cold parallel turbines and maintain a compressor discharge pressure of 1.5 MPa to achieve the required CMS cooldown speeds, as the majority of the cooling capacity was consumed in cooling the long CTL. The operational procedures for cooldown process have been established, and their parameters have been optimized in preparation for the CMS commissioning with hydrogen, scheduled for Spring 2025.

Speaker: Theodoros Vasilopoulos (European Spallation Source ERIC)

230 C2Po3B-03: Results of fundamental operational function tests for the ESS cryogenic moderator system during preliminary commissioning with helium

At the European Spallation Source (ESS), two flat butterfly-shaped hydrogen moderator vessels have been designed and optimized to achieve a maximum neutron brightness under the condition of parahydrogen fraction higher than 99.5%. Currently, these hydrogen moderators are installed above the target wheel. Future plans involve replacing them with four moderators positioned both above and below the target. The nuclear heating at the moderators is estimated at 6.7 kW for the proton beam power of 5 MW, increasing to 17.2 K for the four moderators is 17.2 kW. To supply liquid hydrogen at 17 K with a parahydrogen fraction of 99.5% to each moderator, a Cryogenic Moderator System (CMS) was designed. The flow rate to each moderator is 240 g/s, ensuring the average temperature rise through the moderator remains within 3 K. For 5-MW proton beams, a heat load of 21.9 kW, including a static heat load of 4.6 kW, is removed by the Target Moderator Cryoplant (TMCP), a 20 K-helium refrigeration plant with a maximum cooling capacity of 30.3 kW at 15 K.
The CMS will operate automatically in combination with the TMCP, supported by an automated operation control system currently under development. This system includes seven operational modes: cooldown, steady-state, energy-saving, beam injection, warm-up, quick warm-up and ortho-to-parahydrogen measurement modes. The cooldown operation mode requires two compressors with the discharge high-pressure of 1.5 MPa and two parallel cold turbines, enabling the CMS to reach 17 K within 30 hours. Upon completing cooldown, the system automatically transitions to the steady-state mode. In this mode, liquid hydrogen is circulated at 17 K at a flow rate of 1 kg/s by two hydrogen pumps operating at 7,000 rpm, maintaining a pressure of 1.1 MPa through the pressure control system. This operation mode allows transitions to the beam injection and energy saving modes. During a brief maintenance period of approximately two weeks, the energy-saving mode will be used to maintain the CMS at 17 K without requiring a full warm-up. To conserve energy, one of the cold turbines will switch off, followed by the shutdown of one compressor. Additionally, the discharge pressure is decreased to 1.0 MPa.
In this study, fundamental operational function tests related to the mode transitions such as the transition from steady-state to energy saving mode, were conducted during the commissioning period with helium to establish the automated control logic. Additionally, a simultaneous trip of all turbines, caused by the water-cooling pump trip due to an electrical glitch, resulted in the safe shutdown of the CMS through the failure-action system, as designed. This paper presents the results of the operational function tests and the activation of the CMS failure-action triggered by the accidental turbine trip.

Speaker: Theodoros Vasilopoulos (European Spallation Source ERIC)

231 C2Po3B-04: Thermal fluctuation mitigation in the ESS cryogenic moderator system induced by proton beam injection or trip: cooling power control in Preliminary commissioning

The European Spallation Source ERIC (ESS) will provide long-pulsed cold and thermal neutron fluxes at very high brightness to the research community. Spallation neutrons are produced by a linear proton accelerator with an average beam power of ultimately 5 MW. These neutrons are moderated to cold and thermal energies by two hydrogen moderators and a thermal water pre-moderator. The nuclear heating for the 5 MW proton beam operation is estimated to be 6.7 kW. The ESS cryogenic moderator system (CMS) is designed to circulate subcooled liquid hydrogen at 17 K and 1 MPa with a flow rate of 0.5 kg/s to remove the nuclear heating at the moderators. Heat load is efficiently removed through a plate-fine type He-H2 heat exchanger housed in the CMS cold box by a large-scale 20 K helium refrigeration system, the Target Moderator Cryoplant (TMCP), with a cooling capacity of 30.3 kW at 15 K. High-pressure helium flow at 16 K is transported from the TMCP cold box to a valve box adjacent to the CMS cold box through a 300 m-vacuum insulated cryogenic helium transfer line (CTL). When proton beams are injected, a heat load of 6.7 kW is suddenly applied to the CMS. The feed helium flow rate to the heat exchanger is adjusted by the feed control valve in the valve box to compensate for the heat load, while the bypass valve is automatically adjusted to maintain a pressure drop through the bypass line. Additionally, a mixing valve in the valve box maintains the return temperature at 21.2 K by blending in a helium flow from the TMCP cold end that has subsequently warmed up by an ambient heater at ambient temperature. This mechanism allows the available cooling capacity to be regulated without applying any thermal disturbance to the TMCP cold box. A one-dimensional simulation model of the heat exchanger was developed to study the propagation of thermal fluctuations from the CMS to the TMCP induced by proton beam injection or trip. The simulation results provided insights into the required ramping-up speed of the feed helium flow rate and the timing to initiate the ramp-up mode. In this study, the cooling capacity control approach was experimentally evaluated using the valve box during preliminary CMS commissioning in 2024, where helium was used instead of hydrogen, and the CMS was not connected to the moderators. In the experiment, compressor discharge pressures were varied between 1.0 MPa to 1.7 MPa during the test. The experimental results identified the optimal operational conditions for each proton beam power.

Speaker: Dr Hideki Tatsumoto (European Spallation Source ERIC (ESS))

232 C2Po3B-05: Numerical estimation of pressure drop of subcooled parahydrogen flow in the ESS Cryogenic Moderator System.

The Cryogenic Moderator System (CMS) at the European Spallation Source (ESS) is designed to supply liquid parahydrogen at 17.5 K and 1 MPa for efficient neutron moderation. The hydrogen flow is circulated with the help of a series of two pumps through a piping network (CMS loop) with various components, including heat exchangers, tanks, valves and piping elements such as straight pipes, bends, reducers, corrugated pipes, and branching sections etc. Ensuring optimal hydrogen flow requires accurate estimation of pressure drops across CMS piping network to find out the operating point on the pump characteristics curve that matches with the system pressure drop at different flow rates However, there may be uncertainty in the existing correlations for estimating pressure drops used for non-cryogenic fluids for accurate prediction of this parameter in a parahydrogen flow system. This study utilizes computational fluid dynamics (CFD) simulations to calculate these pressure drops and derives component-specific pressure drop correlations. These correlations can be integrated into a simulation code to estimate flow rate iteratively that will match the pump performance curves. These can aid in predicting optimized operating points, enhancing the CMS efficiency by manipulating pump speed and valve operating characteristics. This work, thus contributes to the precise control and reliable operation of the Cryogenic Moderator System for ESS.

Speaker: Dr Hideki Tatsumoto (European Spallation Source ERIC (ESS))

C2Po3C - New Devices, Novel Concepts, and Miscellaneous I

233 C2Po3C-01: Thermodynamic and mechanical properties of solid-phase media for moving cryogenic energy storage packed beds

Solid-phase cold energy storage represents a scalable approach to thermal energy management, characterized by its suitability for deep low temperature applications, along with advantages related to safety, environmental sustainability, and cost-effectiveness. This technology finds extensive application in large-scale cryogenic systems, such as liquid air energy storage. The thermodynamic properties of solid-phase cold energy storage media play a crucial role in influencing both cold energy storage efficiency and overall system performance, furthermore, their mechanical properties are essential for ensuring operational stability. In this study, a total of five solid-phase media, including rock particles, glass beads, alumina, and brown corundum, were tested for cryogenic thermal conductivity. Based on the obtained thermophysical parameters, the thermodynamic performance of different cold energy storage media during the energy storage and release cycle was comparatively evaluated, employing heat penetration depth as an index. Numerical simulations of the cooling process of different solid-phase energy storage media were performed. In terms of mechanical properties, the mechanical strength of three preferred solid-phase cold energy storage media, namely, glass beads, alumina, and brown corundum, was experimentally investigated after high and low temperature cycling from 80 K to room temperature, and multiple free-fall motions at a certain height.

Speaker: Dr Zhaozhao Gao (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

234 C2Po3C-02: Machine Learning Methods for Cryocooler Performance Optimization and Failure Prediction

Space cryocoolers are required to cool sensitive instruments such as infrared detectors and superconducting devices to cryogenic temperatures. Recent advancements have focused on optimizing the performance and reliability of Stirling pulse tube cryocoolers (SPTCs), a hybrid design combining high efficiency and low vibration. This study explores the integration of machine learning (ML) techniques to benefit a range of aspects pertaining to optimizing cryocooler performance and predict component failures, with a focus on flexure springs, which play a critical role in ensuring long-term operational stability.

The first approach utilizes a Back Propagation Neural Network (BPNN) model to predict the failure of flexure bearing springs based on operational parameters such as frequency, amplitude, cycles, and time. By incorporating techniques such as data augmentation and Bayesian optimization, the model enhances predictive accuracy and reduces reliance on traditional methods like finite element analysis (FEA) and individual experimental testing by drawing from an large experimental dataset. The second approach applies ML for optimizing key design and operational parameters of SPTCs, including frequency, pressure, and phase angles. This optimization improves overall performance metrics, such as cooling power and Carnot efficiency at low temperatures, demonstrating the ability of ML to navigate complex parameter spaces more effectively than conventional simulation-based approaches.

This study highlights the potential of machine learning to transform cryocooler design and operation. By reducing development time, lowering costs, and improving the accuracy of performance predictions, ML methods provide a robust framework for addressing challenges in cryogenic systems. Future research should aim to expand datasets, refine predictive models, and explore a wider range of failure scenarios to further enhance the integration of machine learning into cryogenic engineering. These advancements pave the way for the development of next-generation cryogenic systems with improved performance and reliability, supporting a wide array of scientific and industrial applications.

Speaker: Hannah Rana (Center for Astrophysics | Harvard & Smithsonian)

235 C2Po3C-03: Quantum computer cryogenic cooling system

In 2023 Criotec Impianti Srl awarded the contract with PsiQuantum for the design, manufacturing and commissioning of the PsiQuantum cryogenic distribution system.

PsiQuantum is a quantum computing company located in Palo Alto, California, aiming at the construction of the world’s first useful quantum computer. The idea behind their concept is that if you want a useful quantum computer, you need fault tolerance and error correction, and therefore ~1,000,000 physical qubits– to address commercially useful quantum computing applications. While all mainstream quantum computing efforts require cryogenic cooling, in PsiQuantum’s approach, these cooling requirements are relaxed relative to other prevailing technologies. Differently from the superconducting qubit-based quantum computing approaches requesting for milli-Kelvin temperature and diluition refrigerators in order to operate, the PsiQuantum single-photon detectors operate at liquid helium temperatures. Thanks to this “high temperature” it is possible to use existing high-power cryogenic infrastructures that allow for progressive levels of scaling and could help shorten the time needed to develop a large-scale quantum computer [1].

To achieve this goal, PsiQuantum plans to build a cryogenic system connected to an existing cryoplant and Liquid nitrogen supply in California.

The cryogenic system was the scope of this contract and included the supply of a liquid helium valve box, liquid helium transfer lines, nitrogen and helium vent lines and a helium ambient heater to be installed at SLAC National Accelator Laboratory in California.
The cold valve box, equipped with 12 cryogenic valves DN10 for liquid helium, controls and delivers the liquid nitrogen and supercritical helium to the PsiQ cryostats used to test the PsiQuantum cryogenic quantum modules. The valve box configuration foresees the interface to one PsiQ cryostat with the possibility to upgrade in the future.

The valve box has been designed with an active copper thermal shield cooled down by the feeded liquid nitrogen, reducing the heat loads on the helium pipes as much as possible. Criotec Impianti successfully performed the FAT on the valve box including pressure test, cold shock tests and cold and room temperature leak tests.

The supply of the liquid helium and nitrogen is provided by about 70 meters of vacuum insulated cryogenic line with two headers (one for each fluid) within the same vacuum jacket. The lines is connected to the valve box on one end and to a connection box receiving the helium and the nitrogen from the SLAC infrastructure. The copper thermal shield, used to reduce the heat loads on the helium pipe, is cooled down by the liquid nitrogen pipe.
The vent lines are connected outside the building to a set of helium ambient. The heater has been sized to operate continuously without any active fan or heater to facilitate the warmup of the helium flow and introducing a pressure drop lower than 5 mbar at rated conditions.

All the components provided has been designed according to ASME standard and to the California’s and SLAC’s seismic specifications for buildings.

References
[1] https://www.psiquantum.com/news-import/psiquantum-partners-with-us-department-of-energys-slac-national-accelerator-laboratory-to-access-state-of-the-art-high-powered-cryogenic-cooling-capabilities-for-large-scale-quantum-computing

Speaker: Marco Roveta

236 C2Po3C-04: Impact of Cryogenic Conditions on Lithium-Ion Battery Cell Performance

This study aimed to evaluate and compare the performance of lithium-ion cells under normal and cryogenic conditions by testing battery cells in accordance with IEC standard 62660-1:2018. The experiments were conducted using SAMSUNG (CR18650Z/M lithium-ion cells) under two test conditions: normal conditions and cryogenic soaking (30 and 60 minutes). Data were collected before and after soaking over time intervals of 1, 3, 7, and 10 days. The results indicated that in Part 1, cryogenic conditions reduced the performance of lithium-ion cells compared to normal conditions, with average peaks of 0.26%, 0.06%, 1.60%, 0.27%, and 0.31%, respectively. In Part 2, cryogenic conditions caused a maximum decrease in coulombic efficiency and exhibited a similar trend in energy efficiency, with average reductions of 0.50%, 0.79%, and 1.00%, respectively. Lastly, in Part 3, cryogenic conditions showed no further significant changes compared to normal conditions, suggesting stability over time.

Keywords: Battery, Lithium-ion cell, Cryogenic process, Liquid Nitrogen, IEC 62660-1:2018

Speaker: Nattawut Tharawadee (Silpakorn University)

237 C2Po3C-05: Small Scale Joule Thomson Hydrogen Liquefaction – A Comparison of Two Liquefaction Cycles

With the growing demand for green energy, hydrogen (H2) and liquid hydrogen (LH2) are gaining attention from the industry and research. A critical challenge arises in the supply of LH2, as industrial gas suppliers typically do not deliver small quantities. Consequently, several cubic metres of LH2 must be bought and stored even for small-scale tests. A need for small scale liquefiers with approximately 10 to several hundred litres per hour was identified, in order to accumulate limited LH2 quantities for laboratory purposes. To address this issue, the development of small liquefaction plants is a possible solution. A focus is put on simple and readily available components, as well as the possibility of a quick realization. Two possible liquefaction cycles based on Joule Thomson expansion are presented and compared by relevant performance indicators such as efficiency and complexity.

Speaker: Henrik-Gerd Bischoff (Technische Universität Dresden)

C2Po3D - New Devices, Novel Concepts, and Miscellaneous II

238 C2Po3D-01: Design, manufacturing & commissioning of the high brightness liquid para-hydrogen moderator for the European Spallation Source

The European Spallation Source (ESS) in Lund, Sweden, is designed to become the most powerful accelerator driven spallation neutron source in the world. ESS is currently under construction, and the first beam on target is planned for the second half of 2025, with first user operation expected to start in 2026. As a key component of the neutron production, which was developed, built and tested at Central Institute of Engineering, Electronics and Analytics – Engineering and Technology (ZEA-1) of Forschungszentrum Juelich GmbH, the cryogenic moderator slows down high-energy neutrons released from the spallation target. To gain maximum neutron brightness for condensed and soft matter research, an optimized low dimension liquid para-hydrogen moderator has been developed. Hydrogen with a pressure around 1 MPa, a temperature around 20 K and a para-hydrogen fraction of at least 0.995 will be utilized to interact with neutrons in a unique moderator vessel arrangement. This paper describes the engineering design, manufacturing and commissioning of the low dimension liquid para-hydrogen moderator for the ESS.

Speaker: Dr Yannick Bessler (Forschungszentrum Juelich GmbH)

239 C2Po3D-02: Experimental results from the cryogenic cooling of a rotor using an internal pump

Superconducting motors are a route to the high power-to-weight ratio required for the electrification of large aircraft. In a synchronous superconducting motor, a popular configuration is to have the rotor with DC field coils and the stator with AC coils. This configuration makes the rotor cooling easier, as DC superconducting coils have few losses. However, the heat from the rotor still needs to be transferred across a high-speed rotating interface. Our proposed cooling method uses a helium gas circuit, internal to the rotor, that is circulated by the rotor's motion against that of a cold stationary heat exchanger. Keeping the cold heat exchanger stationary reduces sealing requirements as the internally pumped gas can be kept near ambient pressure whilst the cold heat exchanger could be cooled by either pressurized cryogenic fluid, a two-phase medium, or a cryocooler. The internal rotor pump concept was first validated with a CFD model, which was in turn confirmed by experimentation. This paper presents the results of the proof-of-concept experiments that validated the CFD model and will present further improvements to the concept, demonstrating a feasible cooling method and its application to a superconducting rotor.

Speaker: Dr Alan Caughley (Callaghan Innovation)

240 C2Po3D-03: A deployable barrier preventing liquid oxygen accumulation and safety risks during liquid hydrogen transfers

Uninsulated surfaces exposed to cryogenic temperatures can result in the formation of liquid air, an oxygen-rich mixture. The National Fire Protection Agency NFPA 2-2023 code specifies a non-combustible material must be underneath the transfer line to prevent liquid air from dripping onto combustible materials. Concrete is a non-combustible material commonly used in infrastructure that is heavy and generally immobile. Another common material used in infrastructure is asphalt which is considered a combustible material due to the tar content. Literature has discussed asphalt combustibility with pure liquid oxygen. This work describes experimental attempts to combust asphalt and other common ground surfaces in the presence of liquid air formation. A deployable barrier was designed to comply with the NFPA 2 standard while not requiring expensive materials like concrete. This barrier enables the safe transfer of liquid hydrogen in conditions where concrete pads are unavailable, particularly in off-road applications.

Speakers: Kyle Appel (Washington State University), Matthew Shenton (Washington State University)

241 C2Po3D-04: Catalytic materials for ortho-parahydrogen conversion in a thermoacoustic cryocooler regenerator

Pulse tube cryocoolers utilize pressure waves oscillating within a porous regenerator for active refrigeration. Using hydrogen instead of helium as the working fluid provides increased refrigeration performance over a range of operational conditions due to lower viscous dissipation. Hydrogen also provides the potential to augment the cooling capacity via ortho- to parahydrogen conversion which can absorb or release up to 702 kJ/kg. The practical design aspects of regenerators and catalyzation reactors are synergistic, however this synergy has not been investigated. To achieve both catalyzation and high regenerator effectiveness the material must meet three key aspects: high heat capacity, high thermal conductivity, and the ability for the surface to be oxidized to induce catalyzation. This study investigates the catalytic activity and regenerator performance of 2.5-mm-diameter spheres of oxidized iron, brass, and stainless steel. Acoustic onset temperatures of the system including a thermoacoustic engine, pressure amplitudes, no-load cooling temperatures, and ortho-parahydrogen conversion activity are reported. The goal of this study is to aid in optimization of a catalyzed thermoacoustic regenerator where lower viscous losses are paramount to cooling efficiency.

Speakers: Matthew Shenton (Washington State University), Nathan Jorgensen (Washington State University)

242 C2Po3D-05: Federated Learning Framework to support AI-Driven Prescriptive Maintenance in Large-Scale Cryogenic Infrastructures at CERN

CERN, home of the 27 km long LHC (Large Hadron Collider) particle accelerator, operates and maintains the world’s largest helium cryogenic infrastructure. This complex system is essential to the LHC’s functionality, reliability, and availability.
Big data analytics and machine learning have been successfully applied to CERN’s cryogenic helium screw technology compressors. This approach tested the field, has proven to be a consistent way of extracting prescriptive maintenance models and estimating the Remaining Useful Life (RUL) of critical systems to identify anomalies and their underlying causes with the aim of avoiding costly operational disruptions.

Building on this foundation, we propose a decentralized framework based on Federated Learning (FL). Leveraging a client-server architecture, FL ensures data privacy by aggregating locally trained machine learning models, enabling collaborative model improvement without the need to share sensitive data between participants. CERN provides an optimal testing ground for the solution described, supported by the availability of CAFEIN, a FL platform independently developed at CERN, which will serve as the platform for model aggregation. Moreover, the LHC helium compression infrastructure offers a unique and distributed testbed composed by 20 motor-compressor units organized into five stations around the 27 km accelerator ring. The stations are further divided into low-pressure (Booster) and high-pressure (High Stage) compressor groups, each featuring distinct compressor models, providing a realistic environment to validate the developed solution.

In this setup, each compressor acts as a data source, streaming data into an edge device working as a local client. These edge devices train machine learning algorithms locally, which are then aggregated into global models based on the physical characteristics of the compressor analysed. This results in two distinct predictive models: one for the low-pressure compressors and another for the high-pressure ones. RUL estimation is then performed locally using a hybrid approach leveraging the compressor’s reports and the proven autoencoder (AE) architecture combined with new solutions to take advantage of not only vibration data but also real-time operational data. The newly designed system is optimized to run on low computation edge device to perform analysis on-site and reduce model training power consumption with the aim of creating a ready to use distributed infrastructure that can be adapted to monitor other cryogenic facilities by leveraging the large amount of available data.

The application of CAFEIN FL and the developed algorithms offer a transformative approach to resource optimization, significantly enhancing the quality and robustness of RUL and prescriptive maintenance models as the number of participants involved increase, thanks to the proposed federated infrastructure. By enabling secure, privacy-preserving model training, this solution is an ideal candidate to be used across several international organizations and research centres operating with similar equipment. Paving the way to decentralize model development this infrastructure can incorporate a global range of data inputs without the need for data exchange, streamlining collaboration agreements and protecting sensitive information. The resulting models can be directly employed to optimize the maintenance and operational efficiency of facilities, leading to tangible benefits such as reduced downtime, extended equipment lifespans, CAPEX and OPEX cost optimization and minimized environmental impact. Ultimately, the developed solution powered by CAFEIN FL exemplifies how collaborative AI-driven strategies can foster innovation, sustainability, and economic efficiency in the industrial and research landscapes.

Speaker: Paolo Cacace (Sapienza Universita e INFN, Roma I (IT))

243 C2Po3D-06: The New Valve Era for Cryogenics– Design Considerations and Electric Solutions with focus on liquified Hydrogen and Helium

New green technologies in the energy sector will use more and more Cryogenic gases like helium, hydrogen and sometimes also with neon, nitrogen, or air. Those technical gases have gained today more attraction as enablers as well as further industrial areas as in chemistry, semiconductor, steel and glass production etc.
Cryogenic helium in all stages is used to cool superconducting devices allows efficient high energy research and fusion research. Liquefied hydrogen is a high dense energy vector and could be at the same cooling superconducting cables and power devices. Neon seems a potential candidate to enable highly efficient cryogenic processes. Subcooled liquefied nitrogen is used to cooling high temperature superconductor cables and devices in the power system. The cryogenic process of liquefying and warming up air is used to store fluctuating production renewable power.
Consequently, valve industry face techno-economic complex challenges to answer the demands of this expanding sectors that will play an essential role the upcoming decades.
On the same line the future is a fact of having smart electric driven equipment and this applies also to the valves. Traditional electropneumatic solutions requires big space and pneumatic system in the facility to supply the air to the actuator. These systems consist of compressor, air treatment system with refrigeration air dryer and condensate drain, the distribution lines and buffer tanks, manifolds with stub lines to the valves, connections, couplings and so on. All these requirements evolve to more complex facilities, high capex and mainly opex depending. As EnEffAH study also explained how low the efficiency of pneumatic drive systems is, around 6 to 8 %. Electric driven solutions are key to leverage efficiency, safe space and weight, reduce the consumption and being plug and play there is no need on specific system level equipment, just plug and play.
This poster describes identified techno and economic challenges for a modern cryogenic valve. Focus is on applications in liquified hydrogen but also considerations regarding the special requests for helium are highlighted and electric actuation. Some key design topics are:
 Thermal efficiency and flexibility to absorb thermal contractions in the connection piping.
 Interior and exterior high-level tightness with improvement to the low emissions to the atmosphere.
 Valve flow capacity and precise flow control
 Electric driven system with low energy consumption, electric actuator solutions.
 Suitable for industrial serial manufacturing processes that enable to achieve factor one butt welded and precise machine.
In this poster paper, AMPO POYAM VALVES will present an innovative solution concept that meets the challenges of the cryogenic service condition over the entire temperature and pressure range and brings a modern valve concept to the market considering up to date manufacturing technologies and thus offers added value to the efficiency of the high-tech electric driven cryogenic processes.

Keywords: Valves, Liquid Helium, Liquid Hydrogen, Low Heat Load, Fine Flow Control, Innovative Flex Inset, Fail Safe Electric Actuation

Speaker: Leire Colomo Zulaica (AMPO POYAM VALVES)

244 C2Po3D-07: An integrated tool for helium recovery and evaporative cooling

We present the design of an automated tool that can be used to extract a small amount of left-over liquid helium in an MRI magnet and push it into a helium recovery bag. The main design goals are to minimize the process time and overall footprint of the tool, and not to contaminate helium with hydrocarbons during the process. Also discussed in the paper is another potential application where the same tool is used as an expansion engine for evaporative cooling of an MRI magnet in a warehouse or hospital in much less time compared to a cryocooler based cooldown tool and consume less liquid helium compared to not using the tool.

Speaker: Dogan Celik (GE Healthcare)

245 C2Po3D-08: Concept of structure and testing method of a levitating support for single-channel cryogenic transfer lines

Losses occurring during the transfer of cryogenic media using single-channel transfer lines depend on their length, hydraulic and thermodynamic quality. Single-channel cryogenic transfer lines often have a modular structure and are characterized by the use of many repeatable elements. Each module of the cryogenic transfer line consists of several elements typical of most structures. Bayonet connector, compensation bellows, sliding supports whose task is to ensure stable operation of the bellows and the appropriate distance between the process pipe and the vacuum jacket. Among the above-mentioned elements, the thermal loses of the entire system is influenced by bayonet connectors and sliding supports - these are elements that conduct heat from the environment to the process pipe.
So far, limiting the heat flow by conduction through sliding supports was achieved by minimizing the thickness of the support and reducing the contact area with the vacuum jacket and the process pipe. These treatments lead to a weakening of the support strength and a reduction in the reliability of the structure. The best solution to maintain good strength properties and limit heat transport to the transfered cryogen to be the use of non-heat-conducting supports. Such requirements are met by levitating supports based on the Meisner effect. This paper presents the concept of the structure and operation of the sliding support, as well as the design of a test stand used to test the mechanical properties of levitating supports.

Speaker: Dr Paweł Duda (Wroclaw University of Science and Technology)

246 C2Po3D-09: A Liquid Air Energy Storage (LAES) System Utilizing Upgraded LNG Cold Energy for Air Liquefaction

Liquid air energy storage (LAES) technology has gained recognition as a promising energy storage solution, characterized by its high energy density and independence from geographical constraints. However, conventional cold storage methods, such as liquid-phase and solid-phase storage, suffer from inherent limitations, underscoring the need for more efficient and reliable cold storage solutions to improve LAES performance. This study proposes the integration of cold energy released during liquefied natural gas (LNG) vaporization into the LAES system. By employing a compression refrigeration cycle, the LNG cold energy is upgraded to a temperature range suitable for high-pressure air liquefaction. Nitrogen is utilized as the working fluid in this cycle to eliminate safety risks associated with the direct interaction of LNG and air within the same heat exchanger. This innovative approach not only reduces the cost and enhances the safety of the cold storage unit but also optimizes its functionality. Moreover, the cold energy from liquid air is recovered through Organic Rankine Cycles (ORCs) to generate electricity, further improving the system's overall energy utilization. A thermodynamic model of the proposed system is developed, and the impacts of critical parameters, including compression pressure, liquefaction rate, and expansion pressure, on the round-trip efficiency of the LAES system are thoroughly analyzed. The results provide valuable insights for optimizing cold storage in LAES systems and offer a robust reference for the integration of LNG cold energy with LAES technology.

Speaker: Jiamin Du (Key Laboratory of Cryogenic Science and Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

247 C2Po3D-10: Advances in small scale cryogenic magnetic refrigeration

Existing cryogenic refrigeration systems are both capital cost expensive and extremely energy intensive. Large scale H2 liquefaction plants achieve, at best, 10-20% of Carnot efficiencies (Carnot is theoretical maximum), while small and medium scale cryogenic systems operate with 5-10% efficiencies. These high costs and poor efficiencies are a major pain point for existing industries requiring cryogenic temperatures, and they create an enormous barrier to entry for private investment into H2 infrastructure for fuel cell electric vehicles (FCEV).

Magnetic refrigeration is a promising technology, and likely the only technology, with the potential to significantly improve cryogenic refrigeration. Model predictions indicate >50% efficiencies in the cryogenic temperature regime (sub 80K) are possible. A major hurdle inhibiting the advancement of at-scale magnetic refrigeration systems is the assumption that these systems can only be operational with expensive and energy intensive superconducting magnetic fields, thus, limiting the application solely towards large scale systems (i.e. >$50million dollar, 30 ton per day hydrogen liquefaction plants).

General Engineering & Research (GE&R) is on the cutting edge of magnetic refrigeration technology development. We manufacture and sell our own patented line of high performance low cost magnetocaloric materials which can be used to build high efficiency systems for all refrigeration applications, and these are the only known compositions that will meet both cost and performance requirements to be viable in mass production of magnetic refrigeration systems for residential and commercial refrigeration and air conditioning applications, as well as cryogenic applications (cryocooling and gas liquefaction). Further, GE&R has built an at-scale cryogenic magnetic refrigeration system and successfully demonstrated sustained sub 80K (-193C) magnetocaloric cooling using a Halbach permanent magnet. The successful demonstration of cryogenic magnetic refrigeration using a permanent magnetic field with ZERO energy input requirements, validates this technology, and opens the door for its use in small and medium scale industrial applications, as well as fueling station infrastructure for fuel cell electric vehicles (FCEV). This presentation will provide an overview and status update of GE&R’s magnetic refrigeration technologies.

Speaker: Dr Robin Ihnfeldt (General Engineering & Research LLC)

M2Po3A - Cryogenic Electronics, Detectors, and Topological Materials

248 M2Po3A-01: Ultrafast Optically Pulse Triggered Microwave/Terahertz Emission from an Array of Inductively Charged Superconducting Rings

It is well established that superconducting materials will emit microwave/terahertz radiation when illuminated with a femtosecond infrared laser pulse. Typically, this phenomena is examined by illuminating a constant current biased superconducting thin film bridge. In this investigation an inductively charged superconducting thin film ring is considered. We believe this configuration lends itself to a simple compact microwave/terahertz emitter device as the ring simultaneously plays the part of an antenna, waveguide, and power supply. The rings display a frequency dependence on the ring circumference, a well-defined polarization direction, and a radiation pattern like that of an electrically large loop antenna. With this knowledge we construct an array of superconducting ring emitters and demonstrate that a narrow microwave/THz beam is formed indicating coherent radiation. Results illustrate the rich non-equilibrium superconducting dynamics that span the optical, THz, and microwave regimes, and suggest the possibility of a unique pulsed coherent microwave/terahertz source.

Acknowledgements: This work was supported by the Air Force Office of Scientific Research (AFOSR) Award Nos. FA9550-23AFCOR001 and 18RQCOR100.

Speaker: Tom Bullard (Bluehalo)

249 M2Po3A-02: Optically-Powered and Optically-Controlled Cryogenic Gate Driver

The implementation of cryogenic distribution systems with solid-state switches, such as those required in hydrogen-electric aircraft, faces challenges in achieving both electrical and thermal isolation for gate drivers. Traditional methods, including magnetic and capacitive isolation, are unsuitable for systems requiring thermal isolation. This article introduces a novel, partially cryogenic gate driver for gallium nitride high-electron-mobility transistors (GaN HEMT). It utilizes optical isolation through power over fiber (POF) as well as signal over fiber. POF addresses both the thermal and electrical isolation challenges by leveraging the low thermal conductivity of glass and its demonstrated efficiency in transmitting power under cryogenic conditions. The control of the gate driver can be at ambient temperatures while the GaN HEMT driving side can be at cryogenic temperatures. Following the introduction of the gate driver, the performance will be measured at a range of temperatures using a double-pulse tester and compared to a traditional implementation of a gate-driver.

Speaker: Cody Kaminsky (Georgia Institute of Technology)

250 M2Po3A-03: Low-Temperature Energy Storage: Flexible Supercapacitors with Cotton Fiber and Silver Nanowires

To address the challenges faced by traditional supercapacitors in low-temperature environments, such as hardening, brittleness, and poor fatigue resistance, this study proposes and fabricates a novel low-temperature flexible supercapacitor. By utilizing low-temperature flexible conductive materials with excellent flexibility and stability as electrodes and incorporating PVA-LiCl gel electrolyte, which exhibits outstanding performance at low temperatures, the supercapacitor achieves exceptional low-temperature capabilities. Experimental results show that the supercapacitor retains excellent flexibility and mechanical properties at -60°C and maintains stable electrical performance after 10,000 low-temperature bending cycles, demonstrating superior fatigue resistance. Furthermore, the device maintains significant capacitance at -30°C. This work provides an innovative solution to the challenges of energy supply in low-temperature environments, with promising applications in polar exploration, space exploration, and other extreme environments.

Speaker: Dr Si-Zhe Li (Technical Institute of Physics and Chemistry, CAS)

251 M2Po3A-04: Higher order topology in hydrogenated graphite

In graphite or multilayer graphene, strain can lead to relative twist in the alignment of neighboring interfaces. This results in the formation of stacking faults between regions of different twist angles. In two dimensions, a saddle point in the electronic band structure leads to a divergence in the density of states, also known as a Van Hove singularity (vHs). The energy difference between the vHs of the conduction and valence bands was found to increase with the twist angle between neighboring graphite domains with respect to the c axis.

In this work, we estimate a twist angle for the superconducting (SC)-like nano-size multi-layer granular domain in hydrogenated graphitic fibers*. We show that this twist angle and the twist angles found by others for few-layer graphene might actually form a certain mathematical sequence. We interpret this finding as yet another confirmation that SC in hydrogenated graphite has topological manifestations. By invoking Ginzburg formula, we find the existence of higher order topology as at least quadratic gap flattening.

Charge transport and magnetization measurements on the hydrogenated
graphitic fibers have been done using the Quantum Design’s Physical
Properties Measurement System.

*N. Gheorghiu, C.R. Ebbing, T.J. Haugan, Superconductivity in Hydrogenated Graphites, arXiv:2005.05876 (2020).

Speaker: Dr Nadina Gheorghiu (Previously with AFRL)

M2Po3B - Cryogenic Testing, Standards, Procedures, and Measurements

252 M2Po3B-01: Development of a thermal conductivity test bench at cryogenic temperatures

Thermal conductivity is a critical parameter in cryogenics and plays a fundamental role in the design of components operating in cryogenic environments. As cryogenics gain increasing relevance in fields like energy, understanding the low-temperature thermal conductivity of novel materials becomes ever more essential. Meanwhile, the depletion of helium reserves requires the high-energy accelerator community, including CERN and its Large Hadron Collider (LHC), to explore alternatives to liquid helium for cooling accelerator facilities. Although a complete replacement is nowadays not feasible, cryocoolers represent a promising option for replacing cryogens in a multitude of components. However, the widespread use of cryocoolers on large structures with the current constraints in cooling power requires an advanced thermal design and consideration of thermal transport properties, particularly for their successful integration into particle accelerators.
This study presents a thermal conductivity test bench operating from 4 K up to 300 K using a dry cryostat. The setup accommodates sufficiently large samples to practically measure composite materials such as low-temperature superconducting (LTS) cables and high-temperature superconducting (HTS) tape stacks. Simultaneously, to maximize the sample throughput, the test bench features aside the steady-state potentiometric measurement technique also a dynamic testing based on the pulse power method. Additionally, it is equipped to measure electrical resistivity, providing a comprehensive platform for thermal and electrical transport characterization.

Speaker: Stefan Hoell (CERN)

253 M2Po3B-02: Design and uncertainty analysis of cryogenic spectral emissivity measurement system

Radiation heat transfer is a crucial mode of heat transfer in vacuum as well as cryogenic environments. However, there is no optimal solution to accurately measuring spectral emissivity over a wide temperature range, especially at cryogenic temperatures. This work designed a cryogenic spectral emissivity measurement system based on radiometric methods, aiming to measure the spectral emissivity of various materials in the temperature range of 100 K to 200 K with a G-M cryocooler. The current work emphasized analyses and discussions on how various components change at cryogenic temperatures and the effectiveness of the mirror combination for collecting radiation beams before the use of the Fourier Transform Infrared (FTIR) spectrometers. The study simulated the overall distribution of the cryogenic temperature field, and then evaluated the influence of thermal contraction on the optical path and computed a comprehensive Type B uncertainty of 3.1672% for the modulation regime. This work can serve as a validation of various sources of errors in preparation of experimental setups.

Speaker: Zichun Huang (Technical Institute of Physics and Chemistry)

254 M2Po3B-03: Magnetoresistance analysis and calibration of zirconium oxynitride sensor for low-temperature thermometry

Accurate temperature measurement is essential for exploring material properties at low temperatures and in magnetic field environments. Resistance temperature thermometers are affected by magnetoresistance, which can cause measurement errors when calibrated solely in zero magnetic fields. Zirconium oxynitride thin films, renowned for their extremely low magnetoresistance, are widely used for low-temperature measurements in strong magnetic fields. In this study, a series of zirconium oxynitride thin films were prepared, and their zero-field resistance-temperature (R ( T )) curves were measured across the range of 300 K to 2 K. Additionally, their field-dependent resistance (R (B, T = const)) was evaluated in out-of-plane magnetic fields from 0 to 9 T at fixed temperatures between 2 K and 6 K. The samples exhibited diverse magnetoresistance behaviors—positive, negative, and saturated—highlighting complex nonlinear phenomena. The mechanisms underlying the positive and negative magnetoresistance were analyzed. For samples suitable for temperature measurements down to 2 K, a maximum temperature deviation of 0.48% was observed within the 9 T magnetic field range. The R ( T ) relationship at zero magnetic field was established using Chebyshev polynomial fitting. Subsequently, magnetic field correction factors were introduced into the R ( T , B) relationships within the 2 K to 6 K range, enabling the development of a calibration procedure for low-temperature sensors operating in magnetic fields up to 9 T. This work aims to enhance the accuracy of low-temperature measurements in magnetic field environments through improvements in sensor design and calibration procedures, which are critical for applications in superconducting accelerators, power systems, and related fields.

Speaker: Zhen Geng (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

255 M2Po3B-04: Experimental assessment of the parasitic thermal load on cryogenic envelope for superconductive cables

In the context of the hydrogen economy, transporting hydrogen in liquid state (LH2), instead of the gaseous one, is considered appealing due to the maximization of the energy density. The liquefaction of hydrogen is, however, an expensive process as it requires cryogenic conditions, typically in the range between 20 K and 30 K, depending on operating pressure. To maximize the economic revenue from the transfer of H2 in its liquid state, the combination with other technologies requiring cryogenic operation can be considered, such as the power transfer through superconductors. The main goal is to transfer significant quantities of hydrogen and electricity (typically DC at medium voltage) into a hybrid line where the LH2 is used as coolant to keep the superconducting state of the cable. The MgB2 can be considered an enabler in this application as its operational temperature perfectly matches the LH2 temperature range. In this setting, accurately quantifying the parasitic thermal load affecting the cable typically housed in a cryogenic envelope (Envelope), is critically important. The Envelope is made of coaxial tubes usually designed with a thin corrugated structure to ensure flexibility and resilience against thermal contraction, facilitating connections between terminals and joints positioned at specific intervals. Existing literature provides some scattered data on the parasitic load to the cryogen through the Envelope, and systematic investigations are still scarce. This study analyzes and compares distinct measurement methodologies for assessing the parasitic load through the Envelope. At least the following two methods will be investigated in terms of feasibility, repeatability, safety and accuracy: the first method is based on the Temperature-Pressure correlation on the saturation curves, the second method is based on boil-off measurement and relies on the correlation between the parasitic heating and vapor generation rate from liquid cryogen. For the purposes of this analysis, liquid nitrogen is selected as the cryogen, for the sake of availability, safety and cost. For each method a proper lumped model will be produced in order to describe the behavior of the system. The configuration of the test bench, based on the best measuring approach according to the made comparison, is described in detail and designed so that operative conditions can be easily translated into a numerical model. A methodology is proposed to extrapolate the results to the temperature range relevant for the LH2 operation and extension of the methodology to assess thermal performances of rigid Envelope will be assessed.

Speaker: Giovanni Mangiulli (Politecnico di Torino)

256 M2Po3B-05: Design and development of near field emissivity measuring device for superconducting materials

With the advancement of micro- and nano-machining technologies, the distance between components in devices has continually decreased, leading to heat fluxes that exceed the radiation limits predicted by Planck's law. These rapidly increasing heat fluxes can have detrimental effects on near-field devices in cryogenic temperatures, such as difficulties in heat dissipation and reduced operational lifespans. However, studies have shown that the near-field radiation intensity of superconducting materials decreases in their superconducting state, providing a novel approach for thermal management in near-field devices. Therefore, this paper presents a device designed to measure the near-field radiative heat transfer (NFRHT) of superconducting materials. The device consists of a temperature-controlled calorimetric module, a distance adjustment module, and a parallel ranging module, among others. The temperature-controlled calorimetric module uses a steady-state calorimetric method to measure heat flux by determining the temperature difference between the two ends of a heat flow meter, with a minimum detectable value of 1 microwatt. The distance adjustment module features a mechanical piezoelectric driver and spring-connected moving rods, enabling movement with a precision of 0.1 microns. The parallel ranging module incorporates a planar parallel maintainer with a plane-relative deviation spacing of up to 0.1 microns and a measuring range of less than 100 microns, using a capacitive sensor. This device can drive and measure micrometer-scale step lengths at near-field distances, with a total measurement uncertainty of less than 5%.

Speaker: Bixi Li (Technical Institute of Physics and Chemistry)

257 M2Po3B-06: Electrical Conductivity Measurements of Pressurized Gaseous Helium at 77 K

Utilizing helium gas (GHe) as the coolant for advanced power devices including busbars, superconducting cables, motors, and generators are currently being developed for large scale electric transport applications. The power devices can have an operating temperature ranging from 30-110 K. To achieve this temperature range and to ensure sufficient cooling the GHe is typically pressurized up to 2.0 MPa to increase its density. Given the operating pressure of the helium and the dielectric designs of the power devices, the GHe typically becomes a composite insulation with a solid dielectric material such as Kapton, and polypropylene laminated paper (PPLP).
To enable DC electric field modelling to be conducted on GHe cooled power devices operating at cryogenic temperature, it is necessary to have the electrical conductivity of helium gas as well as the solid insulation material. Unlike relative permittivity (dielectric constant), the electric conductivity is a temperature dependent variable. As such, it is necessary to measure electrical conductivity at the desired temperature and pressure that GHe will be utilized for cryogenic application. As part of our previous work we have designed, fabricated, and verified an electrical conductivity measurement cell which enables measurements to be completed in a pressurized GHe environment. The experimental setup was developed in accordance with ASTM D257. As part of our previous research, we have measured the electrical conductivity of various lapped tape materials such of PPLP and Kapton in GHe at 77 K and 2.0 MPa, as well as in liquid nitrogen. As part of these measurements, we saw the coolant had a slight influence on the electrical conductivity measurement. As part of our continued work, we have explored the electrical conductivity of GHe at 77 K at four pressure level ranging from 0.5 – 2.0 MPa (in step of 0.5 Mpa) as well as at two different electric field configurations (1 kV/mm and 0.5 kV/mm).
This paper provides an overview of the experimental setup to measure the electrical conductivity of GHe at 77 K for pressures ranging from 0.5 – 2.0 MPa and summarizes the experimental results. Commentary is also provided on how these measurements can be implemented to enable DC electric field modelling to be completed for GHe cooled DC power devices at cryogenic temperatures.
This work was supported by the Office of Naval Research (ONR) under grant number N000141612956 and NASA University Leadership Initiative (ULI) #80NSSC22M0068

Speaker: Peter Cheetham

258 M2Po3B-07: Force Measurements for Axial Superconducting Magnetic Bearing

Non-contact bearings are required in many applications where friction losses can be excessive. An option for realization of non-contact bearings with superconductors and permanent magnets exists. The bearings are expected to provide stiffness in the radial and axial direction. The present paper explores axial superconducting magnetic bearings (SMB). The axial SMB leverages the Meissner effect where in the magnetic field is expelled by the superconductor providing levitation. The impurities present in the permanent magnets are the reason for flux trapping which lends stability to the interaction of superconductor and permanent magnets. Thus, resulting in stiffness and force in axial direction. The paper presents the experimental set-up designed for conducting the force measurements. The paper also analyzes the measurement results while considering the temperature variation as well as field and zero field cooling conditions. The lift is impacted by the speed of rotation of the suspended rotor. The paper also characterizes the lift and rotational losses a function of the speed of rotation. A mathematical derivation of lift and losses is obtained and verified.

Speaker: Himanshu Bahirat (IIT Bombay)

259 M2Po3B-08: Fibre-optic quench detection in spiral wound superconducting wires

High temperature superconductors are vulnerable to sudden thermal runaway events, or quenches. The loss of superconductivity and resulting dissipation of energy from the transport current leads to temporary failure of the magnet or power cable, irreversible damage, and possible catastrophic failure of the superconducting component. Voltage based detection of a pre-quench condition is challenging in many application environments, where the milli-Volt scale signals are swamped by noise. Fiber-optic sensing is a promising alternative quench protection system, as it is unaffected by electro-magnetic fields, can operate at cryogenic temperatures, and can be integrated as a distributed sensing system. In this work, we demonstrate the integration of fiber-Bragg grating based optical sensing onto spiral-wound monofilament superconducting wires. The response of the fiber-optic sensors is compared with voltage and temperature measurements during both heater and current-sharing induced pre-quench thermal events. We show that the fiber-optic system can detect ~1 K temperature changes at 78 K, and shows clear responses to thermal runaway. The optical signal typically follows the voltage response for the current-sharing induced quench, but by no more than about half a second. These results support the use of fiber-optic sensing and thermometry for monitoring and protecting superconducting magnets or power cables.

Speaker: Dr Bartholomew Ludbrook (1 Paihau-Robinson Research Institute, Victoria University of Wellington, New Zealand 2 Te Whai Ao - Dodd-Walls Centre for Photonic and Quantum Technologies, New Zealand)

M2Po3C - Nb-Based Superconductors

260 M2Po3C-01: Investigating the microstructure of cold-worked and annealed SRF Niobium using Shannon Entropy

Residual trapped magnetic flux suppresses the quality factor of SRF Nb cavities and thus microstructural features that can trap flux are of particular interest for developing higher performance cavities. We have been investigating tools to help quantify the microstructure of Nb to make it easier to compare microstructures resulting from different cavity processing routes. EBSD mapping is the preferred tool for quantifying crystallographic information in microstructural cross-sections. It can produce reliable grain size data but is expensive and slow if large areas need to be quantified. Backscattered electron imaging by SEM is an economical method of analyzing large areas and is more widely available than EBSD but cold-worked microstructures in Nb have high degrees of lattice distortion making them challenging for standard image analysis techniques. We are investigating the use of Shannon Entropy as a method of quantifying SEM-BSE images of Nb. Claude Shannon theories of information are used in a wide range of interdisciplinary sciences, and using Shannon Entropy of an image, we can extract quantifiable information from SEM-BSE of Niobium using BSE images. We report on 1) the entropy of heat-treated Nb microstructures ranging from as-received (cold-worked) to annealed at 900 °C for 3 hours, 2) the parameters used in the calculation to find the most effective values for adjustable parameters, and 3) a comparison to EBSD images for determination of the recrystallized fraction to see if Shannon Entropy maps can be used as an effective alternative.

Acknowledgements
This material is based upon work supported by the U.S. DOE, Office of Science, Office of HEP under Award No. DE-SC0009960. This work was partially performed at the NHMFL, which is supported by the NSF Cooperative Agreement No. DMR-1644779 (2018-22) -2128556 (2023-) and the State of Florida.

Speaker: Trent Boritz (Florida State University)

261 M2Po3C-02: Enhancing Flux Expulsion Through Microstructural Control in Superconducting Radiofrequency Cavities Made from Cold-Worked Niobium

A well-known source of RF losses that lower the performance of superconducting radio frequency cavities is due to the residual magnetic flux trapped during cool-down. In this presentation, we demonstrate how manipulating the niobium microstructure by changing the strain state of the initial Nb sheet for an elliptical cavity geometry, can improve the flux expulsion behavior. In this study we compare the use of traditional annealed poly-crystalline Nb sheet with sheet from the same origin but without the anneal and therefore retaining cold work strain from the sheet rolling process. We find that an 800 °C heat treatment of the formed traditional sheet leads to a bi-modal microstructure that relates to flux trapping and inefficient flux expulsion. This non-uniform microstructure is related to varying strain profiles along the cavity shape. However, a more uniform microstructure after 800 °C annealing is achieved when using a cold-worked Nb sheet, resulting in better flux expulsion, without the need to perform the annealing at a higher temperature.

The work is partially supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Awards No. DE-SC 0009960. This is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC-06OR23177. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. NSF-DMR-2128556 and the State of Florida.

Speaker: Bashu Khanal

262 M2Po3C-03: Impact of retained cold work on the microstructure and fabrication of SRF Nb cavities

High cryogenic efficiency, measured as the quality factor (Q$_0$, 2K), has been made possible in Nb superconducting radio frequency (SRF) cavities due to advances in understanding the sub-surface micro-chemistry and structure developed in cavity processing. Recent experiments in SRF cavities have demonstrated the role of bulk cavity microstructure and its influence on trapped residual magnetic flux and related expulsion. Importantly, a more homogeneous microstructure can be obtained after heat treatment by initially forming the SRF Nb cavities from Nb sheets that are in the cold-worked state. The improved microstructural uniformity correlates to better flux expulsion and higher overall Q$_0$. In this work, we explore the influence of different levels of cold work on the development of the microstructure of SRF Nb sheet. We report on the following: (1) the microstructure evolution in cold rolled SRF quality Nb sheets undergoing reductions of 30, 40, 50, 70% and after subsequent heat treatments between 600- 900°C, (2) fabricability of 30, 50, and 70% cold work sheets into Nb cavities, and (3) flux expulsion results on Nb cavities fabricated with the above sheets. Based on these results we discuss the issues that must be addressed to harness the potential of using cold-worked sheets for SRF cavity production.

Acknowledgment
This material is based upon work supported by the U.S. DOE, Office of Science, Office of HEP under Award No. DE-SC0009960. This work was partially performed at the NHMFL, which is supported by the NSF Cooperative Agreement No. DMR-1644779 (2018-22) -2128556 (2023-) and the State of Florida. This work was also partially performed at the Thomas Jefferson National Accelerator Facility which is supported by U.S. DOE Contract No. DE-AC-06OR23177.

Speaker: Santosh Chetri (Applied Superconductivity Center, NHMFL, FSU)

263 M2Po3C-04: Characterization of NbTi wires for the electron-ion collider project

The Electron-Ion Collider (EIC) is a proposed machine to explore the behavior of the fundamental particles and forces that bind atomic nuclei together. The design and construction of the EIC are underway at Brookhaven National Laboratory (BNL) in collaboration with Thomas Jefferson National Accelerator Facility. EIC will use several different types of superconducting strands for magnets near the interaction region (IR) of EIC. At beam injection, the magnetic field is usually very low compared with its maximum operating field. This usually created considerable field errors mainly generated from persistent current in superconducting strands even using very fine filament. The accurate magnetization measurement results from those superconducting strands will be critical for the calculation and future correction of persistent current for EIC.
In this work, we characterized 5 types of NbTi strands. The magnetization was measured at 4.2 K and 1.9 K. The critical current at 4.2 K and in magnetic field down to 4 T were also measured. Other properties that are important for the safety margin of superconducting magnet fabrication, operation, and quench protection such as residual-resistance-ratio (RRR), filament diameter, Cu to non-Cu ratio, twist pitch, and mechanical properties will also be presented.

Acknowledgment
This work was supported by Brookhaven Science Associates, LLC under contract No. DE-SC0012704 with the U.S. Department of Energy. This work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR- 2128556, and the State of Florida.

Speaker: Jun Lu (National High Magnetic Field Laboratory, USA)

264 M2Po3C-05: Progress of APC and high Cp Nb3Sn conductors in Hyper Tech

In this paper we will update the progress of the two types of advanced Nb3Sn conductors manufactured in Hyper Tech. One is ternary APC (Artificial Pinning Center) Nb3Sn strand by using internal oxidation technique to increase Jc in high field and lower the magnetization in low field; The other one is high specific heat (Cp) Nb3Sn strand to increase the energy margin against quenching by adding certain high Cp material in the strands. We are working on making kilometer length of both types of wires. The ternary APC Nb3Sn conductors with Ta and either Zr or Hf doping demonstrated substantial grain refinement and significantly increased Jc,nonCu, while retaining the high Bc2 values of the best ternary Nb3Sn conductors. These APC conductors reached the FCC Jc specification for both 61-stack and 217-stack wires. Compared with standard Nb3Sn, APC conductors have higher Birr and Bc2, and their Fp,max shifts to higher field. These two effects lead to flatter Jc-B curves, which enhances Jc at high fields (e.g., >10 T) but reduces Jc at low fields (e.g., < 5 T). This reduces magnetization at low fields, which is very desirable for suppressing low-field flux jumps, field errors, and a.c. loss. We successfully made kilometer length of high specific heat Nb3Sn conductors and demonstrated the Cp of the Wire is 10 times of the control wire at 1.9 K, and 4 times at 4.2 K, which will increase energy margin of the conductor.

Speaker: Dr Xuan Peng

M2Po3D - AC Loss Modeling and Measurements

265 M2Po3D-01: Superconducting Coil Pack Manufacturing and Risk Reduction Testing for NASA’s AC Loss Test Rig

Superconducting coils are designed for carrying high electrical current at low losses for use in future superconducting power transmission lines, transformers, fault current limiters, and electric machines for aircraft. The coils in the armature (typically the stator winding) of electric machines are exposed to highly dynamic magnetic excitation. In this environment, it is critical to understand the alternating current (AC) losses in the superconductor and significantly limit or avoid AC losses in the surrounding structures (coil pack) that provide mechanical support and thermal management to the coil. These coils are often fluid cooled. Accordingly, these coil packs should be electrically insulative and fluid-leak tight. The design and construction of stator coil packs is an open area of research. NASA Glenn has designed and built a new test rig aimed at measuring AC losses of superconducting wires, cables, and coils in a representative stator environment. Before AC losses can be quantified over a range of anticipated operational conditions however, a key challenge that must be addressed is reliable manufacturing of electrically-insulative and fluid-leak tight coil packs. The coil packs must be able to tolerate numerous pressure and thermal cycles anticipated for use in future superconducting electrical machines. Multiple coil packs samples were recently designed and fabricated from G-10 with internal passages for gaseous helium coolant flow. To properly validate that the structure is suitable for future AC loss testing, samples were tested for gas flow rate, thermal cycling (77-300 K), and both static pressure and pressure cycling up to expected maximum operating pressure of 758 kPa in ambient and liquid nitrogen environments. This paper describes the coil pack design and manufacturing in addition to the test results, which indicate that the current coil pack design and manufacturing process are suitable for planned AC loss testing.

Speaker: Frederick Van Keuls (HX5, LLC)

266 M2Po3D-02: Modelica Modelling of HTS Dipole Magnet windings, and the influence of cable defects on Thermal and Electrical Sharing in the Cross Section

This research explored thermal and electrical sharing, as well as quench, in the cable/composite winding cross-section of an epoxy-impregnated HEP dipole accelerator magnet using HTS（ReBCO）Cables. While HTS insert designs can vary, and in some cases, either no insulation tape windings or fully cooled cable windings are being contemplated, this design is for cables with indirect cooling (epoxy impregnation) with specified electrical and thermal inter-cable resistances. The cables also have a defined level of defects within them, both in terms of severity and density. A direct simulation of the magnet winding with full detail in the cable structures would be far too computationally expensive to give sensible run times. However, our approach was to use results from previous modeling runs on cables to develop simple cable proxies which replicated the main results of the cable properties (Temperature and voltage distribution at a given current), but were averaged over length scales smaller than the cable length scale, but larger than that of the tape. These proxies were then used to construct a magnet winding cross-section, where inter-cable electrical and thermal interlayer values could be specified. Due to the complexity of the structure, we used Modelica to guide the research direction which is coarser but faster. For the present study, the magnet was designed with nine cables in each of the four quadrants, and one quadrant was studied. The cables themselves were constructed from thirty tapes each. The tendency for quench as a function of current was explored, and compared to the performance of the isolated cables.

Speaker: Minzheng Jiang

267 M2Po3D-03: Modeling and Analysis of Magnetization in ReBCO Coated Tape Conductor and Helical Wound Tape Conductors

This study presents a comprehensive analysis of magnetization in ReBCO-coated conductor tape and helical wound tape conductors using both numerical and finite element method (FEM) approaches. Magnetization is a crucial factor limiting the practical application of superconducting cables and coils, and accurate prediction and minimization of magnetization are vital for the development of superconducting systems. Numerical models were developed to predict the magnetization behavior of ReBCO-coated conductor tapes and helical wound tape conductors. These models were validated by comparing their results with analytic models and previous experimental data. The numerical simulations enabled the calculation of the M-H response, allowing for the estimation of hysteretic losses. Complementary FEM simulations were also performed to investigate the magnetization behavior of ReBCO-coated conductor tapes and helical wound tape conductors. A diluted superconductor approach was employed for the FEM modeling. The FEM simulations explored various twist pitch values and demonstrated a reduction in losses consistent with the analytical expectation of 2/π reduction from flat tapes in fully perpendicular fields. The combined numerical and FEM studies provide a comprehensive understanding of magnetization in ReBCO-coated conductor tapes and helical wound tape conductors, offering valuable insights for the optimization of superconducting cables and coils.

This work is supported by the United States Department of Energy, Office of Science, Division of High Energy Physics under Grant DE-SC0011721.

Speaker: Tushar Garg (The Ohio State University)

268 M2Po3D-04: AC loss models of standard and non-standard arrangements of Y-Ba-Cu-O tapes in stacks

In this work, semi-analytical models to compute alternating current (AC) power loss in stacks of high-temperature superconductor YBa2Cu3O7-x (or Y-Ba-Cu-O) tapes subjected to a time-varying magnetic field perpendicular to the tapes with zero transport current are developed. Both standard and non-standard arrangements of tapes are considered. The models take into account screening of the interior of a stack and show decreasing dependence of the power loss per tape with . We validate the results by experiments carried out at temperature K under an applied magnetic field with the amplitude of its induction T and frequencies up to 110 Hz. In addition, explicit formula for an error of analytical expressions for the AC loss is derived, which establishes the applicability domain of the models. The approach is extended to compute the AC loss for lower temperatures, larger magnetic fields strengths, and for frequencies up to several kHz. These studies are important for understanding and predicting the AC loss for contemporary motors and generators. As is shown, the AC loss dependence on the arrangement of tapes in the stack can be quite strong, varying by factors up to ~ 200 for temperatures 20–65 K, magnetic fields 2–5 T and frequencies up to 2 kHz .

Speaker: Dr George Y. Panasyuk (NRC Senior Researcher)

M2Po3E - Characterization of REBCO Conductors I

269 M2Po3E-01: Thermal and Mechanical Characterization of REBCO HTS Tapes and Stacks for Magnet Design in the Muon Collider Study

Muon colliders offer a transformative opportunity in high-energy physics, enabling precision measurements and groundbreaking discoveries at the energy frontier. Their compact design and ability to achieve extremely high center-of-mass energies make them a promising alternative to traditional colliders. However, realizing such machines presents several significant technical challenges, particularly in designing the magnets needed to generate the intense fields required to confine and focus muon beams.
The 40 T solenoid proposed for the Muon Collider study relies on advanced high-temperature superconducting (HTS) materials that must withstand extreme thermal and mechanical stresses. As such, a thorough understanding of the thermal and elastic properties of the materials used in the magnet is crucial to develop functional designs that ensure both performance and structural stability under high-field conditions.
Due to the limited available literature on this subject, an extensive experimental campaign has been conducted to characterize a range of REBCO HTS tapes with potential for use in the final design, as well as tin-impregnated stacks made from these tapes. The study focuses on measuring the thermal contraction coefficient, thermal diffusivity, and conductivity, along with the elastic properties of the materials under operational conditions.
The data from this campaign are essential for optimizing magnet design, from material selection to stress management strategies, ensuring the reliable operation of the solenoid. Additionally, these findings could offer valuable insights for other industries and applications utilizing REBCO tapes.

Speaker: Michael Guinchard (CERN)

270 M2Po3E-02: Contact resistance effect on current sharing in defected superconducting REBCO tape stack cables: FEM modeling

High energy physics magnets use superconducting cables to decrease their inductances which limit their induced voltages during magnet ramp rates and quenches. For HTS strands, the minimum quench energy (MQE) is quite large. Heating due to small defects within the cable can be mitigated by strand-to-strand current sharing. In this case of particular interest are REBCO tape stacks, Roebel and CORC cables. Small defects may arise in the original tapes, either during cabling or in service in the magnet. Then local heating can be generated in absence of current sharing. In this paper we modelled the current sharing in tape stack cables containing seven double-sided REBCO tapes with defects present in some of them. Electrical and thermal contact resistances between the tapes in the cables were considered. In the present work, we used Finite Element Method (FEM) modeling, assuming critical current densities of these tapes relevant for operation at 4.2 K (boiling liquid He).

Speaker: Milan Majoros

271 M2Po3E-03: Mechanical characterization and critical current irreversibility limit of different ReBCO tapes

High-magnetic fields of up to 20 T in coils in tokamak-type fusion devices, such as in the Central Solenoid of European DEMO and the Chinese BEST, require use of High-Temperature Superconductors (HTS) and promising candidates are high-current cables comprising ReBCO tape. The large Lorentz force occurring under these operating conditions can locally generate very high values of mechanical stress, which can irreversibly degrade the critical current of the ReBCO superconductor. For the design of the cables, detailed structural finite element analysis (FEA) based on accurate electromagnetic and mechanical material properties under relevant electromagnetic load levels is needed for achieving reliable analysis results and defining optimal operating conditions. Knowledge of the axial tensile and compressive strain irreversibility limits of the critical current of ReBCO tapes is therefore essential.
For this purpose, axial tensile stress–strain measurements on ReBCO tapes from several manufacturers have been performed in the upgraded TARSIS-2 facility. In addition, compressive strain imposed by bending on different core diameters with various winding angles have been performed to mimic closely the CORC cabling conditions. Critical current and n-value were measured at 77 K in self field for stepwise increasing tensile load, and also the effect of cyclic loading were studied. For comparison and reference, the tensile stress strain characteristics were also measured at room temperature.
Full-scale 3D FE models of the tapes have been developed and validated using electrical and mechanical material properties of the used superconducting tapes. Based on these data, simplified stress-strain relations for engineering purposes are proposed. The model predictions are well in agreement with experimental results and are being used to predict quantitively the effect of Lorentz force based loads on ReBCO-CORC based high current Cable In Conduit Conductors in order to achieve performance optimisation.

This work is supported in part by the University of Twente. Part of the funding is also provided by the EUROfusion Consortium, funded by the European Union (Grant Agreement No 101052200 — EUROfusion). Views and opinions expressed are, however, those of the author(s) only. The tapes were kindly provided for free by the involved manufacturers.

Speaker: Mr W.A.J. Wessel (University of Twente, Faculty of Science & Technology, Enschede, The Netherlands)

272 M2Po3E-04: Friction Coefficient Measurements for High-Temperature Superconducting Magnet Design

Accurate prediction of mechanical stress within high-field superconducting magnets is crucial for ensuring their structural integrity and operational reliability. Friction between turns plays a significant role in load transfer and stress distribution within the magnet winding. However, limited experimental data, especially at cryogenic temperatures, hinders precise modeling and design. This study addresses this knowledge gap by measuring the friction coefficient between REBCO and co-winding tapes at both room temperature (295 K) and cryogenic temperature (77 K). A novel experimental setup was developed to measure the friction force under controlled conditions. The influence of various factors, such as transverse load and temperature, on the friction coefficient was investigated. The results of this study provide valuable insights into the tribological behavior of superconducting tapes at cryogenic temperatures. These findings have been used to refine mechanical models and simulations of superconducting magnets, leading to improved design and optimization.

Acknowledgement
This work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1644779, DMR-1839796, DMR- 2131790, and the State of Florida.

Speaker: Dr Aniket Ingrole (National High Magnetic Field Laboratory (NHMFL), Florida State University)

273 M2Po3E-05: Measurement of Transverse Resistance for Stacks of Non-insulated REBCO Tapes

Transverse resistance among adjacent conductors is necessary information to calculate AC losses in stacks of non-insulated conductors. An existing transverse pressure insert (TPI) was modified at Fermilab to measure at nitrogen temperature transverse resistance of stacks made of non-insulated REBCO tapes as a function of transverse pressure. Pressure up to 300+ MPa was applied with a hydraulic cylinder. A small current was flown in the stack sample through REBCO tape segments spliced above and below the stack. The latter had a bending radius larger than 6 cm to prevent damage. The voltage was measured just outside the compressed area. Stack samples included stacks of bare REBCO tapes, of REBCO tapes alternated with stainless steel ribbons of various thicknesses, and of impregnated and soldered stacks. We herein present results of these transverse resistance measurements. Results show a stronger dependence on pressure for smaller pressure vs. larger ones. Also, of the two components of transverse resistance, i.e. contact and bulk, the latter was negligible.

Speaker: Elena Tamagnini (Politenico di Torino)

15:00 Afternoon Coffee Break -- supported by Sumitomo (SHI) Cryogenics of America, Inc.

C2Or4A - Large Scale Refrigeration IV: Beam-Line Energy Physics

274 C2Or4A-01: Status of the PIP-II cryogenic plant

The Proton Improvement Plan-II (PIP-II) is an essential upgrade to the Fermilab accelerator complex, featuring a new 800-MeV Superconducting Radio-Frequency (SRF) linear accelerator (LINAC) powering the accelerator complex to provide the world’s most intense high-energy neutrino beam. The PIP-II Linac contains 23 SRF cryomodules with the SRF cavities operating at 2K, a high temperature thermal shield at 40K and low temperature intercepts at 5K. The cooling power for the cryomodules and the cryogenic distribution system is supplied by a single helium cryogenic plant with max capacity of 2.5 kW at 2.0 K. The cryogenic plant includes a refrigeration cold box, a warm compressor system with ORS/GMP, and helium storage, recovery, and purification systems. This paper describes the current progress in integration design, fabrication and installation status of the PIP-II cryogenic plant.

Speaker: Yi Jia

275 C2Or4A-02: Design of satellite cryogenic plants for the Electron-Ion Collider at Brookhaven National Lab

In support of the Electron-Ion Collider (EIC) at Brookhaven National Laboratory (BNL), Jefferson Lab is contributing to the design of three satellite cryogenic plants. These satellite plants will augment BNL’s central plant, which currently provides cryogenics for the Relativistic Heavy Ion Collider (RHIC) at temperatures down to 4 Kelvin. The primary role of the satellite plants is to further cool the cryogenic loads from the central plant to 2 Kelvin, a critical requirement for EIC operations.
This paper presents a comprehensive evaluation of various process configurations for each satellite plant. It discusses the advantages and disadvantages of each configuration, their integration with the central plant, and the rationale behind the final selection for the satellite plant operations.

Speakers: Blaine Wissler (Jefferson Lab), Shirley Yang (Jefferson Lab)

276 C2Or4A-03: New Helium Refrigerator for Institute of High Energy Physics

Institute of High Energy Physics (IHEP) and Air Liquide Cryogenic China Science (ALCCS) have started a new Helium refrigeration plant to provide 1kW of cold power at 4.5K to cool-down the superconducting cavity to accelerate electrons. The cold box delivering this power was manufactured by ALCCS in China and connected to a KAESER compressor. The Helium expanders manufactured by Air Liquide Advanced Technologies (France) are based on the static gas bearing technologies. This paper presents the performance results of this new refrigerator in the context of the global cryogenic systems of the Institute of High Energy Physics.

Speaker: Jean-Marc Bernhardt (Air Liquide Advanced Technologies)

277 C2Or4A-04: Cryogenic System for the High Energy Photon Source At IHEP

High Energy Photon Source (HEPS) is a high-performance and high-energy synchrotron radiation light source with a beam energy of 6GeV and an ultra-low emittance of better than 0.06nm×rad. HEPS is mainly composed of accelerator, beamlines and end-stations, which would provide the synchrotron beam with will brilliance higher than 1×1022 phs/s/mm2/mrad2/0.1%BW. No less than 90 high performance beamlines and end-stations are capable to be built around the storage ring., the circumference of the store ring is 1.36km. A large cryogenic system has been built for the HEPS, which includes a helium cryogenic system and a nitrogen cryogenic system. The helium cryogenic system is used to cool down five 166.6MHz superconducting cavity cryomodules and two 499.8MHz superconducting cryomodules in the first phase, and in second phase another three cryomodules will be added, the distance from the first to the end cryomodule is around 200 meters, the total cooling capacity of the helium refrigerator is 2000W@4.5K. The nitrogen cryogenic system is used for the precooling of helium refrigerator, thermal shield for the cryogenic transfer line and the cryomodules, cool down of the cryogenic permanent magnet undulator and cryogenic monochromator,the total cooling capacity of the nitrogen system is around 45KW@80K.The project of HEPS will be finished in the end of 2025, the whole cryogenic system nearly to be finished and had been put into use for machine commissioning.

Speaker: Dr Rui Ge (Institute of High Energy Physics, Chinese Academy of Sciences)

278 C2Or4A-05: Overview and status of the cryogenic system for SHINE accelerators

The Shanghai high repetition rate x-ray free electron laser (XFEL) and extreme light facility (SHINE), a quasi-continuous wave hard XFEL facility, is currently under construction. The superconducting accelerators of SHINE require cryogenic cooling at 2 K for cavities, 5 K for cold interception, and 40 K for thermal shields, respectively. In this paper we present the overview and recent progress of the SHINE cryogenics system that mainly consists of the cryoplant generating the cooling power, the cryogenic distribution system that delivers the cryogen to the accelerators, and the utility system to serve liquid nitrogen together with the helium management. With considerable safety margins, three sets of large helium cryoplants are being built in two cryo-stations at the front and end of the SHINE accelerators, respectively. Each cryoplant could provide a cooling power of 4 kW at 2 K. Up to now, all the equipment belonging to the three cryoplants has been installed. The warm compressor station, 4.5 K cold box, 2 K cold box, and the interconnecting cryogenic transfer line in between for the first set of cryoplant have finished the site performance test and are being operated to support the comission of the SHINE injector. This progress improves the cryogenic capability of the SHINE facility and will enable the joint commissioning and operation of the SHINE accelerators in the future.

Speaker: Prof. Zhengrong Ouyang (ShanghaiTech University)

C2Or4B - Instrumentation, Visualization, and Controls II

279 C2Or4B-01: The Use of Temperature Sensors for Liquid Hydrogen Testing at NASA Glenn Research Center

NASA Glenn Research Center has been testing temperature sensors both internal and external to liquid hydrogen tanks for the past 70+ years. A range of sensors have been used including thermocouples, silicon diodes, and Cernox based RTDs. Different application processes for measuring the temperature of the hydrogen fluid, as opposed to solid materials, are used within a tank and within a pipe or hose. Sensors have been used as local wet/dry sensors to determine liquid height. Some of these applications have performed better than others, which is heavily influenced by how the sensors are handled and installed. This paper examines different temperature sensor performance and installation methods that have been used in liquid hydrogen applications at NASA Glenn Research Center and discusses lessons learned from different testing experiences.

Speakers: Wesley Johnson (NASA Glenn Research Center), Mark Kubiak

280 C2Or4B-02: Cernox® versus germanium cryogenic temperature sensor stability comparison over the 1 K to 27 K temperature range

Germanium resistance thermometers (GRTs) have played a crucial role in the dissemination of both the 1976 Provisional 0.5 K to 30 K Temperature Scale and the International Temperature Scale of 1990 to cryogenic experimenters worldwide. GRTs combined a small physical package with a sensing element that possessed high temperature sensitivity and very high stability over thermal cycling and time. The fabrication method allowed for tweaking the GRT response curve to maximize sensitivity for a desired temperature range. For thermometry applications, the best GRTs were fabricated with arsenic doping. and these devices were commercially available from multiple companies for nearly 50 years. At present, however, commercially available GRTs are nearly nonexistent as germanium crystal growers are reluctant to work with arsenic dopants. For cryogenic temperature applications below30 K, the most promising alternative is Cernox® resistance thermometers (CxRTs). CxRTs have characteristics similar to GRTs including small physical size, high stability, and a temperature response curve that can ne tailored to maximize performance over a given temperature range. To date, no direct comparison of calibration stability between CxRTs and GRTs using an identical test protocol has been performed. In the present work, A group of 15 GRTs and 25 CX-1050-CU devices were calibrated against ten NIST/NPL calibrated thermometers over the 1.2 K to 30 K temperature range, and subsequently thermally cycled slowly from room temperature to 1.2 K approximately once per week for 50 weeks. Following the 50 thermal cycles, both groups were recalibrated against the ten NIST/NPL calibrated thermometers. Data was analyzed in terms of temperature shift between the pre- and post-thermal cycling for both groups of thermometers. For GRTs, the preliminary results show the post- versus pre-thermal cycling calibration data average stability ranging from 0.5 mK (standard deviation <1.0 mK) for temperatures less than 4.2 K, and less than 1.5 mK (standard deviation <1.7 mK) for temperatures up to 30 K. For CxRTs, the preliminary results show the post- versus pre-thermal cycling calibration data average stability to be similar to that of GRTs, with lightly higher standard deviations about the average ranging from 1.0 mK for temperatures less than 4.2 K, and less than 2.1 mK for temperatures up to 27 K.

Speaker: Scott Courts (Lake Shore Cryotronics, Inc.)

281 C2Or4B-03: Particle Levitation Velocimetry for boundary layer measurements in high Reynolds number liquid helium turbulence

Understanding boundary layer flows in high Reynolds number (Re) turbulence is essential for advancing fluid dynamics across a range of critical applications, from enhancing aerodynamic efficiency in aviation to optimizing energy systems in industrial processes. Accurate characterization of turbulence, including scaling laws for mean velocity and turbulence intensity, is vital for developing robust predictive models. However, generating such flows typically demands large-scale, power-intensive facilities. Furthermore, conventional measurement tools, such as hot wires and pressure sensors, often introduce disturbances due to intrusive support structures, thereby compromising measurement fidelity. In this paper, we discuss a new method that leverages the vanishingly small viscosity of liquid helium to produce high Re flows, combined with an innovative Particle Levitation Velocimetry (PLV) system for precise, non-intrusive flow-field measurements. The PLV system utilizes magnetically levitated superconducting micro-particles as flow sensors to capture near-wall velocity fields in liquid helium. We present the detailed design of the PLV system, which employs four coaxial coils to create a trapping zone with strong transverse energy gradients, allowing for particle trapping even in the presence of high Re flows. Through comprehensive theoretical analysis, we demonstrate that the PLV system enables quantitative measurements of the velocity boundary layer over a wall unit range of 44 ≤ y$^+$ ≤ 4400, with a spatial resolution that, depending on the particle size, can reach down to about 10 μm. This non-intrusive, high-resolution measurement capability represents a significant advancement in the study of wall-bounded flows, with profound implications for both fundamental turbulence research and practical engineering applications.

Speaker: Yinghe Qi (National High Magnetic Field Laboratory, FSU)

282 C2Or4B-04: Accelerator cavity quench spot detection using particle tracking velocimetry

Superconducting Radio-Frequency (SRF) cavities cooled by superfluid helium-4 (He II) are critical components of modern particle accelerators. Tiny defects on the inner surface of SRF cavities can cause Joule heating, leading to cavity quenching. Developing reliable technologies to locate these defects for subsequent removal is essential for improving the performance of SRF cavities. Existing methods for detecting quench spots, such as temperature mapping and second-sound trilateration, are often limited in precision and practicality. Our lab has demonstrated an alternative detection technique based on Molecular Tagging Velocimetry (MTV) in He II, which provides significantly improved spatial resolution. However, the complexity of the laser facilities required for MTV makes it challenging to implement in accelerator laboratories.
In this study, we investigate a novel method utilizing Particle Tracking Velocimetry (PTV) with solidified deuterium (D₂) tracer particles. A preliminary experiment was conducted using a miniature heater in He II to simulate a cavity quench spot. Our results show that the velocity field of the tracer particles near the heater can accurately localize the heater's position. Given the simplicity and practicality of the PTV setup, this method shows great potential as an alternative approach for quench detection in accelerator labs.

Acknowledgment: We would like to acknowledge the support from the U.S. Department of Energy under Award No. DE-SC0020113. We also acknowledge the support and resources provided by the National High Magnetic Field Laboratory at Florida State University, which is supported by the National Science Foundation Cooperative Agreement No. DMR-2128556 and the state of Florida.

Speaker: Yousef Alihosseini (Mechanical Engineering Department, FAMU-FSU College of Engineering, Florida State University, Tallahassee, FL 32310, USA National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA)

283 C2Or4B-05: Replacement and expansion of the cryogenic control system for the Electron Ion Collider at Brookhaven National Laboratory

The Electron Ion Collider (EIC) at Brookhaven National Laboratory represents a major advancement in particle physics, requiring sophisticated cryogenic infrastructure to support its superconducting elements. This effort involves the conversion of the existing cryogenic control system, originally developed for the Relativistic Heavy Ion Collider (RHIC), to meet the specific demands of the EIC. The cryogenic control system will coordinate cooling for components operating at various temperatures, including superconducting magnets at 4.6K, 1.92 K and Superconducting Radio Frequency (SRF) cavities at 2.0 K.
Key to this transition is the integration of 2K satellite cryogenic systems distributed around the Collider ring. These systems will function in tandem with the existing central plant and the existing 4K distribution system. The central plant will provide supplemental capacity to the 2K satellites and ensure seamless operation across diverse cooling loads. Upgrades to the control system architecture will focus on enabling precise management of expanders, heat exchangers streams, and supply and return flow streams from the various loads to accommodate the expanded functionality. The cryogenic control system also interfaces to other Collider systems such as the magnet system, SRF systems, vacuum systems, beam permit/abort system, VODH system, and utilities systems for controls and interlocks.
This effort is a cooperative endeavor between Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLAB). The collaboration leverages the expertise and resources of both institutions, ensuring the cryogenic control system meets the stringent performance and reliability requirements of the EIC. By working together, BNL and JLAB aim to deliver a state-of-the-art cryogenic solution that supports the groundbreaking scientific goals of the EIC.
This paper outlines the strategy for transitioning the RHIC cryogenic control system to the EIC, detailing the architectural modifications, operational protocols, and enhanced monitoring required to support EIC's advanced scientific objectives. By leveraging the existing infrastructure while introducing targeted enhancements, the cryogenic control system will play a critical role in achieving reliable, efficient, and scalable performance for the EIC.

Acknowledgment
This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.

Speaker: Patrick Talty (Brookhaven National Laboratory)

284 C2Or4B-06: Fermilab PIP-II CDS & CM Cryogenic Controls System

Details on Final design for Cryogenic Electrical & Controls System for Fermilab' s next-gen particle accelerator PIP-II. Electrical Controls System includes instrumentation and controls of Cryogenics Distribution System and Cryomodules. Design includes Siemens PCS7 Controls System with 26 Remote IO Rittal Cabinets and 48 Relay Racks for Temperature Readouts, Valve Positioners, Level, Heater Controls etc. Electrical Drawings and Design have been completed with focus now on fabrication of the 26 Rittal Cabinets and 48 Relay Racks. All materials have been procured also. EPICS will be used as a SCADA system communicating to S7 Controllers via OPC UA.

Speaker: Pratik Patel (Fermilab)

285 C2Or4B-07: Design, installation and commissioning of the cryogenic control system for the DALS cryogenic test facility

The Dalian Advanced Light Source (DALS), is a linear accelerator based on continuous wave superconducting radio frequency(SRF) technology aiming to produce high-quality electron beam with repetition rate up to 1 MHz. The cryogenic test facility is designed to provide the cooling capacities and maintain 2 K temperature operation for the SRF cavity and the cryomodules, which includes Horizontal Test Bench(HTB),Vertical Test Cryostat (VTC), Cryogenic Test Bench (CTB) and Injector Test Bench (ITB).The cryogenic control system consists of Programmable Logic Controllers (PLCs) with local human machine interfaces (HMIs) and the Experimental Physics and Industrial Controls System (EPICS) for normal operations and data acquisition. This paper reports on the design choices selected and experiences in installation and commissioning of the DALS cryogenic control system. After the second round cool-down PID parameters of the important devices in the cryogenic distribution system(CDS) are tuned.

Speaker: Haining Li (Institute of Advanced Science Facilities (IASF))

286 C2Or4B-08: The design of a flow boiling visualization experiment for liquid hydrogen

Liquid hydrogen is the highest specific impulse rocket fuel available and is used on roughly 25% of active United States rocket launch systems. However, these systems are informed by heat transfer correlations, the most recent of which has 50% root-mean-squared error when used with liquid hydrogen. No previous experiment has optically determined multiphase hydrogen flow regimes with heat transfer measurements, contributing to this error. To address this gap, this publication presents the design and preliminary results of a two-phase hydrogen visualization flow cell that can address uncertainty in existing models by providing velocity, mass flow rate, void fraction, and pressure drop data while identifying flow regimes in two-phase hydrogen. Preliminary results using liquid nitrogen are provided with uncertainty analysis. The resulting system will be used to characterize departure from nucleate boiling and heat transfer criticality for increased confidence in multi-phase liquid hydrogen flow estimates for system design.

Speaker: Ian Wells

C2Or4C - Cryogenic Components III

287 C2Or4C-01: Development of a two-phase, variable nozzle jet-pump for pressure control in liquid hydrogen systems

Liquid hydrogen systems require pressure control methods when flowing through complicated plumbing networks. Methods vary from autogenous pressurization, introducing a secondary fluid, buffer volumes, or utilization of transfer pumps. To address this need, a jet pump was designed, built, and tested with liquid hydrogen to assess variable primary nozzle position in relation to secondary fluid mixing and inlet/outlet pressure differentials. This paper reviews the technology development, testing, and results of the efficiency when using a venturi jet pump for liquid hydrogen applications. This new liquid hydrogen pumping paradigm has the potential to reduce the frequency of maintenance required by reducing complex sealing surfaces while decreasing the two-phase mixture quality at the outlet.

Speaker: Yulia Gitter (Washington State University HYPER Lab)

288 C2Or4C-02: Design and testing of a submersible laboratory-sized cryogenic liquid hydrogen pump

As the hydrogen market expands, the need for the efficient distribution of liquid hydrogen (LH2) becomes increasingly important. Reducing flash gas losses during LH2 transfer and ensuring adequate pressurization of downstream applications, such as fuel cells and combustion engines, are challenges. It is therefore essential to develop pumps for liquid hydrogen. To overcome transfer losses a three-staged liquid hydrogen turbo pump, as well as a test rig for small cryogenic pumps was developed. This paper presents the general concept of this submersible liquid hydrogen pump and gives insight into component and system testing of this pump.

Speaker: Henrik-Gerd Bischoff (Technische Universität Dresden)

289 C2Or4C-03: Lightweight, high-flow valve for cryogenic propellant management on aircraft and spacecraft

Recent development of hydrogen-powered aircraft and cryogenic-propellant-powered rockets has created demand for smaller, lighter, and lower-power solutions to classic fluid handling problems. Valves, seals, and couplings rated for use with liquid hydrogen and liquid oxygen are critical to enable advanced aerospace system architectures. Creare is helping meet this need through development of our lightweight, high-flow valve designed for cryogenic propellants. Our valve uses a floating seal to provide low flow restriction without the bulky housing typically required of valves with large orifices. We have demonstrated high flowrates (Cv > 200) in a small package (2″ nominal line size) with weight (~18 lbs) appreciably lower than existing commercial alternatives. Low internal leakage (< 1 sccm) and all-welded construction (zero external leakage) make our device a leading candidate for SWaP-sensitive cryogenic fluid management applications. In this presentation we will provide an overview of our device design, valve scaling for different applications, and share recent performance data gathered at cryogenic temperatures.

Speaker: Lucas O'Neill (Creare LLC)

290 C2Or4C-04: Enhanced Power Control and Maintenance-Free Turbine Retrofit in a Cryogenic Hydrogen Process for Tritium Removal

Linde replaces an oil-bearing turboexpander, prone to oil contamination and component damage, with a maintenance-free dynamic gas-bearing turboexpander while adding a new cooling power control system to an existing cold box in a hydrogen process within a cryogenic tritium removal facility.
The dynamic gas-bearing turboexpander with proven technology, successfully used for years, significantly enhances efficiency, reduces energy consumption while boosting the cooling power output. Moreover, its superior reliability surpasses that of its oil-bearing predecessor and will allow more reliable operation of the cryogenic tritium removal facility.
The new cooling power control system allows the use of the new more efficient turboexpander at the specific original operating conditions and at potentially new optimized operating conditions for the tritium removal process. The power control diverts mass flow from the turboexpander to allow load adaption at constant process mass flow.
The presentation covers the design and the control strategies for load adaption.

Speaker: Mr Johannes Schreiber (Linde Kryotechnik AG)

291 C2Or4C-05: Development and validation of a 1D oil-injected screw compressor model for helium cryogenic system applications

Oil-Injected twin screw compressors are widely used in cryogenic helium refrigeration systems as the prime mover. They provide all the thermodynamic availability for the cryogenic refrigeration system and account for more than one-half of the input power losses and two-thirds of total system availability losses. These machines are generally designed for freon or other common refrigerants and are retrofitted for helium applications. Oil is injected into the compression cavity to address the high heat of compression of helium and lubricate and seal the rotating components during the compression process. These systems were not explicitly studied for helium compression application, suffer from relatively low system efficiencies, and can largely benefit from improvements in the compression process. To better understand the compression process of helium-oil mixtures through an oil-injected screw compressor, a steady-state, one-dimensional, non-equilibrium model has been developed and validated using published datasets. The 1D model is derived from an energy and mass balance of the gas and oil mixture, including empirical correlations of heat transfer and gas leakage internal to the compressor. Primary parameters investigated in the present study include oil-gas mass ratio, pressure ratio, discharge temperature, and isothermal efficiency. The simulations are compared against experimental data obtained from a hermetically sealed oil-injected helium screw compressor test bench. Such a predictive model for the compression process applies to the design of compressor skids used in either small or large-scale helium cryogenic systems. It can be utilized with a refrigeration system process model to evaluate the cryogenic system efficiency and optimum operating modes under various operating process conditions.

Speaker: Mr Scott Anthony (Michigan State University)

292 C2Or4C-06: Modeling and Analysis of Graded Heat Exchangers for Cryogenic Power System of Electric Aircraft Using the AeroCryoX

This paper presents a modeling approach for graded heat exchangers designed to support cryogenic power systems of hydrogen-fueled electric aircraft implemented within our comprehensive MATLAB/Simulink-based tool, AeroCryoX. The graded heat exchanger concept employs graded and partitioned to accomplish distinct temperature grades to provide multiple secondary cryogen flows to efficiently cool various superconducting and cryogenic components operating at different temperatures: high-temperature superconducting (HTS) generators (20-40 K), HTS cables (50-60 K), and cryogenic power conversion systems and motors (110-140 K). Using AeroCryoX, we develop comprehensive thermal models that model heat transfer and fluid dynamics within each temperature grade.
The paper focuses on two critical cooling loops: the primary loop utilizing liquid hydrogen as coolant and the secondary loop employing gaseous helium. The simulations account for various operational parameters including the cryogen mass flow rates, thermal loads of different components under varying aircraft flight profiles, and the performance characteristics of impellers used to establish fluid flows. Ee systematically evaluated the implementation of graded heat exchangers in aircraft applications. The models enable the determination of critical design parameters such as required hydrogen flow rates for each temperature grade, optimal sizing of cryogenic pumps, and helium flow requirements in the secondary loops.
Results from the models provided valuable insights into the practical implementation challenges and design considerations for graded heat exchangers in aircraft cryogenic systems. The simulation framework is a tool for optimizing cooling system design to predicting hydrogen consumption rates for next-generation electric aircraft. Additionally, the model helps establish operating parameters for the secondary helium loops, ensuring efficient thermal management while maintaining the system’s stability across all temperature grades.

Speaker: Chul Han Kim (FAMU-FSU College of Engineering)

293 C2Or4C-07: Gas bearing turbo compressor and expander technology for cryogenic applications

Cryogenic applications require high complexity air and gas handling. Hydrogen is liquefied for ease of storage and transportation. Once liquefied, boil-off is avoided by cooling the hydrogen (zero-boil off). For both liquification and zero-boil off the reverse Brayton cycle is the most efficient and therefore preferred technology. Driven by a turbo compressor and a turbo expander, it is referred to as a reverse turbo-Brayton cycle cryocooler. Such cryocoolers have a low specific power (lower than 100 W/W possible at 20 K cooling temperature) and therefore are more efficient and can achieve higher cooling power per cryocooler weight and size than Gifford-McMahon or Stirling type cryocoolers. Finally, for recirculation and transport of cryogenic gases, cryo fans are employed. For all these applications, a compressor, a fan and/or an expander are key components.

Gas bearing turbo compressor, fan and expander technology has significant advantages to other technology: small size and weight due to high-speed operation, maintenance free due to an oilfree bearing and no rotating sealings, high efficiency, low amount of wetted materials and therefore no outgassing or compatibility issues, and low microvibration emission due to the continuous flow operation. The gas bearing technology, which does not require sensors, allows to fully immerse the fan and expander into the cryogenic temperatures in a cold box down to 20 K and below. However, running gas bearing turbo compressors and expanders at cryogenic temperatures is a challenge.

This presentation introduces gas bearing turbo compressor, fan and expander technology feasible for cryogenic temperatures, its advantages, limitations and key characteristics. The applicability of the gas bearing turbo compressor technology to cryogenics is demonstrated with design calculations for gas bearing stability, mechanical stability and motor/generator performance. Furthermore, an experimental proof-of-concept of a gas bearing turbo machine is presented with a cryogenic cold test.

Speaker: Mr Martin Bartholet (Celeroton AG)

C2Or4D - Aerospace Applications I

294 C2Or4D-01: Advancing liquid hydrogen storage: GTL’s composite vacuum-jacketed cryotank innovations

Gloyer-Taylor Laboratories (GTL), a leader in cryogenic composite technologies, has spent over a decade developing ultra-lightweight cryotanks to transform liquid hydrogen (LH2) storage and transfer systems. Focused on aerospace and hydrogen-electric propulsion, GTL’s composite vacuum-jacketed dewar tanks deliver hydrogen weight fractions between 60% and 80% while reducing tank mass by up to 75% compared to conventional solutions. Recent LH2 experimental tests validated the technology, demonstrating hard vacuum levels of 2.8e-6 torr, LH2 storage for over 21 hours with minimal boil-off (~1% per day), and rapid chill-down to 20 Kelvin in under 20 seconds. Subscale tanks withstood multiple cryo-thermal cycles without degradation, confirming durability and readiness for real-world applications. Building on these successes, GTL is advancing toward flight hardware production, fabricating scalable composite dewar tanks for hydrogen-powered aircraft, drones, and space missions. These advancements position GTL at the forefront of hydrogen storage innovation, enabling safer, cost-effective, and sustainable hydrogen propulsion across a range of aerospace and energy applications.

Speaker: Mr Paul Gloyer (Gloyer-Taylor Laboratories)

295 C2Or4D-02: Investigation of chill-down process of cryogenic tank

When cryogenic liquids or propellants are transferred from a storage tank to another empty atmospheric storage tank, a chill-down process occurs in the empty tank. The wall temperature of the empty tank is relatively high compared to the cryogenic liquids; thus, evaporation of the cryogenic fluid and a temperature reduction process occur during the filling of the empty tank.
The tank had a diameter of 2.5 m and a height of 4.7 m. Several thermometers were installed evenly along the height of the tank walls and inside the tank. The wall temperature, ullage, and fluid temperature were measured during the filling process of the empty cryogenic tank, and these results were compared with the simulation results. The wall temperatures along the tank height were simulated and analyzed based on the experimental results. Differences in the chill-down process between the empty tank and pipe flow are also discussed in this paper.

Speaker: Seungwhan Baek

296 C2Or4D-03: Efficiency of CryoFILL Liquefaction Tests

The Cryogenic Fluid In-situ Liquefaction for Landers (CryoFILL) tests were performed by NASA to demonstrate a technique for liquefaction of oxygen gas that will be produced on the Lunar or Martian surface. The test setup included a 2.1 cubic meter tank with a broad area cooling (BAC) network. A commercial cryocooler provided cooling to the BAC working fluid. Nearly forty steady state and transient liquefaction tests were conducted during the CryoFILL test series. Test variables included gaseous oxygen flow rate, tank initial fill level and pressure, environmental temperature, and the effective BAC cooling. A thermal/fluid model of the CryoFILL tank and its BAC system was developed in Thermal Desktop to simulate the experimental runs. To assess the performance of the CryoFILL tests an efficiency is defined for the BAC liquefaction process. A comparison of the experimental efficiency and that obtained from the model is presented here.

Speaker: Ali Kashani (ASRC Federal)

297 C2Or4D-04: Development of a method for estimating tank internal conditions during cryogenic fluid filling

As mankind expands its sphere of activity into outer space, such as the moon and Mars, it is expected that cryogenic fluids management technology in the environment that its gravity acceleration differs from that on the earth will be increasingly required. In general, when developing equipment that uses cryogenic fluids, especially for use in space, it is extremely difficult to conduct experiments in the actual operating environment. Therefore, it is essential to use CFD or numerical models to numerically predict the fluid flow in the equipment. In this situation, this research mainly focusses on cryogenic fluid filling into tank. To predict the condition of cryogenic fluid tanks over a long period of time, a low-dimensional model that models the phenomena inside the tank is necessary. On the other hand, the simplest method that assumes that thermal equilibrium is established inside the tank is not suitable for predicting the pressure in the tank at the time of filling. Generally, in a tank that storing cryogenic fluids, there is liquid with a temperature lower than the saturation temperature, called subcooled liquid, at the bottom of the tank, gas and liquid with a saturation temperature near the gas-liquid interface, and gas with a temperature higher than the saturation temperature, called superheated gas, at the top of the tank, if the fluid in the tank is not mixed. This temperature distribution has a significant effect on the pressure inside the tank, and therefore, the temperature distribution inside the tank must be considered within the prediction model for more accurate prediction. This study aims to develop a tank filling model that can consider thermal non-equilibrium condition, and to enable numerical prediction of phenomena in environments where experiments cannot be easily conducted.
The tank model divides the interior of the tank into several layers, and layers are tracked in a Lagrangian manner, that allows to track easily the gas-liquid interface. Each layer exchanges heat with the tank wall and other layers and the temperature distribution inside the tank can be considered. The solver that calculates the layer properties is the same for single-phase and gas-liquid two-phase, which has the advantage that there are less “if” branches during the calculation. Since this model is a one-dimensional model, the computational cost is very small compared to CFD. It can analyze long-time phenomena that are difficult to predict with using CFD, in a sufficiently realistic time.
To verify the accuracy of the model, the results of the model calculations were compared with the results of ground tests. Numerical experiments were also conducted during the process of model validation to understand the phenomena inside the tank during filling. The results of the model validation showed that the pressure time history calculated by the model and that the test results were well matched, by using the amount heat absorption of the fluid to be filled, which has a significant influence on the tank pressure, from the test results. And more, it was revealed that the factors that have a large influence on the tank pressure are the heat absorption, the initial conditions, and the temperature distribution in the tank from the discussion about the experiment results and some numerical experiment using the model. In detail, the dominant factor is the initial temperature of the tank wall, which has a large heat capacity, for the initial stage, and is the temperature distribution in the tank after some time has passed. It is also revealed that the temperature distribution in the tank is greatly affected by the effect of the tank wall surface acting as a heat path to diffuse the temperature. Some of the effects of different gravity accelerations were also discussed.

Speaker: Mr Shin Sakai (The University of Tokyo)

298 C2Or4D-05: Cryogenic droplet-spray impact and rewetting dynamics in tank chilldown applications

In a cryogenic tank chilldown, cryogenic sprays are used to rapidly cool the ullage gas and the tank wall. During chilldown, droplets generated from the spray impinge on the tank wall and exchange heat through boiling regimes such as film boiling, transition boiling, nucleate boiling, and single-phase convection. Since cooling rates differ in each regime, developing computational sub-models requires a detailed description of the droplet impact dynamics. Although the existing literature provides correlations of heat flux in each regime, it lacks detailed time-resolved visualization of cryogenic spray-droplet impact outcome as the solid wall undergoes chilldown. The objective of this investigation is to map cryogenic droplet impact outcomes at different wall temperatures and their dependence on the droplet Weber number. Additionally, this study also examines the differences between the droplet impact and spray impact. In the experimental setup, a full cone spray of liquid nitrogen was impinged on a thin stainless-steel disc instrumented with several thermocouples. The droplet impact dynamics was captured using a high-speed shadowgraph. Results show that the characteristics of droplet impact outcome were governed by rewetting temperature. Above the rewetting temperature, the heat exchange mechanism includes droplet rebound, rebound with droplet breakup, and droplet splash. Below the rewetting temperature, the droplets wet the surface leading to the formation of the thin liquid film. The detailed visualization provides unique insights into the dynamics of a single droplet and spray impact with rewetting temperature as a key factor for computational sub-models

Speaker: Mr Bhushan Patil (School of Mechanical, Aerospace and Manufacturing engineering, University of Connecticut)

299 C2Or4D-06: Cryogenic Two-Phase Flow Boiling Correlations for Terrestrial and Reduced Gravity

To enable the design of future terrestrial as well as in-space cryogenic propellant transfer systems such as Lunar and Martian ascent and descent stages, cryogenic fuel depots, nuclear thermal propulsion systems, and ground transportation equipment for liquid hydrogen systems, high accuracy analytical and design tools of various phases of the propellant transfer process are highly desired. This presentation focuses on steady state single or two-phase flow through the transfer line that connects a propellant tank to an engine or customer receiver tank. Using the largest ever collection of available historical cryogenic heated tube data in the world, along with recently gathered test data, universal cryogenic flow boiling correlations have been developed and anchored to over 17,000 data points. A complete set of cryogenic flow boiling correlations that span the entire boiling curve, from single-phase liquid to single-phase gas have been developed for the onset of nucleate boiling, nucleate boiling heat transfer coefficient (HTC), critical heat flux (CHF), film boiling HTC, and two-phase pressure drop. The nucleate boiling HTC and CHF correlations also apply to reduced gravity applications. This presentation provides an overview of each universal correlation, an explanation of the physics of each functional form, and the logic for patching the curves together to form a seamless flow boiling curve. Resulting flow boiling curves are presented for a variety of flow conditions, for illustration.

Speaker: Jason Hartwig

300 C2Or4D-07: Heat transfer characterization of a flat plate liquid cryogenic jet impingement with inverse method

The use of hydrogen as an energy source to fuel aircraft is one of the alternatives currently being evaluated by Airbus. For this type of application, a liquid hydrogen cryogenic storage is considered and heat transfer phenomena involved by the cooling of a structure by the impingement of cryogenic liquid jet should be understood. To this purpose, the phenomena will be described based on the exploitation of a dedicated experimental campaign, together with a methodology to characterize spatially and temporally the heat flux at the wall. Due to the complexity induced by the use of liquid hydrogen, this work has been done based on the results of a test campaign carried out with liquid nitrogen as a representative cryogenic fluid. An inverse method for nonlinear thermal problems has been used in order to numerically evaluate the heat fluxes at the wall from the plate temperature measurements. The on-set of the different boiling regimes is in agreement with the temperature differences found in literature. The effect of the jet release pressure will also be compared in terms of evolution of wall temperature and respective heat transfer coefficients, also confronted with recent studies available in the literature.

Speaker: Clément Louriou

M2Or4A - [Special Session] Transportation II: System Level

301 M2Or4A-01: [Invited] Multi-MW Class Electrification Enabled by Zero/Net Zero Aviation Fuels

Speaker: TBD

302 M2Or4A-02: [Invited] Current Status of Development of Fully Superconducting Propulsion Systems for Aircrafts in Japan

In Japan, the development of fully superconducting propulsion systems for aircrafts have been conducted as a NEDO project. The target is a 20 MW propulsion system for an aircraft with 100-200 passengers. It is planned to be composed of 2 10-MW fully superconducting generators, 10 2-MW fully superconducting motors, superconducting cables, inverters which operate at liquid nitrogen (LN2) temperature, 2 hydrogen gas turbines and so on. Superconducting generators, motors, cables and inverters are cooled by subcooled LN2 at 65 to 77 K. The fuel is liquid hydrogen (LH2). LN2 is cooled through heat exchange between LH2 and LN2. The first phase of NEDO project for 5 years ended in March 2024. Here a 400 kW fully superconducting synchronous machine was designed and manufactured by way of trial. It can operate as a synchronous motor and a generator. The rotating field winding and armature winding were made of YBa2C3O7-d coated conductors. The field winding was wound of a single REBCO tape. The armature winding was wound of stacked six REBCO tapes with adequate transpositions during the winding process. The casing of the fully superconducting synchronous machine was made of CFRP, which contributed to less eddy current loss. The rotor was cooled by helium gas at around 60 to 70 K. The armature winding was cooled by forced-flowed subcooled LN2. As a motor test, it was operated up to 460 rpm by using three bipolar power supplies. And, as a generator test, it was operated up to 2500 rpm as a rated rotation speed by using a conventional synchronous motor. The output power of 250 kW was confirmed. In addition, a lightweight superconducting cable, which had corrugate tubes of resin as an inner and outer walls of vacuum thermal insulation layer, was developed. It was flexible even at LN2 temperature. The second phase of NEDO project started in June 2024. It will continue for three years. We will develop a 1-2 MW fully superconducting synchronous machine using REBCO tapes. As the armature winding, a distributed-type winding, which was developed in the previous phase of NEDO project, will be adopted instead of a concentrated-type winding. And a mechanical seal which was developed using a surface texture technology will be adopted instead of a magnetic fluid seal which was used as a seal system around the rotating axis in the previous phase of NEDO project. In this conference, we will report the test results of the 400 kW fully superconducting synchronous machine and introduce the development plan of a 1-2 MW fully superconducting machine in the present NEDO project.

Speaker: Masataka Iwakuma

303 M2Or4A-03: [Invited] The “IZEA-light” zero-emission aviation conceptual design

The Integrated Zero Emission Aviation (IZEA) consortium is a NASA-funded University Leadership Initiative that explores the conceptual design of regional passenger aircraft with reduced greenhouse gas emissions. The project concept explores liquid hydrogen as both a fuel and as a cryogenic coolant to facilitate high power-density components such as superconducting generators, superconducting power transmission, and cryogenic motors. Power generation by fuel cells increases the opportunities for emission reduction but come with a tradeoff for increased weight due to their low power density. This presentation will overview IZEA’s present focus on a “light” configuration where about 20% of the 7 MW needed during the cruise mission segment is generated by fuel cells. The vehicle is a blended wing-body airframe with a mission range of 2,200 nautical miles carrying 112 passengers and their cargo. Input to multidisciplinary design and optimization frameworks have resulted in specifics for engines, efficiency, take-off weight, airfoil design, contrail production, and other factors important for considerations of fleet evolution. Thermal balancing of the integrated sub-systems across the broad temperature range from 20 to 350 K presents opportunities for efficiency optimization. The present thermal model has produced detailed information regarding liquid hydrogen tank size, rate of coolant flow and energy consumption, motor configurations with integral cooling, and heat exchange requirements for power electronics and fuel cells. Novel concepts such as skin cooling and co-flow jets are proposed where technological solutions do not presently exist to manage challenges such as removing waste heat from fuel cells.

Speaker: Lance Cooley (NHMFL/FSU)

304 M2Or4A-04: [Invited] Overview and Progress Update on a Superconducting Powertrain for CHEETA

The field of electrified aircraft propulsion is undergoing a transformative evolution driven by the breakthrough advancements in superconducting electrical machines and cables. This paper highlights the significant progress achieved in developing a superconducting electric drivetrain under the Center for High-Efficiency Electrical Technologies for Aircraft (CHEETA) project. The team is conducting an extensive experimental campaign to mitigate risks in critical subsystems and ensure the successful demonstration of prototypes. This paper provides a comprehensive overview of the CHEETA system, along with progress updates on development and testing efforts. Topics include system design, hydrogen storage tank development, superconducting motor and cable advancements, risk-reduction experiments, and detailed test plans.
To evaluate the integrability of a hydrogen fuel cell power architecture and a distributed propulsion system for CHEETA aircraft concepts, current developments are underway to construct a 5%-scale flight test aircraft. This configuration will utilize advanced aero-propulsive optimization capabilities in the design of the high-volume airframe system, as well as an on-board avionics package to measure flight performance during testing. The outcomes of this flight test campaign will be used to understand the feasibility of cryogenic energy storage systems in an aerodynamically efficient aircraft system.
The CHEETA liquid hydrogen composite tanks are designed for minimum weight mass fraction while satisfying all aircraft operating conditions. This paper discusses the most promising design approaches including lightweight components that penetrate the shells. As part of the testing and validation effort we compare lined as well as liner-less liquid hydrogen tank designs and model the composite outgassing modes.
A two-pole cable, junction and terminations for the CHEETA high power electrical wiring and interconnection system (EWIS) demonstration are being developed for the 750-kW rated ground demonstration. This EWIS will consist of a two-pole high temperature superconducting (HTS) cable connected in series with a cryoresistive aluminum multi-stranded two-pole cable, to partially derisk a high power cryoresistive cable branch off of a HTS main cable. The HTS and cryoresistive cables will be joined by a novel electrical and cryogenic fluid flow quick-connect junction.
CHEETA envisions a groundbreaking approach to electric aviation through a hydrogen-powered system, featuring a 2.5 MW fully superconducting electric machine. Designed to achieve a specific power exceeding 25 kW/kg and an efficiency of 99.9%, this machine leverages liquid hydrogen for cooling, enhancing overall system performance. To tackle technological challenges and reduce risks, Hinetics is developing a 750-kW cryogenically cooled electrical machine that integrates innovative cooling solutions for both the stator and rotor.
Key advancements in the CHEETA motor include the following features, with ongoing demonstrations to reduce risks: a rotor-mounted Stirling-cycle cryocooler that integrates a commercial off-the-shelf (COTS) Stirling-cycle cryocooler into a rotationally compatible configuration for closed-loop conduction cooling; a rotor cryogenic thermal management system (TMS), which incorporates a novel coil suspension system that transfers torque between the cold field winding assembly and the warm rotor shaft while minimizing conduction heat load to the cryocooler, along with innovative methods to reduce radiation heat leakage to less than 10 W; quench-tolerant HTS magnets, demonstrating the passive quench tolerance of conduction-cooled, no-insulation (NI), double-pancake (DP) high-temperature superconducting (HTS) magnets; and a lightweight slotless air-core armature, designed to handle the high dB/dt levels generated by the superconducting rotor field and featuring effective cooling using cryogenic liquids such as liquid nitrogen (LN2). Hinetics is currently prototyping the motor, which is planned for testing towards the end of 2025.
The entire drivetrain is scheduled for testing at the POETS test facility in Champaign, Illinois, in 2026. These findings contribute to the advancing field of superconducting electric propulsion, paving the way for cleaner and more efficient air transportation.

Acknowledgement: This work was funded by NASA ULI grant (80NSSC23M0063)

Speaker: Thanatheepan Balachandran (HInetics Inc)

305 M2Or4A-05: [Invited] Motor configuration selection for a new technical challenge to develop a 5 MW cryogenic motor and drive

Due to aviation’s appreciable and growing share of humanity’s impact on our environment and estimates that CO2 emissions only account for 34% of aviation’s total effective radiative forcing [1], there is a need to reach beyond climate goals that focus only on CO2 emissions, such as the US Aviation Climate Action Plan’s [2] goal to reach net-zero carbon emissions by 2050. There is motivation to develop technology that pushes toward future large transport aircraft with net zero climate impact that are highly electrified (i.e., have higher power electrical propulsion system components). This paper describes a new, 6-year technical challenge to address this need by developing a 5 MW superconducting motor and cryogenic drive. Section 1 will detail the motivation for this work. Section 2 will describe the technical challenge and the selected specifications for the motor. Section 3 will present the results of a motor configuration trade study and the down selection of one configuration to develop a detailed design for.

The technical challenge focuses on the design of a 5 MW superconducting motor and cryogenic drive and demonstration of it at a MW scale to achieve TRL 3. Both fully superconducting (superconducting stator and rotor) and fully cryogenic (superconducting rotor and cryogenic stator) machine configurations will be explored. An emphasis will be placed on addressing the key tall poles for high power superconducting machines. Further details will be included in the full paper.

The requirements and goals of the motor will be detailed. The rated speed (2,000 to 3,000 rpm) is defined to be appropriate for directly driving multi-MW fans or propellers. A range of rated speed is permitted because the motor is not designed for a specific aircraft and to provide design flexibility if AC losses in the stator winding are found to be a significant constraint (i.e., a lower speed can be selected to reduce electrical frequency). Relatively conservative requirements for efficiency (99%) and specific power (20 kW/kg) are defined, because TRL advancement and pushing toward flight readiness is emphasized over performance optimization. However, more aggressive efficiency and specific power goals are specified (99.9% and 40 kW/kg).

The 3rd section will present the results of a motor configuration trade study. The study started with a qualitative assessment of sixteen motor configurations based on geometric, mechanical, thermal, and electromagnetic criteria. This assessment has been completed with three evaluators scoring all nine criteria. A configuration down select was made by prioritizing the sixteen configurations into four tiers based on each configuration’s total score and consideration of manufacturability, complexity, and support hardware (e.g., rotary vacuum seals, bearings). Configurations in priority A and B will be further evaluated through quantitative assessments, whereas those in priority C will only be further evaluated if time permits and priority D will not be further evaluated. Eight of the sixteen configurations were down selected for quantitative assessment, which will include analytical calculations and low- to moderate-fidelity finite element analysis to produce a preliminary Pareto front of efficiency versus specific power for each configuration. This assessment emphasizes the calculation of AC losses in the stator winding and an exploration of thermal management approaches to remove that heat and maintain cryogenic temperature.

The final paper will include a description of each motor configuration that was considered. The quantitative assessments are underway, and an assessment of one configuration is complete for multiple stator conductor options. The remaining assessments are scheduled to be completed by late March so that the final down select to one configuration can be included in this paper.

[1] D.S. Lee et al., “The contribution of global aviation to anthropo-genic climate forcing for 2000 to 2018,” Atmos. Environ. 244, 117834, 2021.
[2] Federal Aviation Administration, “United States 2021 Aviation Climate Action Plan,” 2021.

Speaker: Dr Justin Scheidler (NASA Glenn Research Center)

M2Or4B - Growth & Characterization of REBCO and Iron-based Superconductors

306 M2Or4B-01: [Invited] High quality FF-MOD REBCO films prepared from ready-made REBCO

The fluorine-free metal organic decomposition (FF-MOD) method is considered to be the lowest cost one for mass production of REBCO thin films among various methods such as Pulsed-Laser-Deposition (PLD), Metal-Organic-Chemical-Vapor-Deposition (MOCVD), trifluoroacetate (TFA)-MOD and Reactive Co-Evaporation by Deposition & Reaction (RCE-DR). Fast crystal growth of REBCO via simple reaction, flat and clean surface, simple and low cost production system and less material loss are the advantageous points FF-MOD method. However, FF-MOD processed REBCO tapes have not been popular because of low Jc under magnetic field originated in very high crystallinity of REBCO layer with less defects acting as pinning centers. Recent successful studies on the introduction of fine nonsuperconducting precipitates in REBCO layer, increase in the thickness of the layer by multiple sintering process and establishment of coating techniques to fabricate long tapes [1] strongly suggested the high potential of FF-MOD method.
Acetates or acetylacetonates (acac) of constituent metals are used in most of studies to fabricate REBCO films by the FF-MOD method, however, these reagents are not inexpensive and some of them are hydrates, resulting in difficulty in precise control of the cation composition. Recently, we have developed a new method to prepare FF-MOD solutions with low cost, high productivity, high homogeneity and well-controlled cation compositions.
YBCO fine powder was found to be dissolved in propionic acid at room temperature, which is an exothermic reaction. Increasing dissolving temperature up to the boiling point (414 K) of propionic acid promotes reaction and, therefore, we can use ready-made REBCO sintered bulks.as starting materials. After evaporating excess solution, propionate crystals containing RE, Ba and Cu were obtained. Powder X-ray analysis revealed that the propionate crystals contain multiple cations, such as RE, Ba and Cu. FF-MOD solutions were prepared by dissolving the propionate crystals in a mixed solvent of methanol, butanol and water. Through coating solutions on SrTiO3 single crystals and IBAD substrates and heat-treatments, high Jc REBCO films were successfully synthesized with high reproducibility under wider sintering conditions expanding lower temperature down to 993 K for YbBCO. These characteristics are preferable for development of long length tapes as well as fabrication of superconducting joints connecting REBCO tapes. Details of the critical current properties of REBCO films including the doping effect will be shown.

[1] T. Yoshihara, G. Honda, T. Nagaishi, S. Kobayashi, K. Kanie, T. Okada, and S. Awaji, IEEE Trans. Appl. Supercond., 33, 6600205 (2023)

Speaker: Prof. Jun-ichi Shimoyama (Aoyama Gakuin University)

307 M2Or4B-02: Innovative buffer Architectures for REBCO Coated Conductors

The architecture of REBa2Cu3O7+δ (REBCO, RE = rare earth) coated conductors has been essentially unchanged for more than 20 years with a REBCO film deposited on an insulating oxide buffer stack on Hastelloy C276 substrate. In this work, we explored two innovative buffer stack designs, (1) double-sided conductor to improve critical current (Ic) and (2) electrically- conductive buffer stack for defect tolerant REBCO tapes. We have demonstrated a reel-to-reel manufacturing process for double-sided oxide buffer tapes in 30-m-lengths, utilizing an in-house electropolished Hastelloy substrate with an average surface roughness (Ra) < 1 nm on both sides, Out-of-plane texture and in-plane texture values on both sides are in the range of 3.3±0.3 and 7±0.5 degrees respectively. On an insulating buffer stack, 250nm thick alumina diffusion barrier layer on both sides has proven effective in withstanding higher Joule heating currents for REBCO growth by Advanced Metal Organic Chemical Vapor Deposition (MOCVD). Using the double-sided buffer stack, double-sided REBCO tapes with ~ a 4.6-µm-thick REBCO film on each side have been achieved with a Ic > 1,050 A/4mm at 20 K, 20 T which is 7x the Ic of typical industrial REBCO tapes at 20 K, 20 T. IBAD titanium nitride (TiN) has been used as an electrically-conductive substitute for IBAD magnesium oxide (MgO) in standard superconductor buffer architectures. A strong biaxial texture has been achieved in IBAD TiN grown on Hastelloy C276 substrate. Additionally, Ti3AlN was utilized as a suitable oxidation-resistant epitaxial film with low resistivity in the electrically-conductive buffer stack. The conductive buffer enables efficient current shunting from the REBCO layer to the substrate, to effectively mitigate the impact of localized defects and enhance reliability in cryogenic environments. This innovation paves the way for the development of double-sided electrically conductive buffers for multiple benefits of high Ic, reduced cost ($/kA-m), and inherent defect tolerance capabilities.

Acknowledgement:
This work was funded by Advanced Research Projects Agency-Energy (ARPA-E) award DE-AR0001374 and the Naval Sea Systems Command Small Business Technology Transfer award N68335-23-C-0228 award through AMPeers LLC.

Speaker: Susancy S

308 M2Or4B-03: Systematic Studies to Enhance Flux Pinning of (BaZrO3/YBa2Cu3O7-x)N Multilayer Thin Films for the Full Landscape of T = 5K to 77K

The addition of nanosize defects to (Y,RE)Ba2Cu3O7-z (Y,RE-Ba-Cu-O or (Y,RE)BCO) superconductor thin films have been studied by many groups world-wide, to enhance flux pinning and strongly increase critical current densities (Jcs). A large variety of defect additions have been studied, including so-called 1D, 2D and 3D defects. The (M/(Y,RE)BCO)N multilayer system has been studied by many groups, and achieves interesting variations of Jc(H,T,Ɵ) in the operation space of T = 5-80K, Happl = 0-9T and 0° ≤ Happl(Ɵ) ≤ 90°. Herein provides a wide-ranging optimization study of (BaZrO3, y/YBa2Cu3O7-x ,z)N multilayer films prepared by pulsed laser deposition with y,z layer thickness and N # of layers. Process parameters studied include YBa2Cu3O7-x (YBCO) layer thickness from 3-300 nm, BaZrO3 (BZO) layer thickness from 0.5-1.5 nm, and film growth temperature from 775-825 °C. Systematic results of critical transition temperature (Tc) and Jc(H,T,Θ) were plotted as function of YBCO layer thickness and BZO addition up to 16 volume %. Optimization of Jc(H,T,Ɵ) was found to vary with process parameters from 30-77 K, for example at 77 K flux pinning was optimized and only clearly exceeding pinning YBCO-alone films for 825 °C process temperature. However, for 30 K operation temperature, flux pinning was much less sensitive to BZO+YBCO film parameters, and slightly optimized for 805 °C process temperature. For all H,T conditions studied, the Jc(H,T) values achieved a maximum peak for BZO = 8-12 volume % additions in close agreement with published models of flux pinning, and required BZO layer thickness < 0.6 nm.

Acknowledgments. This research was funded by the Air Force Office of Scientific Research (AFOSR) LRIR #18RQCOR100, #23RQCOR008, and #24RQCOR004 and the U.S. Air Force Research Laboratory, Aerospace Systems Directorate (AFRL/RQ).

Speaker: Timothy Haugan

309 M2Or4B-04: Role of Ca diffusion in BaZrO3 nanorods/YBa2Cu3O7-x multilayer nanocomposite films

In a recent study in probing the effect of the pinning efficiency of BaZrO3 (BZO) nanorods in BZO-doped YBa2Cu3O7-x (BZO/YBCO) nanocomposite films, Ca diffusion from two Ca0.3Y0.7Ba2Cu3O7-x spacers that form multilayers through alternative stacking with three BZO/YBCO layers was found to significantly enhance the pinning by approximately five folds at high fields up to 9.0 T. This raises a question on the role of Ca diffused into the multilayer BZO/YBCO nanocomposite films. In order to answer this question, this work investigates the Ca0.3Y0.7Ba2Cu3O7-x films of variable thickness in the range of 30-190 nm to understand whether the carrier over-doping induced by Ca substitution of Y would lead to enhanced pinning. In addition, the effect of the thicknesses of the constituent YBCO and Ca0.3Y0.7Ba2Cu3O7-x layers was also studied. By varying the YBCO thickness in the range of 50-330 nm, the effect of Ca diffusion from the two Ca0.3Y0.7Ba2Cu3O7-x spacers of 10 nm in thickness is investigated. Furthermore, the amount of Ca in Ca0.3Y0.7Ba2Cu3O7-x spacers may be controlled by varying their thickness ranging from 1 nm to 15 nm. Our result suggests the benefit of overdoping via Ca/Y substitution is minimal on pinning. In addition, the amount of Ca in the Ca0.3Y0.7Ba2Cu3O7-x spacers indeed affects the Ca diffusion and hence pinning enhancement dramatically, which reduce as the spacer thickness is below 5 nm threshold. Above this threshold, the Ca diffusion is highly effective through large BZO/YBCO thicknesses up to 330 nm (total film thickness ~ 1 µm) and significantly enhanced pinning has been obtained in multilayer BZO/YBCO nanocomposites. At 20 K and 9.0 T, the Ic is up to 654 A/cm-width at B//c, which is close to 753 A/cm-width at B//ab due to the intrinsic pinning has been achieved.

Keywords: BZO/YBCO nanocomposite film, vortex pinning efficiency, multilayer, Ca diffusion, overdoping

Acknowledgements
This research was supported in part by NSF contracts Nos: NSF-DMR-2413044, the AFRL Aerospace Systems Directorate, the Air Force Office of Scientific Research (AFOSR LRIR # 24RQCOR004). J. S. and H.W. acknowledge the support from the U.S. Office of Naval Research (ONR, No. N00014-20-1-2600) and the U.S. National Science Foundation (No. DMR-2016453) for the TEM/STEM work.

Speaker: Dr Judy Wu (University of Kansas)

310 M2Or4B-05: Charge carrier density and critical current density variations of superconducting layers of GdBCO and EuBCO coated conductors as a result of high pressure oxygenation

Oxygen overdosing may be a way to further increase the critical current density of coated conductors. It has recently been shown that overdosing of of YBCO thin film coated with an Ag layer was achieved by processing at low temperature and 1 bar oxygen pressure, which allowed increasing the charge carrier density and achieving whatever high critical current 90 MA•cm−2 at 5 K, which corresponds to a fifth of the depairing current. We used commercial GdBCO and EuBCO with BHO nanorods coated conductors (CC) from Fuijkura Ltd with model numbers FYSC-S12 and FESC-SCH12 to study the effect of subsequent high pressure oxygenation (in the pressure range 1-160 bar) at temperatures 250-800 oC on charge carrier density, lattice parameters of superconducting phase and critical current density variations. Before the treatment GdBCO and EuBCO CC were all chemically treated for removing the protective Cu or Cu and Ag layers.
The evidences of overdoping were observed about what were witnessed an increase of nH(100 K), reduction of c-lattice parameters of RE123 (RE=Eu, Gd) of superconducting layers, behavior of normalized resistivity before superconducting transition, and Jc variation, however, the conditions to achieve optimal doping were not found yet. Treatment under 100 bar of oxygen for 3 h of GdBCO_CC (with Ag layer) at 600 °C led to an increase in Jc (77 K, 0 T) from 2.57 to 2.67 MA/cm2 , nH(100 K) increased from 6.551021 to 6.911021 cm-3, and Jc(5 K, 0 T) =28.94 MA/cm2 was observed after the treatment. The increase in Jc (77 K, 0 T) from 2.10 to 2.28 MA/cm2 for GdBCO_CC (without Ag layer) was observed after treatment at 300 °C under 100 bar of O2 for 3 h. In the both cases c-parameter of Gd123 decreased from 1.1735(1) to 1.1731(0) nm. For EuBCO_СС after treatment a decrease in c-parameters of Eu123 was observed: from 1.1738(8) to 1.1734(5) nm (for the Ag-coated sample under 100 bar O2 at 300 °C) and from 1.1740(2) to 1.1736(3) nm (for the sample without Ag under 160 bar O2 at 800 oC). The studies are still ongoing.
This work was supported in part by the funds from MICIU/AEI/FEDER for SUPERENERTECH (PID2021–127297OB-C21), FUNFUTURE “Severo Ochoa” (CEX2019–000917-S); MUGSUP (UCRAN20088) project from CSIC scientific cooperation with Ukraine; Catalan Government 2021 SGR 00440; and NAS of Ukraine Project III-7-24 (0788).

Speaker: Tetiana Prikhna ((1) V. Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine, (2) Institut de Ciencia de Materials de Barcelona, CSIC, (3) Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden e. V.)

311 M2Or4B-06: Rapid engineering short-segmented columnar defects in seconds for 20 MA/cm^2 supercurrent density in iron-based superconductors

Realizing ultra-high supercurrent density in iron-based superconductors (IBS) is a crucial step toward practical applications at high magnetic fields. However, engineering the most effective pinning structure to maximize the critical current density (Jc) remains an open challenge. In this work, Ba1-xKxFe2As2 single crystals were irradiated by low-energy Xe ions within seconds, achieving an exceptionally high Jc of 20 MA/cm^2 at 2 K. Remarkably, the Jc remains 8.7 MA/cm^2 at 5 K and 4 T, which is the highest value ever reached at high-fields for IBS. This enhancement is attributed to the replacement of intrinsic weak collective pinning by strong pinning of segmented discontinuous columnar defects. The advantageous pinning landscape minimizes superconductivity degradation and efficiently suppresses the motion of vortex kinks across a wide temperature range, yielding an extraordinary 178-fold enhancement of Jc at intermediate temperatures. These findings pave the way for further Jc enhancement by optimizing the defect geometry and density, providing valuable insights for the development of high-performance superconducting materials.

Speaker: Chiheng Dong (Institute of Electrical Engineering, Chinese Academy of Sciences)

312 M2Or4B-07: Increased nonreciprocal current in iron-based superconductor antiferromagnet interface

Superconductivity in iron-based materials is an active area of research due to the unconventional nature of the electron-electron interactions. The simplest material in this family is the layered 11 type iron chalcogenides. Iron selenide(FeSe) when alloyed with tellurium(Te) can alter many superconducting properties. The layered nature of this material allows for unique interactions with other materials due to the 2D nature of the interface.

Nickel phosphorus trisulfide(NiPS$_{3}$) is a Van der Waals material with a bandgap of 1.8eV. The layered material undergoes an in-plane zig zag type antiferromagnetic(AFM) ordering at a Neel temperature of 150K. To explore interactions between materials, a 56nm thick sample of FeTe$_{0.7}$Se$_{0.3}$ was placed, on metal contacts deposited on silicon dioxide, using the hexagonal Boron Nitride(hBN) pickup method. The sample was partially covered with a 13nm thick sample of NiPS$_{3}$ and all materials were covered with 10nm of hBN. The partial covering allows resistive measurements on the heterostructure and the hBN encapsulated segment of the iron-based superconductor. Assembly occurred in a nitrogen environment with <0.1 ppm O$_{2}$ and H$_{2}$0 to minimize environmental impacts. Four other samples were measured with similar results to those presented.

Resistivity of both materials remains similar until the onset of superconductivity.
The superconducting transition shows the Berezinskii-Kosterlitz-Thouless(BKT) transition, which describes a phase change to bound vortex-antivortex pairs. The heterostructure displays a sharper superconducting transition and increase of the critical temperature of the BKT transition. The Halperin-Nelson model that describes the BKT transition in resistive measurements was fitted to both the FeTe$_{0.7}$Se$_{0.3}$ and heterostructure measurements. The heterostructure showed an increase in BKT transition from 13.1K (FeTe$_{0.7}$Se$_{0.3}$ sample) to 13.8K, representing a rise of approximately 0.7K. These results were confirmed when a power law fit was applied to the voltage response of an applied current across various temperatures. The nonlinear I-V characteristic indicates a transition where V is proportional to I$^{3}$.

Effective pining energy was estimated according to the thermally activated flux flow theory. The effective pinning energy was extracted from resistivity measurements using an Arrhenius equation. The effective pinning of the heterostructure was 35% higher than the encapsulated sample at zero field. This higher pinning value decreased but remained 20% higher in the heterostructure under a 9T magnetic field. The increase in effective pinning energy enhances the critical current density of the heterostructure. At 2K the critical current density is increased 50% from 0.528 MA/cm$^{2}$ in the encapsulated sample to 0.799 MA/cm$^{2}$ in the heterostructure.

The superconducting diode effect(SDE) was recently demonstrated in materials that lack inversion and time reversal symmetry. The substitution of Te into FeSe can induce structural changes and topological phases. The breaking of time reversal symmetry occurs from the proximity effect of the AFM. This symmetry breaking leads to a nonreciprocal critical current with an upper and lower critical current. This unequal flow of charge can be exploited to produce low power electronics. Many displays of SDE rely upon an external magnetic field or ferromagnetic junction which can negatively impact superconductivity. The field-free nature of this heterostructure was demonstrated from rectification of a square wave pulse at 1 Hz with a current above the lower critical current for over one hundred cycles. A figure of merit is the diode efficiency which is defined as the difference of the absolute values of the positive and negative current divided by their sum. This device shows a maximum efficiency of 1% at 2K which is not uncommon for simple structures. The device is tunable by an external magnetic field, but a better way to increase efficiency is the inclusion of the AFM in improved superconducting diode devices such as nano bridges or junctions.

In conclusion, a field free superconducting diode was formed from the interface of an iron based superconductor and an AFM. An increase of critical current and field pinning was explored, which has not been reported previously.

Speaker: Mr Christopher Luth (The University of Texas at Austin)

Wednesday 21 May

Plenary: Parag Kshirsagar [Technology Needs for High Power Electric Systems in Aerospace and Defense Applications] & CSA Awards

313 M3PL1-01: Technology Needs for High Power Electric Systems in Aerospace and Defense Applications

Abstract pending.

Speaker: Parag Kshirsagar (RTX Technology Research Center (RTRC))

09:00 Cryo Expo Open

C3Po1A - Cryogenic Test Facilities

314 C3Po1A-01: Cryogenic Testing of HL-LHC Q1/Q3 Cryo-Assemblies at Fermilab

Fermilab is conducting horizontal cryogenic testing of Q1/Q3 Cryo-Assemblies for the high-luminosity LHC upgrade (HL-LHC). Cryo-Assemblies are installed on the upgraded Fermilab horizontal test stand previously used for testing the LHC inner triplet quadrupoles. The cryogenic process requirements of these tests include controlled cool-down and warm-up with a 100 K maximum temperature differential between the two ends of the cold mass, operation of a 1.3 bar, 1.9 K bath of subcooled superfluid helium during power testing and magnetic measurements, and operation at pressure up to 18 bar with full helium recovery after a quench. This paper presents the operational experience gained from the first tests as well as operational improvements for subsequent tests.

Speaker: Roger Jon Rabehl (Fermi National Accelerator Lab. (US))

315 C3Po1A-02: Operational experience of the NML cryogenic plant at the FAST facility

The NML cryogenic plant cools two individually cryostated superconducting radio frequency (SRF) capture cavities and one prototype ILC cryomodule with eight SRF cavities. This complex accelerates electrons at 150 MeV for the Integrable Optics Test Accelerator (IOTA) ring, located at the Fermilab Accelerator Science and Technology (FAST) facility. The cryogenic plant is composed of two nitrogen precooled Tevatron satellite refrigerators, two Mycom 2016C compressors, a cryogenic distribution system, a Frick purifier compressor, two charcoal bed adsorber purifiers, and a liquid ring vacuum pump with a roots booster. The SRF cavities are immersed in a 2.0 K liquid helium bath, shielded with a 5 K gaseous helium shield and a liquid nitrogen cooled thermal shield. Since 2019, this R&D accelerator complex has gone through four science runs with an average duration of 8 months. Operational experience for each run, availability metrics, performance data and common outages are presented in this paper.

Speakers: Joaquim Creus Prats, Tim Wallace (Fermilab)

316 C3Po1A-03: Structural Design of Distribution Valve Box of S3FEL Test Facility Cryogenic System

Shenzhen SRF Soft Free Electron Laser (S3FEL) is a project in construction phase at Institute of Advanced Science Facilities, Shenzhen (IASF), in China. The purpose is to produce high intensity coherent X-ray with laser properties. The S3FEL accelerator is based on the TESLA technologies and will deliver electrons with the energies of up to 2.5GeV. The electrons will be accelerated by 1.3 GHz superconducting cavities cooled down to the 2 K level.
A 500 W@2 K helium refrigerator will be used for the test facility including two vertical test benches (VTB) for cavities, one magnet test bench for the superconducting magnet (MTB) and three horizontal test benches (HTBs) for cryomodules. The test benches are managed via a main cryogenic distribution valve box which is designed to operate each test facility independently.
This paper describes the detailed structural design of the main distribution valve box including: cryogenic valve arrangement diagram, mechanical compensation for deformation in low temperature, thermal analysis as well as static structural analysis in low temperature. A design method of cryogenic valve box is also discussed in aim of accelerating the design iteration progress. Design results regarding overall temperature profile, heat load performance and static structural stress is described in this paper.

Speakers: Lei Yang (IASF), Ms Yaqiong Wang (IASF), Mr Xiaohe Lu (IASF), Mr Guanglong Cui (IASF), Ms Huikun Su (IASF), Mr Xu Shi (DICP), Mr Zheng Sun (DICP), Mr Xilong Wang (IASF)

317 C3Po1A-04: Fabrication of the HFVMTF Double-Bath Cryostat

The High Field Vertical Magnet Test Facility (HFVMTF) is an advanced experimental platform currently under construction at Fermi National Accelerator Laboratory (FNAL). Designed to test large superconducting magnets weighing up to 20 tons and measuring up to 1.3 meters in diameter, the facility features a double-bath superfluid helium cryostat capable of reaching temperatures as low as 1.8 K at a pressure of 1.2 bar. A key component of HFVMTF’s capabilities is its integration with a superconducting dipole magnet developed by Lawrence Berkeley National Laboratory (LBNL), enabling the testing of high-temperature superconductor (HTS) cables for future fusion magnets under a background magnetic field of 15 T. This state-of-the-art facility aims to advance research and development in superconducting magnet technology, with a particular focus on fusion energy applications.
The double-bath cryostat was fabricated by Ability Engineering Technology Inc., and this paper highlights its innovative design and the challenges encountered during the fabrication of its two most complex components: the lambda plate and the 2 K heat exchanger. The 2 K heat exchanger, comprising multiple copper tubes that thermally link the saturated superfluid bath to the pressurized superfluid bath, was specifically designed to comply with the ASME Boiler and Pressure Vessel Code. It is engineered to withstand a maximum pressure of 6.9 bars while minimizing thermal resistance between the sub-atmospheric and pressurized helium baths.
The lambda ring, a critical sealing surface that thermally insulates the superfluid helium at 1.8 K from the liquid helium at 4 K, has an inner diameter of 1.4 meters. This component must support the combined weight of the magnet and top plate—exceeding 20 tons—while withstanding a pressure differential of 1.3 bar between the two sides of the lambda plate. Fabricated with an overall flatness tolerance of ±0.05 mm, the lambda ring ensures effective sealing between the 4 K and 1.8 K baths. A Finite Element Analysis (FEA) of the entire helium vessel was conducted to validate the unique design of these components and to verify the mechanical stress limits of the vessel walls under maximum pressure conditions.

Speaker: Romain Bruce (Fermilab)

318 C3Po1A-05: Cryogenic binary fluid test bench for studying transport phenomena

A state-of-the-art binary fluid test bench has been developed enabling advanced experimentation with single and binary fluids across a wide range of thermodynamic conditions. The facility accommodates experiments with all fluid concentrations, ambient temperatures spanning 100 K to 600 K, and pressures between 1 bara and 10 bara. The system features dual inputs for binary gases and a third input to control heating or cooling of the mixture. Comprehensive sensor arrays enable precise thermodynamic mass and energy balance calculations over all inputs and outputs of the reactor. In other words, absolute pressures, temperatures, massflows of all incoming and outgoing lines are monitored. Additionally, it is also possible to probe temperatures at different locations inside the reactor. Furthermore, the setup incorporates optical capabilities to visually observe changes within the reactor, given that a transparant reactor is used.
Designed for versatility, the system supports a broad spectrum of transport phenomena related experiments, including investigations into phase change reactors, heat exchangers, and membrane technologies, with seamless integration of new reactors or components to expand temperature and pressure ranges or explore novel applications. To show its capabilities, a test case will be presented.

Speaker: Wouter Eppink (University of Twente)

C3Po1B - Instrumentation, Visualization, and Controls III

319 C3Po1B-01: Visualization of film condensation onset and microscale cryogenic condensate film

In-space cryogenic resource utilization (ISRU) is a critical technology for long-duration space exploration missions. The condensation of cryogen is a fundamental heat and mass transfer process of ISRU operations such as the liquefaction of gases at the colder wall temperatures, and the condensation-induced pressure collapse in a cryogenic tank during the fill. Due to their low surface tension, cryogens primarily condense by forming a thin condensate film on cold walls. Using Nusselt's theory for saturated vapor, this condensate film is estimated to be tens of microns thick, reflecting the microscale nature of the phenomena. For superheated vapor with non-negligible vapor velocity, condensate thickness is expected to be smaller than saturated vapor. Yet, detailed visualization of the onset of condensation and measurement of film thickness at superheated conditions has not been reported in the literature. In this research, measurements of condensate film thickness and the transient onset of condensation are investigated for the superheated vapor of cryogens. Experiments were conducted with the three ISRU-relevant pure gases namely methane, oxygen, and nitrogen. An experimental setup was developed to induce condensation of the superheated gas on a cold vertical wall, while a visualization setup captured the phenomena of downflow film condensation. The micro-scale thickness of the cryogenic condensate film was measured using a high-resolution shadowgraph. The transient phenomena of the condensation onset was captured using a high-speed visualization. The onset of condensation occurred at the localized cold spot near the trailing edge of the cold wall. Later, the condensation front exhibited growth from the cold spot towards the leading edge against the direction of gravity. The measured steady-state condensate film thickness was compared with Nusselt's theory and existing correlations. These insights into timescale and length scales of condensation will support the development of accurate sub-grid models for ISRU operations.

Speaker: Mr Bhushan Patil (School of Mechanical, Aerospace and Manufacturing engineering, University of Connecticut)

320 C3Po1B-02: Design of a test facility for evaluating liquid hydrogen fuel level probes

Liquid hydrogen advances as vehicular fuel emphasizes the need for continuous and reliable fuel gauging systems in dynamic environments. More specifically there is a need for reliable comparisons and verifications of various fuel level system technologies. To address this need, an existing 180L liquid hydrogen dewar was retrofitted for the simultaneous comparisons between modular liquid level probes. A GM cryocooler mounted on the custom dewar neck allows for variation of subcooling and management of ullage conditions within the dewar under static conditions. To simulate dynamic slosh conditions, a servomotor will be utilized to oscillate the dewar at a frequency conducive to sloshing. This paper describes the integrated design and safety plan of the facility, including theoretical performance estimates of cool down and sloshing, in addition to Failure Modes and Effects Analysis in advance of system construction and commissioning.

Speaker: Ms Sophia Abi-Saad (Self)

321 C3Po1B-03: How digital twins can help with operator training, an example with ATLAS and CMS detector’s cryogenics at CERN

This paper presents the implementation of a cryogenic process simulator applied to A Toroidal LHC Apparatus (ATLAS) and the Compact Muon Solenoid (CMS) experiments at CERN (European Organisation for Nuclear Research). Building upon the development of a digital twin of the complex LHC accelerator cryogenic system, this work extends its application to the specific needs of the ATLAS and CMS experiments and their dedicated cryogenic systems. These particle large detectors rely on superconducting magnets, each weighting hundreds of tons, which must be maintained at 4.5 K. The cryogenic simulator replicates the helium refrigerators and the proximity system connected to the detectors reproducing real operational case scenarios, enabling cryogenic operator training for both routine and special operations. This digital twin is using identical features as the real infrastructure, integrating multiple layers forming the process control system: the simulation model, Programmable Logic Controllers (PLC), and Supervision Control And Data Acquisition (SCADA) system, that shares data in real time between them. The objectives of this digital twin are threefold: first, to provide a comprehensive off-line training tool for the operators, second to improve the knowledge on the installations and third, to simulate and evaluate the reactions of the cryogenic plants in new scenarios or configuration changes before implementation.

Speaker: Lorenzo Luc Jimenez

322 C3Po1B-04: The cooling machnism of liquid nitrogen cooling system

National Synchrotron Radiation Research Center (NSRRC) designed, fabricated, and implemented a cooling system for a liquid nitrogen (LN2) tank in the storage ring in 2021. During cooling tests, two significant phenomena were observed: a boiling phenomenon associated with two-phase flow and a rapid cooling phenomenon influenced by the physical properties of oxygen-free copper. This article examines the underlying cooling mechanisms.

Speaker: Hsing-Chieh Li (National Synchrotron Radiation Research Center)

323 C3Po1B-05: Upgradation of the SCADA-Based Control Systems for the SST-1 Cryogenics Facility

This paper details upgrading the SCADA (Supervisory Control and Data Acquisition) system for the SST-1 cryogenic subsystems from Wonderware InTouch version 9.5 to the latest release, Wonderware InTouch 2017 R2. The upgrade was necessitated by the obsolescence of the earlier software, which lacked compatibility with modern Microsoft operating systems. Critical subsystems, including the Integrated Flow Distribution Control System (IFDCS), Current Feeder System (CFS), LN2 Management System, and the 80 K Booster System, have successfully transitioned to the updated SCADA system. Each subsystem operates with dedicated control stations that incorporate in-house developed applications using Programmable Logic Controller (PLC) and SCADA. The updated SCADA platform offers enhanced functionalities, such as real-time data acquisition, storage, and historical data retrieval for in-depth analysis. The upgrade process involved migrating existing applications to the Wonderware InTouch 2017 R2 platform, alongside developing new applications to utilize the advanced capabilities of the updated software. This paper explores the additional features integrated into the upgraded SCADA system and addresses the technical challenges encountered during the development and optimization of system performance. The successful activation of licenses and deployment of the new SCADA applications represents a significant enhancement in the automation and monitoring capabilities of the SST-1 cryogenic subsystems. The paper concludes by sharing insights gained during the upgrade process and provides recommendations for the future maintenance and enhancement of the SCADA system.

Speaker: Mr Gaurang Mahesuria (Institute for Plasma Research)

324 C3Po1B-06: Development of the 17 kW orifice-type heater control system for thermal compensation induced by nuclear heating at the ESS hydrogen moderators

The European Spallation Source (ESS) is one of the largest science and technology infrastructure project being built in Sweden. Protons at 2 GeV (with a normal current of 62.5 mA) are delivered by a superconducting linear proton accelerator and are injected onto a rotating tungsten target at a pulsed repetition rate of 14 Hz. Neutrons via spallation reaction are moderated to cold thermal energies by two dedicated moderators. The cryogenic moderator system (CMS) was designed to circulate subcooled liquid hydrogen at a temperature of 17 K and a pressure of 1.0 MPa to remove static and dynamic heat load induced by the nuclear heating at the moderators, which is estimated to be 6.7 kW for a 5-MW proton beam power. The liquid hydrogen is transferred from the CMS cold box (CBX) to a distribution box (DB) via a main transfer line (HTL) and is split into each moderator transfer line. A 17kW orifice type heater is used for thermal compensation induced by the nuclear heating by the moderators when the proton beams are injected and tripped.
The CMS Process Control System (PCS) is based on multiple Programmable Logic Controllers (PLCs) and is responsible of controlling a wide array of equipment, consequently the system logic was designed with modularity, ease of expansion, and maintainability in mind. Different device types are implemented using custom software control blocks providing a wide range of features and Operator Interface (OPI) block icons and faceplates.
The heater is composed out of 15 separate sheathed heater elements that are submerged in liquid hydrogen allowing for fast process response times. From electrical design and control logic perspective, the most important objective is to ensure that the all the heater elements combined function as one single heater element providing the highest response times and accuracy of the power output possible.
In order to provide high reliability, good cost to performance ratio and easier serviceability the controller hardware used is an industrial grade one manufactured by SIEMENS from the SIPLUS HCS product family. These components however lack in certain functionalities such as current and voltage monitoring, compensation for electrical grid fluctuations and accepting setpoints in energy units such as watt. To combat these shortcomings a multi-functional energy measuring device was used as well.
To provide easy control and overview with all the necessary functionalities a new device type was implemented in the PCS. This software block provides functionalities such as accepting setpoints in watts, calculating the total and per heater element power output, even power distribution across all elements, line voltage compensation, health monitoring of the heater elements and the electrical supply, setpoint ramping, overheating protection and PID control algorithm for temperature control beside other.
The basic functions of the electrical heater together with its controller hardware and software functionalities were successfully tested during the preliminary CMS commissioning using helium at 17 K prior to hydrogen operation.

Speaker: Attila Zsigmond Horváth (European Spallation Source)

325 C3Po1B-07: Performance test and optimization of the control system for the ESS cryogenic moderator system

The European Spallation Source (ESS) is one of the largest science and technology infrastructure project being built in Sweden. Protons at 2 GeV are delivered by a superconducting linear proton accelerator and are injected onto a rotating tungsten target. Neutrons via spallation reaction are moderated to cold thermal energies by two dedicated moderators. The cryogenic moderator system (CMS) was designed to remove both static heat load (2 kW) and dynamic heat load induced by the nuclear heating at the moderators, which is estimated to be 6.7 kW for a 5-MW proton beam power, by circulating subcooled liquid hydrogen at 17 K and 1.0 MPa. The liquid hydrogen is transferred from the CMS cold box (CBX) to a distribution box (DB) via a transfer line (HTL) and is split into each moderator transfer line. The CMS is cooled via a plate-fin type heat exchanger by a large-scale 20 K helium refrigeration system, referred to as the Target Moderator Cryoplant (TMCP), with a cooling capacity of 30.3 kW at 15 K. Two compressors are operated at a discharge pressure from 1.0 MPa to 2.0 MPa (HP) and a compression ratio (CR) of 4.1. A feed helium flow rate can be varied from 200 to 900 g/s when all the three expansion turbines are operated.
The CMS Process Control System is comprised of three Programmable Logic Controllers (PLCs) that manage a variety of equipment. Meanwhile, the TMCP PCS also includes three PLCs: one for business logic and one for each of the compressor skids. A direct data exchange between the two systems creates an interface that enables the integration and synchronization of their core functionalities.
A goal of the CMS Process Control System (PCS) is to establish automated operational controls for processes such as cooldown, warm-up, steady-state, beam injection modes and safe shut-down when failure event happens. In this study, additional device types were developed to provide various features, all accessible from the OPI block icons and faceplates, as well as the PLC logic. Most important ones are hydrogen pumps, vacuum pumps, valves, electric heaters, PID controllers with setpoint ramping and holding functionality, various feedback devices, tuning profile selection, and a customizable auto-profile selector for fast controller tuning. Subsequently, a custom device type was developed within the CMS PCS to manage the TMCP operation. This device offers several features, accessible via the Operator Interface (OPI), and PLC logic, which allow for control of the feed helium temperature using a split-range controller, a return helium temperature controller, and controlling the cooling capacity through a floating pressure process where the HP and CR controllers are directly manipulated by the CMS, alongside other functionalities.
Based on the results of the TMCP commissioning, setpoint ramping functions with various hold options have been implemented for cooldown and warm-up operations. These functions enable monitoring of the TMCP status during transient operations and intervene when necessary. It was helpful to ensure smooth operation during the CMS commissioning.
The basic functions of the CMS PCS together with the TMCP PCS were demonstrated to work effectively during the preliminary CMS commissioning using helium at 17 K, prior to hydrogen operation.

Speaker: Attila Zsigmond Horváth (European Spallation Source)

326 C3Po1B-08: New process instrumentation with Profinet APL for EPICS

The cryogenic facilities at DESY in Hamburg (Germany), originally built for the HERA accelerator, is now in operation for more than four decades. Starting in 2005, the commercial control system and the 4..20 mA based process instrumentation were renewed step by step. DESY chose the free and open source software suite EPICS (Experimental Physics and Industrial Control System) for the control system. The process instrumentation was replaced by PROFIBUS fieldbus devices. For almost 20 years, the PROFIBUS fieldbus components have proven the very high reliability and robustness of PROFIBUS process instrumentation in 24/7 continuous operation. In terms of reliability, PROFIBUS is still state of the art today. However, new requirements such as Industrial 4.0 demand higher transmission rates right down to the process device level. With the release of the PROFINET-APL (Application Physical Layer) specification, it is now also possible to connect process instrumentation directly to Ethernet networks via a 2-wire connection. PROFINET provides the infrastructure to connect intelligent sensors and actuators directly via Ethernet to the free process control system EPICS. This paper describes which requirements are necessary to successfully connect PROFINET-APL to the process system EPICS. The required modification, PROFINET driver, I/O configuration and I/O cabling are described.

Speaker: Torsten Boeckmann

C3Po1C - Thermophysical Properties and Transport Processes III

327 C3Po1C-01: Measurement of directional hydrodynamic parameters of woven mesh screen by Computational Fluid Dynamic (CFD)

This study examines the directional hydrodynamic resistance parameters of woven mesh screens under steady-state and oscillating helium flows, relevant for both small-scale and large-scale regenerative cryocoolers. Computational fluid dynamics (CFD) simulations are employed to analyze commercially available mesh screen fillers and determine pressure drops in both axial and lateral (radial) directions under steady and oscillatory mass flow conditions. These findings can guide the selection of appropriate mesh screen lengths for use as flow straighteners, such as at the bounding ends of pulse tubes or in novel regenerator designs, and highlight the importance of anisotropy in mesh screen fillers.

Speaker: Dr Ali Ghavami (Georgia Tech)

328 C3Po1C-02: Dynamic Performance Simulation of a Liquid Air Energy Storage System from Startup to Steady Operation

Liquid air energy storage (LAES) technology is distinguished by its high energy density, long-cycle energy storage capacity, and geographic independence, presenting substantial potential for large-scale integration of renewable energy and grid management. Current studies on LAES system performance predominantly focus on steady-state models, with an emphasis on improving round-trip efficiency and optimizing system performance. In contrast, research on the dynamic performance of LAES systems, which is essential for engineering and commercial applications, remains limited. This paper develops a dynamic model for an LAES demonstration project under construction, examining its dynamic performance in depth. Under designed operating conditions, the dynamic variations in parameters such as net input power, net output power, liquefaction rate, and system round-trip efficiency during both energy storage and discharge phases are thoroughly analyzed. Special attention is given to understanding how these parameters fluctuate under different operating conditions, providing insights into system behavior during startup, operation, and shutdown. This study aims to provide theoretical guidance for the practical engineering applications of liquid air energy storage (LAES) systems. Furthermore, through dynamic performance analysis, it establishes a foundation for future improvements in system design and performance optimization.

Speaker: Jiamin Du (Key Laboratory of Cryogenic Science and Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

329 C3Po1C-03: Modeling of the Cryogenic Liquid Regasification Process with Consideration of Evaporation and Superheating

The study proposes a model for the regasification of cryogenic liquids that accounts for both the evaporation process and the subsequent superheating of the liquid. In the model, the boiling cryogen was represented as a solid with appropriate thermophysical properties. This approach significantly accelerated the computations and ensured their stability. The model was developed using the OpenFoam CFD toolboxM, enabling its direct application in simulations involving complex geometries. Additionally, the model incorporates the freezing process of the heating fluid, a critical phenomenon that can adversely affect the operation of cryogenic regasifiers. As an example of the model's application, 3D simulations were conducted for an actual a shell-and-tube heat exchanger consisting of 37 tubes, each 1 meter in length. The modeling results were compared with experimental data, showing satisfactory agreement.

Speaker: Ziemowit Malecha

330 C3Po1C-04: A mesoscopic approach for simulating boiling phase change of liquid hydrogen

Liquid hydrogen has garnered unprecedented attention due to its unique advantages in low-carbon energy economies and the realm of high-thrust and environmentally friendly space propulsion systems. The boiling phase change is a fundamental and inescapable physical process in every aspect of liquid hydrogen storage, transportation, and vaporization applications. Accurate prediction of boiling characteristics is crucial for the design, verification, operation, and diagnostics of related industrial equipment and processes. However, precise numerical simulation of boiling phenomena, especially including the initiation of nucleation, is difficult using conventional multiphase flow models such as the Volume of Fluid (VOF) and level set. These approaches often relay on empirical correlations, which typically deviate from physical basis for different specific scenarios. In addition, different from other cryogenic fluids, liquid hydrogen exhibits an even more complex phase change mechanism due to its unique physical properties, such as extremely low density, low viscosity and high wettability. In this work, a numerical model based on the mesoscopic lattice Boltzmann (LB) method is developed to simulate the boiling process of hydrogen. The high-accuracy fundamental equation of state for hydrogen proposed by Leachman et al. is integrated into the LB method for the first time, which significantly improves the thermophysical property data accuracy that reflects the non-ideal fluid’s behavior. A film evaporation numerical experiment is used to validate the proposed model. A boiling simulation of liquid hydrogen on a two-dimensional smooth and flat surface is performed, which successfully renders the nucleation, growth, and detachment of hydrogen bubbles. The findings provide insights into the nucleation mechanism of liquid hydrogen at the mesoscopic level.

Speaker: Zhaoqi Zheng (Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University)

331 C3Po1C-05: Experimental study on inclined two-phase flow cooling of multi-stranded aluminum cable

An important aspect to enable widespread adoption of electric aircraft propulsion is to develop lighter and higher-ampacity cables to carry the high current and voltage at the same time. To address this, we developed a power transmission cable for electric aircraft that utilize cryogen-flow cooling to enhance transmission efficiency. The cable uses multi-stranded aluminum wire as the conductor, and “bubble breakers” made by polyether ether ketone (PEEK) with 15% volume silica is used to center the conductor and prevent overvoltage breakdown due to the high voltage. Liquid cryogen flows around the multi-stranded aluminum wire and bubble breakers to counteract the Joule Heat. Our previous study demonstrated that a three-meter horizontal multi-stranded aluminum cable with two-phase boiling liquid nitrogen flow achieved a current ampacity ranging from 30 to 70 A/mm², depending on the flow rates. Since cables in aviation are not always horizontal due to takeoff and maneuvering, we hypothesized that the inclination angle of the cable could impact its thermal hydraulic balance which changes the current ampacity of the cable due to gravity and bubble accumulation in two-phase boiling flow. In this study, we conducted a series of flow tests for multi-stranded aluminum cables at various inclination angles to investigate how tilting and flow rate affect current ampacity. The angles tested included 0 degrees (horizontal), 15 degrees inclined towards the outlet, 30 degrees inclined towards the outlet, 15 degrees inclined towards the inlet, and 30 degrees inclined towards the inlet. We first put the multi-stranded aluminum cable in a one-meter-long transparent glass cryostat and conducted ampacity flow tests with these angles of inclination to observe the bubble accumulation due to gravity. Then we placed the cable in the three-meter-long flexible cryostat for the same inclined ampacity flow test, to demonstrate the impact of cable length. The result revealed the influence of tilting angle and flow rate on the current ampacity of cryogen-flow multi-stranded aluminum cable. This study was supported by NASA ULI program (CHEETA).

Speaker: Mr Yang Guo (The Ohio State University)

332 C3Po1C-06: Three-dimensional simulations for evolving thermodynamic scaling laws in cryogenic cavitating fluid transients

Cavitating fluid transients occur when sudden changes in flow, such as rapid acceleration or deceleration, cause significant pressure variations in a pipeline. These variations generate oscillatory pressure waves, leading to the formation and collapse of vapour cavities when the pressure during the rarefaction wave drops below the vapour pressure. During collapse, these cavities can emit high-pressure acoustic waves, resulting in significant pressure fluctuations. Such oscillations may exceed safe operating limits, posing risks of permanent damage to equipment and disrupting the flow operations of the fluid networks. In cryogenic systems, this phenomenon becomes even more complex due to the extremely low operating temperatures, significant variations in thermophysical properties, and the thermosensitive nature of cryogenic fluids. Cavitation in cryogenic flows is strongly influenced by the latent heat drawn from the bulk fluid, leading to a significant decrease in its temperature and thermal boundary layer formation, eventually resulting in the thermal delay or suppression of cavitation. Also, studying these cryogenic fluid transient events experimentally is challenging and expensive due to the need for strict thermal insulation to prevent heat in-leak.

This study presents detailed three-dimensional numerical simulations performed using Ansys Fluent for cavitating fluid transients in cryogenic pipelines triggered by the rapid closure of a valve. Existing cavitation models are evaluated and compared to analyse key flow features, including pressure fields, velocity fields, and vapour distribution. These simulations offer insights into the interaction of fluid dynamics and thermodynamic effects, which are critical for the design of cryogenic flow networks, such as the cryogenic propellant management systems used in rocket engines. To address the limitations of existing cavitation models, we identify gaps in their predictive capabilities and propose a modified cavitation model tailored to cryogenic fluid conditions. Furthermore, thermodynamic scaling techniques are developed, including the formulation of a novel non-dimensional number to characterize cavitating cryogenic fluid transients. Using this scaling approach, we determine the operating temperature at which an alternative fluid exhibits similar cavitation behavior as cryogenic fluids. Finally, three-dimensional simulations are performed for the alternate fluid at the identified temperature, and the results are compared with cryogenic fluid simulations to validate the scaling methodology. The results suggest an approach of replacing cryogenic fluids with a surrogate fluid under scaled conditions to mimic similar cavitation behaviour and resulting effects, making experimental studies more feasible. This comprehensive study enhances the understanding of cavitating transients in cryogenic pipelines, which will help design the scaled experimental setup with thermodynamically similar fluid and improve the safety and reliability of cryogenic systems.

Speaker: Arjun Garva (Indian Institute of Technology Kharagpur, India)

333 C3Po1C-07: Study on the flow nucleate boiling heat transfer of slush nitrogen

A three-dimensional numerical simulation method is developed to predict the heat transfer characteristics during the flow boiling of cryogenic slurry in horizontal circular pipes, based on Euler-Euler model with a boiling model for liquid-vapor mass transfer. The model incorporates the Ishii model for vapor-liquid interaction and the Huilin-Gidaspow model for solid-liquid interaction, also with the modification accounting for slush effective viscosity. The modification enables to simulate the effects of solid particle on bubble detachment. The model can well demonstrate the heat transfer characteristics of subcooled liquid hydrogen, and also the solid phase distribution in slush nitrogen pipe flow. The simulation results show that an increased heat flux can result in a higher vapor volume fraction at the wall and a corresponding decrease in solid volume fraction. At low heat flux, an increase in solid volume fraction enhances the boiling heat transfer, while at higher flux, the solid phase suppresses the heat transfer. Consistent trends are observed in both bottom and surrounding heating layouts. Furthermore, turbulence analysis shows that solid particles can increase turbulent kinetic energy near the wall but inhibit its diffusion toward the pipe center, which indicates that the bubbles will induce the solid particles to accumulate toward the pipe center, while the solid particles inhibit the bubbles releasing from the pipe wall, thereby suppressing the boiling heat transfer.

Speaker: Prof. Tao Jin (Zhejiang University)

334 C3Po1C-08: Completion of vapor-liquid equilibrium measurements of the helium-neon system at temperatures below 36 K

The efficiency of hydrogen liquefaction and other cryogenic applications is potentially increased by using mixed refrigerants. The cryogenic phase equilibria test stand CryoPHAEQTS at KIT enables the measurement of physical property data of all cryogenic fluid mixtures in a temperature range from 10 K to 300 K and at pressures up to 150 bar.
Neon and helium are essential components of low-boiling mixtures. The vapor-liquid equilibrium (VLE) of the helium-neon system was measured for three different isotherms at 27.0 K, 32.9 K, and 35.9 K. These measurements allow for comparison with existing isotherms from literature. This contribution presents the completion of the isotherm measurements at 27.0 K, which allows for direct comparison with experimental results from two other sources. The comparison aims to resolve some inconsistency present in the existing data.

Speaker: Mr Julian Schunk (Karlsruhe Institute of Technology (KIT))

335 C3Po1C-09: Modeling of thermal performance in self-pressurized liquid helium tanks

A thermal multi-zone model is used to describe the self-pressurization process in a liquid helium storage tank. This model divides the liquid and ullage of the tank into multiple zones taking into account the effects of the boundary layer in each zone. Combined with helium property parameters from REFPROP, the model can calculate the self-pressurization process of a liquid helium storage tank under various filling rates and heat leaks. The validity is verified by comparing its results with existing liquid helium storage tank experiments. Finally, the self-pressurization process of liquid helium storage tanks with different filling rates and heat leaks is simulated to obtain the pressurization curves of liquid helium storage tanks and the temperature and thermal stratification effects. The simulation results are further compared to identify the reasons contributing to the pressurization of liquid helium storage tanks.

Speakers: Xiujuan Xie (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences), Liang Guo (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, China), Ye Chen (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, China), Wei Wu (Technical Institute of Physics and Chemistry,CAS), Mr Qiming Jia (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences), Shaoqi Yang

C3Po1D - Liquid Hydrogen Transfer Components

336 C3Po1D-01: Simulation and experiment of a hydrogen pump with an integrated closed impeller

In order to improve the efficiency and anti-cavitation performance of the liquid hydrogen transfer pump, a newly type of closed impeller which integrates both the inducer and the centrifugal impeller is designed to replace the traditional separated impeller. The design specifications include a head of 145 m, a rated speed of 8000 rpm, and a flow rate of 10 L/s. The operational conditions for liquid hydrogen are converted into those for liquid nitrogen using a similar conversion principle to assess the pump's performance. Through simulation calculation, the designed pump head is 154.4 m under the designed condition of liquid hydrogen. After similar conversion, the head under liquid nitrogen condition is 20 m. The flow characteristics, pressure distribution, velocity distribution and cavitation distribution under liquid nitrogen condition were analyzed by simulation. The entropy production under different operating conditions is also analyzed. Ensuring accurate control of clearance size and managing it effectively through gap sealing are vital components of the design and assembly process. The experience of liquid nitrogen experiment will provide guidance for subsequent liquid hydrogen testing.

Speaker: Ziwei Li

337 C3Po1D-02: Performance improvement of a hydrogen condensation heat exchanger applying intermittent reciprocating flow

In a decarbonized society, hydrogen is attracting attention as an energy carrier. There are several forms of hydrogen transportation and storage, including liquefied hydrogen, ammonia, methylcyclohexane, and compressed hydrogen, each of which has its advantages and disadvantages, so it is expected that hydrogen will be used in a form appropriate to the method of use. Of these, attention is focused on liquefied hydrogen, which can be reduced to about 1/800 the volume of normal hydrogen at normal temperature and pressure, has high purity, and does not require purification. The disadvantages of liquefied hydrogen are its liquefaction temperature of 20 K and the large amount of energy required for liquefaction. Highly efficient hydrogen liquefaction is expected to help reduce the cost of hydrogen supply. In this study, we expect to improve the liquefaction efficiency by magnetic refrigeration, which can realize an ideal refrigeration cycle that does not use Joule-Thomson expansion in the refrigeration cycle. Magnetic refrigeration is a refrigeration cycle that utilizes the magnetocaloric effect of magnetic materials. The magnetocaloric effect is a phenomenon in which magnetic entropy is manipulated by applying a magnetic field change to a magnetic material, causing a temperature change in the magnetic material. With this temperature change, the refrigeration cycle is constructed by repeated heat absorption and heat exhaustion with the external system. Ideally, a Carnot cycle with adiabatic and isothermal processes is shown. However, this cycle has the disadvantage that the cooling temperature range cannot be extended because the temperature of the magnetic materials changes uniformly during the adiabatic process. To solve this problem, magnetic materials with high specific heat and magnetic calorimetric effect are processed into particles, and helium, a heat exchange fluid, flows between the particles during the adiabatic process to create a temperature gradient in the magnetic materials. This method draws a small Carnot cycle at each temperature, which occurs continuously with respect to temperature, thus drawing an Erickson cycle as a whole and increasing the cooling temperature range. This is called Active Magnetic Regenerative Refrigeration (AMR). The flow of the heat exchange fluid in AMR is an intermittent reciprocating flow, in which the flow is stopped at the timing of the excitation and demagnetization of the magnetic material due to its operating principle. The heat transfer rate during the flow stoppage time is expected to be lower than that of continuous reciprocating flow. By reducing this reduction in heat transfer, the cold heat generated by the magnetic caloric effect of the magnetic material can be transferred to hydrogen with less loss. As a result, it can help improve the liquefaction rate of the whole liquefaction system. The heat transfer rate was measured by using the fabricated heat exchanger with different flow stop time. The results and discussion are reported.

Speaker: Mr Tsuyoshi Shirai (University of Tsukuba)

338 C3Po1D-03: Top Load Cryogenic Large Size Ball Valves With Focus on Liquified Hydrogen and Helium

Angle globe valves have been traditionally used in all cryogenic systems. The energy sector is transitioning towards environmentally sustainable technological facilities. Hydrogen represents a key value chain within this sector's focus. Nevertheless, the expansion of these plants presents certain inherent techno-economic challenges.
Ball valves can offer significant advantages to this emerging field by providing superior flow capacity performance, resulting in improved Kv flow coefficient values. These enhancements are particularly valuable to process engineers aiming to boost efficiency and, consequently, optimize the hydrogen liquefaction value chain. Competitiveness and process efficiency are paramount objectives for innovative solutions in large-scale systems.
The main motivations of this new thinking are:
-Large-sized valves require flow Kv coefficient values that render ball valve suitable.
-Majority of the big Energy Players are considering the actual LNG value chain and business model for the projected LH2 supply chain with cargo vessels are the drives to design the large-scale value chain.
-Low-pressure distribution for storage and transportation cargo processes conditions are at ambient temperature.
-High-pressure processes demand a higher differential Temperature in the inlet at cryogenic plant.
Throught this poster paper, AMPO POYAM VALVES will present a large top load-valve with the following focus:
-Vacuum jacketed top-load cryogenic ball for G/LNG and G/LH2 as well as also for L/GHe
-Low heat load attributed to the innovative design and jacket design configuration.
-Double-jacket concept aimed at reducing operating cost by maintaining the vacuum within pipeline.
- Comparison with angle globe cryogenic designs of equivalent Kv values.
A novel approach grounded in an innovative solution concept that addresses the challenges of cryogenic service conditions across the full temperature and pressure spectrum. This modern valve concept, incorporating the latest manufacturing technologies, enhances the efficiency of cryogenic processes and delivers added value to the market.

Keywords: Top Load Ball Valves, Big size, Liquid Helium, Liquid Hydrogen, Low Heat Load, Low Maintenance.

Speaker: Mr Ander Gabirondo (AMPO POYAM VALVES)

339 C3Po1D-04: Development of quick connect liquid hydrogen coupler utilizing 3D printing

Liquid hydrogen couplers currently under development require extensive purging, are cumbersome to handle, and cost prohibitive. Our hypothesis is that by combining cryogenically conformable polymer gaskets with 3D printed metal alloys, we can create a coupler that enables purge-less connecting and disconnecting of liquid hydrogen transfer lines at a reduced weight and cost. We recently demonstrated fully collapsible polymeric fuel bladders and novel conformable seats for pressure relief valves at cryogenic temperatures. This conformable polymer advance can be adapted for use in quick-connect coupler valve seats. Concurrently, 3D printed metal alloys are disrupting what is possible for cryogenic materials. We have identified 3D printed aluminum alloys with properties comparable to stainless steel at 20 K with 1/3 the density. These technologies can not only reduce weight and cost but mitigate thermal and mass leakage that are common with conventional LH2 couplers.

Speakers: Alexis Williams (Washington State University), Reagan Dodge (Washington State University)

340 C3Po1D-05: Fundamental insights into liquid hydrogen flow boiling: bubble dynamics and flow characteristic parameters

Hydrogen, as a promising alternative energy carrier, has garnered significant attention. Liquid hydrogen (LH₂) exhibits a high density of 70.9 kg/m³, approximately 1.8 times that of hydrogen compressed at 70 MPa. Its high energy density, efficient transport characteristics, and ability to be stored and transported at low pressures make LH₂ an attractive solution for large-scale commercial hydrogen storage and distribution. However, due to its extremely low boiling point and latent heat of vaporization, LH₂ is prone to rapid phase transition within storage and transport systems, leading to two-phase gas-liquid flow. The development of high-efficiency, high-precision cryogenic fluid management technologies is therefore crucial for enhancing the performance and reliability of LH₂ systems. From both economic and environmental perspectives, minimizing LH₂ losses during pipeline precooling remains a critical challenge.
In this study, a three-dimensional numerical model for LH₂ flow boiling in cryogenic pipelines was developed based on the Euler–Euler two-fluid model. The simulation results exhibited strong agreement with experimental data and predictions from empirical heat transfer correlations. The study systematically investigates the governing mechanisms of bubble dynamics during LH₂ boiling, including bubble departure diameter, detachment frequency, and nucleation site density. Notably, significant discrepancies were observed among different theoretical models used to predict LH₂ boiling heat transfer performance. The findings reveal that bubbly flow, characterized by small bubbles, is a dominant feature in LH₂ boiling. This behavior can be attributed to the low saturation vapor pressure of LH₂, which results in minimal pressure differentials between the liquid and vapor phases, thereby suppressing bubble growth. Additionally, the extremely low surface tension of LH₂ prevents bubble coalescence, further inhibiting the reduction of surface energy. Furthermore, the influence of LH₂ thermophysical properties on pipeline cooling efficiency was examined, considering key parameters such as inlet mass flow rate, operating pressure, and degree of subcooling. The effects of gravity orientation and microgravity conditions were also explored as critical factors. This study provides valuable insights into the fundamental two-phase flow and heat and mass transfer mechanisms of LH₂ boiling, offering theoretical guidance for the development of high-efficiency pipeline cooling strategies.

Speaker: Dr Shaolong Zhu (Zhejiang University)

341 C3Po1D-06: Dynamic Characteristics of Transfer Processes in Port-Based Liquid Hydrogen Receiving Terminals

Liquid hydrogen (LH2), known for its exceptionally high energy density and suitability for long-distance transport, is expected to play a pivotal role in the future of hydrogen energy storage and distribution. Central to this transition are port-based liquid hydrogen receiving terminals, which facilitate the seamless loading and unloading of transport vessels. These terminals integrate large-scale storage tanks for long-term LH2 storage, auxiliary systems for transfer and vaporization, and interfaces for tank trucks, hydrogen pipelines, and tube trailers. However, the complexity of managing pipelines, pumps, heat exchangers, and valves presents significant operational challenges. This study addresses these challenges by analyzing the dynamic performance of liquid hydrogen receiving terminals, with a focus on pre-cooling processes in unloading pipelines—a critical step in advancing maritime LH2 transportation technology.
The research develops a conceptual design for the functional zones of an LH2 terminal and creates a system-level model to simulate its operations. A staged pre-cooling scheme is proposed, emphasizing optimized valve coordination, pressure equalization, and flow control strategies tailored to LH2 properties. Quantitative analyses reveal that factors such as transfer mass flow rate, transfer pressure, and liquid subcooling significantly affect pre-cooling efficiency, while frequency-domain modal analysis highlights pipeline pressure drops and storage tank pressure variations as key operational parameters. In a 12-inch, 300-meter-long unloading pipeline, the optimized system improves the utilization efficiency of LH2 cooling energy by 10.56% and reduces LH2 consumption by approximately 67.3%.
These findings provide strategies for mitigating pressure fluctuations and enhancing terminal reliability. This research offers valuable insights for improving the design and operational efficiency of future LH2 receiving terminals, contributing to the broader adoption of hydrogen energy systems.

Key Words: Liquid hydrogen receiving terminal, System Modeling, Transfer process, Dynamic characteristics, Pipeline precooling.

Speaker: Xinyu Lu (Zhejiang University, CN)

342 C3Po1D-07: Optimization of liquid hydrogen tank-to-tank transfer: A comparative study of six transfer systems

Liquid hydrogen is considered as one of the most promising carriers for large-scale hydrogen storage and transport. However, boil-off losses that occur during the transfer of liquid hydrogen from the trailer to storage at refueling stations pose a significant challenge to the efficiency and cost-effectiveness of these processes. Therefore, the design of the liquid hydrogen transfer system is crucial for ensuring the efficient transfer. In this study, six liquid hydrogen transfer systems based on different methods are proposed, including self-pressurization pressurization-based transfer systems (with and without vapor return), pump-based transfer systems (with and without vapor return) and pressurization-pump integrated transfer systems (with and without vapor return). The transfer process of liquid hydrogen from a 50-m3 trailer (source tank) to a 30-m3 station storage tank (receiver tank) is considered as a case study for assessing the energetic and economic potential of the six proposed systems. The six systems are compared in terms of the transfer process time, source tank holding time after liquid hydrogen offload, boil-off losses, and total costs of the infrastructure. The results show that transferring the excess gas from the receiver tank to the source tank prior to the transfer process significantly enhances the overall energy balance of liquid hydrogen. The transfer process time of the self-pressurization-based system with vapor return is 1.4 h, with boil-off losses of 7.43%. This work may provide guidelines for configuration selection and optimum design of liquid hydrogen transfer systems in liquid hydrogen supply chain.

Speaker: Haoran Gan (Zhejiang University)

343 C3Po1D-08: Stress Distribution and Sealing Performance Analysis of Metal Sealing Joints in Liquid Hydrogen Pipelines

Metal sealing joints are widely used in cryogenic fluid storage and transportation systems, where their sealing performance is critical under extreme low-temperature conditions. In cryogenic environments, changes in material properties can lead to uneven stress distribution at the contact interface, thereby affecting the sealing effectiveness. This study first investigates the variations in the mechanical properties of metals under cryogenic environments, with a particular focus on the changes in the elastic modulus and yield strength of 304 stainless steel with temperature. A leakage model for the metal sealing joint is developed to establish the relationship between contact stress at the sealing surface and the leakage rate at cryogenic temperatures. Additionally, a macroscopic static analysis is used to map the relationship between the preload force and torque of joint. Finite element analysis is employed to simulate the stress distribution of the cryogenic metal sealing joint under varying preload forces, highlighting potential stress concentration regions in the joint structure and their impact on sealing performance. The findings of this study offer valuable insights for improving the sealing effectiveness and safety of metal sealing joints in cryogenic environments.

Speaker: Ms Yihan Tian (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

344 C3Po1D-09: Simulation Study on the Thermal Insulation Performance of Liquid Hydrogen Transport Pipelines

Hydrogen engines, compared to traditional gas engines, offer higher energy density and combustion efficiency. These advantages not only significantly enhance the propulsion performance of aircraft but also extend their range, presenting substantial potential for applications in the aviation sector. As a crucial component of hydrogen engine systems, the design and performance of liquid hydrogen transport pipelines directly influence the efficiency and safety of hydrogen delivery, making them essential for ensuring a stable supply and efficient utilization. This study focuses on the thermal insulation performance of liquid hydrogen transport pipelines by developing a multi-physics coupling model that incorporates heat conduction, radiation, and convection. Simulation research based on vacuum multilayer insulation technology was conducted to explore the effects of material thickness, vacuum level, support structure, and thermal bridge design on the overall heat loss of the pipeline. Additionally, the contribution of different structural components to total heat loss is quantified. The findings provide theoretical guidance for optimizing the insulation system of liquid hydrogen transport pipelines, which is crucial for improving hydrogen storage and transportation efficiency, reducing cold energy loss, and advancing the industrial application of hydrogen energy technologies.

Speaker: Ms Yihan Tian (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

345 C3Po1D-10: A novel nozzle design method for hydrogen Turbo-Expanders

Hydrogen energy is a clean and efficient energy source with significant potential in the global energy transition. Liquid hydrogen, with its high energy density and ease of transport, is vital for large-scale liquefaction systems. Hydrogen turbo-expanders, as key components in this process, greatly influence efficiency and stability. However, the unique properties of hydrogen, such as low viscosity and high speed of sound, create challenges for turbo-expander design and optimization. To address these challenges, this work focuses on optimizing the nozzle blade profiles in hydrogen turbo-expanders. The interaction between the nozzle and impeller is critical yet challenging. Improper nozzle design can cause impact losses, uneven flow distribution, and increased secondary flows, reducing efficiency and stability. High flow velocities can also lead to transonic flows and aerodynamic disturbances, further impacting performance. Through computational simulations and refined design approaches, the optimized nozzles enhance flow quality, reduce losses, and strengthen nozzle-impeller coupling, significantly improving turbo-expander efficiency and operational stability. These findings provide valuable guidance for hydrogen turbo-expander optimization and support the efficient operation of hydrogen liquefaction systems.

Speakers: Changlei Ke (Technical Institute of Physics and Chemistry), Mr Hongmin Liu (Technical Institute of Physics and Chemistry, CAS)

C3Po1E - Magnetic Coolers

346 C3Po1E-01: Research on temperature control of Adiabatic Demagnetization Refrigerators

In astronomical observations, detectors operating in the sub-Kelvin temperature range require extremely stable working temperatures. Adiabatic demagnetization refrigerators (ADR), as the sub-Kelvin refrigerator that is independent of gravity and offers high temperature control precision, have become the preferred choice for astronomical observation missions. The high temperature control precision originates from the intrinsic nature of ADR, which generates cooling power through demagnetization. By controlling the demagnetization rate through PID control, high stability in the order of μK can be achieved. Here we present the study of temperature control for the second stage of a two-stage ADR. The influence of P, I, or even D has been analyzed. Simulation of the influence of PID has also been compared with the experimental results. Additionally, the effects of factors such as environmental noise, the resolution of the magnet power supply, excitation and filtering in temperature measurement, on temperature fluctuations are investigated.

Speaker: Prof. Wei Dai (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

347 C3Po1E-02: Design of a Three-Stage Continuous Adiabatic Demagnetization Refrigerator for Ultra-Low Temperature Applications

The demand for extremely low temperatures in quantum computing and quantum devices has led to significant interest in advanced refrigeration methods. Among these methods, the continuous adiabatic demagnetization refrigerator (cADR) presents a promising alternative that does not rely on the increasingly scarce He3. While traditional dilution refrigerators (DR) are effective in reaching low temperatures, they require He3, leading to complexities in design and operation due to their large size and intricate components.
In contrast, the adiabatic demagnetization refrigerator (ADR) operates using the magnetic enthalpy of a solid, allowing for a more compact design. However, a significant challenge remains in maintaining low temperatures, as the ADR's operation inherently involves temperature fluctuations. To address this issue, the multi-stage configuration of the cADR has been proposed, which enhances temperature stability during operation.
This research focuses on the design of a three-stage cADR system utilizing Gadolinium Gallium Garnet (GGG) and Chrome Potassium Alum (CPA) as the magnetic materials. The first stage will employ a commercially available pulse tube cryocooler to achieve cooling down to 4 K. Heat switches will be strategically placed between each stage and the final cold end to control thermal transfer during operation, ensuring efficient temperature regulation.
The selection of appropriate paramagnetic materials is critical for optimizing the cADR's performance. GGG, with its high magnetic susceptibility and thermal conductivity, is well-suited for the initial cooling stage. CPA, on the other hand, offers advantageous thermal properties for subsequent stages. By implementing this multi-stage design, our cADR aims to maintain a steady temperature around 60 mK, which is essential for various applications in quantum technology.
The results of this study will contribute to the development of cADR systems capable of achieving and sustaining ultra-low temperatures without the reliance on He3. Our findings will pave the way for the construction of a 60 mK cADR, ultimately facilitating advancements in quantum computing and other low-temperature applications.

Speaker: Mr Changhyung Lee (Changwon National University)

348 C3Po1E-03: Design and fabrication of CPA salt pill for adiabatic demagnetization refrigerator

As interest in quantum-related research continues to grow, so does the demand for ultra-low temperatures below 1 K. Cooling systems designed to achieve such ultra-low temperatures include Dilution Refrigerators (DR), Pulse-Tube cryocoolers with Joule-Thomson modules (PT-JT), and Adiabatic Demagnetization Refrigerators (ADR). Unlike DR and PT-JT systems, ADRs do not rely on fluids but instead utilize the magnetocaloric effect of paramagnetic salts. This approach offers advantages such as miniaturization and high efficiency due to the absence of mechanical moving parts. A critical component of ADRs, the salt pill, significantly influences system performance, with its design, fabrication process, and the material properties of the salt playing key roles. Chromium Potassium Alum (CPA), a representative magnetocaloric material for ADR, has a Curie temperature of approximately 9 mK. However, due to its low thermal conductivity at ultra-low temperatures, a dedicated thermal bus and a sealed cylinder for vacuum environment stability are required. Copper wires used as thermal buses are subject to eddy current losses in varying magnetic field environments. To reduce such losses, multiple thin wires are employed, providing the required heat transfer area while effectively minimizing eddy current losses.
This study presents the design of a single-stage ADR capable of achieving ultra-low temperatures below 100 mK, as well as the design and fabrication process of a CPA salt pill. The single-stage ADR was designed to reach temperatures below 100 mK by exchanging heat with the second stage of a two-stage 4 K cryocooler. The specifications of the CPA salt pill were determined based on the ADR cooling cycle, and its performance was evaluated using FEM analysis. Subsequently, a fabrication method for the CPA salt pill was proposed, and basic evaluations were conducted. The results of this study are expected to provide foundational data for the development of multi-stage continuous ADR (cADR) systems.

Speaker: Mr Jangdon Kim (Changwon National University, Changwon, South Korea)

349 C3Po1E-04: Design and testing of a tin superconducting heat switch for adiabatic demagnetization refrigerators

The superconducting heat switch is a critical component in an adiabatic demagnetization refrigerator (ADR) to achieve a temperature lower than 50 mK, and its switching performance significantly affects the overall efficiency of the ADR. We have designed a superconducting heat switch utilizing high-purity tin (99.99%) as the superconducting material, and have carried out experimental testing on its performance. The results show that the superconducting heat switch achieves full conduction under an applied magnetic field of 0.07 T. With a heat load of 100 μW, the measured thermal resistance in the conducting state is 4542.25 K/W, while in the off-state, the thermal resistance is 10391.1 K/W, resulting in a switch ratio of 2.28. This heat switch is expected to be primarily used in temperature regions around 500 mK to manage the thermal connection between the ADR and the pre-cooling system.

Speaker: Mr Zijie Pan (Technical Institute of Physics and Chemistry, CAS)

C3Po1F - Aerospace Applications II

350 C3Po1F-01: Conceptual design of a lab-scale low-noise He-II liquefier using a pulse-tube cryocooler with a Joule-Thomson cycle

The Einstein Telescope (ET) is a 3rd generation gravitational wave detector planned in Europe, combining a low-frequency (LF) and a high-frequency (HF) laser interferometer. Cryogenic operation of ET-LF in the temperature range of 10 K to 20 K is essential to suppress the suspension thermal noise (STN), which dominates the detection sensitivity at frequencies below 10 Hz.
The ERC project GRAVITHELIUM aims to investigate the suitability of static He-II for the heat extraction from the cryogenic core optics in ET-LF. It requires a low-noise He-II supply unit that can provide 400 mW of cooling capacity at 1.8 K via a 5 m long transfer line. Using a pulse-tube cryocooler in combination with a Joule-Thomson cycle, an in-depth process analysis and optimization is conducted. Significant improvements to the process efficiency are achieved by a novel heat exchanger technology, the so-called foil-frame counterflow heat exchanger (FFCFHX), which allows for large heat transfer areas while maintaining low kinetic pressure losses.
The contribution also contains the characterization of the transient cool-down process, which happens in two phases: The cool down of the He-II supply unit and the transfer line using a supercritical helium flow, and the final cool-down via pumping on the liquid helium tank. The results show that He-II temperatures can be reached in less than one day, depending on the cool-down behavior of the experimental cryostat.

Speaker: Mr Timo Weckerle (Karlsruhe Institute of Technology (KIT))

351 C3Po1F-02: A 100 mW@4.0 K hybrid 4He Joule-Thomson cryocooler for space applications

The 4He Joule-Thomson cryocooler (JTC) utilizes the JT effect of 4He to typically achieve the temperature of about 4 K. It can be used to cool the detectors with the operating temperature of 4 K and precool the sub-Kelvin refrigerators, which is widely used in space missions such as Astro-H, SPICA, ATHENA, and etc. Based our laboratory’s research, an engineering prototype of the 4He JTC precooled by a two-stage pulse tube cryocooler (PTC) is designed as a precooling stage of the closed-cycle dilution refrigerator. After experiment studies, the 4He JTC successfully obtained a cooling power of 100 mW at 4.0 K with a total input power of 600 W.

Speaker: Yuexue Ma (Technical Institute of Physics and Chemistry, CAS)

352 C3Po1F-03: Performance optimization of a 4K hybrid JT cooler for space application

A 4K hybrid JT cooler is developed to precool the adiabatic demagnetization refrigerator (ADR) of Hot Universe Baryon Surveyor (HUBS) mission which is proposed to study “missing” baryons in the universe. The 4K hybrid JT cooler is composed of a 4He JT cooler precooled by a two-stage thermally coupled pulse tube cooler. Recently, the two-stage pulse tube cooler is optimized to provide more precooling power for the JT loop. The performance of the hybrid JT cooler has been improved and special efforts have been made to optimize the compression system of the JT loop. Eventually, cooling power of 100mW is achieved at 4K which is able to meet the requirements of the ADR of HUBS.

Speaker: Yuexue Ma (Technical Institute of Physics and Chemistry, CAS)

353 C3Po1F-04: Study on Cryogenic Fluid Circulation Loops for Efficient Heat Transfer of Small Cooling Capacities in the 4-20 K Temperature Range

In cryogenic refrigeration systems, such as those used in space exploration instruments, heat loads (e.g., detectors) are typically fastened directly to cold sources (e.g., cryocooler cold heads) to minimize thermal resistance. However, in certain scenarios where a considerable distance exists between the detector and the cold source, direct connection is not feasible. In such cases, transitional connections, such as copper plates or braided copper straps, are employed. The heat transfer capacity in these configurations is inherently limited by the thermal conductivity of the connecting materials. This study proposes a cryogenic fluid circulation loop utilizing helium as the working fluid, which replaces the conventional solid thermal conduction with convective heat transfer, thereby enhancing the heat transfer performance. Through simulation calculations and experimental testing, the effects of operational and structural parameters, including charging pressure, operating temperature range, and connection tube length, on heat transfer performance were investigated. The computational and experimental results provide practical insights for the design of efficient small-capacity heat transfer systems operating in the 4-20 K temperature range.

Speaker: Dr Liubiao Chen (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

354 C3Po1F-05: Development and preliminary testing of cryogenic pump for TVS test

Handling cryogenic propellants in space is very difficult.
In particular, in micro-gravity, liquid and gas are not separated and mixed, so when the vent valve is opened to reduce the increased tank pressure due to external heat inflow, propellant loss occurs.
Therefore, in order to reduce propellant consumption and internal tank pressure, a thermodynamic vent system, TVS, is required to reduce internal pressure and manage temperature.
The components of TVS can be composed of a heat exchanger, internal injection/mixing, vent, pump, etc.
This paper contains the development and preliminary testing of a cryogenic pump, a TVS component.
For the TVS test, a test tank was placed in a vacuum chamber, and the TVS pump needed to be developed to be able to operate in this vacuum and cryogenic environment.
The magnetic coupler type was used to improve the sealing performance by separating the inside and outside of the tank, and the issues such as internal shaft alignment were resolved, and the applicability was examined through a flow rate/pressure confirmation test.
In the future, we plan to continuously research cryogenic fluid management technology in space environments by utilizing this TVS cryogenic pump.

Speaker: Isang Yu (korea aerospace research institute)

355 C3Po1F-06: Development and projected capabilities of Chamber D

Chamber D is a Thermal Vacuum (TVAC) chamber that is currently being developed by the National Aeronautics and Space Administration (NASA) Crew and Thermal Systems Division (CTSD) Systems Test Branch (EC4) to simulate the thermal profile of a lunar Permanently Shadowed Region (PSR). To achieve the target thermal environments, a gaseous helium cooled shroud is being integrated into an existing vacuum chamber. Chamber D is in the NASA Johnson Space Center (JSC) Space Environment Simulation Laboratory (SESL) which also includes the large TVAC chamber, Chamber A. A liquid nitrogen thermosiphon system and a state-of-the-art helium refrigeration system are used to control the temperature of the Chamber A shrouds. The same helium refrigeration system that cools the inner shroud of Chamber A is being used to cool the gaseous helium cooled shroud of Chamber D. Despite a significant smaller working area, Chamber D will have a similar cooling capacity to Chamber A. Chamber D also includes a mechanical actuation system in the lunar PSR simulated environment to perform thermal contact testing with test articles, including space suit components, and an actively cooled surface. The development and projected capabilities of Chamber D will be discussed.

Speaker: Stephen Baker (NASA Johnson Space Center)

356 C3Po1F-07: Thermal Control Units for Space Vacuum Chambers

Criotec Impianti awarded the contract for the design, manufacturing, installation and commissioning of the temperature control system of the Large Earth Observation Thermal Vacuum chamber (LEO LARGE TVC) under construction at Customer premises.

For this project Criotec Impianti developed two different sizes of so-called Thermal Control Units (TCUs) that will be used for the thermal conditioning, in both cold and hot conditions, of the vacuum chamber’s thermal shrouds, baseplate and of the thermal ground support equipment units under test (UUT TGSE).
The technical specification for the thermal vacuum chamber requests an operative temperature range between 82K to 333K with a spatial uniformity up to 2K on the baseplate and a maximum of heating/cooling rate of 2K/min on the shrouds.
To achieve these requirements, Criotec Impianti designed the TCUs as vacuum insulated valve boxes operating with gaseous helium as working fluid.

Each TCU consists of the following main components:
- a warm temperature helium blower fan providing the requested gas flow rate
- a cold heat exchanger cooling down the working fluid using liquid nitrogen during the low temperature operation
- an electrical heater to heat up the working fluid during the high temperature operation and for the precise temperature control (+/- 1 K) during the operations at steady state conditions
- a regenerative heat exchanger used as economizer in order to reduce the liquid nitrogen consumption
- a helium/water heat exchanger to remove the heat dissipated from the helium blower.

The warm temperature high speed helium blower has been completely designed by Criotec Impianti for this project in order to optimize the performance for the requested operating conditions.
Instrumentation for the measurement of the main working parameters allows to monitor and regulate the operating condition of the TCU in terms of temperature and flow rate. The TCUs will be operated at a pressure in the range 6.5÷9.5 barg and with a temperature range of 82÷400K on the helium side.

The TCUs design data are as follow: design pressure of 9 barg + external vacuum on the helium side and a design temperature of -205/+130°C since it can work also with saturated liquid nitrogen at sub-atmospheric pressure.

The three larger TCUs, two used for the temperature control on the thermal shrouds and one for the temperature control of the baseplate, have a rated nominal helium flow rate of 250 g/s while the smaller TCU, used for the temperature control of the UUT TGSE, has a rated nominal helium flow rate of 40 g/s. Each TCU is equipped with a He buffer to compensate for the volume variation of the gas from the cold to hot working conditions.

These TCUs are a valid solution for the thermal control of TVC when conditioning down to cryogenic temperature is requested together with a good spatial uniformity. Depending on the specific application the units can be scaled in the range of the nominal flow rate of the two sizes developed or can achieve higher thermal powers installing multiple units in a modular way.

Speaker: Marco Roveta

357 C3Po1F-08: Power requirements and energy recovery in Stirling and pulse tube cryocoolers for space missions

Space cryocoolers permit cryogenic cooling of space-based astronomy instruments and a range of other sensors and detectors across electromagnetic wavelengths. This study investigates the energy requirements and performance of various cryocooler designs, with a focus on Stirling, pulse tube, and Stirling pulse tube cryocoolers (SPTCs). These systems are essential for missions requiring high reliability, minimal vibrations, and efficient cooling. The Stirling cryocooler utilizes a displacer to transfer heat efficiently, while the pulse tube cryocooler achieves low vibration by eliminating moving parts at the cold end. The SPTC integrates advantages from both systems, offering high efficiency and minimal thermal noise, making it particularly suited for next-generation space missions. Key aspects analyzed include power requirements, cooling efficiency, and energy recovery mechanisms. Innovations such as displacers for energy recovery and advanced phase shifters are highlighted, demonstrating their impact on improving system performance. Comparative evaluations reveal the operational trade-offs between different cryocooler types, emphasizing the importance of design choices for specific mission requirements. The study investigates in further detail the SLSTR cryocooling instrument on-board Sentinel-3 and pulse tube systems in the James Webb Space Telescope, and discusses the design considerations undergone to permit their long-term reliability and precision. Despite advancements, challenges remain in optimizing energy usage and further reducing thermal noise. This work consolidates knowledge on cryocooler technology, providing a foundation for future research and development. By addressing current limitations and exploring novel energy recovery methods, the study paves the way for more efficient and reliable cryogenic systems in space exploration.

Speaker: Ojas Khadakban (Center for Astrophysics | Harvard & Smithsonian)

358 C3Po1F-09: Performance and qualification of the HTS flux pump bound for the international space station on the Heki mission

Despite repeated proposals to utilize superconducting magnets in space since at least the 1970s [1], examples of their use remain scant [2]. One of the technical challenges is to maintain suitable cryogenic temperatures on a spacecraft. This challenge can be alleviated by the use of flux pumps [3] to reduce the required cryogenic cooling power needed to energize the superconducting magnet.

This talk/poster details the flux pump implemented in the Heki mission [4] - a mission that will operate an open-bore high-temperature superconducting magnet to at least 0.3 Tesla on an external platform of the International Space Station in 2025.

We provide an overview of the mission and its requirements, highlighting the how flux pump technology proved to be mission enabling due to the reduction in the required cryogenic cooling power it affords compared with conventional current leads [5]. We then describe the design methodology to meet the flux pump's performance requirements, particularly relating to the distinct aspects of operating the system in space. Finally we show the flux pump's performance measured during the qualification testing of the integrated payload for the Heki mission, in which we could demonstrate the system exceeded its performance requirements.

We anticipate an on-orbit demonstration mid 2025, with launch scheduled for April. Such a demonstration will signal a maturing of this emerging superconducting technology for both in-space and terrestrial applications.

[1] Sullivan D B and Vorreiter J W, 1979 Cryogenics, 19 627–631, doi:10.1016/0011-2275(79)90063-8
[2] Poulturak et al., 2000 IEE trans. microwave theory and techniques, 48, doi:10.1109/22.853476
[3] van de Klundert LJM, ten Kate HHJ, 1981 Cryogenics 21 195–206, doi.org/10.1016/0011-2275(81)90195-8
[4] Pollock R et al., 2024 IEEE Aerospace Conference, p1–11, doi:10.1109/AERO58975.2024.10521198
[5] Mallett BPP et al., 2024 Superconductivity, 12 100129, doi:10.1016/j.supcon.2024.100129

Speaker: Ben Mallett (Robinson Research Institute)

09:15 Morning Coffee Break -- supported by Sumitomo (SHI) Cryogenics of America, Inc.

M3Or1A - Magnetic Design and Applications II

359 M3Or1A-01: Design and test of the HTS magnet of the robust and low maintenance magnetic billet heater “RoWaMag”

In the manufacture of semi-finished metal products, metal billets need to be annealed at temperatures up to 1100°C in order to soften the materials for further forming. The annealing process can be performed in conventional furnaces using fossil fuels or by induction heating. The advantage of induction heating is a higher efficiency, shorter heating times and a better temperature homogeneity in the metal billet. However, in conventional induction heaters, where an AC coil surrounds the metal billet, losses are high due to the required AC operation mode. This limits the maximum efficiency to about 50 - 60 %. Magnetic billet heaters with superconducting DC magnets achieve higher efficiencies of 70 - 80 % by rotating a metal billet in a DC magnetic field.
In the framework of the German project „RoWaMag“, a robust, low-maintenance magnetic billet heater with a DC magnet on the basis of 2G REBCO coated conductors is being built. The conduction-cooled magnet with an iron yoke is designed to generate a magnetic field of 600 - 700 mT at the center of the heating axis of metal billets with a maximum length of 750 mm and a diameter up to 225 mm. At the ends of the billet, a magnetic field of 500 – 550 mT is required. The HTS magnet consists of three rectangular double pancake coils made of 3110 m Theva tape and has outer dimensions of 1179 mm x 1041 mm x 35 mm. The operating current is 505 A.
In first tests of the magnet and cryogenic system, the magnet reached temperatures below 25 K. Stable magnet operation was observed for several days for currents up to 250 A, however, during a further current increase the REBCO part of the current leads burnt due to underestimation of magnetic field and Lorentz forces. In a new design with higher current carrying capability, the current leads were mechanically stabilized and the thermal contact between the warm end and the first stage of the cryocooler was improved.
In this paper we present the design and construction of the HTS magnet, the HTS current leads and the cryogenic system of the magnetic billet heater. We present test results for the magnet and the cryogenic system and give an outlook to the final project stage with integration and operation of the magnet in the billet heater.

Speaker: Dr Sonja Schlachter (Karlsruhe Institute of Technology)

360 M3Or1A-02: The latest progress of all-superconducting high-field magnet at the ASIPP in China

All-superconducting high-field magnets are in high demand across various scientific disciplines, including large-scale science devices, materials science, and biology. They play a crucial role in researching material properties, the origin of life, and disease prevention and treatment. These magnets offer significant advantages, such as compact size, low power consumption, flexibility, and convenience.
With the continuous advancement in superconducting materials and magnet technology, a key focus is placed on developing the essential technology for large aperture all-superconducting high-field magnets with independent intellectual property rights. This effort, driven by the national "13th Five-Year" major science and technology infrastructure project known as "Fusion reactor Key System Comprehensive Research Facility (CRAFT)," aims to develop the homemade high-field superconducting magnet. The ultimate goal is to achieve the domestic commercialization of all-superconducting high-field magnets with apertures exceeding 15T.
After over two years of accumulating experience and conducting extensive technical research, the project team successfully realized the commercial value of a 15T&77mm aperture all-superconducting hybrid magnet. The magnet's dimensions are Ø306mm×340mm, with a central magnetic field reaching 15.12T at an operating current of 118.6A. The axial magnetic field uniformity is ≤1%@Ø60mm×42.6mm cylindrical area, and the central magnetic field reaches the target value after two excitation exercises.
Building on the key technology of designing and preparing full superconducting high-field magnets, the project team plans to develop a larger aperture (≥150mm) high-field (~15T) all-superconducting hybrid magnet. This will be achieved by combining it with high-temperature superconducting interpolation magnets, aiming to create a central magnetic field strength of ~35T&80mm aperture for a high and low-temperature all-superconducting hybrid magnet. The overarching goal is to provide technical reserves and core component support for high-field material scientific research in fusion reactor development and contribute to the national strategic layout for high magnetic field development.

Speaker: Peng Gao (Institute of Plasma Physics Chinese Academy of Sciences)

361 M3Or1A-03: Simulations of a modified CLIQ System using Split MgB2 Coils and Simultaneous Joule Heating Using a Lumped Parameter Model

In this work, we performed numerical studies of a quench protection system relevant to MgB2 based 3T conduction cooled magnetic resonance imaging (MRI) machines using a lumped parameter model in Open Modelica. Our initial approach was similar to the CLIQ scheme, which we modelled for one coil (OD 901 mm, winding pack 44 mm thick×50.6 mm high, conduction-cooled, react-and-wind, with 1.7 km of MgB2 strand). In previous simulations, the required capacitor, other component sizes and ratings are determined. However, a large maximum voltage was required for this system. There is a breakdown voltage, and a high voltage could burn the coil. By splitting the coils, the voltage could be reduced, but not sufficient. We found we could split the coil in such a way to reduce further the inductance of the combined set and the resultant maximum voltage. We then explored a method that would allow further voltage reductions while still generating sufficient heating in the coil for protection. A lumped parameter model was built in Open Modelica to describe the resistance of the coil for operating current larger than critical current (I > Ic), and we explored directly driving the coil into overcurrent for protective heating to AC loss induced heating. This mixed approach using split coils and Joule heating in the matrix might be possible. This model in Open Modelica, including both thermal and electrical components, describes the interface between the superconducting wire and its environment. In this case, liquid helium (4.2 K) surrounds the wire, and a thermal conductor has G = 0.4 W/K as interfacial liquid-solid thermal conductance. The heat capacitor describes the heat capacitance (4e4 J/K) of the superconducting wire itself, how much heat it can store. The results are testing under different cases with different superconducting wire parameters, voltage supplies, and inductors conditions.

Speaker: Xianhao Zhang

C3Or2A - Remote Cooling and Regenerative Coolers

362 C3Or2A-01: Integrated remote cooling system using a GM cryocooler

Sumitomo (SHI) Cryogenics of America Inc has developed a novel cryogenic cooling system integrating a remote cooling gas flow circuit with a Gifford-McMahon (GM) cryocooler to cool a remote load. This innovative approach eliminates the need for a separate gas flow circuit and circulator, leading to an efficient, compact, and cost-effective solution for various cryogenic applications. This system utilizes helium scroll compressors to supply gas to a GM cryocooler. A portion of the return gas flow from the cryocooler is then diverted into the remote cooling circuit, where it is first cooled by a counter-flow heat exchanger and further cooled by the cryocooler. This cooled gas is then delivered to the remote load through vacuum-jacketed lines before returning to the main system. The system is equipped with a vacuum pump and valves, allowing for independent maintenance and cleaning while ensuring seamless operation of the main refrigeration system. In this paper, we will discuss and present system configuration, cooling performance, and system losses.

Speaker: Mr Joseph Koch (Sumitomo (SHI) Cryogenics of America Inc)

363 C3Or2A-02: Cryogenic helium circulation cooling system with high capacity GM Cryocooler

Sumitomo (SHI) Cryogenics of America, Inc. has investigated the capabilities of a circulating cooling system utilizing a Sumitomo CH-160 High-Capacity Gifford-McMahon (HCGM) cryocooler and helium gas circulator for cooling a remote thermal load (e.g., a superconducting magnet). System cooling performance was investigated for circulation loop pressures of up to 20 bar-g. The system is comprised of a CH-160 HCGM cryocooler with an integrated heat exchanger, an off-the-shelf circulator, bayonets (which are housed in a cryostat), vacuum jacketed transfer lines, a vacuum pump and electrical controls for system operation and testing. In this paper, we present system configuration, cryocooler performance, input power, and net system cooling performance delivered to the remote thermal load. Cooling losses of the circulation loop associated with the cryostat, transfer lines, circulator are discussed and analyzed to characterize the system. An example of using the system for constant cooling and cool-down applications are discussed and presented.

Speaker: Eric Seitz (Sumitomo (SHI) Cryogenics of America, Inc.)

364 C3Or2A-03: Performance Test and Analysis of a High-Capacity Stirling Type Pulse Tube Cryocooler with Orthogonal Room Temperature Displacers

Stirling-type pulse tube cryocoolers are known for their compact design, reliability, and long operational life, but traditional systems are primarily limited to small-scale cooling applications. To meet the growing demand for high cooling capacity in fields such as superconducting power transmission, small-scale gas liquefaction, and BOG (Boil-Off Gas) management, this paper presents a single-stage Stirling-type pulse tube cryocooler with orthogonal room temperature displacers. This design enhances the reliability of the displacer, as it operates at room temperature, thus improving reliability, and optimizes acoustic field distribution, leading to significant performance improvements over traditional pulse tube cryocoolers. By combining theoretical analysis with experimental validation, we examined the effects of key parameters, including pressure ratio, frequency, and displacer stiffness, on cooling capacity across cold head operating temperatures from 40 K to 100 K, considering working at different ambient temperatures. Experimental results show that the optimized cryocooler achieves a minimum temperature of 36.5 K and a cooling capacity of 340 W at 77 K, with an input power of 4.5 kW, demonstrating a relative Carnot efficiency of approximately 21.2%. The cryocooler has a total weight of 82 kg, making it suitable for applications where weight is a crucial factor.

Speakers: Mr Shuai Chen (Lihan Cryogenics Co., Ltd.), Xiaotao Wang (Key Laboratory of Cryogenic Science and Technology, Technical Institute of Physics and Chemistry)

365 C3Or2A-04: Numerical Investigation of Alternative Regenerators in Regenerative Cryocoolers Operating Below 20K

In regenerative cryocoolers, the regenerator plays a pivotal role, and often represents the largest source of losses among all components. Traditional materials, such as stainless-steel mesh, exhibit insufficient heat capacity below 20K, which leads to a decrease in system efficiency. While materials like HoCu2 and Er3Ni offer higher volumetric heat capacity, they are typically fabricated into spherical forms, resulting in high flow resistance. In light of these limitations, this study investigated and compared three present alternative configurations through a numerical model of a Stirling cryocooler. The first approach involves coating stainless steel mesh with high heat capacity materials. Specifically, stainless steel mesh coated with HoCu2 and Er3Ni was examined. The results indicate that, around 20K, this configuration offers improved performance compared to HoCu2 spheres by reduced flow resistance. However, the limited volume fraction of the coating material still limits the heat capacity. The second approach explores open-cavity structures, which can be filled with helium under oscillating flow. Simulations of stainless-steel capillaries reveal that the excessively large hydraulic diameters, due to manufacturing limitations, result in insufficient heat exchange area, which leads to poor performance. The third approach investigates the use of highly adsorptive materials, such as carbon nanotubes, to retain helium through physical adsorption. Compared to HoCu2 spheres, carbon nanotubes demonstrate comparable performance around 10K and exhibit further improvement as the temperature decreases, if not considering the thermal effect caused by adsorption and desorption. These numerical investigations effectively guide the search for better regenerator configurations for temperature below 20 K.

Speakers: Prof. Wei Dai (Technical Institute Of Physics and Chemistry, Chinese Academy of Sciences), Dr Zhengkun Li (Key Laboratory of Cryogenic Science and Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

366 C3Or2A-05: Comparison study on a large-scale free-piston Stirling cryocooler

Large-scale free-piston Stirling cryocoolers, capable of delivering several hundred watts of cooling power at 80 K, have significant potential applications in boil-off gas re-liquefaction and precooling processes. Recently, we proposed a novel parallel regenerator layout aimed at suppressing local acoustic streaming, which could enable further scaling of the cryocooler while maintaining high thermal efficiency. Numerical modeling was performed, and an experimental prototype was developed based on this design. Experimental results demonstrated reasonable agreement with the numerical predictions in terms of cooling power. However, discrepancies in thermal efficiency were observed, likely due to inconsistencies among the individual regenerators.

Speaker: Guoyao Yu

C3Or2B - Large Scale Refrigeration V: Performance and Optimization

367 C3Or2B-01: Development and verification of a steady-state operating methodology for wide-range operation of 2K cold compressor system

Superconducting radio frequency (SRF) cavities used in modern particle accelerators require operation at 2 K with sub-atmospheric (saturation) pressure. For large-scale systems, the most practical approach is to use multi-stage cryogenic centrifugal compressors (cold compressors or CCs) to compress the sub-atmospheric helium returning from the load to positive pressure. This compressor train is typically controlled with a lead compressor while the remaining compressors are coupled to the lead compressor through electronic speed ratios. Historically, the steady-state system parameters (e.g. speed ratios) for a specific operating point were obtained empirically from extensive testing. Hence, the operating regime for these systems remained limited to the design point regardless of the actual 2 K load requirement. However, stable operation of the cold compressor system over a wide range of (mass flow) capacities is a major factor in terms of operational cost savings. Each gram per second of reduction in CC mass flow can result in a 15 – 20 kW reduction of input power at the main compressor. The overall cryogenic system operational cost savings from turning down the CC flow (perceived as a partial liquefaction load by the 4.5 K cryo-plant) can significantly outweigh the inefficiencies due to operation of the cold compressor system outside its peak efficiency regime. A steady-state operating algorithm has been developed to improve 2 K system reliability and stability over a wide range of steady-state operational conditions. An in-house 1D mean line centrifugal compressor characterization model is used in conjunction with the developed algorithm to estimate the selection of electronic speed ratios for optimal stability under a given load (flow). Functionality and validity of the developed steady-state methodology is tested using the FRIB cold compressor system up to 2:1 turn-down capacity range. An excellent agreement between the model predictions and the FRIB cold compressor system response is observed as presented.

Speaker: Dr Jonathon Howard (Michigan State University)

368 C3Or2B-02: Development and verification of a transient operating methodology for pump-down operation of 2K cold compressor system

Multi-stage cryogenic centrifugal compressor (cold compressors or CCs) trains used in 2 K sub-atmospheric refrigeration systems require a transient process operation (or ‘pump-down’) to establish the target low-pressure steady-state conditions. In sub-atmospheric refrigeration systems for superconducting radio frequency (SRF) cavities, the pump-down process establishes a pressure ratio of approximately 40 (i.e. ~ 30 mbar at the load) across the cold compressor train starting from unity. The compressor train is typically controlled with a lead compressor while the rest of the compressors are coupled through electronic speed ratios. Historically, the transient variation of the electronic speed ratios and the mass flow during the pump-down process has been determined empirically through a tedious trial and error testing process. Often this empirical approach resulted in a pump-down process path that is either unstable or longer than optimally possible. A 1D transient numerical model for the cold compressor pump-down process has been developed to predict and characterize dynamic behavior of the sub-atmospheric system (cold compressors, loads and associated cryogenic distribution). A transient operating algorithm to select the system parameters, i.e. CC speed ratio and overall flow variation, during the pump-down process utilizing the developed model and cold compressor performance maps is proposed. Extensive tests have been performed using the FRIB sub-atmospheric refrigeration system to validate the developed model and to check the applicability of the proposed algorithm. Excellent agreement between the model predictions and the test data provided evidence that improvement in theoretical understanding of the sub-atmospheric system has resulted in simplifications of the pump-down process path. Simplicity of the pump-down process path provides additional benefits of increased reliability and stability of the transient pump-down process.

Speaker: Dr Jonathon Howard (Michigan State University)

369 C3Or2B-03: Optimising cryogenic solutions for STEP: addressing cooling challenges and enhancing energy efficiency

The STEP program is an ambitious initiative designed to demonstrate, for the first time, a fusion energy prototype power plant capable of delivering net power (>~100 MWe) to the electrical grid. Planned for construction in West Burton, Nottinghamshire, UK, the tokamak system will utilise high-temperature superconducting (HTS) coils to generate and sustain the magnetic field needed to confine plasma. These superconducting magnets will operate at approximately 20K, cooled by supercritical helium, requiring substantial cryogenic power. Additionally, systems such as fuel cycling, thermal shielding, and current feeders will contribute to significant cooling power demand. STEP and future commercial fusion power plants will require substantial refrigeration capacity at various cryogenic temperatures, approximately 80K, 50K, and 15K, with an estimated total cooling power demand equivalent to ~100 kW at 4.2K. So far, STEP has developed a concept for the cryogenic plant and is currently exploring innovative ideas for distributing cryogenic coolants and optimising energy efficiency. Achieving commercial viability for STEP requires addressing key challenges, including minimising parasitic electrical loads to maximise net power generation. This work focuses on the challenges of developing a cryo distribution system for the STEP Prototype powerplant. This cryo distribution must comply with a number of critical requirements such as:
1) Distributing cryogens of different temperatures
2) Managing transient impacts (linked to powerplant operations) - this may be achieved with a cryo buffer
3) Managing supply of different cryogens across a multitude of locations within the powerplant
The proposed buffer plays a crucial role in managing cooling circuits. Through a simulation study handling heat loads of up to 10 kW, the work outlines the associated electrical and refrigeration capacity requirements.
This work represents a significant step forward in the development of large-scale cryogenic systems essential for STEP and future fusion power plants.

Acknowledgements
This work has been funded by STEP, a major technology and infrastructure programme led by UK Industrial Fusion Solutions Ltd (UKIFS), which aims to deliver the UK’s prototype fusion power plant and a path to the commercial viability of fusion.

Speaker: Dr David Aliaga (UKAEA)

370 C3Or2B-04: Performance Testing of the 4kW ESR 2 Refrigerator at JLab

The End Station Refrigerator 2 (ESR2) is the eventual replacement for the ESR1. ESR2 is a refurbished cryoplant comprised of the cold box and compressors of the 4 kW at 4.5K ASST-A plant from the Superconducting Super Collider in Texas. Additionally, ESR2 is equipped with a 10 m3 liquid helium Dewar, cryogenic distribution system including more than 50m long cold transfer line, control system, utility system. ESR2 cryoplant was repurposed to produce cold helium supply at 15K, 12K and 8K temperatures for the experimental hall target loads. The MOLLER target is the most demanding, 5kW equivalent at 15K temperature target load for the ESR2. This paper reports the commissioning results of the 4.5K refrigeration system at max refrigeration, max liquefaction, and 50/50 at both 100% and 50% capacity modes; the expected MOLLER load, and compares the current performance with past commissioning performance for the cold box when it was part of the ASST-A plant.

Speaker: Christopher Perry (Thomas Jefferson National Accelerator Facility)

371 C3Or2B-05: Impact of Power Outage for Large scale cryogenic system operation

The SLAC National Accelerator Laboratory is home to LCLS-II, a world-class X-ray laser. The LCLS-II superconducting linac is supported by a cryogenic system comprising two identical subsystems, each featuring a warm helium compressor system, an 18 kW (at 4.5 K) coldbox, and a 5-stage 2 K cold compressor train with a cooling capacity of 4 kW at 2.0 K. Installed and commissioned between 2018 and 2022, the cryogenic system has encountered several power outages since beginning operation in 2022, presenting significant operational challenges. This paper highlights the most notable power outage incidents, their impact on the cryogenic infrastructure, and the measures undertaken to address these challenges. The lessons learned provide valuable insights into enhancing the resilience of complex cryogenic systems to power and other utility outages.

Speaker: Swapnil Shrishrimal (SLAC National Accelerator Laboratory)

C3Or2C - Cryogenics for HTS Applications

372 C3Or2C-01: Conceptual cryodistribution system layout and modeling for Infinity One

The Infinity One Fusion machine is an HTS-based stellarator currently being designed by Type One Energy Group Inc. Several components of this machine such as its superconducting magnets, current leads, thermal shields, vacuum pumping system, and fuel injection system require cooling at cryogenic temperatures. The cryogenic distribution system is responsible for delivering helium at the appropriate temperatures, pressures and flow rates to some of these interfacing systems. This work presents the design of such a cryodistribution system working across many sub-systems and operational modes. The initial modeling results are presented to demonstrate how the various challenges are addressed.

*Affiliations are based on people’s employment at Type One Energy at the time the work was performed.

Speaker: Dr Ben Hamilton (Type One Energy)

373 C3Or2C-02: Thermal shield design for Infinity One

Infinity One is an HTS based stellarator currently being designed by Type One Energy Group Inc. Its superconducting magnets require thermal shielding to efficiently operate at cryogenic temperatures. The machine has two thermal shields, one between the cryostat and the magnets (the cryostat thermal shield) and the second between the vacuum vessel and the magnets (vacuum vessel thermal shield). This work will discuss the design aspects of these thermal shields as well as other heat intercept mechanisms.

Speaker: Dr Mark Vanderlaan (Type One Energy)

374 C3Or2C-03: A compact, exchangeable and fast-cooling cryogenic system for HTS antennas

This paper explores the cooling demands of high-temperature superconducting microwave receiver front-ends, specifically aiming at microstrip antennas within a cryogenic subsystem. Firstly, a transient heat transfer model was developed based on experiments with a 3W@77K pulse tube cryocooler. Then, a cryogenic system with a 15W@77K cryocooler was designed from this model, achieving a cooling time to 75K of 17 minutes and a minimum temperature below 50K, after optimization of heat transfer paths and interface thermal resistance. Furthermore, a thermo-mechanical coupling structure was designed to facilitate rapid cryocooler replacement without compromising the devices’ vacuum environment. This configuration allows the antenna to reach 75K in 22 minutes, with a minimum temperature below 55K. The research contributes valuable insights for the design and optimization of cryogenic subsystems in high-temperature superconducting microwave receiver front-ends.

Speaker: Hongwei Zhang (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)

375 C3Or2C-04: Testbed for high current and high voltage characterization of gaseous helium cooled HTS power cables for electric transport systems

High temperature superconducting (HTS) power cables offer promising solutions for electric aircraft and ships with power demands of up to 50 MW and 100 MW, respectively. However, their cryogenic cooling requirements present challenges. While liquid nitrogen is used for the grid applications of HTS cables, its limited temperature range (63-77 K) and asphyxiation risks make it suboptimal for transport applications. Gaseous helium emerges as a superior alternative, offering operational flexibility and broader temperature ranges without a phase change, despite its lower heat capacity and low dielectric strength of 4 kV/mm at 20 bar and 77 K. HTS cables’ low mass and footprint make them particularly suitable for transport applications, leading to several ongoing developments in gaseous helium cooling systems, high-voltage designs, and cryogenic dielectrics.
The reliable operation of HTS cables at their intended voltage and current levels requires characterizing their electrical insulation systems and cryogenic thermal designs. Partial discharge inception voltage (PDIV) is a critical diagnostic tool for dielectric design validation. Partial discharge, when localized electrical stress exceeds the dielectric strength of small voids or defects within the insulation, generates tiny electrical pulses typically measured in picocoulombs (pC). These microscopic discharges, while small, can indicate insulation degradation and potential failure points, making PD monitoring essential for evaluating the long-term reliability of cryogenic cable systems. PD measurements present unique challenges in cryogenic circulation systems due to their inherent sensitivity to electromagnetic interference and noise. Traditionally, PD measurements in HTS systems have been conducted using Faraday cages for electromagnetic shielding, with the dielectric samples being investigated in a stagnant helium gas environment created through immersed gas cooling in liquid nitrogen. However, integrating a helium circulation system into the test loop introduces complexity due to the electromagnetic noise generated by operational components, such as compressors, circulation systems, and vacuum pumps, that can interfere with precise PD measurement. This dynamic environment necessitates implementing different measuring techniques and noise filtering strategies beyond conventional shielding methods. To address these challenges, we studied a 3-meter long HTS cable testbed integrated with a cryogenic circulation system, incorporating specialized measurement methodologies to tackle the measurement challenges in this dynamic setting. We performed comprehensive PD measurements to evaluate the dielectric properties and thermal management capabilities of GHe-cooled power cables. A custom-designed electrical break was incorporated into the testbed to ensure the safe isolation of the high voltage components from the cryogenic circulation system, enabling reliable PD measurements while maintaining thermal performance. The correlations between PD activity, operating conditions, and system parameters establish critical design guidelines for high-voltage and high current cryogenic power distribution systems in electric transportation platforms where partial discharge resilience is important for long-term reliability. The paper discusses the cable models, measurement techniques, experimental results, and practical insights derived from the testbed.

Speaker: Paul Mensah

376 C3Or2C-05: Low-loss cryostat for high-Tc-superconducting cables

As the demand for electric energy continues to grow, high-$T_c$-superconducting (HTS) power cables are an attractive opportunity to strengthen the electrical grid, owing to the fact that they can carry high amount of currents with low losses and a relatively compact cross section.
However, all practical superconducting materials still require operation at cryogenic temperatures. These temperatures need to be maintained over a long cable length with minimal amount of cooling power. Engineering and manufacturing a low-loss thermally insulating pipe is thus one of the crucial building blocks in order to enable commercialization of superconducting power cables.
In order to achieve a low thermal inleak, vacuum super-insulation has proven to be the most promising approach. Vacuum-insulated cryogenic lines are commonly used for transport of cryogenic liquids such as nitrogen, helium and liquefied natural gas.
Superconducting power cables, however, pose more stringent requirements on the vacuum insulated line: In addition to the extremely low thermal leaks that are needed to enable long transmission length, mechanical constraints play an important role. The most relevant of these constraints are the weight of the cable, a low bending radius for transport and installation in urban environments, and high forces during cable pulling.
This contribution presents a novel design for a vacuum-insulated cryogenic tube, taking into account the specific requirements for HTS power cables. The thermal performance of a 12-m prototype was measured with boil-off calorimetry in different load scenarios, showing a < 1 W/m thermal leak even under unfavorable conditions such as mechanical load from the cable and bends.

Speakers: Dag Willen, Martin Pitzer (NKT GmbH & Co KG)

M3Or2A - High Purity Aluminum for Low Temperature Conductor Applications

377 M3Or2A-01: [Invited] The effects of monotonic and cyclic plastic strain at 4.2K on the electrical resistivity of bulk Al High Purity Aluminum”

The use of high purity aluminum (HPAL) for low temperature electrical conductor applications has been a subject of study for more than 50 years. The attractions include low density, very low electrical resistivity material at reasonable cost, and very low magneto-resistivity, all compared to those metrics for oxygen free high conductivity copper (OFHC Cu). The chief drawbacks to using Al are very low mechanical strength and difficulties in making electrical joints. Cu is chosen over Al for low temperature cryo-conductor or composite superconductor stabilizer applications primarily because of its mechanical and electrical contact and joining advantages. Because of the increased interest in low temperature conductor materials for aerospace and space applications in recent years, where weight is important, the possible use of HPAL for cryoconductors has enjoyed a comeback. An important aspect of a low resistivity conductor is that it retains its low resistivity during fabrication and use. Plastic strain to HPAL will cause an increase in resistivity, so it is important to understand the relationship between these variables. The work reported will discuss how monotonic and cyclic plastic strain at cryogenic temperatures influence the electrical resistivity of HPAL. This work involved cryogenic tensile and cyclic plastic strain experiments on centimeter diameter bars of 4N to 5N5 Al. Resistivity measurements were taken by a contactless method during the plastic strain testing. An interesting result of cryogenic cyclic plastic strain on HPAL is that the material becomes fully hard after several hundred strain cycles.

Speaker: Karl Hartwig

378 M3Or2A-02: Developing practical Cryogenic high purity aluminum (HPAL) conductor to enable high speed power density motors and generators.

Cryogenic high purity aluminum (HPAL) conductor was originally developed and reported at the Air Force Research Laboratories in the 1980s. The basic idea was to exploit the potential to fabricate very high purity aluminum (5 or 6 ‘nines’ Al), which could achieve exceedingly low resistivity values in the 20 K and below temperature range. By using very high purity Al, the resistivity ratios (RRR) of 2000 or more became possible at 20 K. Since typical RRR is 100 for standard oxygen free, high conductivity (101) Cu, this leads to a resistivity potentially 20 X lower than cryogenic Cu, or > 2000 X times lower than ambient temperature Cu. HPAL transports high current densities with minimal Joule heating. However, it’s mechanical softness requires the addition of a strengthening component. Efforts to strengthen the material utilizing an Al-Fe-Ce sheath were successful, but this sheath had a moderately low resistivity that showed a significant anomalous magnetoresistance due to Hall effect around the sheath. Hyper Tech have successfully developed a multi-filamentary HPAL conductor which employs matrices and sheaths with higher resistivity to suppress the anomalous magnetoresistance counterpart. Such conductors would be similar to commercially available Cu Litz cables but with the advantage of low resistivity at low temperature of HPAL. We also made it into a cable, and wound it to form coils. In this paper, we will present the progress of making long length HPAL conductor and its applications on high frequency stator and generators in Hyper Tech.

Speaker: Dr Xuan Peng

379 M3Or2A-03: The Ultrafine Copper-Clad Super-High-Purity Aluminum Wires

To achieve Net Zero CO2 Emissions by 2050, aircraft industries are conducting extensive studies for future aircraft using new technologies such as hydrogen aircraft and electric aircraft. Since those new aircraft should carry liquid Hydrogen, its cryogenic temperature of 20K could be expected to be used as a coolant for the efficient fan motor and generator. Super-high-purity aluminum is a promising conductor material for cryogenic electric aircraft because of its excellent electrical and thermal conductivity and lightweight. However, pure Aluminum shows very soft and weak yield strength, which makes it difficult the wire-drawing to small diameters. In addition, general solders using conventional tin alloy would not be acceptable because of the existence of the passivation thin film on the surface of pure Aluminum.
In this study, we have successfully fabricated the copper-clad super-high-purity aluminum ultrafine wires 0.05 mm in diameter, which are smaller than human hair. An initial simple billet was prepared in which a super-high-purity aluminum rod (5N5) 6.0 mm in diameter was inserted into the pure copper tube with 8.0 mm outer and 6.4 mm inner diameters. The aluminum rods and copper tube were carefully cleaned using the ultrasonic bath before assembling the billet in the clean booth of class 1,000 (USA Fed. Std. 209E). The rotary swaging was applied at the beginning of area reduction and then the continuous diamond die-drawing was applied using the slip-typed multi-die drawing machine. There was no wire breakage on the cold drawing from 8.0 mm to 0.05 mm. The maximum drawing speed was 800m/min, which is comparable to the mass-production speed of general electro-copper fine wires. The volume fraction of super-high-purity aluminum on 0.05 mm wire is approximately 54%, and the maximum tensile strength and elongation at room temperature are 342 MPa and 2.4%, respectively. Resistivity from room temperature (300K) to 10K has been measured by a DC four-probe method and RRR (residual resistivity ratio, 300K/20K) will be reported.

Speaker: Dr Akihiro Kikuchi (National Institute for Materials Science)

380 M3Or2A-04: Investigating the impact of tensile stress-induced/annealing-affected dislocation and grain boundary on the performance of High Purity Aluminum Wire by EBSD.

It is essential to develop lightweight cables with low AC loss in the application of electric aviation. High Purity Aluminum (HPAL), which operates effectively at cryogenic temperature, has been developed to compete with superconductors especially in higher frequencies. HPAL, characterized by 99.999% aluminum purity, achieves a residual resistivity ratio (RRR) up to 1000. It has minimum impurities, dislocations, and defects resulting in remarkably low resistivity at cryogenic temperatures, but at the same time, the mechanical properties of HPAL itself are inadequate for practical application. HyperTech Research developed a multi-strands HPAL wire with Cu-Ni matrix and Nb barrier to provide sufficient mechanical support. However, we wish to explore the microstructure and performance of HPAL wire under strain due to tensile stress, thermal stress. In this study, we performed Electron Backscatter Diffraction (EBSD) analysis on various HPAL wires to evaluate the impact of tensile stress and annealing on density of dislocations and grain boundaries which influence RRR. The yield stress and ultimate tensile stress of the HPAL wire were first measured using a material testing system (MTS). Subsequently, we prepared three samples for tensile stress analysis: i) As received; ii) Subjected to 0.5 × yield stress; iii) Subjected to 1 × yield stress. To investigate the effects of annealing temperature, we prepared additional samples: i) No heat treatment; ii) Annealed at 200°C; iii) Annealed at 400°C. We measured the RRR of these samples and conducted EBSD analysis to characterize dislocations and grain boundaries. The results indicate that tensile stress induces dislocations, reducing the RRR of HPAL. Conversely, annealing decreases the density of dislocations and grain boundaries, leading to an increase in RRR. In addition, future study will include EBSD analysis to further investigate how cyclic stress affects dislocations and grain boundaries. This study is funded by NASA phase I SBIR

Speaker: Mr Yang Guo (The Ohio State University)

381 M3Or2A-05: Impact of anomalous magnetoresistance and cyclic deformation on RR values of HPAL composites at low temperatures

High power-density motors are required to meet demand for increasing interest in aircraft electrification. To reach these requirements high current density and lightweight conductors are required in the motor windings. With liquid cryogen on-board, low temperatures (20 K with LH2) are achievable where very high purity normal metals benefit from resistance ratio (RR) values of up to 1000. This high RR occur not only due to high purity, but also low levels of defects (including grain boundaries and dislocations). High-purity Aluminum (HPAL) is one such material where 99.999% or higher purity allows for highly competitive mass-specific amperage capacity due to high RR values at 20 K and its low mass density of 2.7 g/cm3. However, HPAL intrinsically possesses low yield and tensile strength and requires a strengthening matrix for use in applications. Previous work on HPAL multifilamentary composites successfully developed Al-alloy metal matrix to increase composite strength without degrading HPAL purity, but faced degradation in RR values in electric windings due to an anomalous magnetoresistance contribution. We demonstrate here that a higher resistivity matrix can quench this anomalous magnetoresistance. A second issue seen in previous HPAL composites was the presence of RR degradation with cycling. However, the new composite design has a higher elastic modulus in order to enable higher stress before RR degradation. In this work we measure the effect of cyclic deformation on RRR in HPAL composites at low temperatures in a new testing fixture. We correlate this with SEM and EBSD measurements.
Work was performed under NASA Phase I SBIR

Speaker: Mr Jin Kwon

C3Or3A - Cryogenic Test Facility Commissioning

382 C3Or3A-01: Commissioning of the DALS Test Facility Cryogenic System

Dalian Advanced Light Source (DALS), located at Dalian, China, aims to construct a new light source that can generate high brightness X-Ray pulses. The DALS, which consists of 12 cryomodules, based on the Superconducting Radio Frequency (SRF) technology for the linear accelerator operating in continuous wave. Before the construction of the DALS, a series of test facilities, including vertical test cryostats (VTC), horizontal test bench (HTB) and injector test bench (ITB), have been built to test the key SRF components. A Test Facility Cryo-Plant (TFCP) with an equivalent cooling capacity of 370 W@2 K has been built to provide the cryogens for the test facilities. The cold box of TFCP was designed to provide 2500 W cooling capacity at the temperature range 40-80 K, and a total mass flow of 29 g/s helium at a pressure of 3.5 bara and a temperature of 4.6 K. The cryogens from the cold box are distributed to each test bench, where liquid helium (LHe) is converted to saturated 2 K He-II through a Joule-Thomson (J-T) valve, a 2 K heat exchanger (JTHX), and a process vacuum pump system (PVPS). After three years of development, the entire cryogenic system has been constructed and thoroughly tested. This paper gives an overview of the cooling requirements, the process design and the commissioning results of the installed cryo-plant.

Speaker: Huikun Su (Institute of Advanced Science Facilities ,Shenzhen)

383 C3Or3A-02: Commissioning and cooldown results of DALS test facility distribution system

The purpose of the Dalian Advanced Light Source (DALS) Test Facility project is to test core components of DALS accelerators, such as cryomodules and superconducting cavities. The project includes a horizontal testbench (HTB) for cryomodule test, a vertical testbench (VTB) for superconducting cavity test, and an injector testbench (ITB) for beam test. The cryogenic system of the test facility has a capacity of 370 W@2 K. In addition to the refrigerator system, the most critical part of the cryogenic system is the distribution system (CDS). The distribution system has now been installed and successfully commissioned with the VTB and HTB. Its first cooldown process has also been completed. This paper introduces the distribution system process and cooldown requirements, analyzes the commissioning results, and discusses the possible improvements in the future operation.

Speaker: Zheng Sun (Dalian Institute of Chemical Physics)

384 C3Or3A-03: First cool down of the vertical test cryostat for DALS SRF cavities

The Dalian Advanced Light Source (DALS) test facility has developed a vertical test cryostat to measure the quality factor and accelerating gradient of SRF cavities at a nominal temperature of 2 K. The cryostat employs a dedicated insert that can accommodate four cavities simultaneously. A built-in phase separator of the cryostat aims to pre-cool the supply helium and further facilitates the conversion of liquid helium into He Ⅱ. Commissioning and first cool down of the vertical test cryostat were finished in November 2024. The maximum helium flow rate of 57 g/s at 4.5 K was provided when the cavities cooled through Tc. The static heat load measurement of the cryostat was conducted, which agrees qualitatively well with the simulation results. This paper presents the flow scheme, design, cold commissioning and heat load performance of the vertical test cryostat.

Speakers: Xu Shi (Dalian Institute of Chemical Physics, Chinese Academy of Sciences), Zheng Sun (Dalian Institute of Chemical Physics, Chinese Academy of Sciences)

385 C3Or3A-04: INFN DarkSide-20k AAr cryogenic purification system

In 2023 Criotec Impianti Srl was awarded the CERN contract covering the design, manufacturing, and installation of the cryogenic system for the Neutrino Platform Dark Side-20k proximity cryogenics.
The DarkSide-20k experiment consists of an inner detector housed within a sealed stainless steel vessel and an outer muon veto, deployed within a ProtoDUNE-style membrane cryostat. It is currently under construction in Hall-C of the Gran Sasso National Laboratory, the world largest underground laboratory for neutrino and astroparticle physics, located in Italy It is designed to either detect eventual Weak Interacting Massive Particle (WIMP) dark matter or to exclude a large fraction of the favored WIMP parameter space.

The scope of the CERN contract included the design, manufacturing and installation of:
- eight cryogenic valve boxes
- one warm valve box
- sixteen cryogenic vacuum super-insulated transfer lines distributing liquid and gas argon and liquid and gas nitrogen between cryogenic storage vessels, the valve boxes, and the 600-Ton liquid argon cryostat, for a total length of more than 200 m.

Each cold valve box, vacuum insulated and equipped with cryogenic valves between DN10 and DN65, performs a specific function within the proximity cryogenic system.

As the liquid argon used in the detection process needs to have a purity level in parts per million (ppm) oxygen equivalent and shall be cleaned from radon, the required detector sensitivity entails stringent purity requirements for the liquid argon, at the levels of less than 0.1 ppm for oxygen and less than 1 ppm for water and nitrogen. For this purpose, the cold and warm argon gas, as wel as the liquid argon are purified by means of several purifiers equipped with a molecular sieve to trap water, a copper-coated alumina to trap oxygen, and an activated charcoal filter to trap radon particles.

The cryostat boil-off argon is recondensed in the gas argon condenser box by vaporization of the liquid nitrogen.

A liquid nitrogen phase separator is used to ensure a saturated liquid nitrogen phase to the argon condenser, while a liquid argon phase separator is used to ensure a saturated liquid argon phase returning to the cryostat.

The circulation of liquid argon from the condenser and from the cryostat through the filtering systems is guaranteed through two liquid argon pump valve boxes, each of them equipped with a liquid argon circulation pump.

All the valve boxes, having a diameter in the range 900-1700 mm and a weight between 400 and 1300 kg, are installed on a 4-floors, 14 m high metal structure.

During the design phase, detailed FEM structural analysis have been performed to assess the mechanical performance of the cryogenic system under different load cases, including severe seismic conditions.

Speaker: Marco Roveta

386 C3Or3A-05: Experimental investigation of moisture freeze-out in a cryogenic heat exchanger for helium purification

Purification of the process gas is vital for reliable operation of cryogenic systems. For helium cryogenic systems operating at 4.5 K or below, this is critical as any matter other than the process gas (helium) will freeze and act as a solid contaminant. Persistent low-level contamination (mainly the constituents of air and moisture) at levels greater than 1.0 ppmv, will degrade the performance of the refrigerator by freezing out on the heat transfer surface of heat exchangers as well as freezing out on other localized areas such as valves and turbo-expanders. Removal of low levels of moisture (1-100 ppmv) through fixed bed adsorbers loses effectiveness over the operational life, and the regeneration process can be tedious. In contrast, moisture removal by freeze-out process provides excellent control over a wide range of concentration and a relatively effective and quick turnaround for the regeneration process. However, the freeze-out process requires a heat exchanger design that is well suited for contaminant solidification distribution with a minimal impact on the flow distribution and heat exchange process. It also requires a better understanding of the moisture freeze-out from a process gas stream, subsequent frost formation on the heat exchanger surface, and the underlying conjugate heat and mass transfer processes. Frost formation in a cryogenic (300-80K) multi-pass tube in tube heat exchanger, integrated in a commercial helium purifier, is studied. An experimental test bench incorporating the commercial helium purifier and a novel low level contaminated (with 10-100 ppmv of moisture) process gas generator is developed. The moisture freeze-out process in the test heat exchanger is studied under controlled conditions as well as real world scenario. Transient data relating heat exchanger performance (NTU), associated pressure drop, and deposited frost mass are collected. The effect of moisture concentration and heat exchanger cooling profiles (due to flow imbalance) on the heat exchanger performance (NTU) degradation and frost deposition characteristics are investigated. Simulations from a 1D transient numerical model developed at FRIB have been used to get insights on the frost formation profile in the test heat exchanger and volume averaged frost properties. Outcomes relating the frost properties, frost collection capacity, and heat exchanger performance degradation are reported.

Speaker: Dr Duncan Kroll (Michigan State University)

C3Or3B - New Devices, Novel Concepts, and Miscellaneous III

387 C3Or3B-01: High pressure burst tests at cryogenic temperatures

So called moderators are key components of a neutron source and are used to slow down high energy neutrons, released by a nuclear reaction, to a required energy. Cold neutrons (ca. 10 meV energy) are required for a variety of experiments, which is why (cold) moderators are an important part of a neutron source. A pressure vessel filled with liquid para hydrogen is for example a suitable cold moderator. The vessel must be made of aluminum with thin walls so that not too many neutrons are absorbed. The challenge is to manufacture an aluminum pressure vessel with minimal material content that meets the high safety requirements of a nuclear facility. Moderators for various facilities have been designed, manufactured and tested at the ITE of Forschungszentrum Jülich. In order to validate the results of the simulations, a test method has been developed in which the moderator vessels to be tested are made to burst at the temperature of liquid nitrogen. In this presentation, high speed camara video sequences showing the explosive failure of various moderators at cryogenic temperatures will be compared with the predictions of dynamic simulations.

Speaker: Eberhard Rosenthal

388 C3Or3B-02: Cryogenics in the drilling of deep, multi kilometer geothermal wells

The potential of geothermal resources is currently limited by existing drilling technology. To address this issue, the DeepU project is investigating the use of laser and cryogenic gas to drill deep wells (>4 km) to create a U-shaped closed-loop geothermal heat exchanger. This technology includes a high-power laser source and optics, a drill string, a drill head, a flushing system and some ancillary systems required for successful rock penetration. Supercritical nitrogen is transferred down the borehole, then after isenthalpic expansion of the gas, vitrifies the rock and flushes the rock debris to the surface. A complex mathematical model of nitrogen flow during the laser drilling was developed. Pneumatic transport modeling provided preliminary information on the required supply of supercritical nitrogen to provide the necessary cooling power and pneumatic transport of cuttings to the surface.
Vacuum insulation was selected for the supercritical nitrogen transfer pipe. No commercially available cryogenic transfer line couplings suitable for the DeepU operating parameters were found, so a custom coupling system was designed to ensure tightness, robustness and ease of assembly. Potential failure modes of the proposed system were identified and mitigation steps were proposed. The study demonstrates the feasibility of delivering supercritical nitrogen to a borehole several kilometers deep. The test campaign of selected process phenomena and design solutions is ongoing.

Speaker: Maciej Chorowski

389 C3Or3B-03: A methodology for evaluating MEMS switch reliability at cryogenic temperatures

Our goal is to develop testing methodologies to evaluate the performance and reliability of commercial off-the-shelf fully packaged MEMS switches for cryogenic applications. RF Micro Electro Mechanical Systems (MEMS) switches possess a number of advantages over conventional switches, such as lower insertion loss, high isolation and linearity, faster switching speed, smaller size, and very low power consumption. However commercially available MEMS switches are designed for room temperature operation and may exhibit several potential issues at cryogenic temperatures and with thermal cycling. When operated at cryogenic temperatures MEMS switches can have operational or reliability issues including material property changes, and temperature-induced thermal stresses, which can gradually affect the device’s performance over time. Since commercial MEMS are enclosed in sealed packages, we developed experimental methods to evaluate and monitor the gradual changes in the MEMS structural behavior . We purchased a single-pole, four-throw, electrostatically actuated commercial MEMS switch. The switch is sealed in a ceramic package on a printed circuit board. Next, we mounted the board on a custom thermal adapter on a cryostatic chamber’s cold stage. We cycled the cryostat from room temperature to around fifty degrees Kelvin in fifty-degree increments. Switch one had previously been tested at cryogenic temperatures and extensively tested at room temperature, as we had reported at CEC 2023. For this new set of tests, only switches one, two and three were operated at cryogenic temperatures. The fourth switch was also cycled through the temperature profile but was not operated below room temperature to serve as a control. Our team developed a set of four tests for the switches. The first test measured the resistance across a closed switch for one hour. Next, two types of hysteresis tests were performed, ramping power voltage to the switch from fifty to ninety volts and then back to fifty volts in one-volt increments. MEMS switches exhibit hysteresis, the voltage to turn on the switch (pull-down) is higher than the return voltage that opens the switch (pull-up). Two different measurements were made for the hysteresis tests. First, we measured resistance across the switch. Next, we measured a three-volt carrier voltage across the switch. For the final test, we cycled power to the switches at low frequency (0.5 Hertz) and measured residual voltage across the switch each time power was turned off. Our tests show that a single cooling cycle down to 55K was enough to induce subtle but permanent changes in a commercial MEMS switch’s characteristics. Therefore, these tests may be used to help monitor fully packaged commercial MEMS switches for potential drift or damage accumulation. It is envisioned that these test methods and data may help to predict and thus avoid MEMS switch failures in applications involving cryogenic temperatures. Future work involves testing the MEMS to lower temperatures and performing high-cycle tests.

Speaker: Mr Peter Bradley (1National Institute of Standards and Technology, Colorado USA)

390 C3Or3B-04: Development of hydrogen-filled traveling-wave thermoacoustic engine for powering pulse-tube and traveling-wave refrigerators

Current cryocooler technologies rely on compressors and displacers to generate pressure oscillations requiring high electrical power and regular maintenance intervals. These requirements limit the convenience of cryocoolers for renewable energy, specifically zero-boil-off applications. Thermoacoustic instabilities are spontaneously excited sound waves in resonators, which transport energy along a piping network. Utilizing these sound waves to remove heat from the cold space creates a robust paradigm for cryogenic refrigeration (cryocooling) with no moving parts. This study discusses the design and implementation of a thermoacoustic cryocooler using hydrogen as the working fluid. A toroidal acoustic resonator system is designed to excite traveling sound waves using an imposed temperature gradient on an engine regenerator between the ambient and hot heat exchangers. The generated acoustic waves then propagate into the pulse-tube or traveling-wave setup producing refrigeration in the cooler regenerator. Modeling techniques, results, and the optimal geometric configurations for the engine-refrigerator combinations are reported. The geometric configurations are selected to minimize the temperature gradient required in the engine core to reach a cryogenic temperature below 100 K for a single-stage pulse-tube or traveling-wave setup and produce acceptable cooling power and COP at 110 K. A goal of this initial study is to establish the feasibility of this new cooling paradigm which can be scaled up to intercept heat leak in liquid hydrogen storage vessels.

Speaker: Matthew Shenton (Washington State University)

391 C3Or3B-05: Large diameter helium pulsating heat pipe as promising thermal link for cryocooler-cooled superconducting magnet systems

Cryogenic pulsating heat pipes (PHPs) are considered as alternative efficient thermal link to cool moderate heat load superconducting devices to replace heavy thermal braids or gravity-assisted cooling loops associated in general to cryocooler as cold source. A perfect application to these type of heat pipe is rotating application such as Gantry system where gravity-assisted loops are prohibited. This motivates the development of cryogenic PHPs and especially at helium temperature. This work presents an experimental characterization of the thermal performance of a 0.4 m long helium PHP which consists of 20 turns of 1.0 mm inner diameter stainless steel tube with 120 mm long copper evaporator and condenser. The inner diameter of the tube is ˜1.75 times larger than that prescribed by the well-known Bond number criteria that is used to ensure that capillarity effect is dominant allowing plug/slug PHP mode. Despite the large diameter, the PHP presents interesting overall thermal resistance even if the PHP mode is not sustained. At higher heat loads, the PHP evaporator temperature is seen to surpass the helium supercritical temperature although the overall thermal resistance can be as low as 1.0 K/W. We have studied the effect of the orientation in testing the PHP in horizontal and vertical orientation. A study of the effect of filling ratio has also been showcased.

Speaker: Bertrand Baudouy (CEA Paris-Saclay)

392 C3Or3B-06: Compact nitrogen pulsating heat pipes – Experimental thermal analysis with numerical insights

With the increasing cryocooler-based cooling techniques, there is a growing demand for thermal links that efficiently transfer heat load to the cryocooler stages. This demand can be addressed by pulsating heat pipes (PHPs) designed to operate effectively at cryogenic temperatures.
Despite progress in this field, the current literature does not allow for precise prediction of PHP performance under cryogenic conditions. To address this gap, we propose a numerical model developed in OpenFOAM leveraging its flexibility for source code modification to meet specific research needs. The implementation of the model includes customized equations for phase fraction, momentum and energy, thereby incorporating phase change dynamics based on the Volume of Fluid approach.
In order to validate this numerical model, a compact PHP has been constructed with a simplified geometry to minimize computational resource requirements while maintaining functionality. A laboratory setup has been built to experimentally test the designed PHP at different cryogenic temperature ranges. The cooling is provided by a two-stage cryocooler having a cooling capacity of ~30 W at 77 K. The PHP is fabricated from stainless steel tubes with an inner diameter of 1.3 mm. It has projected overall dimensions of approximately 0.19 m x 0.11 m. Nitrogen is used as the working fluid with operating temperatures ranging from 77.3 to 94 K. The experimental tests reveal one of the highest effective thermal conductivity values reported for cryogenic PHPs of this size. We also present preliminary results validated against experimental data demonstrating the precision of the implemented model in predicting the thermal performance of cryogenic PHPs.

Speaker: Marcin Opalski (CEA Paris-Saclay, Wrocław University of Science and Technology)

393 C3Or3B-07: 50 Years of Innovation: Cryogenics and Superconductivity in Biomedical Applications

Cryogenics and superconductivity have revolutionized biomedical applications, particularly in cryosurgery and cryo-diagnostics. These technologies enable groundbreaking instruments and methods for precise medical interventions and advanced diagnostics. The development journey has been marked by significant technical challenges and milestones. This paper summarizes key achievements （including those of the authors） in this field and explores future advancements. Highlights include major cryosurgery instruments designed for various diseases, specialized particle accelerators for medical treatment, and superconducting quantum interference devices (SQUID) for cardiac and brain diagnostics, etc. Additionally, the paper briefly examines superconducting MRI and in-cell structural biology by NMR technologies, and as well as the potential of cryogenic organ preservation for transplantation. Together, these innovations underscore the transformative impact of cryogenics and superconductivity on modern medicine.

Speaker: Dr Quansheng Shu (Cryospc)

394 C3Or3B-08: Optimizing cryoprobe tip geometry for enhanced cryoablation efficacy: A numerical simulation approach

Cryoablation has emerged as a vital minimally invasive technique for treating localized cancers, leveraging cryogenic probes to freeze and destroy tumor tissues. The geometry of cryoprobe tips significantly influences the freezing dynamics, including heat transfer efficiency, ice ball propagation, and the preservation of surrounding healthy tissues.
This study investigates the impact of cryoprobe tip design on cryoablation efficacy through numerical simulations using COMSOL Multiphysics®. A two-dimensional axisymmetric tumor model embedded within tissue layers is constructed, integrating the Pennes bioheat transfer equation and tissue-specific thermophysical properties. Different cryoprobe tip geometries—spherical, cylindrical, and novel designs featuring conical and cylindrical protrusions—are evaluated under constant and pulsating freezing cycles.

Simulations reveal that the novel tip design, with its enhanced surface area, outperforms conventional geometries by achieving a higher frozen tumor fraction with a reduction in injury to healthy tissues compared to conventional tips, as well as improved thermal isotherm control. Additionally, the pulsating freezing cycle demonstrates improved preservation of surrounding healthy tissues while maintaining effective tumor ablation. Comparative analysis of frozen fraction versus time plots underscores the dependence of cryogenic activity on tip geometry, suggesting that optimized tip designs can enhance cryoablation efficacy while minimizing collateral damage. These findings provide valuable insights into cryoprobe tip engineering and contribute to advancing cryosurgical interventions for cancer treatment.

Keywords: Cryoablation, Cryoprobe Tip Geometry, Ice Ball Propagation, Pulsating Freezing Cycles, Numerical Simulation

Speaker: Dr Arpit Mishra (Indian Institute of Technology Kharagpur, India)

C3Or3C - Aerospace Cryocoolers III: Pulse Tube and Stirling II

395 C3Or3C-01: Characterization testing of the Thales LSF9589 cryocooler

Two Thales LSF9589 commercial off-the-shelf (COTS) Stirling cryocoolers were parametrically performance tested for cold tip temperatures between 37 K and 250 K, heat rejection temperatures between 0°C and 40°C, and drive frequencies between 46Hz and 51Hz . The effect of compressor and expander temperature difference is also discussed. Both LSF9589 coolers had identical transfer line configurations. The test results revealed small unit-to-unit thermodynamic performance variation between the two units tested. The thermodynamic performance of the LSF9589 is compared to that of the COTS LPT9510 pulse tube cooler that utilizes the same compressor as the LSF9589.

Speaker: Bradley Moore (JPL/Caltech)

396 C3Or3C-02: ABI life test cryocooler system 2025 update

The Advanced Baseline Imager (ABI) Pulse Tube Cryocooler System is a two-stage pulse
tube cryocooler designed to service space applications requiring simultaneous cooling of two separate optical assemblies at different temperatures, ultra-high reliability, and long lifetime. The mechanical cryocooler is a two-stage variant of the Northrop Grumman HEC (High Efficiency Cryocooler), consisting of an integral linear coldhead and a remote coaxial cold head. This two-stage HEC was designed to provide simultaneous cooling power of 2.27W at 53K at the linear stage and 5.14W at 183K at the remote stage. The ABI Cryocooler System was designed to meet 10-year lifetime requirements – to characterize long-term operation, a life test has been underway since 2009 under the supervision of L3Harris. From inception of the test, the total uptime has been 122,480.90 hours and achieved over 6.7 years of stable performance prior to launch on GOES-R. From June 2018, the life test has been operating at an elevated rejection temperature. The ABI Cooler System performance has remained anchored long past mission requirement life with no degradation in cooling performance. As presented in this paper, the test has shown that there is some performance variation in beginning of life to end of life, however data indicates this variation is predictable. This paper presents the performance data collected on the cooler during acceptance testing and over the course of the cooler’s life test and analyzes the relevant performance parameters against predicted performance.

Speaker: Harold Dzigiel (Northrop Grumman Corporation)

397 C3Or3C-03: Stationary testing of a 50 K pulse tube cryocooler designed to rotate with the shaft of a 1.4 MW electric machine

Electrified aircraft are being developed to address climate change and pollution by reducing the fuel burn and emissions of aircraft. Achieving a substantial impact necessitates focusing on single- and twin-aisle aircraft, which currently dominate world-wide emissions and contain propulsion systems with about 20+ MW ratings. Multi-MW superconducting electric machines are being developed to electrify these aircraft due to their very high specific power and, often more importantly, their very high efficiency. Most of these electric machines employ superconductors on their rotor, thereby requiring cryogenic cooling of the rotating system. An attractive solution is to conductively cool the rotor using a cryocooler that rotates with the rotor. NASA has been developing a 50 K pulse tube cryocooler for its high efficiency megawatt motor (HEMM) that can operate while rotating at 6,800 rpm. The design of this cryocooler and testing of its linear motor have been discussed in prior work [1-3].

This paper will present the first measurements of the complete HEMM cryocooler. The design and results of a stationary (non-rotating) test of the cryocooler will be described. The data will include the heat lift and coefficient of performance as a function of temperature, displacement of the piston, temperature distribution and the performance of the thermal management system, and vibration. A discussion of lessons learned in the manufacture and assembly of the cryocooler will also be presented. The primary performance data will be compared to existing predictions for the cryocooler obtained from commercial cryocooler design software and computational fluid dynamics simulations of the cryocooler’s heat exchanger. These predictions account for the measured performance of the linear motor.

The status of this work is as follows. All the fabricated parts of the cryocooler have been received. Most of those parts have been assembled to verify that the manufacturing was completed successfully. The test rig hardware has been received and assembly is underway. The linear motor has been assembled and tested, including successful operation at resonance using open loop control of the piston’s measured displacement. The remaining instrumentation will be received by end of December. The remaining tasks include completing the in-house joining of some feedthroughs and the regenerator (by end of December), assembling the remainder of the cryocooler and pressure testing it (by end of January), instrumenting the cryocooler and integrating it into the test rig (by end of February), and completing the testing (by mid-April). This leaves adequate time to prepare the presentation and secure internal approval to release it.

1. Dyson, R.W. et al., “High Efficiency Megawatt Machine Rotating Cryocooler Conceptual Design,” AIAA/IEEE Electric Aircraft Technologies Symposium, Indianapolis, IN, 2019.
2. Duffy, K.P. et al., “Design, Analysis, and Testing of the HEMM Cryocooler Linear Motor,” AIAA/IEEE Electric Aircraft Technologies Symposium, New Orleans, LA, 2020.
3. Duffy, K.P. and Szpak, G., “Dynamic Bellows for a Pulse Tube Cryocooler Application,” AIAA SCITECH 2022 Forum, AIAA 2022-0446, San Diego, CA, 2022.

Speaker: Mr William Sixel (NASA Glenn Research Center)

398 C3Or3C-04: Four-Stage Pulse Tube Cryocooler for NewATHENA

Lockheed Martin is one of three teams funded by NASA’s Goddard Space Flight Center to build demonstration model cryocoolers for the European Space Agency’s Advanced Telescope for High-Energy Astrophysics (NewATHENA) X-ray space telescope mission. The NewATHENA X-ray instrument presents some design challenges, including the requirement to separate the 4.5 K cryogenic stage approximately one meter away from the cold head’s warm interface. These challenges led Lockheed Martin to develop a unique “split cold head” configuration. The status of the development model cryocooler will be presented in this paper, along with some trade studies related to the unusual split cold head configuration.

© 2024 Lockheed Martin Corporation. All Rights Reserved

Speaker: Jeff Olson (Lockheed Martin Space)

399 C3Or3C-05: A Novel 3D Printed Regenerator Filler for Large Stirling and Pulse-Tube Cryocoolers

Large cryocoolers are needed for future In-Situ Resource Utilization (ISRU)-based production of cryogenic fuel material. This paper reports on the design and preliminary testing and simulation of a novel regenerator filler for Stirling and pulse-tube cryocoolers with 150W cooling power at 90K temperature. The regenerator is loaded with 3D printed 1 cm-thick ceramic disks that have flow features that are 75 µm wide. Each ceramic disk comprises 36 wedges. The disks are stacked to fill the regenerator. The disks are separated from each other by 200 µm-deep gaps to avoid flow blockage caused by misalignment among adjacent disks. Experimental data and CFD simulations addressing the flow and pressure drop in the stacks are presented and discussed.

Speakers: Ali Ghavami (Georgia Tech), Proshat Mehdizad

400 C3Or3C-06: Experimental research on a highly compact miniature coaxial pulse tube cryocooler at 80 K

Miniature coaxial pulse tube cryocoolers are widely used for cooling instruments in space science missions and military exploration fields due to their low vibration, long life, and high reliability and rapid cooling. In this study, a highly compact 0.91 kg miniature coaxial pulse tube cryocooler is developed. When the charging pressure is 4 MPa and 72 W of electrical power is inputted into the cryocooler, it can achieve a cooling power of 2.26 W at 80 K. The relative Carnot efficiency is 8.45% with a reject temperature of 295 K, and the operating frequency is 114 Hz. The cooling power per unit mass reaches 2.48 W/kg, which is the highest value in the 80 K temperature zone publicly reported in the miniature coaxial pulse tube cryocoolers, which means that while maintaining a compact structure, more cooling power can be provided under the same weight. In addition, the influence of input electrical power and charging pressure on the optimum frequency and the influence of frequency on the cooling rate are also experimentally studied. When the input power increases from 20 W to 60 W, the optimum frequency gradually increases. At low input power, there is an obvious optimum frequency to maximize the relative Carnot efficiency, but with the increase of input power, there is a frequency range to keep the performance basically stable, and only deviations from the range can cause the performance to decline significantly. When the charging pressure is reduced from 4 MPa to 3 MPa, the optimum frequency basically remains constant when the cold end temperature is about 51 K, but as the cold end temperature rises to 80 K, the charging pressure changes make the optimum frequency change. The research also found that in the early stage of the process where the cryocooler cools down from the ambient temperature to 80 K, not operating at the optimum frequency for the target temperature zone doesn't have a significant impact on the cooling rate. However, during the process when the cold end temperature drops from 120 K to 80 K, operating at the optimal frequency for the target temperature zone can obviously reduce the cooling time. That is, the influence of the frequency on the cooling time lies in the difference in the time required for the process in which the cold end temperature gradually approaches the target temperature zone in the later stage of cooling. This research provides valuable references for the further study and practical application of miniature pulse tube cryocoolers.

Speaker: Mr Zhixiang Yang (浙江大学)

401 C3Or3C-07: Research on the Influence of Average Pressure on the Thermodynamic Cycle and Performance of Pulse Tube Cryocoolers

With the increasing demand for miniaturized and high-performance pulse tube cryocoolers in space exploration, infrared remote sensing and other fields, how to improve the refrigeration quantity of pulse tube cryocoolers per unit volume has become the key to meet this demand. To improve the refrigeration quantity of a pulse tube cryocooler per unit volume, it is necessary to increase the energy transfer density of the working fluid per unit volume. The average pressure, as a key parameter affecting the energy transfer density of the working fluid, not only affects the thermodynamic cycle inside the pulse tube cryocooler, but also has a significant impact on the refrigeration performance of the cryocooler. In this study, a one-dimensional model of linear type pulse tube cryocooler based on Lagrange method is developed, and the mechanism of the influence of average pressure on the energy transfer density of working fluids is researched by this model. This study also validated the accuracy of numerical calculations and the rationality of theoretical analysis based on experimental research. The experimental results are consistent with the theoretical analysis, and the deviation between the numerical calculations and experimental results is between 10% and 20%. Based on the above mechanism, the selection methods of average pressure in different situations are summarized, and it provides theoretical support for high energy density pulse tube cryocoolers.

Speaker: Dr Liang MengLin (Technical Institute of Physics and Chemistry, Chinese Academy of Science)

C3Or3D - Large Scale Cryogenic Systems VIII: Fusion Systems

402 C3Or3D-01: ITER Cryogenic System Commissioning and Performance Testing

The ITER Cryogenic System is one of the largest Cryogenic facilities to build and commission. Main challenge is not only to demonstrate quite large cryogenic performance of machines but also to coordinate start-up and operation of a very large number and diversity of equipment in a multi-contract environment. To give overview, ITER Cryogenic System is mainly composed of three identical Liquid Helium plants of 75kWeq at 4.5K, two 80K Plants of 840kW at 80K, two nitrogen liquefiers with equivalent capacity of 26 LN2 trucks/day, a large Helium recovery & inventory management system and five Auxiliaries Cold-Boxes to distribute cryogens to Tokamak’s users.
While Cryodistribution system is entering its installation phase finalization with arrival of distribution boxes and associated warm panels in Tokamak’s galleries, Cryoplant is presently facing intensive commissioning phase with a very challenging performance testing plan to be achieved to support both Cryopumps & TF Coils Cold Test Facilities. This is key for ITER to achieve this objective duly on time to not alter Tokamak assembly schedule. Main challenges, outcomes and testing plan will be described.

Disclaimer: The views and opinions expressed herein do not necessarily reflect those of the ITER Organization

Speaker: Marie Cursan (ITER Organization)

403 C3Or3D-02: ITER LHe plants first tests results

ITER liquid helium plants (LHe plants) provide 75kW of cold power at 4.5K to cool-down the 10 000 tons of magnets, the cryopumps and the current leads of the tokamak. The 3 cold boxes delivering this power are one the most powerful equipment ever built at this level of temperature. Before being connected to the tokamak, these LHe plants shall pass a complex series of tests to demonstrate their performance in different operation modes, and their ability to operate together to mutualize their capacity. The test complexity will increase all along the test program. This paper describes the results of the 1st steps of this test program, namely, the performance of an individual plant operating in steady state mode and with pulsed heat loads. The final step of this ambitious test program is the operation of the 3 plants in parallel with pulsed heat loads.

Speakers: Jean-Marc Bernhardt (Air Liquide Advanced Technologies), Yannick Fabre (Air Liquide)

404 C3Or3D-03: Status of the ITER Cryodistribution System and future challenges

The ITER Cryodistribution (CD) system is designed to distribute and control the cooling power into the cold components of the Tokamak machine at appropriate temperature, pressure, and mass flow rate levels by forced convection. It consists mainly of one (1) Cryoplant Termination Cold Box (CTCB), five (5) Auxiliary Cold Boxes (ACBs), the (in-Tokamak) TS cooling system (TSCS) and a network of Cryogenic Lines (CLs) making the link between different cold boxes and connecting the CD to the final Tokamak machine clients.
The aim of this paper is to provide the current status of manufacturing and installation of CD system, as well as the upcoming phases. After detailed description of the ITER CD system and its design particularities, the manufacturing status of ACBs and the assembly and site-installation plan of the entire system will be presented. A focus will be made on developed installation procedures of ACBs and CLs considering the layout constraints and complexity arising from the integrated installation within the Tokamak building. Testing activities to demonstrate the mechanical integrity of Cryolines system will be discussed and results will be presented.
The views and opinions expressed herein do not necessarily reflect those of the ITER Organization

Speaker: Lahcene Benkheira

405 C3Or3D-04: Analysis of a cryogenic refrigerator solution for the ITER Isotope Separation System

The ITER project aims to build a fusion device with the goal of demonstrating the scientific and technical feasibility of fusion power. It is a joint project between the European Union, China, India, Japan, South Korea, the Russian Federation, and the USA. ITER is being built in Europe, at Cadarache in the south of France.
The ITER tokamak will be fuelled by streams of deuterium and tritium. The ratios of these injections will be varied to optimize the performance, and they will be injected by different systems. Additional gases for operation or by outgassing add to the fuelling gases and a gas mixture is exhausted from the tokamak. To reuse again the hydrogen isotopes in the fuel cycle of the ITER machine the exhaust gases need to be separated and purified.
After the separation of the hydrogen isotopes from any other gas species the hydrogens are transferred to the Isotope Separation System (ISS). To achieve the required purification rates the ISS uses cryogenic distillation to separate the hydrogen isotopes. The cryogenic distillation relies on the slight differences in boiling points (within 20 – 25 K range at atmospheric pressure) for the hydrogen isotopologues. Overall, six interconnected cryogenic distillation columns are needed to fulfil the functional requirements of the ISS.
The gas feeds to the cryogenic columns require cooling, prior entering the distillation columns at 20-25 K. Overall five actively cooled heat exchangers are needed in addition to the six condenser units of the distillation columns. Each of these eleven actively cooled components have quite different heat loads varying between a few 10ths of Watt to several 100s of Watt.
A further complexity for the cryogenic supply is that for the distillation of protium a supply temperature of 18 K is required but as this temperature is below the triple point temperature of D2, DT and T2 a solidification of these gases could occur in the process piping and lead to a blockage of the systems. Therefore, two supply temperatures need to be delivered by the refrigerator: One at 18 K with a power of ~600 W and one at 20 K with a power of ~900 W. For these reasons, in between the refrigerator and the components a cryogenic distribution valve box needs to be integrated to supply the required cooling flows at the right supply temperatures to the different clients of the Isotope Separation System.
This contribution will outline the required cryogenic cooling needs of the ITER ISS and compare a conventional helium refrigeration system with a Turbo Brayton Cycle based refrigerator. The conventional system is based on screw Helium Compressors with their required oil and heat removal systems followed by the expansion turbines with the counterflow heat exchangers. These systems are optimized for achieving high efficiency at 4 K and are therefore not ideal for the ISS, operating at different conditions. The conventional refrigerators are also very elaborate and require complex maintenance efforts. The Turbo Brayton Cycle refrigerators can be optimized to the supply cooling power at ISS temperature needs and is an oil free system. The development of high frequency sealed compressors and expansion turbines in the last years have made this technology attractive as it could be much more compact and needing much less maintenance as the conventional refrigerators.
The current available Turbo Brayton based refrigerators on the market do not achieve the required cooling powers in the available space of the ISS. Studies with industrial partners have been launched to compare the two refrigerator solutions and to determine the advantages and disadvantages of each solution for a future procurement decision.

Speaker: Matthias Dremel (Fusion for Energy)

406 C3Or3D-05: Overview of Design Developments for Condensable Vapor Devices for ITER

The ITER, meaning “the way” in Latin, aims to achieve sustainable fusion energy through self-heating plasma with a gain ≥ 10. The United States is one of the seven members of this prestigious project, which is in the advanced stages of construction in the south of France. The vacuum systems at ITER are critical to the project as they handle the evacuation and exhaust of the gases from the tokamak machine. The ITER Roughing Pump System (RPS), which is part of the vacuum system, consists of a series of roughing pumps and provides a means to evacuate all gases or mixtures of gases originating from the tokamak. These gases are then appropriately transferred to other systems such as the Tokamak Exhaust Processing (TEP), De-tritiation System (DS) or Heating, Ventilation and Air Conditioning (HVAC). These exhaust gases contain helium, isotopes of hydrogen and their combinations. Additionally, they contain water (H2O) and its isotopes such as heavy water (Deuterium Oxide, D2O) and tritiated water (T2O). The Condensable Vapor Devices (CVD), which are part of the RPS, are designed to separate such water content in order to protect downstream pumps and transfer the water to TEP for further processing. The CVDs operate on the principle that a cooling fluid (i.e., liquid nitrogen) cools the exhaust process gas from the tokamak, causing the water present in the process gas to condense and freeze, thereby trapping it in the CVD. The CVDs are then regenerated to release the trapped water molecules, which are sent to the TEP.
The present article will describe the technical requirements, challenges, and design progress made so far in the development of the CVDs.

Keywords: ITER, Vacuum systems, Roughing Pump Systems, Condensable Vapor Devices, cryogenic water traps

Disclaimer: This work was supported by the U.S. Department of Energy contract DE-AC05-00OR22725. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.

Speaker: Ketan Choukekar (Oak Ridge National Laboratory)

407 C3Or3D-06: Cooling the SPARC fusion reactor – A large-scale helium refrigerator designed for transient loads and high availability

A large-scale cryoplant is supplied by Linde Kryotechnik for the SPARC project, where a fusion reactor of type Tokamak requires a dedicated cooling. The cryoplant provides various combined cooling powers of up to 100kW shield load between 80K and 100K, up to 15kW at 15K and up to 25kW at 8K.
The compressor station consists of two large oil-lubricated screw compressors with variable frequency drives, an oil-removal system, and a gas management panel. In addition, the plant accommodates a purification unit.
The refrigerator process, housed in a horizontal cold box, is based on a Brayton cycle with three turbine strings (6 LKT TED turbines) as well as special nitrogen pre-cooling. The 15K and the 8K cooling loops are each connected to heat exchangers of the primary cycle by a secondary loop, where cold circulators establish the demanded flows.
Due to the pulsed operation of the fusion reactor, the refrigerator will face transient loads and return temperatures, thus requiring unique solutions for process design and process control. To ensure high reliability even under these transient loads, the system is equipped with various redundancies regarding equipment and instrumentation.
Besides the steady-state operation, the cryoplant can provide around 300kW between 80K and 130K. Furthermore, due to the immense cold mass of the fusion reactor, a fast-controlled cooldown/warmup that offers more than 300kW is requested. Both requirements have been efficiently tackled by a special nitrogen evaporator design.

Speaker: Dr Markus Diehl (Linde Kryotechnik AG)

408 C3Or3D-07: MCTB Cryogenic Systems Design and Analysis

The Magnet Cold Test Bench (MCTB) cryogenic systems are composed of one as-built LHE plant, Cryolines with Interconnection Valve Box (IVB) which are under development, and MCTB auxiliary System. MCTB tests include phase I: CICC jumper test, and phase II: full TF magnet test. The MCTB cryogenic systems are specifically designed and tailored for cryogenic clients such as TF coils, LTS busbars, TF case, Magnet Supports and Shields at 4.5K, as well as the HTS current leads at 50K. The average equivalent cooling power of one LHE Plant is 25kW at 4.5K, which needs to be turned down to approximately 5kW at 4.5K to meet the heat load requirements of magnet testing. A total of approximately 150 meters of cryogenic transfer lines are used to transport and distribute helium to the Coil Terminal Box (CTB) and TF magnet. The IVB serves to connect the CTB with the Cryoplant and condition helium states.
This paper presents the design and development progress of the new cryogenic system and highlights the challenges encountered. It also includes an analysis of the cryogenic plant's customized turndown performance tailored to the MCTB's requirements, supported by simulations and dynamic analyses of heat loads under various operating scenarios. These studies provide practical insights for the MCTB commissioning and future cold tests.

Speaker: Lilong Qiu (ITER Organization)

M3Or3A - [Special Session] Transportation III: High Power Components, Thermal Management

409 M3Or3A-01: [Invited] Cryogenic Thermal Management of Power Conversion Devices on Liquid Hydrogen Fueled Electric Aircraft

Cryogenic propulsion with hydrogen-burning electric generators and fuel cells is a promising way to reduce aviation carbon emissions. Liquid hydrogen serves as aircraft fuel and a 20 K heat sink for superconducting and other electrical devices. Power electronics are a crucial component of an electric aircraft power system. As aviation transitions toward electric aircraft, power conversion systems with high efficiency and high-power density are needed. Power converters are required to connect AC devices, such as generators and motors, to the DC distribution bus. Conventional power electronics add significant heat load to cryogenic systems, requiring specialized interfaces between cryogenic and room-temperature conductors. Cryogenic power electronic systems completely change how aircraft power systems are designed and minimize the complexity of power transition between the room temperature and the cryogenic devices for power conversion.
Hybrid power and distributed propulsion systems will make future electric aircraft more efficient and environmentally friendly. However, a major challenge is that the necessary technology is not yet available for large commercial electric aircraft. One technology gap is high-efficiency, high-density power electronics, including cryogenic power electronics.
The primary motivation for developing cryogenic power electronic devices is to improve power density, enhance system-wide efficiency, and boost the reliability of these devices. This paper explores cryogenic power electronics through experimental studies on semiconductor devices, passive components, integrated circuits, and dielectric materials. It analyzes superconducting device requirements and cooling concepts essential for cryogenic systems. The study discusses principles for cryogenically cooled converters, achieving high efficiency using an advanced testbed that simulates varying temperatures and high-altitude conditions, cryogenic thermal insulation, and partial discharge tests at cryogenic temperatures. Cryogenic helium gas circulation is the primary mode of thermal management of cryogenic power conversion systems, and it is the primary focus of the modeling and experimental investigations.

Speaker: Mr Yai Pioth Yai Deng (Florida State University)

410 M3Or3A-02: [Invited] Liquid hydrogen cooling of superconducting motor AC windings

Electric machines for aviation applications are under intensive development at present. Pushing performance to 30kW/kg at the 10-20MW scale requires a step change in air-gap field and hence current density. Fully superconducting machines show great promise for achieving the power to weight ratios required, and the use of liquid hydrogen as the aircraft propulsion energy source presents the opportunity to cool the superconductors with minimal additional refrigeration plant.
However, designing such a cooling system is not a simple task. Superconducting armature windings in a 3MW motor will generate many kW of heat at cryogenic temperatures, due to AC losses, depending on the conductor used. Liquid hydrogen will likely be stored at 24-26K, not the 20K required for some conductors. Intermediate coolant loops of pumped helium will be needed, if flowing liquid hydrogen through the motors is not practical or desirable.
In this paper we explore the design-trade-space of cooling systems targeted at two different armature conductors for a 3MW synchronous air-core motor: a magnesium diboride (MgB2) winding requiring a nominal 20K operating temperature, and a REBCO Roebel-cable winding requiring a nominal 40K operating temperature.
MgB2 performance has a strong temperature dependency at greater than 20K which alters the physical dimensions of the windings as well as the losses generated, which in turn impacts the heat transfer characteristics. The dependency is lower with Roebel cable, but to ensure these effects are captured, each conductor is evaluated at a range of temperatures around the nominal, assuming a fixed safety factor below critical current. AC losses have been calculated for each of the windings, based on experimental correlations and heat transfer coefficients and areas are estimated for the likely coil geometries and cooling system components. A lumped-parameter model has been developed to simulate the cooling circuit thermodynamics and this allows us to estimate coolant flows, temperatures and pressures in the systems being considered.
The two conductors lead to very different cooling system options and we can compare the advantages of each from an overall powertrain complexity and performance perspective.

Speaker: Grant Lumsden

411 M3Or3A-03: [Invited] Development of high-temperature superconducting CORC® power cables for electrified aviation and naval applications

Electric power systems on future electric ships and twin aisle electric aircraft require lightweight high-temperature superconducting (HTS) dc cables and connectors capable of delivering electric power in the order of tenths of MW. Conductor on Round Core (CORC®) power cables developed by Advanced Conductor Technologies (ACT) provide a unique solution by offering high operating currents, in the order of 5 kA per pole, that in combination with an operating voltage of 10 kV, results in a capacity of 50 MW. The cables being designed with fault-current-limiting (FCL) abilities that will increase the safety to the electric propulsion of the aircraft. ACT has also developed practical cable terminations that for a compact interface between the helium gas cooled CORC® cables and room temperature.
An overview of the advancement of CORC® power cables for electric aircraft and shipboard uses is provided. The lapped dielectric we developed for CORC® power cables is rated for up to 12 kV and designed to be coolant independent. The dielectric is suitable for the gaseous helium cooling most likely present in aviation and naval applications, while allowing for customization depending on the required voltage rating. The results of our recent test of a 2-pole dc CORC® power cable containing compact terminations that was operated at a current of 4 kA and a voltage of 12 kV while cooled with cryogenic helium gas are outlined.

Speaker: Danko van der Laan

412 M3Or3A-04: [Invited] Lightweight cryoresistive and superconducting aerospace power transmission cables: experiments and theory

A NASA University Leadership Initiative program with The Center for Cryogenic High-Efficiency Electrical Technologies for Aircraft (CHEETA) and a separate ARPA-E Connecting Aviation By Lighter Electrical Systems (CABLES) program have been developing cryogenic, medium voltage, high amperage, and lightweight aerospace power cables. The research presented here includes the motivation behind these demonstrations, cable and termination designs paradigms, theoretical modeling using a 1 D lumped parameter model and finite element modeling, and results of sub scale ground demonstration experiments. The final two-pole design and testing will include HTS and cryoresistive cables from both ARPA-E and NASA demonstration programs joined electrically in series, using a novel cryogenic junction.

Acknowledgements: We would like to acknowledge support by NASA University Learning Initiative (ULI) #80NSSC19M0125, DOE ARPA-E funding under DE-AR0001460, and Air Force Office of Scientific Research (AFOSR) and the Aerospace Systems Directorate (AFRL/RQ) LRIR#s 24RQCOR004 and 23RQCOR008.

Speaker: Chris Kovacs (Scintillating Solutions LLC)

413 M3Or3A-05: [Invited] Cryogenic Bus Bar Design for Electric Aircraft Power Distribution

The aviation industry is undergoing a transformative shift towards electrification to address urgent environmental challenges and reduce operational costs. While electric propulsion has been successfully demonstrated in small aircraft, the transition to larger aircraft presents substantial technical challenges, particularly in power distribution systems that must efficiently manage megawatt-level power while optimizing power density and ensuring system reliability. As part of our continued research on power distribution for electric aircraft, we have performed trade space analysis on various power distribution configurations. For electric aircraft which employ turbo-electric distributed propulsion multiple terminations are required near one another to supply the power demands of the propulsion motor. We have seen where it is advantageous to employ a high temperature superconducting (HTS) cable coupled with a cryogenically cooled aluminum busbar.
We have begun the conceptual design of a 4 MW cryogenically cooled aluminum busbar with an intended operating current of up to 4 kA and an operating voltage of 1 kV DC. As part of our design, we are investigating having both poles of the busbar within the same cryostat with an inner diameter of 85 mm. We have also begun to explore techniques to enable low electrical resistance connections to be made utilizing various spring connections. Utilizing the spring connections is seen as a technique to reduce the overall volumetric packaging of the busbar and enable a design with discrete cryogenic cooling to the busbar compared to other electrical devices in the power distribution system. This is of great importance as failure of the cryogenic cooling to the busbar is seen as one of the worst failure modes that can occur.
As part of the paper, we will discuss the design process of the 4 MW busbar, including how interfaces with other power devices within the distribution network are made. We will also provide commentary on material selection/grade for the aluminum busbar, electrical insulation design, thermal management optimization, and anticipated contact resistance of interfaces.

Speaker: Muhammad Tahir Mehmood Khan Niazi (Florida State University)

414 M3Or3A-06: [Invited] A high power two-pole quick connect junction between lightweight cryoresistive and superconducting aerospace power transmission cables

A NASA University Leadership Initiative program with The Center for Cryogenic High-Efficiency Electrical Technologies for Aircraft (CHEETA) and a separate ARPA-E CABLES program have been developing cryogenic, medium voltage, high amperage, and lightweight aerospace electrical wiring and interconnection systems (EWISs). The research presented here includes the design and results of derisking tasks for the high power quick connect cryogenic junction unit between the ARPA-E (aluminum cryoresistive) and NASA (REBCO CORC$^{TM}$) cables and cable cryostats.

Acknowledgements: We would like to acknowledge support by NASA University Learning Initiative (ULI) #80NSSC19M0125, DOE ARPA-E funding under DE-AR0001460, and Air Force Office of Scientific Research (AFOSR) and the Aerospace Systems Directorate (AFRL/RQ) LRIR#s 24RQCOR004 and 23RQCOR008.

Speaker: Chris Kovacs (Scintillating Solutions LLC)

M3Or3B - AC Loss

415 M3Or3B-01: A low AC loss, fast ramp HTS solenoid prototype for compact fusion energy system

We aim to build and test a Bi-2212 insert prototype coil designed by Princeton Plasma Physics Laboratory (PPPL) for the feasibility study of next step compact device such as compact stellarator or spherical tokamak (ST) ohmic heating central solenoid in a fusion pilot plant (FPP) beyond the present National Spherical Torus eXperiment Upgrade (NSTX-U). Low AC loss is critical for fast ramping of pulsed machine operations. The Rutherford cable is one potential promising configuration for testing such a prototype coil for fusion tokamak applications.
As part of FES-HEP collaboration, LBNL has an unique cabling capability to fabricate round wire of 2212 into a 17 strand Rutherford configuration. In particular, the model coil is expected to be tested at PPPL in a self-field and in the background field up to 3 T and 10 T/s pulsed test facility for fast ramp testing. The basic parameters for a 5T model coil assumes a Bi-2212 spool with performances such as Ic (5T, 4.2K) = 323 A after 50 bar over-pressure heat treatment (OPHT).
The US Magnet Development Program supplied a non-desirable 10 kg Bi-2212 wire (billet drawn to 0.8 mm diameter and would be about 2 km long). Such a 2212 wire can make about 100 meters of Rutherford cable of 17 strands. As the first step, LBNL completed the fabrication of a 17-strand Bi-2212 Rutherford cable in December 2024 so the model coil can be fabricated for testing in 2025. Two design options for the model coil HTS solenoid will be presented based on the 17 strand Rutherford cable. The Rutherford cable has a 7.8 mm width and 1.44 mm thickness and a cable engineering current density of >390 A/mm2 for the model coil operating at 4393 A (assume 80% of Jc at 4.2K, 5T).
The 17 strand Rutherford cable will be tested first in a fast ramp pulsed test facility (up to 3 T, 10 T/s) at PPPL to evaluate AC loss characteristics. AC losses measurement is planned either via voltage current or calorimetry measurement. Possible quench tests and a targeted mechanical loading testing can be performed to validate the cable operation repeatability.

Speaker: Yuhu Zhai (Princeton Plasma Physics Laboratory)

416 M3Or3B-02: AC Loss in Round, Multifilamentary Superconducting Strands at High Frequencies

This paper focusses on the AC loss of round multifilamentary superconductors over a wide frequency range, but with a focus on higher frequencies. We review the loss expressions for multifilamentary conductors and apply them to specific cases including several MgB2 conductors (some intended for low loss) as well as a Bi:2212 conductor. The different critical frequency regimes (bounded by fc1, fc2, and fcs) are described as well as the critical ramp rates for filamentary zone saturation ((B_c ) ̇ and (B_cs ) ̇). Cases considered include those with applied fields larger or smaller than the filamentary penetration field, as well as conditions where filamentary zone saturation occurs above or below fc2 or fc2 (depending upon B0 and other parameters). The methods of properly combining coupling current and hysteretic loss are given in different regimes, and losses are compared for several low loss conductors over a large frequency range. The modifications required to account for the effects of flux creep (or power law behavior) on loss are included. The influences of magnetic permeability, as well as various conductor matrix regions, including the outer sheath, are also described. The loss contribution of transport currents are also given for a multifilamentary conductor, including both hysteretic and coupling terms, at low and high frequency. Finally, the loss expressions developed are used to evaluate loss from low amplitude, high frequency harmonic excitations of these conductors.

Speaker: Michael Sumption

417 M3Or3B-03: AC loss in MgB2 and Bi-2212 wires excited by a permanent magnet rotor

Electrified aircraft are being developed to address climate change by reducing the fuel burn and emissions of aircraft. The large majority of aviation’s impact on the environment is caused by large transport aircraft, or those that can carry about 150+ passengers. At this scale, megawatt-class electrified propulsion systems are required. Superconducting and cryogenic electric machines are an attractive technology for such applications due to their very high specific power and, often more importantly, their very high efficiency. Most of these electric machines employ superconductors only in a machine’s field winding (typically on its rotor) where the superconductor is only excited by direct current and essentially constant magnetic field. Improved specific power and efficiency can be achieved if superconductors are also used in the machine’s armature winding (typically on its stator). However, doing so requires superconductors with low AC loss. In the past 5 years, promising progress in the development of low AC loss superconductors has occurred, but experimental validation of the loss is still lacking, especially under magnetic loading that is representative of electric machines.

This paper will present measurements of the AC loss in unpowered MgB2 and Bi-2212 superconducting wires excited by a permanent magnet rotor. Data for two different MgB2 and one Bi-2212 wires will be included. Each wire was designed to achieve state-of-the-art levels of AC loss. Details on the construction of each wire will be included in the final paper. Losses are measured using two methods: (a) conventional calorimetry of the gaseous helium coolant and (b) null calorimetry. Losses are measured for a range of temperature and a magnetic field with fixed strength but variable frequency (0 to 400 Hz). Predictions of the temperature difference between the wires and helium gas will be included to refine the reported temperature. Data will be compared to AC loss calculations based on equations available in the literature.

The test rig used to obtain the measurements will be commissioned in January. A number of the rig’s check out tests have been completed. The wire specimens and coil pack hardware is in hand. The test articles will be assembled in early January. This will leave more than enough time to troubleshoot any issues, complete the testing, complete the paper, and receive internal approval to release the presentation before the May 18 upload deadline.

Speaker: Justin Scheidler (NASA Glenn Research Center)

418 M3Or3B-04: Test Results for the Commissioning of NASA’s AC Loss Superconducting Coil Test Rig

Achieving sustainability in commercial aviation hinges on the transformation of large transport aircraft (>150 passengers), which are the principal contributors to aviation emissions. These 150+ passenger aircraft have powertrains with rated power in excess of 20 Megawatts. System studies have shown that the highest possible aircraft efficiencies can be obtained for fully superconducting electrified aircraft, which rely on electric machines that contain superconducting coils. Two superconducting wires that may meet NASA’s demands for electrical current density and low alternating current (AC) loss under dynamic magnetic and electrical excitation are magnesium diboride (MgB2) and BSCCO-2212 (Bi:2212). To enable these aircraft that utilize fully superconducting motors and generators, testing of high-current, low-AC-loss superconducting wires, cables, and coils such as MgB2 and Bi:2212 must be performed. NASA Glenn Research Center has recently developed an AC loss test rig that can excite specimens with magnetic fields of about 0.5 T at frequencies up to 400 Hz while cooling them to temperatures between room temperature and 20 K. The magnetic field excitation is relevant to electric machines, because it is applied by a spinning permanent magnet rotor. This presentation will summarize the capabilities of the new test rig and cover test results towards commissioning of the rig that have been performed to-date.

Speaker: Jason Hartwig

419 M3Or3B-05: AC-loss Analysis in Stacks of Non-insulated REBCO Tapes

High-current HTS cables made of stacked REBCO tapes are being considered for large superconducting magnet systems for fusion and other applications. AC losses are critical when analyzing a stack of non-insulated tapes. Using finite element software such as COMSOL, it is possible to model a 3D stack of non-insulated REBCO tapes and assess how AC losses vary, depending on factors such as the stack's width, length or the number of tapes it contains. Each REBCO tape was modeled as a high-temperature superconductor (HTS) layer, surrounded by two copper layers. Stacks were formed by adding several tapes into the model. The stack sample is exposed to an external, time-varying magnetic field, applied to its outer surface. To model the superconducting behavior of the HTS layers, the well-established H-formulation (derived from Maxwell's equations) and the E-J Power law have been used. A key input parameter to the AC loss model is the transverse resistivity among the superconducting tapes. This parameter has been experimentally measured at liquid nitrogen temperature for stack samples of bare REBCO tapes, and of REBCO tapes alternated with stainless steel ribbons of various thicknesses. The measurements were performed at Fermilab’s Superconducting R&D lab as a function of transverse pressure using a modified transverse pressure insert (TPI). These experimental data were used in the COMSOL model. This paper describes the COMSOL model and presents the results of the AC loss studies in various REBCO stacks.

Speaker: Elena Tamagnini (Politenico di Torino)

420 M3Or3B-06: Tradeoffs Curves and Penalty Functions for AC losses and Je relevant to high-power-density motor applications and their use in comparing various superconductors and normal metal conductors

To achieve MW class high power-density aircraft propulsion motors, conductors with high ampacity but low overall losses are required. Aircraft powered by such motors are often designed to be zero or low emissions with the use of cryogenic fuel such as liquid hydrogen (LH2) or liquid natural gas (LNG). In this work we consider an operating point of 20 K, enabled by pool boiling LH2, which allows operation of a number of superconducting options, including MgB2, BSCCO 2212, and ReBCO, while also enabling low resistivity cryo-conductors to be used. Previously we created a new metric “total AC loss per length per amp of achievable operating current” W/m/A to accurately compare the performance of cryo-conductors and multifilamentary MgB2 superconductors for this application. We were able to find a global minimum in our metric, which could be viewed as an optimum. However, in reality, a full consideration of the tradeoff surface is required, since different designers of different devices in this space will potentially make different tradeoffs. In this work we consider various conductors and conditions, generating a tradeoff curve in 2-D space, adding in a penalty function to our analysis help define the optimum spot on the tradeoff curve for a specific penalty function weighting. MgB2, Bi:2212, ReBCO, and HPAL conductors are considered.
Work was performed under NASA Phase 1 SBIR

Speaker: Mr Jin Kwon

421 M3Or3B-07: Flux Jumping in High Magnetic Fields for Stack Tape Cables and its Mitigation

This study presents experimental measurements of the magnetization of ReBCO tape stack cables in magnetic fields up to 30 T at 4.2 K. The M-H response of these conductors is important for various applications, including particle accelerators, fusion reactors, and other emerging technologies. We employed a susceptibility technique, utilizing the NHMFL's Bitter magnet as the primary coil. A custom-designed sample holder was fabricated, featuring a secondary pick-up coil and a compensating bucking coil. Our experiments shows large scale flux jumping, present at low fields, but also persistent up to 17 T. This effect, while initially surprising, is on reflection clearly required for such stacks because the penetration fields becomes dependent on sample width rather than film thickness, and the relevant length exceeds the critical width for flux jumping. We attempted to mitigate this effect by introducing small gaps between the tapes to allow for flux penetration in the stack and thus to reduce the effective penetration depth. To do this, we introduced Cu and G-10 spacers between the tapes. We prepared and measured three distinct samples: a 60-tape ReBCO stack cable without spacers, a 60-tape ReBCO stack cable with Cu spacers, and a 30-tape ReBCO stack cable with G-10 spacers. As anticipated, the flux jumps were significantly reduced when using Cu spacers and were completely eliminated with G-10 spacers. These findings have significant implications for the implementation of tape stack cables in high-field applications. The results of this study are vital for advancing our understanding of ReBCO tape stack cables and their potential uses in fusion magnets, particle accelerators, and other cutting-edge technologies.

Speaker: Tushar Garg (The Ohio State University)

422 M3Or3B-08: Research and development of reel-to-reel REBCO multi-filamentary tape

REBCO high-temperature superconductor are widely used in high magnetic field applications, due to their excellent critical current properties and high critical temperature. However, the width-to-thickness ratio of REBCO tapes is very large (typically in the range of 1000-10000) resulting in excessive power dissipation in the applications. One of the effective ways to reduce AC loss is to divide the superconducting layer in the REBCO tape into filaments. The degradation of the current-carrying performance of the prepared multi-filamentary tape is concerned. In this study, the copper-stabilizing layers and superconducting layers were cut by the independently developed through a self-developed reel-to-reel ultraviolet picosecond laser cutting device to prepare REBCO multi-filamentary tapes with different numbers of filaments (2-filament, 6-filament, and 10-filament). The research results show that the depth of the cut groove is about 30 μm and the width of the groove on the superconducting layer is about 15 μm. The study systematically characterized the cut multi-core materials and found that ultraviolet picosecond laser cutting did not lead to significant degradation of Ic performance. It is found that the cutting multi-core material can make a significant reduction in AC loss. After low temperature testing, it was found that the high-field inserted superconducting coil had good high-field current carrying characteristics and low-temperature characteristics after copper plating. This study solves the preparation process problem of ReBCO high-temperature superconducting multi-core materials and studied the materials' low-temperature and high-field performance characterization. The research results show that the preparation process of multi-core belts has practical potential.

Speaker: Zhan Zhang (Institute of Energy(IE) Hefei Comprehensive National Science Center(HCNSC))

16:00 Grab & Go Coffee Break

C3Or4A - LH2 and LNG II: Storage and Utilization

423 C3Or4A-01: Energy of Fluid (EOF) simulations of large-scale zero boil-off hydrogen storage systems

This study evaluates a Computational Fluid Dynamics (CFD) model's ability to predict the flow fields and thermal behavior of liquid hydrogen (LH₂) during zero boil-off (ZBO) operation in the Ground Operations Demonstration Unit for Liquid Hydrogen (GODU-LH₂) tank at NASA's Kennedy Space Center. The model focuses on capturing natural convection and heat transfer effects driven by the Integrated Refrigeration and Storage (IRAS) system within a large-scale cryogenic storage tank. A pressure-based finite volume solver, enhanced with User Defined Functions (UDFs) and an internal energy-based formulation, was employed to achieve computational efficiency while resolving complex thermal and flow fields. Simulations were validated against experimental data, showing strong agreement with measured temperature and pressure profiles. Results highlight the IRAS system's role in generating recirculation patterns that regulate temperature distribution and optimize heat transfer to sustain ZBO conditions. The analysis provides insights into the interaction between the heat exchanger and the bulk fluid, demonstrating the system's effectiveness in maintaining cryogenic stability and minimizing propellant losses. This work establishes a reliable framework for modeling ZBO operations, advancing thermal management strategies, and supporting the development of next-generation cryogenic storage technologies for aerospace and industrial applications.

Speaker: Dr Colin Mahony (Gloyer-Taylor Laboratories)

424 C3Or4A-02: Management of Boil-Off-Gas along the LH2 supply chain

Liquid hydrogen is considered as future energy carrier as well as preferred fuel for future mobility applications on the road, rail, sea and air. The expectation is that large amounts of liquid hydrogen will be transported intracontinentally or even intercontinentally in near future.
As typical for cryogenic fluids, the boil off gas can impact the economics of the transport chain considerably. Therefore, an appropriate management of BOG is necessary.
In first part of this paper, concerns about BOG and main sources of BOG will be considered. In the second part, the strategy for management of BOG will be discussed. In the third part, examples of successful BOG management will be presented, followed by summary and outlook.

Speaker: Alexander Alekseev (German)

425 C3Or4A-03: Novel concept of cryo-adsorbed hydrogen energy storage system

The transition of the energy market to sustainable resources demands a variety of energy storage technologies. Existing systems propose energy storage from kWh to GWh levels, each with its strengths and limitations. The presented research proposes a novel energy storage method (patent pending) of cryo-adsorbed hydrogen energy storage (CAHES), aiming for large scale applications, in order of up to GWh and power outputs of a few GW. The main strength of the CAHES is low power consumption (high efficiency), in comparison with alternative existing technologies, mainly hydro pumped and compressed air energy storage. The technology can be implemented in any location, it doesn’t need specific geographical conditions, and it has the potential for small dimensions and low-cost.
CAHES method consists of storing energy in adsorbed hydrogen at cryogenic temperatures, normally between 80 and 200 K, and pressures of a few tens of bars. CAHSE includes a compressor, which elevates the supplied hydrogen pressure to a higher value. The pressurized hydrogen flows through a thermal energy storage unit (TESU), where it is cooled down by emitting heat to the TESU. The pressurized cold hydrogen then expands at a cold turbine reaching its storage temperature and pressure. At this state the hydrogen is adsorbed in the adsorption cell and stored for a few hours, days or even weeks. When the hydrogen has to be provided it leaves the adsorption cell and flows through the TESU to extract heat from it. The warm hydrogen expands through a hot turbine to the required pressure, it flows again though the TESU, because its temperature is dropped again, and finally it is provided to the consumer. When all the possible hydrogen is provided, the remaining hydrogen in the systems serves for re cooling the adsorption cell, to be ready for an additional cycle.
A thermodynamic analysis of the cycle is presented, providing the energy consumption of the CAHSE, as function of the hydrogen storing temperature and pressure, system configuration, and energy storage duration. Calculated results show energy consumption of about 2 MJ per 1 kg of stored hydrogen, relative to published performance of existing compressed hydrogen energy storage systems, which consume at least 10 MJ per 1 kg of stored hydrogen. In addition, this paper presents two experimental plans, which are under construction in our lab, aiming for validating the numerical model of the cycle. The objective of one setup is to validate the hydrogen adsorption processes in the cell during the different cycle phases, and the objective of the second setup is to validate the TESU performances.

Speaker: Dr Nir Tzabar (Ariel University)

426 C3Or4A-04: Transient system-level cryogenic thermal management models of liquid hydrogen-fueled electric aircraft

Liquid hydrogen-fueled electric aircraft is a promising approach to achieving zero-emission aviation goals, particularly when combined with high-temperature superconducting (HTS) power device technology. Liquid hydrogen serves as an energy source and a cryogenic heat sink, enabling multiple high power-density superconducting devices and conventional components onboard the aircraft. Liquid hydrogen and oxygen are used as fuel and oxidizers for turboelectric generators and fuel cells. The cooling demands of the power devices are at the temperature range between 20 and 300 K. Efficient thermal management at the system level is critical for the lightweight and space-constrained design of electric aircraft. To address safety concerns and mitigate significant pressure changes caused by the phase transitions, a thermal management system has been developed by employing multiple gaseous helium secondary cooling loops to handle the diverse cooling demands of the electrical devices. The liquid hydrogen flow rate in the primary cooling loop must be determined based on fuel consumption for power generation and the overall cooling requirements of the system. Helium flow rates in the secondary cooling loops are determined by the specific heat loads of individual electrical devices at their operating temperatures. An integrated control strategy for the primary and secondary cooling loops is essential for efficient and safe power generation demands dictated by the mission profiles. This paper outlines the details of the thermal management system, modeling methodology, and flow control schemes, focusing on developing a cryogenic thermal management system design protocol.

Speaker: Dr Youngjun Choi (Florida State University)

427 C3Or4A-05: New design data for ortho-parahydrogen converters

The increased demand for hydrogen as an energy vector and storage medium drives the need for higher liquefaction capacities. However, the design of the necessary ortho-parahydrogen converters has long been associated with substantial uncertainty. Until now, the only available data on the activity of the standard catalyst, hydrous ferric oxide—commercially available as the “Ionex-Type O-P Catalyst” (Ionex) from Molecular Products—were both outdated and contradictory.
At Dresden University of Technology, the HyCat project was conducted to overcome this long-standing issue by establishing a new, highly accurate set of design data. Building on previously presented efforts, the final results for Ionex’s conversion activity are now available across an extensive range of temperatures and pressures, addressing both ortho-para and para-ortho conversion directions. The collected data have been employed to parameterize kinetic models, resulting in an improved prediction accuracy of ortho-para conversion processes. This work summarizes the kinetic measurements and modeling endeavors, facilitating the design and optimization of hydrogen liquefaction plants.

Speaker: Sebastian Eisenhut

428 C3Or4A-06: Process simulation and techno-economic assessment of hydrogen liquefaction plants with integrated ortho-para conversion

As the demand for climate-friendly mobility solutions increases, hydrogen stands out as a key enabler, especially in heavy-duty sectors like transportation and aviation. Liquid hydrogen, with its high energy density, holds significant promise for these industries. Many studies focus on the application of liquid hydrogen in these sectors. However, also the supporting infrastructure – including hydrogen generation, storage, transportation, and liquefaction – requires thorough investigation to enable large-scale adoption.

In this context, the HyNEAT project, funded by the German Federal Ministry of Education and Research (BMBF), investigates liquid hydrogen supply networks and their evolution for air transport. A crucial part of this infrastructure is the liquefaction process, which is energy-intensive and costly, but essential for building a CO2-emission-free hydrogen aviation sector. As the global demand for liquid hydrogen rises tremendously, particularly driven by the requirements of hydrogen-powered transportation, a fast scale-up of worldwide liquefaction capacities and the development of energy- and cost-wise optimized large-scale hydrogen liquefaction facilities are critical.

In hydrogen liquefaction plants, hydrogen is first precooled with either liquid nitrogen or mixed refrigerants, followed by cryogenic refrigeration and liquefaction. Additionally, the conversion of hydrogen from its ortho- to parahydrogen form plays a vital role. As hydrogen at ambient conditions consists of a mixture of 75% ortho- and 25% parahydrogen, while at cryogenic temperature, hydrogen consists almost entirely of its parahydrogen form, the conversion between ortho- and parahydrogen must take place within the liquefaction process. This exothermic conversion is catalytically driven and integrated continuously into the plate-fin heat exchangers within the cryogenic refrigeration process.

This study presents detailed steady-state simulations of small- and large-scale hydrogen liquefaction plants, developed in the process simulation tool UNISIM. Thereby, these models accurately consider the continuous ortho-para conversion and the corresponding conversion heat within the heat exchanger channels of the refrigeration process. Therefore, an approach is applied that utilizes the Boltzmann distribution to calculate the equilibrium parahydrogen fraction and the Van’t Hoff equation to determine the conversion heat [1].

An integrated techno-economic analysis of the hydrogen liquefaction plants of different scales is performed to evaluate the cost-effectiveness and energy efficiency of the processes. The results are validated against industrial key performance indicators. By combining steady-state simulation with techno-economic evaluation, this study's results provide valuable insights into the performance and cost efficiency of hydrogen liquefaction processes and, therefore, contribute to advancing sustainable hydrogen infrastructure and improving the economic viability of hydrogen as a clean energy carrier.

[1] Kanz, B., Tafone, A., Stops, L., Massier, T. Klein, H. (2024). A Novel Approach to Simulate Ortho-Para Conversion in Hydrogen Liquefaction based on the van’t Hoff Equation. Submitted for publication.

Speaker: Laura Stops (Technical University of Munich, TUM School of Engineering and Design, Department of Energy and Process Engineering, Institute of Plant and Process Technology, Garching, Germany)

429 C3Or4A-07: Upgrades and initial weathering test results of the liquefied natural gas testbed at NASA Kennedy Space Center

Responding to commercial space launch vehicle providers developing rocket engines fueled by liquefied natural gas (LNG) in recent years, NASA began exploring the so-called “weathering” of the cryogenic mixture—the preferential evaporation of lower boiling point constituents over time, leading to a change in the bulk liquid composition. Due to relatively long delays between launches historically, cryogenic propellants sit idle in storage tanks, with the normal boiloff vented to atmosphere. In the case of LNG, boiloff gas would primarily be methane, the main constituent in the mixture, leading to a build-up of other species in the bulk liquid, which could affect engine performance or cause a violation of launch commit criteria. To better understand LNG weathering, in 2019 NASA performed boiloff testing using a custom 400-L dewar with five vertical sample ports within the fluid volume. Samples were routed to a gas analyzer to determine the compositional change over time. Although successful, numerous system improvements were identified following the 2019 campaign. In 2022, NASA funded an effort to perform these improvements and conduct additional testing, which culminated in two successful LNG tests in 2024. Upgrades to the LNG testbed will be presented, as well as the new weathering test results.

Speaker: Adam Swanger (NASA)

430 C3Or4A-08: Effect of sloshing conditions on the boil-off rate of cryogenic liquid in membrane tank

Evaluating the boil-off rate (BOR) of liquefied natural gas (LNG) transported in cargo containment systems is crucial for assessing system performance. Research has focused not only on static cryogenic storage tanks but also on tanks under sloshing conditions. Numerical simulations have demonstrated that sloshing significantly affects the thermophysical processes and boil-off gas (BOG) generation in LNG tanks. However, experimental data to validate these numerical simulations remain limited. This study aims to address this gap by experimentally investigating the effect of sloshing on the BOR of a cryogenic liquid stored in a prismatic membrane tank. Liquid nitrogen was employed as a substitute for LNG to ensure safety. A custom-designed shaker was developed to generate oscillatory motions of the tank. Two lab-scale tanks with identical inner dimensions were used in the experiments: a transparent Plexiglas water tank to observe sloshing behavior and measure impact pressures, and a cryogenic membrane tank for BOR measurements. The effects of key parameters, including excitation frequency, amplitude, and tank filling level, on BOR were systematically analyzed. Additionally, the mechanisms driving BOG generation during sloshing were thoroughly analyzed. The findings of this study are expected to provide valuable insights into BOG generation mechanisms under sloshing conditions and offer an experimental dataset to validate numerical models, thereby contributing to the design of more efficient LNG transport systems.

Keywords: Liquefied Natural Gas; Cryogenic Membrane Tank; Sloshing Dynamics; Boil-Off Rate.

Acknowledgments
This research was supported by Korea Institute for Advancement of Technology (KIAT) grant funded by the Ministry of Trade, Industry and Energy (Grant Number: P19270001) and Korea Evaluation Institute of Industrial Technology (KEIT) grant funded by the Korean government Ministry of Trade, Industry and Energy (MOTIE) (Grant number: 00437681).

Speaker: Dr Le-Duy Nguyen (Korea Institute of Machinery and Materials)

C3Or4B - Large Scale Cryogenic Systems VII: Commissioning

431 C3Or4B-01: Operation of CERN’s major tests facility with upgraded cryogenic infrastructure for superconducting magnets, power links, inner triplets String and radio-frequency cavities for HL-LHC

The largest cryogenic multipurpose test facility at CERN (SM18), recently significantly upgraded, provides helium refrigeration capacity for testing at nominal conditions, superconducting magnets, power links, radiofrequency (RF) cavities and the IT String (Inner Triplet) for the High Luminosity - Large Hadron Collider (HL-LHC) upgrade project, towards increased luminosity at interaction points 1 (ATLAS) and 5 (CMS) in the LHC accelerator.
The SM18 cryogenics infrastructure and test benches have been progressively upgraded along the last 8 years to meet the technical requirements of the HL-LHC project. In parallel, cryogenic interfaces and process controls have been developed to adapt the operational requirements related to the use of new materials like Nb3Sn for the HL-LHC magnets, to the tests of innovative MgB2 powering links and to the new design of RF crab-cavities as well as crab-cryomodules.
In addition, the inner triplets string test bench, also located in the SM18 facilities, will be dedicated to the test of HL-LHC magnet’s collective effects anticipating the operational behaviour of the structure powered by a superconducting link.
This paper outlines the development of advanced cryogenic process controls over the past two years, focusing on automation for safety and efficiency in the cryogenic test benches. Operational results will be presented including overall cryogenic capacity & tests parallelization. The paper concludes with perspectives for the expected future dense testing program.

Speaker: Remi Mauny (CERN)

432 C3Or4B-02: Upgrade of the CERN cryogenic test facility for the HL-LHC superconducting magnets and superconducting links

New superconducting magnets, many of them based on Nb3Sn technology, have been developed for the HL-LHC project, the High-Luminosity upgrade of the LHC (LHC Hadron Collider) at Interaction Points 1 and 5. These magnets require thorough testing in cryogenic conditions at 4.5 and 1.9 K before their installation into the LHC. Additionally, the HL-LHC includes high-current superconducting transmission lines (SC Links) for feeding the magnets of the Inner Triplets and Matching Sections at LHC Point 1 and Point 5, which also require cryogenic testing and validation before installation. The existing test benches built in the early 2000s to test the LHC magnets in SM18 needed to be upgraded because the HL-LHC magnet apertures and internal line routings were not compatible. CERN has upgraded five test benches of the major LHC magnet test facility to perform the cryogenic powering tests and magnetic measurements of the HL-LHC magnets and SC links. The upgrade included additional shuffling modules, anti-cryostats and new current leads. The paper presents the details on the cryogenic characteristics of the upgraded test benches and reports on the first operational results.

Speaker: Olivier Pirotte (CERN)

433 C3Or4B-03: Design and implementation of the joint operation of SHINE cryoplant and SHINE test facility cryoplant

To enable the cryogenic test of superconducting components for the Shanghai High Repetition Rate X-ray Free Electron Laser and Extreme Light Facility (SHINE), a cryoplant with a 1 kW@2 K cooling capacity, supplied by Air Liquide Advanced Technologies (ALAT), was constructed and commenced operations in 2020. However, with the progression of cryogenic test requirements, the existing cryoplant's is not able to supply sufficient cooling power under certain conditions. Subsequently, the No.3 Cryoplant from SHINE (CP3), equipped with a 4 kW@2 K cooling capacity, was strategically planned to supply the requisite additional cooling power to support the operation of the SHINE Test Facility. This paper details the design and implementation of the joint operation between the two cryoplants associated with SHINE and the SHINE Test Facility. The renovation project encompassed the cryoplants, helium storage systems, and cryogenic transfer systems. The joint commissioning of the two cryoplants was executed in December 2024. The commissioning results indicated that, with the support of CP3, the end-user requirements were met, and the cryoplants operated stably in conjunction.

Speaker: Shuai Zhang (Shanghai Advanced Research Institute, Chinese Academy of Sciences)

434 C3Or4B-04: Performances of the JT-60SA cryogenic system in the integrated commissioning test

Toward an early realization of fusion energy, a Broader Approach (BA) Agreement between Japan and the European Union was established in 2007. As part of this agreement, a tokamak-type fusion experimental device, JT-60SA, was constructed in Japan as a collaboration between Fusion for Energy and the National Institutes for Quantum and Radiological Science and Technology (QST). The JT-60SA uses a superconducting magnet system involving 18 Toroidal Field (TF) coils, 4 Central Solenoid (CS) modules, 6 Equilibrium Field (EF) coils, superconducting feeders, and 26 high-temperature superconductor current leads. The total cold weight is around 766 tons. A helium cryogenic system with an equivalent refrigeration capacity of 9.5 kW at 4.5 K cools the magnet system, the thermal shield, the current leads and provides refrigeration for the Divertor Cryopumps. CS and EF coils are operated with changing currents during plasma experiments to initiate and control the plasma inducing strongly variable heat loads by AC losses and eddy currents. To mitigate the impact of transient heat fluctuations and ensure stable operation of compressors, turbine expanders and cryogenic circulators the cryogenic system uses a thermal damper system with 7-m3 of liquid helium. The assembly of JT-60SA was completed in March 2020, and the cool-down of the magnet system for the integrated commissioning of the entire system started in October 2020. However, the test was interrupted due to an electrical short at the electrical terminals of the EF1 coil. From 2021 to 2023, repair of terminals, insulation reinforcement, and high voltage tests were conducted. From May 2023, the integrated commissioning test was resumed. It took 41 days to cool the magnet system from room temperature to reach the transition to the superconducting state. At steady state condition, the cryogenic system provided 2 kg/s of supercritical helium for magnet and feeders, 0.04 kg/s of helium gas at 50 K to the HTS current leads, and 0.4 kg/s of helium gas at 80 K to the thermal shield. The cryogenic system operated continuously for 7 months, and JT-60SA successfully achieved the first plasma and a maximum plasma current of 1.2 MA.
In this presentation, we report the outline of the cryogenic system, heat load profiles, and the behavior of the cryogenic system during cool-down and plasma experiments.
JT-60SA was jointly constructed and is jointly funded and exploited under the Broader Approach Agreement between Japan and EURATOM.

Speaker: Kazuya Hamada (National Institutes for Quantum Science and Technology)

435 C3Or4B-05: Commissioning results of the ESS cryogenic moderator system using helium

At the European Spallation Source (ESS), a 5 MW beam of 2.0 GeV proton with a nominal current of 62.5 mA driven by an accelerator will impact a tungsten wheel target at a repetition rate of 14 Hz and a pulse length of 2.86 ms. Fast neutrons produced via spallation process are moderated to cold and thermal neutrons of lower energy levels by passing through a thermal water pre-moderator and, subsequently, up to two liquid hydrogen moderators. The nuclear heating is estimated to be 6.7 kW for the proton beam power of 5 MW, with a projected increase to 17.2 kW for the four moderators in the future. A cryogenic moderator system (CMS) has been designed to continually supply subcooled liquid hydrogen at 17 K with a parahydrogen fraction of exceeding 99.5% to each moderator placed in parallel. A flow rate of over 240 g/s is maintained to limit the average temperature rise across the moderator to within 3 K. Heat load is effectively removed via a heat exchanger by a large-scale 20 K helium refrigeration plant, the Target Moderator Cryoplant (TMCP), which provides a maximum cooling capacity of 30.3 kW at 15 K. The TMCP commissioning was completed independently, without connecting the CMS, in December 2022. Operational procedures, including a cooldown, warm-up and beam injection modes, were thoroughly studied to establish an automatic TMCP-CMS control system. Meanwhile, the CMS installation into the Target building was finalized by June 2024. Prior to hydrogen operation, CMS commissioning was performed using helium, bypassing the moderators. The CMS was successfully cooled down to 17 K utilizing the developed controllers while maintaining a pressure of 0.56 MPa, ensuring that the helium densities matched those of gaseous hydrogen at an operational cooldown pressure of 1.12 MPa. Performance tests were conducted at 17 K while evaluating pressure drops over the entire loop, heat load, and liquid hydrogen pump performances at varying pump speeds, all of which aligned with design specifications. Additionally, a newly developed 17-kW orifice type heater demonstrated outstanding fast-response characteristics, achieving a ramp-up to 500 W within one second. This paper presents detailed performance test results during the preliminary commissioning using helium.

Speaker: Dr Hideki Tatsumoto (European Spallation Source ERIC (ESS))

C3Or4C - Aerospace Cryocoolers IV

436 C3Or4C-01: Characterization of SWaP COTS rotary coolers for space application

High resolution space IR detection requires the use of cooled detectors. The broadness of the landscape of cooling systems that are available nowadays allows to choose the suited cryocooler for each of the applications.
Yesterday, rotary Stirling coolers were usually not the preferred choice in space application context because of their lower level of reliability and availability compared to other cooling solutions as pulse tube coolers for instance. Nevertheless, recent improvements on rotary coolers offer now extended lifetime for these products and their natural advantages in field i.e. of compactness, efficiency and cost make them as attractive contenders especially when volume is reduced. Furthermore there are new space applications where the lifetime of rotary cryocoolers is adequate for the mission and the SWAP advantage rotary coolers offers is an adbvantage.
These aspects can be advantages for applications where space claim, consumption, thermal management, shorter mission lifetimes, and costs are critical. This is the case for CubeSat.
Thales current portfolio initially address tactical market. Nevertheless, it can address a large range of space applications from the smallest at intermediate temperatures, which is addressed by the RMs1 (1W@150K, 20°C), to more stringent applications requiring larger power requirements, that are efficiently fulfilled by the RM3 or RM4 (resp 550mW and 730mW@77K, 20°C). Some tests have been realized in collaboration with the CNES (French Space Agency) in order to characterize Thales COTS rotary coolers behavior in space conditions. First of all, cryogenics performances were characterized in vacuum and temperature. In a second time, launch mechanical stress were applied with success on the coolers. Finally, we subjected coolers to radiation stress.
This presentation proposes to discuss advantages and drawbacks of Stirling rotary coolers to be used in space applications. This discussion will be based on tests and characterization performed in space environments. After an introduction, the paper will describe trends and constraints for space application and their impacts on cryogenics, then the current Thales portfolio will be described. Finally we will describe the coolers characterization performed in collaboration with CNES.

Speaker: James Wade

437 C3Or4C-02: BAE Low Cost, High Capacity, Scalable Cryocooler Solutions

Over the past eight years, BAE Systems Inc. has been working with teammates that include Sunpower/Ametek, Iris, and SDL on next generation cryocooler systems. These cryocooler systems have been sponsored by both internal and external customers and has resulted in development of a product line of low cost, low EFT, high capacity, high reliability cryocooler systems. A key element is the high efficiency, long life, low cost Sunpower cryocoolers. Specifically, Sunpower products include the DS-30, MT, GT, and DS-Mini coolers. BAE has augmented these coolers by integrating them with several EFT and launch vibration attenuating platforms. Additionally, these cryocoolers systems are scalable from Mission Class A to C using cryocooler control electronic solutions from Iris Technology or BAE Systems Inc. The result has been a flight qualified product line of cooling systems that compared to traditional space coolers are 2-5X lower cost, 10-40X lower EFT output, 3-5X higher capacity and efficiency. These cooler products have been delivered for several flight programs.

Speaker: Dr Ryan Taylor (BAE Systems Inc.)

438 C3Or4C-03: Reliability approach for high-availability cryocoolers

Reliability is a major driver in design decisions for the products of Thales Cryogenics. In the past years Thales Cryogenics has put their attention to the High-Availability 24/7 application of cryocoolers in combination with detectors. Several technical decisions have been aimed at the improvement in increased availability.
This paper highlights an updated approach of Thales Cryogenics to Reliability, with regards to Availability and how it relates to Weibull analysis and MTTF. Summarized in a whitepaper, with the usage of field- and lifetime data, and a specific set of failure modes and mechanisms.
Furthermore an updated overview of the Thales product portfolio with respect to reliability numbers will be provided. As well as the statistical approach that was undertaken to reach these reliability results.

Speaker: Jimmy Wade

439 C3Or4C-04: Cryogenic Thermal Margins: Key to IR Sensor Success

Thermal margins are critical to the development, the production, the test, and ultimately the performance of thermal subsystems. And, the subset of thermal subsystems that are cryogenic are even more reliant on thermal margins for success. Thermal uncertainty margins cover the inherent uncertainty, due to both design and analysis limitations, of predicting performance in space. They are not equivalent to sensitivity analyses that focus on the impact on performance of individual design and analysis parameters and assumptions. Thermal margins cover all the areas of uncertainty in the design. These include areas that are inherently nearly impossible to eliminate uncertainty such as: thermal interstitial joints (workmanship influenced), orbit environments (transient), surface properties (vary with individual surfaces), thermophysical properties (vary with individual material lots), MLI (empirical ranges), etc. These areas often have empirically derived ranges. At British/Ball Aerospace, cryogenic margin is based on the MIL-STD philosophy and this section will cover that in more detail. It is critical to not only establish, but track margins throughout a program, from pre-proposal to on-orbit. Examples will be provided that show the tracking of margin on several actual Ball programs.

Speaker: David Glaister (Ball Aerospace)

440 C3Or4C-05: Advances in Cryocooler Control Electronics for Linear Cryocoolers

An increasing number of space missions developed for Tactical and Strategic space applications require the development of custom linear cryocoolers cryocoolers and control electronics that are adapted to meet the specific size, weight, power, cost, and reliability requirements unique to each mission. Creare and West Cost Solutions present enhancements to our micro-sized cryocooler control electronics (MCCE) family. The MCCE, originally developed for CubeSat applications in the 100 W class, has been enhanced to provide additional features required in many space applications, including higher power operation, wider operating voltage, and active vibration cancelation. In this paper, we present updated results showing improved reduction of emitted vibrations achieved with an engineering model of the Air Liquide LPTC pulse-tube cryocooler at reduced (100W) and full-power (160W) operation.

Speaker: Mark Zagarola (Creare LLC)

441 C3Or4C-06: BAE Modular Advanced Cryocooler Control Electronics (MACCE)

Over the past four years BAE Systems Inc. has been developing the Modular Advanced Cryocooler Control Electronics (MACCE). This new cryocooler control electronics architecture leverages modularity and scalability in performance supporting a wide range of cryocoolers including 4K Hybrid Systems (J-T + Pre-Cooler), Pulse Tube Cryocoolers, and Stirling Cryocoolers. The MACCE design includes the primary CCE box and an Accelerometer Pre-Amp (APA) box that can be remote mounted. The MACCE architecture is scalable across all mission classes and includes four high power drive channels and two low power channels supporting >500W of output power, three independent accelerometer feedback control loops for vibration cancellation, high efficiency using GaN FET technology, and a combination of six thermistors and six precision RTD circuits for telemetry. An initial flight model of MACCE has been completed and has been through successful flight qualification. MACCE performance coupled with improvements from a previously discussed engineering model are discussed along with immediate applications.

Speaker: Ryan Taylor (BAE Systems Inc.)

442 C3Or4C-07: The road to 1K – Iris Technology’s continued development of high power CCEs

As enhanced cryocooling capabilities for space imaging technology continue to advance, Iris Technology is committed to pioneering the development of high performance Cryocooler Control Electronics (CCE) to deliver significantly increased power output and facilitate the concurrent operation of multiple cryocoolers within a discrete system.
Iris Technology's upcoming high power CCE is a leap forward with an electrical power capacity reaching 1000 watts— a fivefold increase over existing Iris CCE solutions. At its core, the design will feature a flexible architecture in the input ripple filter (IRF) and augmented output capabilities, aligning with the dynamic requirements of today's burgeoning space economy and allowing the standardized application of this architecture across the Iris CCE lineup.
For this presentation, Iris Technology will explore its continued development of this architecture to illustrate the challenges faced, identify potential opportunities and present data collected including assessments of power consistency, operational efficiency, control strategies, and other design aspects.

Speaker: RJ Victoria (Iris Technology Corporation)

443 C3Or4C-08: Numerical investigation & optimisation of a small-scale travelling-wave thermoacoustic Stirling cryocooler

Thermoacoustically driven cryocoolers have been an area of significant interest due to the driving mechanism being heat, which hence eliminates the need for moving mechanical parts and thus increases simplicity and reliability. A small-scale travelling-wave thermoacoustic Stirling cryocooler of this nature was designed and optimised in the thermoacoustic modelling software ‘DeltaEC.’ The cryocooler consisted of a resonator connected to a looped tube containing two thermoacoustic cores: one which acted as an engine to produce acoustic work (TASE), and one as the cooler that converted this acoustic work to thermal energy to produce cooling (TASC). The purpose of the project was to investigate whether a small-scale version could be feasible and how the geometry could be optimised to improve its performance. Parameter studies focusing on the mesh number and wire diameter for the regenerators as well as the plate spacing and length for the heat exchangers were conducted to explore how they affect the cooling capacity and coefficient of performance (COP) of the machine. The results showed that for the TASC increasing the wire diameter decreases the cooling capacity for all mesh numbers but increases the COP for mesh numbers below 200, whilst for the TASE both the cooling capacity and COP decreases. However for the heat exchangers in both the TASC and TASE it was found that increasing the length initially increases the cooling capacity and COP for all plate spacings but beyond 30 mm they begin to plateau and eventually decrease. Then various combinations were evaluated in DeltaEC to determine the optimal dimensions that would maximise the cooling capacity and COP. Using the optimised dimensions, the cooling capacity improved significantly from 106.38 W to 633.80 W, and the COP from 6.93 % to 23.70 %.

Speaker: Holly Butson (Auckland University of Technology)

M3Or4A - [Special Session] Transportation IV: Motors and Generators

444 M3Or4A-01: [Invited] 3D Numerical Modelling of AC Loss of Multifilamentary MgB2 Wires at 20 K

All-superconducting rotating machines, utilizing superconductors for both field windings and armature windings, are a promising candidate for future all-electric aircraft, due to their high-power density and low weight. However, very high AC loss can be generated in the armature windings because they carry AC current under AC magnetic fields. The resulting total AC loss consists of magnetization loss due to the AC magnetic field and transport loss originating from the transport AC current. To reduce AC loss in the armature windings, round non-magnetic MgB2 wires with multifilamentary structure, small filament size and tight twist are required. To date, most of the 3D AC loss simulations on MgB2 wires have been performed at low magnetic field/frequency at 4.2 K, and they are not relevant to aviation applications. In addition, the MgB2 wires contain magnetic sheaths which is not preferable for AC loss reduction. Therefore, AC loss estimation for multifilamentary MgB2 wires with a non-magnetic sheath operating under realistic conditions is an urgent task for aviation applications.
In this work, we first systematically study the magnetization loss of a twisted, non-magnetic superconducting wire with two filaments using the finite element method, based on the H -formulation. The amplitude of the AC field ranges from 0.1 T to 2 T. The frequency, twist pitch, filament size, matrix resistivity and inter-filament gap are varied to study their impacts on each loss component. Then 3D AC loss simulations on two non-magnetic multifilamentary MgB2 wires at 20 K, manufactured by Hyper Tech Research, were carried out. The wire diameter, filament diameter, and number of filaments of the two wires are 0.48 mm/0.32 mm, 25 μm/10 μm, 54/114, respectively. The DC critical current Jc(B, T) and power-law index n(B, T) of the wires were measured and used in the 3D AC loss simulations as input parameters. The simulation transport AC current was varied from 10% to 90% of the critical current and the amplitude of the AC magnetic field ranged from 0.1 T to 2 T with frequency up to 200 Hz. The dependence of each loss component, as well as the total AC loss, on the matrix resistivity, frequency, and twist pitch of both MgB2 wires are presented and discussed. The magnetic field and critical current density distributions are analysed to better understand the AC loss characteristics.

Keywords: all-superconducting rotating machines, total loss, magnetization loss, MgB2 wires, 3D modelling

Acknowledgement
This work was partly supported by the New Zealand Ministry of Business, Innovation and Employment (MBIE) Strategic Science Investment Fund “Advanced Energy Technology Platforms” under contract No. RTVU2004 and was partly supported by the CSC (China Scholarship Council).

Speaker: Prof. Zhenan Jiang (Victoria University of wellington)

445 M3Or4A-02: [Invited] A Double Rotor Flux Switching Machine with HTS Field Coils for All Electric Aircraft Applications

The increasing demand for high-power density motors in electric transport industries opens a new research opportunity to develop motor topologies with less weight and high efficiency. In particular, all-electric aircraft applications require very high-power density motors. This study designed a new 1 MW 20pole/15slot double rotor Flux Switching Machine with high-temperature superconducting field coils (DRFSM-HTS). The construction of the motor constitutes an air core stator that carries both the normal state conductors and REBCO superconducting tapes. Aluminum Litz Wire (ALW) is used as armature conductors, and the Yttrium Barium Copper Oxide (YBCO) high-temperature superconducting material is used as field coils. The motor was designed to operate at either 65K cooled with a secondary loop of subcooled liquid N2, or 20K with liquid hydrogen cooling. The machine operates under cryogenic temperatures. At 20K the power density obtained with the proposed design is > 100 kW/kg for the active elements and > 29 kW/kg for all components including the thermal-management-system and inverter drive. And at 65K both power density and efficiency decrease slightly. The unique properties and benefits of this motor design for aerospace and transportation applications will be presented.

Acknowledgments. ARPA-E Award # DE-AR0001355 and Subaward # 89703021SAR00022, AFOSR LRIR #18RQCOR100 and LRIR #24RQCOR004, and the AFRL/RQ Aerospace Systems Directorate

Speaker: Timothy Haugan

446 M3Or4A-03: [Invited] Development of a 1 MW+ High power density induction motor for electric aircraft propulsion using Cryogenic Aluminum Windings

Our team is developing and demonstrating a 1 MW plus high power density motor intended for electric aircraft propulsion as part of an ARPA-E program. The target power density is > 16 kW/kg with 97+% efficiency. The motor is an asynchronous design with an outrunner rotor configuration, based on previous developments at OSU CAR. However, the stator and rotor windings are cryogenically cooled monolithic aluminum conductors. The Al is 3 nines, and the target operational temperature is between 60-120 K. Originally conceived as using LNG as the cooling media, we have broadened the design to allow for a secondary cooling loop with a variety of primary fuel coolants, including LNG and liquid hydrogen. In this talk, basic motor architecture is discussed, including aspects of the design which allow for a very lightweight and simple cryostat and minimal bearings issues. Our approach starts with the rotating machine requirements and the cryogenics are adapted as needed for a novel solution. We also describe the potential for motor drives integrated into the cryogenic machine and discuss testing performed to de-risk this approach. Flow cooling studies are described along with basic magnetic circuit, coolant flow design, and structural design. The present state of machine fabrication and test is described.

Speaker: Michael Sumption

447 M3Or4A-04: [Invited] The thermal management of superconducting and aluminum conductors in motors, generators and cables for electric aircraft

This talk will discuss the work on power density and efficiency potential for single and double aisle electric aircraft motors, generators and cables by Hyper Tech and Ohio State University. There are a few options on motors: ambient temperature, cryo (77-120K), and cryo 20-30K. Ambient temperature and cryo (77-120K) motors use aluminum conductors while cryo (20-30K) uses superconductors or high purity aluminum (HPAL). There is also the potential for cryo cables using MgB2 and HPAL. The talk will also discuss Hyper Tech’s latest results for magnesium diboride (MgB2) and High Purity Aluminum (HPAL) conductors, cables and coils

Speaker: Dr Xuan Peng

448 M3Or4A-05: [Invited] Superconducting Electric Machine with Cryogenically Cooled Stator for CHEETA

Superconducting electrical machines are emerging as transformative technologies for electric propulsion, with several ongoing efforts focused on advancing their development. This paper highlights significant progress in developing a superconducting electric machine with a cryogenically cooled stator under the Center for High-Efficiency Electrical Technologies for Aircraft (CHEETA) project. An extensive experimental campaign is underway to mitigate risks in critical subsystems and ensure the successful demonstration of the prototype motor.

CHEETA envisions a groundbreaking approach to electric aviation, utilizing a hydrogen-powered system featuring a 2.5 MW fully superconducting electric machine for a full-scale aircraft. In this system, hydrogen serves as both fuel for fuel cells and coolant for the electrical system. By leveraging cryogenic cooling without incurring weight or efficiency penalties, the motor achieves an impressive efficiency of over 99.9% and a specific power exceeding 25 kW/kg.
The conceptual design of the 2.5 MW fully superconducting electric machine poses significant challenges, including superconducting winding manufacturing, thermal management, and handling AC losses. To address these, the CHEETA project is developing a cryogenically cooled superconducting motor that employs aluminum litz wires in the stator instead of superconductors. This approach eliminates the need to operate the stator at 20K, allowing the use of liquid nitrogen (LN2) for stator cooling. To further mitigate technological challenges and reduce risks, Hinetics is developing a 750-kW cryogenically cooled electric machine with innovative cooling solutions for both the stator and rotor.

Key advancements in the CHEETA motor demonstrator include:
• Rotor-mounted Stirling-cycle cryocooler: Integration of a commercial off-the-shelf (COTS) Stirling-cycle cryocooler into a rotationally compatible configuration for closed-loop conduction cooling.

• Cryogenic thermal management system (TMS): A novel coil suspension system that transfers torque between the cold field winding assembly and the warm rotor shaft while minimizing conduction heat loads to the cryocooler, along with innovative methods to reduce radiation heat leakage to less than 10 W.

• Quench-tolerant HTS magnets: Passive quench tolerance of conduction-cooled, no-insulation (NI), double-pancake (DP) high-temperature superconducting (HTS) magnets.

• Lightweight slotless air-core armature: Designed to handle high dB/dt levels generated by the superconducting rotor field, with effective cryogenic cooling using LN2.

To mitigate risks associated with the motor, Hinetics has conducted several risk-reduction experiments. A rotor-mounted cryocooler has been tested for up to 100 hours of operation under load, including vibration and shock tests following military standards. The full-scale rotor has been cooled using an integrated cryocooler with advanced radiation management. A rotational multilayer insulation (MLI) system has been developed and validated for mechanical performance during rotation. Spokes have been tested for rated tension, and the full rotor assembly has been validated for the motor’s rated torque. No-insulation (NI) coils have been manufactured and tested for quench performance. Aluminum litz wire resistance has been measured at liquid nitrogen temperatures to validate its residual resistivity ratio (RRR). Stator samples have been manufactured and cooled with LN2 to evaluate thermal expansion mismatch and other thermal properties.

Hinetics is currently prototyping the motor, with testing planned for late 2025. This paper provides a comprehensive overview of the CHEETA demonstration motor, alongside updates on risk-reduction efforts, including electromagnetic (EM) design, thermal and mechanical design, risk-reduction experiments, and detailed test plans. The entire drivetrain is scheduled for testing at the POETS test facility in Champaign, Illinois, in 2026. These efforts contribute to advancing the field of superconducting electric propulsion, paving the way for cleaner and more efficient air transportation.

Speaker: Thanatheepan Balachandran (HInetics Inc)

449 M3Or4A-06: A sustainable flight demonstrator using a retrofit high-temperature superconducting (HTS) brushless DC motor in an RC plane

In the United States, the transportation sector was the largest contributor to CO2 emissions, responsible for ~28% of the total in 2022, whereas the residential sector accounted for around 13%. While batteries are making significant progress in reducing emissions in the transportation and residential sectors, commercial aircraft remain a mode of transportation where electrification poses significant challenges with current technologies. To address the challenges of electrifying commercial aircraft, two innovations are necessary: (1) the development of new, carbon-neutral, readily available fuels and (2) innovative approaches to deliver power to propel the airplane. Electrified aircraft allow architectural enhancement to improve aerodynamic, propulsive, environmental, and power management efficiencies dramatically. Presently, the gross take-off power needed for a single-aisle 150-passenger aircraft is greater than 20MW. Electrifying aircraft with such power demands using conventional electrification technologies is extremely challenging. Hence, the next generation of technologies such as cryocooling, superconductivity, and power conversion systems (i.e. fuel cells, etc.) will play a crucial role in power generation, transmission, and propeller drivetrains. A ground-based demonstration of a cryocooled high-temperature superconductor (HTS) powertrain was previously presented at SciTech 2025 on an RC scale. The current work will focus on a first-of-its-kind RC plane flight demonstration using a liquid nitrogen (LN2) tank and an HTS conductor-based BLDC motor.
For the first prototype, we modified a battery-powered, twin-motor EC-1500 cargo-style RC airplane by installing a custom-built HTS motor in the nose of the aircraft, making it a tri-motor configuration. The key challenge was modifying an existing brushless DC motor (EFLM15650) by incorporating HTS windings in the stator. Another challenge was to design and integrate a cryogenic Thermal Management System (TMS) that includes a liquid nitrogen (LN2) tank on the airplane. The first HTS motor prototype was tested by immersing it inside an LN2 tank as proof of concept. A second round of systems testing showed the implementation of the motor in the nose of the EC-1500 RC airplane.

This paper will showcase an advanced science project undertaken at Greenwich High School and the University of Connecticut. It will validate the feasibility of a sustainable Radio-Controlled (RC) aircraft, propelled by an HTS brushless DC motor (peak power 600W) while using batteries and a fuel cell. The purpose is to develop flight demonstrators for future aviation technologies that will operate in a real-world environment while offering an affordable path for educational institutions. The focus of this paper is on creating a redundant TMS for the superconducting stator to operate as demonstrated in previous works. For the LN2 tank, a Styrofoam model created through CAD software will prevent the tank from caving, decrease the weight for better flight optimization, and allow for a more aerodynamic design that is flush with the aircraft fuselage. The jacket and rotor will be 3D printed with carbon fiber-reinforced filament, aiding structural rigidity and weight reduction. In previous designs, the PLA structures would bend and crack, which created challenges with the concentricity and integrity of the design. Lastly, to solve condensation issues, the shaft and bearings of the motor will be replaced with a thermally insulating material and self-lubricating material, such as garolite (G-10/FR4) or polyetheretherketone (PEEK).
Further testing will demonstrate the flight capabilities and characteristics of this motor and fuel cell via an onboard data acquisition system to measure motor performance and AC losses when operating under load. This supported the development of an affordable RC aircraft fleet of technology demonstrators for instructional and R&D purposes. Ongoing work, such as the NASA ULI Cheetah program, shows promise of efficient electric power trains with cryogenics and fuel cells. We aim for this effort to accelerate the technology transition into future commercial aircraft.

Speaker: Ishan Ambastha (Greenwich High School)

M3Or4B - [Special Session] Materials for High Field Magnets

450 M3Or4B-01: [Invited] Quality assurance testing of materials for the 40 T superconducting magnet project

High quality materials are essential to the success of large magnet projects. National High Magnetic Field Laboratory (NHMFL) has been funded by the US National Science Foundation to design a 40 T superconducting magnet which uses REBCO coated conductor tapes for the insert coil winding co-wound with copper and stainless-steel tapes. Characterization and incoming quality assurance (QA) testing for these materials are obviously critical to the success of test coils in this project.
The critical current (Ic) of commercial REBCO tapes is typically characterized by the vendors at 77 K. But Ic at 4.2 K, the temperature the 40 T magnet is designed for, and many other important properties are not tested by the vendors. Therefore, we carry out a comprehensive QA sub-project. The following tests are performed on each spool of the received tapes: transport Ic at 4.2 K in magnetic field up to 15 T; Ic versus field angle using torque magnetometry at 4.2 K up to 15 T; residual-resistance-ratio (RRR) of copper stabilizer; thickness profile across tape width; REBCO ab plane tilt angle; peel strength; and lap joint resistivity at 77 K. In addition, the electromagnetic property such as Ic versus longitudinal tensile strain, and tensile fatigue properties are measured every 10 spools at 77 K. The mechanical properties of copper and stainless-steel co-wind tapes are characterized as well.
In this talk, we present results from these comprehensive QA tests of over 150 spools of REBCO tapes (total of >20 km). Important experiences of carrying out these incoming QA measurements will be shared.

Acknowledgment
This work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR- 2128556, DMR- 2131790, and the State of Florida, and by DMR-1644779 through User Collaborations Grants Program.

Speaker: Jun Lu (National High Magnetic Field Laboratory, USA)

451 M3Or4B-02: [Invited] Composite materials for electrical insulation of superconducting coils

Research on high-field magnets has always been instrumental for high energy colliders. Amongst many aspects in magnet design and construction, the electrical insulation system is of paramount importance to ensure required performance. Concerning the manufacturing of Nb3Sn magnets, superconducting coils undergo a vacuum impregnation process which requires the impregnation system to have a low viscosity and high processing time. The typical cable insulation process involves braiding a layer of mineral fibre, commonly S-glass onto Rutherford cables, which are subsequently wound into coils, reacted at high temperatures to form the superconducting phase, and vacuum-impregnated with epoxy resin. During operation, superconducting magnets as well as their insulation systems are exposed to cryogenic temperature, high radiation levels and mechanical loads.
This presentation aims to give an overview of the advancements in composite materials and the parameters to consider when selecting an electrical insulation for superconducting coils to fit the magnet requirements with adequate margin. The first aspect concerns the investigation of polymer matrices, starting from their chemistries, followed by the study of their process, physico-chemical and electrical properties to their mechanical properties. The end properties of the composites are greatly influenced by several parameters such as the toughness or the radiation hardness of polymers, properties directly linked to their chemistries. To evaluate their properties after irradiation, many test campaigns were implemented to reproduce real ageing conditions in superconducting magnets, through different irradiations sources, environments and temperatures. This screening includes the most used epoxy resin systems for impregnation of superconducting coils among the stakeholders of the domain.
The second aspect to consider is the fibre reinforcements. These fibres have different functions, such as providing mechanical support to the coils to withstand Lorentz forces while in operation or serving as spacers between cables for electrical insulation. A sizing is required on those fibres for handling during braiding or increasing the matrix/fibre adhesion. However, Nb3Sn coils need to be reacted at a peak temperature of typically 650 °C to create the superconducting phase and this directly degrades the sizing, leaving conductive residues before impregnation, hence impacting negatively the electrical insulation properties. Thus, this second part investigates strategies to enhance cable insulation robustness, focusing on the selection of high-performance fibres, optimization of braiding layouts, and the refinement of de-sizing processes to improve fibre-resin compatibility and electrical performances. Robustness is assessed using electrical testing, including resistivity and voltage withstand tests.
Finally, the combination of polymer matrices and fibre reinforcements, i.e. composite materials are addressed. This starts with the manufacturing process, applied at different scales including the study of the process parameters, followed by the investigation of their mechanical and electrical properties, towards the manufacturing of real magnet prototypes tested at cold.
Overall, this work aims to provide insights about the choice of composite materials depending on the desired properties and type of magnet targeted, to meet the stringent demands of next-generation superconducting magnets, contributing to advancements in particle accelerator technologies.

Speaker: Vincent Schenk

452 M3Or4B-03: [Invited] Cryogenic Performance of Superconducting Magnet Structural

Speaker: Dina Yuryev (Commonwealth Fusion Systems)

453 M3Or4B-04: [Invited] Cryogenic mechanical properties of large forgings for high field fusion magnets

Nuclear fusion represents a promising pathway to a sustainable and virtually inexhaustible energy future, offering a low-carbon alternative to conventional power sources. Achieving fusion relies on high-field superconducting magnets to confine plasma within reactors, which in turn depend on advanced structural materials capable of withstanding extreme cryogenic environments, high magnetic fields, and steep thermal gradients.
This presentation examines the metallurgical and fabrication challenges encountered in developing these critical materials. Drawing on historical and contemporary examples, we trace the evolution of design strategies and highlight key lessons learned from early alloys that have guided modern developments. Recent advances in alloy design and fabrication have significantly enhanced cryogenic mechanical properties, notably increasing toughness and yield strength at cryogenic temperature. However, achieving isotropic and homogeneous properties in the large, forged parts required for these magnets is exceptionally challenging due to material inhomogeneities and the complexities associated with scaling, thereby demanding innovative processing and manufacturing solutions.
For certain complex shapes, additive manufacturing is essential; yet a major challenge remains in guaranteeing that the mechanical properties match those of traditionally forged parts while maintaining homogeneity. Additionally, the exploration of new material compositions holds the potential to further boost toughness and yield strength, opening new design possibilities for next-generation nuclear fusion systems. This discussion provides a comprehensive overview of current structural material challenges and emerging solutions, setting the stage for more reliable and performant fusion devices.

Speaker: Markus Kind (Rolf Kind GmbH)

454 M3Or4B-05: [Invited] Material Characterization at Cryogenic Temperature

Speaker: O. Socristan

19:00 Farewell Event

Thursday 22 May

Plenary: Thomas Abraham-James [Securing America’s Helium Future: Pulsar’s Topaz Project and the Changing Landscape of US Helium Supply] & Closing

455 C4PL1-01: Securing America’s Helium Future: Pulsar’s Topaz Project and the Changing Landscape of US Helium Supply

Abstract pending.

Speaker: Thomas Abraham-Jones (Pulsar Helium Inc.)

09:00 Grab & Go Coffee Break

M4Or1A - [Special Session] Transportation V: Materials

456 M4Or1A-01: [Invited] Supply Chain of YBCO and Bi2212 (tentative)

Speaker: Prof. Lance Cooley (NHMFL/FSU)

457 M4Or1A-02: [Invited] REBCO Magnets for Fusion Propulsion

REBCO (Rare Earth Barium Copper Oxide) high-temperature superconducting (HTS) magnets are redefining fusion-based propulsion systems by enabling compact, high-field solutions critical for plasma confinement and acceleration. Operating at higher temperatures (20–77 K), REBCO magnets reduce cryogenic complexity and weight while achieving magnetic fields exceeding 2 Tesla, offering unmatched efficiency and scalability for deep-space missions.
This paper presents recent advancements in REBCO magnet development, emphasizing their application in fusion propulsion systems like magnetic shielding and high-field thrusters. Results demonstrate improved thermal stability, efficiency, and compactness, addressing key challenges in plasma confinement and thrust generation. These innovations accelerate progress toward interplanetary exploration.
Canyon Magnet Energy specializes in HTS technology, providing cutting-edge REBCO magnet systems for energy, healthcare, and space. The company is committed to delivering transformative solutions for sustainable energy and advanced propulsion.

Speaker: Honghai Song

458 M4Or1A-03: [Invited] Low ac loss HTS-2212 wire, cables and coils for operating above 22K in much higher power density rotating machines

Higher field, much lighter-weight and more efficient ac magnets that can operate at affordably cooled temperatures above 22 K require a new HTS conductor design. Stator coils for example operate in fast AC modes where HTS tapes cannot be used due to excessive induction-driven losses, requiring instead HTS as small cross-sectioned, fine-filament, axially twisted wires in transposed cable forms. An approach has been previously described that builds all required loss reducing features into small, nominally 0.16 mm diameter round Bi2212 wires, with non-merged, small-sized. to order 10 mm filaments, short twist pitch lengths in the 5 to 10 mm range, and increased inter-filament resistances. Recently, through process and material science developments, the Je levels attained in these wires now match those attained in the highest performance 2212 magnet wires that do not include loss reducing features. In parallel, wire fabrication was also successfully scaled to produce 3 km piece lengths. Building on these advances, fully transposed low loss cable design developments are under way. Recent wire-related advances and application of these low loss wires to develop advanced, fully transposed low loss 2212 cables, with attributes that are tailored to meet all the specific requirements of applications of for example high power density electric plane propulsion motors. A long length generic cabling line has been developed, cabling processes established, and prototypes made, including a baseline 16-strand Rutherford design and a cable-of-cables 48-strand design and also with even higher strand count cables under development. The processes and designs of these of the 16-strand cable has been optimized with respect to performance to where to strand Je levels are approaching the Je levels non cabled wires and that enable stator operation at above 22 K. Techniques for reinforcement have also been developed and validated. Their suitability to the fabrication of advanced coil designs is now also under development and in excess of 70 prototype test coils have been made to optimize coil designs and fabrication

Speaker: Dr Alexander Otto (Solid Material Solutions LLC)

459 M4Or1A-04: [Invited] AeroCryoX: A Comprehensive Library of Cryogenic Power System Component Models for Designing Electric Aircraft

This paper discusses AeroCryoX, a MATLAB/Simulink-based modeling library developed to support the design and analysis of cryogenic power systems of electric aircraft as part of the NASA-funded University Leadership Initiative, Integrated Zero-Emission Aviation (IZEA). IZEA aims to achieve zero-emission regional aviation through a novel hybrid powertrain architecture utilizing liquid hydrogen as fuel and cryogen. The aircraft integrates fuel cells and gas turbine-powered HTS generators, with cryogenic components operating at multiple temperatures (20-140K). Integrating thermal, electrical, and fuel systems, combined with competing design requirements of reliability, power density, and efficiency, requires a unified modeling approach. AeroCryoX provides the integrated platform, enabling comprehensive system-level analysis and optimization to find design solutions that balance the often contradictory requirements of hydrogen-powered aircraft.
AeroCryoX incorporates detailed models of crucial components of superconducting generators, fuel cells, HTS cables, protection devices, and power conversion systems (motor drives, rectifiers, DC-DC converters). The library's thermal management modules enable heat load estimation for each component and its cryogenic cooling infrastructure. The models include cryogenic transfer lines, fluid circulation impellers, and heat exchangers that couple the liquid hydrogen heat sink and gaseous helium secondary loops.
AeroCryoX tracks and optimizes hydrogen utilization across multiple systems: as fuel for both gas turbines and fuel cells, as a cryogenic heat sink in the thermal management system, and its transition between liquid and gaseous states. Components such as evaporators and hydrogen gas compressors are modeled to represent the complete hydrogen flow path through the aircraft systems.
AeroCryoX incorporates weight estimation models for all system components, enabling rapid evaluation of design trade-offs between thermal performance, system weight, and power density. This integrated approach allows designers to optimize component sizing while meeting both thermal, electrical, and weight constraints. AeroCryoX's modular architecture facilitates sensitivity analyses and system-level optimization studies, supporting informed design decisions for complex cryogenic power systems.
AeroCryoX will accelerate the development of efficient, reliable cryogenic power systems for electric aircraft by providing designers with detailed insights into system behavior, performance limitations, and optimization for next-generation electric aircraft.

Speaker: M. Tahir Khan Niazi (FAMU-FSU College of Engineering)

460 M4Or1A-05: [Invited] Liquid Hydrogen for Sustainable Energy Systems: Latest Development, Challenges and Opportunities

Fossil fuels and their low efficiency and emissions have impacted our climate and energy resilience. The focus on Net-Zero targets and general awareness of the negative impacts of emissions on climate change and sustainability triggered a paradigm of new energy sources for electricity generation. Expanding our reliance on renewable energy sources requires large scale energy storage. Liquid Hydrogen (LH2) is emerging as an effective way of storing the excess energy generated by renewable sources to use as a fuel for electricity production, transportation, and industrial energy needs. Economical production, distribution, and use of LH2 are still in their infancy. The cryogenic technologies to produce and store LH2 economically are under development. This paper highlights the latest research and development of LH2 technologies and the technology gaps that need to be addressed through R&D to enable commercial LH2 technologies to penetrate everyday life. Hydrogen liquefaction through magnetocaloric refrigeration and transportation and dispensing using tube trailers, cryogenic tanks, and chemical carriers will be highlighted. Furthermore, pressurized tanks, cryogenic vessels, material-based storage, LH2, cold/cryo-compressed storage, and geological caverns are also covered under storage.

Keywords: Electrolyzers, Electrocatalysts, Cryogenic, Liquefaction, Cryopumps

Speaker: Mr David Mensah Sackey (FAMU-FSU College of Engineering, Department of Electrical & Computer Engineering)

C4Or1A - Adiabatic Demagnetization Refrigerators

461 C4Or1A-01: The Continuous Adiabatic Demagnetization Refrigerator for PRIMA: Dual Instrument Cooling

The Probe far-Infrared Mission for Astrophysics (PRIMA) contains two instruments: an imager (PRIMAGER) and a multi-band spectrometer (FIRESS). These two instruments require detector cooling to 100 mK and require parts of the optical train to operate at 1.0 K. From a base temperature of 4.5 K, provided by a James Webb Space Telescope-like cryocooler, a 5-stage Continuous Adiabatic Demagnetization Refrigerator (CADR) will provide this cooling to both instruments. Cooling two separate instruments comes with several challenges including operating temperatures, somewhat remote locations and shared parasitics. The CADR will provide 700 microW of lift at 1.0 K and 9 microW of lift at 100 mK to meet the two instruments (PRIMAGER and FIRESS) cooling requirements with a factor of 2 margin. This paper will describe these challenges to the CADR design, requirements, and operation. In addition we will discuss the CADR heritage and design features incorporated into the development model CADR.

Speaker: Michael DiPirro

462 C4Or1A-02: The first continuous sub-millikelvin refrigerator

Sub-millikelvin (sub-mK) temperatures, or even lower, were first achieved in 1956 by adiabatic demagnetization cooling of nuclear spins in copper [1]. Since then, the use of such extremely low temperatures has long been limited to researchers in fundamental science such as superfluid 3He and nuclear magnetism [2]. In general, lowering temperature have their own advantages, e.g., improved measurement resolution due to reduced thermal noise and protection of pure (quantum) states from thermal disturbances. The recent rise of millikelvin environments down to 10–100 ｍK obtained by adiabatic demagnetization refrigerators (ADRs) using electronic spins or 3He-4He dilution refrigerators (DRs) for the development of quantum computers and quantum sensors is utilizing these advantages. If so, even lower temperatures may represent a new frontier for quantum technologies in the future.

Here we present the first successful construction and test results of a continuous sub-mK refrigerator capable of continuously maintaining a base temperature down to 0.57 mK with cooling powers of 19 nW and 290 nW at 1 mK and 5 mK, respectively. The continuous refrigeration mechanism [3] is based on independent demagnetization cooling of two nuclear magnetic refrigerants of PrNi5, a hyperfine enhanced nuclear magnet [2], with two zinc superconducting heat switches [4]. Precooling of this continuous nuclear demagnetization refrigerator (cNDR) is achieved by a commercially available cryogen-free DR. The size of the cNDR is 156W×84D×240H (mm each), excluding the Pt-wire NMR thermometer used for test cooling, and the total weight is currently less than 5 kg. Due to its compactness, the cNDR can be mounted on most DRs and possibly on the extended version of ADR without introducing any magnetic disturbance to the nearby measurement setup.

Our cNDR is a nuclear spin version of the cADR developed by NASA [5], which can maintain 50 mK and is operating successfully in space. However, due to the extreme temperature environment, we had to solve several technical difficulties for cNDR by developing a new type of thermal insulation support for the coolant, a compact shielded superconducting magnet (1.3 T) [6] and its flexible thermal link, thermalization techniques for the PrNi5 coolant [7], etc. Some of these will also be useful for other cryogenic devices at higher temperatures. In my presentation, I will provide details of the development and test results of this first continuous sub-mK refrigerator.

[1] N. Kurty et al., Nature 178, 450 (1956).
[2] F. Pobell, Matter and Methods at Low Temperatures, 3rd edn. (Springer, Berlin, 2007).
[3] R. Toda et al., J. Phys.: Conf. Ser. 969, 012093 (2018).
[4] R. Toda et al., arXiv:2209.08260v1.
[5] P. J. Shirron et al., Cryogenics 74, 2 (2016).
[6] S. Takimoto et al., J. Low Temp. Phys. 201, 179 (2020).
[7] S. Takimoto et al., J. Low Temp. Phys. 208, 492 (2022).

Speaker: Prof. Hiroshi Fukuyama (Cryogenic Research Center, The University of Tokyo)

463 C4Or1A-01: High-Fidelity Modeling of the Continuous Adiabatic Demagnetization Refrigerator for PRIMA

The 5-stage continuous adiabatic demagnetization refrigerator (CADR) on the Probe far-Infrared Mission for Astrophysics (PRIMA) is designed to provide continuous cooling at two temperatures: 100-120 mK for the focal planes of the imaging instrument (PRIMAger) and multi-band spectrometer (FIRESS), and at 1.0-1.2 K for parts of the optical train. The CADR will use a James Webb Space Telescope-like 4.5 K Joule-Thomson cryocooler as its heat sink to provide 700 microW of lift at 1.0 K and 9 microW of lift at 100 mK. The JT cryocooler cools other cryogenic components, allowing only 10 mW of the expected 53 mW total cooling power to be allocated to the CADR’s operation. Meeting both the required cooling power and temperature stability requirements is challenging given how close the CADR must operate to practical limits of thermodynamic efficiency. In order to assure such operation is possible, a high-fidelity model of the system has been assembled, based on the performance of identical components flown on Astro-H/Hitomi and the X-Ray Imaging and Spectroscopy Mission (XRISM). The model and predicted performance of the CADR will be presented.

Speaker: Peter Shirron

464 C4Or1A-04: Space-oriented adiabatic demagnetization refrigerator adapted for quantum applications

Adiabatic demagnetization refrigeration (ADR) is an efficient and reliable cooling technology well used for temperatures below 1 K. It is particularly well suited for space applications, thanks to the absence of fluid refrigerant and of moving parts and to a competitive Carnot efficiency. A multi-ADR cooler, that is the last stage of a cryogenic chain, is proposed for the LiteBIRD and Athena space missions. This technology can also be used to meet the increasing cryogenic needs of quantum technologies and to prevent the potential future crisis in 3He supply. In this context, our laboratory is involved in two national projects for quantum applications, in which ADR is a candidate for beeing an alternative to helium based dilution refrigerator.
In particular, the Cryonext project aims to build an ADR stage for the 20 mK – 100 mK temperature range, the stage providing up to 10 µW at 100 mK.
We report here on the developpement process of such a stage. The setup is based on the space environment expertise of the laboratory which is tranfered to build a prototype for cooling ground quantum applications. One of the aim is to focus on the application requiring small cooling power at low cooling temperature. This would be well suited for initial qbit characterizations or for operations in remote environments. Hence, a focus will be put on the reliability, portability and compactness of the ADR stages. As for the design of the stage, a numeric tool was created for optimising ADR stage dimensions. The code is based on thermodynamic equations and a strong experimental data base (magnetic properties of materials, ultra low temperature magnetic hysteresis curves, thermal conductances and heat losses). For this project, it is used to optimize the dimensions of the paramagnetic material, coil and magnetic shield and to predict the efficiency of the overal ADR device. Finally, the targetted temperature range requires dedicated temperature sensors and readout electronics. A part of Cryonext aims to design a ADR technology to be industrialized.

Speaker: Mrs Adele Leon (Univ. Grenoble Alpes, CEA, IRIG-DSBT, 38000 Grenoble, France)

465 C4Or1A-05: Design Study of Suspension Systems for Continuous Adiabatic Demagnetization Refrigerators

Upcoming probe missions, such as the Probe far-Infrared Mission for Astrophysics (PRIMA), are requiring Continuous Adiabatic Demagnetization Refrigerator (CADR) with larger temperature spans within their stage’s architecture. These temperature spans will require novel designs to those that have flown in the past. In this design study, we will be developing spaceflight suspension systems that are simpler, more compact, and/or span larger temperature gradients. We will be looking into the use of plastics such as Vespel, metals such as Ti 15-3-3-3, Kevlar designs, passive launch locks, and heat intercepts in the attempt to span temperatures between 30 mK to 4.5 K, like those seen between the salt pill and magnet of some of our coldest CADR stages. This paper will describe the challenges of the design concepts studied and their pros and cons.

Speaker: Richard Ottens (NASA GSFC)

466 C4Or1A-06: Characterization of single-crystal GdLiF4 entropy

Gadolinium lithium fluoride (GLF) is an attractive material for Adiabatic Demagnetization Refrigerators (ADRs) because it has a high density of active ions and a relatively low effective ordering temperature. We have encapsulated a large GLF crystal in a thermal bus, integrated it into an ADR, and have characterized this salt pill through operation of the ADR. From these measurements, we are able to extract the entropy of single-crystal GLF as a function of temperature and field. Measurements at zero field with different heat loads applied allow us to characterize the parasitic heat load, as well as the zero-field heat capacity. This agrees with the results of Numazawa [1] for polycrystalline GLF. Isothermal demagnetization measurements with different heat loads allow us to extrapolate to the zero heat flow (reversible) entropy as a function of field. They also allow us to determine the degradation of entropy capacity with increasing heat flow into the pill. We have developed a relatively simple functional form, derived from the independent-ion approximation, that fits the entropy well with several free parameters.

Speaker: Ed Canavan

467 C4Or1A-07: Performance characterization of a large CPA salt pill below 0.5K

Paramagnetic salt CrK(SO4)2·12H2O (CPA) is one of the main refrigerants in the temperature range below 0.5K for adiabatic demagnetization refrigerator (ADR). In practical applications, to improve the thermal performance of salt pill containing CPA, thermal bus structure is generally used. A CPA salt pill typically includes CPA crystal, a high-purity copper thermal bus, and thermal interface. The cooling efficiency and capacity of the CPA salt pill are contingent upon several factors including grain size uniformity, thermal bus quality, and the Kapitza resistance. So far, there are few published detailed studies dedicated to the evaluation of CPA salt pill. In this paper, a comprehensive experimental and numerical investigation is undertaken to assess the performance of a 212 g CPA salt pill with the crystal growing on copper fingers made through electric discharge machining. In the experiments, a two-stage ADR system is built, which includes a 4 K pulse tube cooler, a first-stage using a GGG salt pill, a second-stage using the CPA, and two thermal switches. Isothermal demagnetization of the second stage is conducted at different temperatures below 0.5K through PID control. The cooling performance as well as the heat leakage are thus evaluated using different methods. Meanwhile, a COMSOL model for the CPA salt pill is established to help understanding its performance. Specially, influence of the copper RRR value and the temperature-dependent Kapitza thermal resistance are evaluated.

Speaker: Prof. Wei Dai (Technical Institute Of Physics and Chemistry, Chinese Academy of Sciences)

468 C4Or1A-08: Design and performance testing of the 3-stage ADR

As an important sub-Kelvin refrigeration technology, the adiabatic demagnetization refrigeration (ADR) is used for space detector cooling and ground-based experiments because of its wide temperature coverage, high efficiency and gravity-independence. We design a 3-stage adiabatic demagnetization refrigerator pre-cooled by a GM-type pulse tube cooler and operating from 4 K to 50 mK. Gadolinium Gallium Garnet (GGG) is used for high temperature stage and chromium potassium alum (CPA) is used for low temperature stage. All the salt pills are supported by polyether ether ketone (PEEK) suspensions. The active/passive air-gap heat switches are used to control heat transfer between stages. The system has achieved a lowest temperature of 35mK in a single-shot mode as well as 100mK intermittent cooling. This paper introduces the refrigeration performance of the 3-stage ADR as well as details of critical components. An interesting configuration for realizing an ADR with multiple continuous cooling stages will also be discussed.

Speaker: Ms Yanan Li (Technical Institute of Physics and Chemistry,Chinese Academy of Sciences)

C4Or1B - [Special Session] NASA's Cryogenic Fluids for Aerospace Propulsion Applications

469 C4Or1B-01: [Invited] Fuel Cell-Based Hydrogen Aircraft Architecture

NASA aeronautics goals include pioneering new technology to increase commercial aircraft efficiency and reduce emissions from air travel. The feasibility of using fuel cells and on-board cryogenic hydrogen systems in combination with electric motors for commercial transport aircraft has been examined in the past at NASA and in the aircraft industry. Growing emphasis on increasing efficiency and implementation of zero emission air transportation resulted in the development of strategic programs on hydrogen aviation, including developing new capabilities at the airports, expansion of hydrogen infrastructure, and fuel cells manufacturing both in the US and EU. A NASA cross-organizational multidisciplinary project team developed an integrated conceptual and experimental methodology to realize a medium-range hydrogen aircraft design based on fuel cells, advanced power management and distribution, and cryogenic hydrogen storage systems combined with an integrated aircraft concept of operations both during the flight and at the airports. The resulting analyses identified possible aircraft architecture options, sizes and layouts for propulsion subsystem and propellant tankage, taking into account appropriate weight scaling factors for a medium-range aircraft carrying 100-200 passengers flying 1000 - 5000 km.

Speaker: Vadim Lvovich (NASA Glenn Research Center)

470 C4Or1B-02: [Invited] NASA Cryogenic Fluid Management Portfolio Project – Overview and 2024-2025 Highlights

The Cryogenic Fluid Management (CFM) Portfolio Project (CFMPP) was established by NASA in 2021 to achieve the primary goal of closing CFM technology gaps essential to NASA’s future missions in science and exploration. The office is comprised of Marshall Space Flight Center as the lead, with key support from Glenn Research Center and other NASA Centers. The CFMPP office organization, portfolios of development activities, and stakeholder engagements will be summarized. Highlights from office accomplishments in 2024 – 2025 will be reviewed. Progress towards defining future development roadmaps and new technology development activities will be summarized.

Speaker: Robert Kenny

471 C4Or1B-03: [Invited] NASA Cryogenic Fluid Management Portfolio Project - Modeling and Technologies Portfolio Overviews

The Modeling and Technologies Portfolios are part of The NASA Cryogenic Fluid Management (CFM) Portfolio Project’s (CFMPP). The Modeling Portfolio develops, enhances, validates, and demonstrates Computational Fluid Dynamics (CFD) and Nodal tools to address capability gaps for predicting cryogenic fluid behavior in 1-G and microgravity environments for use as design tools for future NASA missions. The Technologies Portfolio designs, develops, tests, and evaluates critical-need cryogenic components enabling long-duration CFM storage and propellant transfer. Major activities within the Technologies Portfolio include valve technology and cryogenic sensors. This portion of the NASA cryogenic propellant/fuel panel provides an overview including goals, objectives, and status for both the Modeling Portfolio and the Technologies Portfolio in the CMFPP.

Speaker: Erin Pisciotta

472 C4Or1B-04: [Invited] Cryocooler Technology Developments at NASA

NASA is developing technologies for long duration missions utilizing cryogenic propellants. Zero boil-off storage is necessary to achieve human exploration missions to Mars. Active cooling will enable these missions. Current and future cryocooler technology development efforts will be presented for storage of Liquid Hydrogen, Oxygen, and Methane.

Speaker: Sean Kenny

473 C4Or1B-05: [Invited] NASA Cryogenic Fluid Management Portfolio Project’s Demonstrations Portfolio overview

The NASA Cryogenic Fluid Management Portfolio Project’s (CFMPP) Demonstrations Portfolio designs, builds, and tests integrated flight and ground systems comprised of multiple CFM subsystems, enabling TRL 5 - 7 maturation for technologies for in-space applications both through activities performed by NASA and partnerships with industry. These partnerships are through Tipping Point contracts, a NASA Science and Technology Mission Directorate investment in advancement of on-orbit cryogenic fluid management technologies with the primary objective of reducing development costs and schedules for infusion into long duration missions utilizing cryogenic propellant. This portion of the NASA cryogenic propellant / fuel panel provides a summary of the CFMPP Demonstrations Portfolio top-level goals, objectives, and status.

Speaker: Allyson Thomas

474 C4Or1B-06: [Invited] NASA’s Human Landing Systems Program (HLS) Cryogenic Propulsion Systems Status and Overview

As part of the Artemis Program, NASA’s Human Landing Systems (HLS) Program is responsible for the development of spacecraft that will land the next American astronauts on the Moon and return them safely to a staging vehicle in lunar orbit. NASA has partnered with SpaceX and Blue Origin to lead the design and development of these human landing systems, and NASA is providing critical insight and expertise, particularly in the area of cryogenic fluid management and cryogenic propulsion systems. Both landing system architectures require advancement of cryogenic propulsion technologies such as on-orbit transfer, long-duration storage, and passive and active fluid management to achieve the lunar landing mission. This portion of the NASA cryogenic propellant / fuel panel will provide a summary of the HLS architectures, concept of operations, development status, and future test and flight plans.

Speakers: Juan Valenzuela (NASA), Reid Ruggles (NASA)

475 C4Or1B-07: Panel Discussion

M4Or1B - Hydrogen Technology and Compatible Materials

476 M4Or1B-01: Carbon-fiber Composite Cryogenic Tank for Liquid Hydrogen: Thermo-structural Analyses

The potential for use of Hydrogen fuel in aviation and ground transportation industry is growing, and along with it, the need for light-weight tanks to store liquid & sub-cooled hydrogen. Fiber-reinforced composite materials, especially, carbon-fiber composites, are widely used in aerospace industry and have replaced Aluminum, Steel and in some cases Titanium in aircraft and engine components. However, the use of composites in cryogenic applications for aviation and ground transport has started to gather interest only recently. Unique challenges exist for composite structures and materials under cryogenic conditions, in aviation and ground transport, given the long length of service, lasting years.

The RTX Technologies Research Center (RTRC) is designing and manufacturing a tank to store liquid Hydrogen (LH2) for heavy duty ground transport applications [1], through a DOE-HFTO program. This is a dual-tank concept, with an inner tank storing liquid Hydrogen under pressure, and an outer tank at atmospheric pressure. The final design follows a conformal geometry allowing for increased usage of cubic space with a largely circular tank geometry. A preliminary test article of this tank involves a cylindrical geometry. This paper describes the thermo-structural response of this cylindrical tank under pressure and thermal loading.

The inner tank, holding liquid hydrogen under pressure, is made out of carbon-fiber composite. A finite element (FE) model of the entire composite tank is set up in the commercial finite element software Abaqus [2] to assess thermal stresses in composite, which arise due to a thermal mis-match between the fiber and polymer, and also due to directional structural properties of individual plies in a composite. The inner tank is modeled with continuum shell and solid elements. A continuum damage criterion is applied to capture intra-ply damage. Inter-ply delamination is captured via the use of cohesive zone elements [3]. The applied load consists of a thermal cool-down to 20K, followed by a internal pressure in the tank. Composites are susceptible to micro-cracking due to cooling and this study examines the propensity for, and location of resulting damage. A localized model of the tank-boss interface with 3D hexahedral elements to capture stresses in more detail is set up. Stresses due to cooling from room temperature to 20K are modeled. Locations of highest stresses and the margin of safety is assessed from the analysis, permitting an assessment of the structural failure modes of the tank.

1. R K Ahluwalia, H.-S. Roh, J.-K. Peng, D. Papadias, A.R. Baird, E.S.Hecht, B.D. Ehrhart, A. Muna, J.A. Ronevich, C. Houchins, N.J. Killingsworth, S.C. Aceves; “Liquid hydrogen storage system for heavy duty trucks: Configuration, performance, cost, and safety,” IJHE, 48-35 (2023) 13308-13323
2. ABAQUS/Standard User's Manual, Dassault Systèmes Simulia Inc., 2023
3. S. R. Voleti, Prabhakar M. Rao and M. Periera “Impact response of thermoplastic composites – Experiments and modeling”, Journal of Composite Materials, https://doi.org/10.1177/00219983241304688, 2024

Speaker: Dr Sreenivasa Voleti (RTX Technologies Research Center)

477 M4Or1B-02: Investigating the effect of cryogenic conditions on the elastic behaviour of fibre-reinforced polymer composite materials under tensile loading

As the aviation industry moves toward decarbonization, liquid hydrogen (LH2) emerges as a promising alternative fuel, offering the potential for zero carbon emissions during combustion. However, the successful use of LH2 in aircraft systems relies on understanding the structural integrity of composite materials under extreme temperature conditions as LH2 boils at 20 K (-253 ºC). The tensile properties of polymer composite materials are essential to characterize and measuring them at cryogenic temperatures is therefore critical for assessing their viability in applications involving liquid hydrogen.

Several publicly available studies have indicated priority lists of materials and mechanical properties that need to be characterized under cryogenic conditions and within a liquid hydrogen environment to assess for compatibility with aerospace applications. For polymer composite materials, the top priority is carbon fibre-reinforced polymers (CFRP), followed by glass fibre-reinforced polymer (GFRP) materials. Both types of materials are typically selected for high-performance components in aircraft structures, due to their exceptional specific stiffness and strength properties. In addition, a range of auxiliary components will be essential for the adoption of LH2 as a fuel, however these are unlikely to pose such high requirements on properties but will still need thorough characterisation under cryogenic conditions. One such example is single-polymer composite (SPC) materials that, as the name implies, although consisting of a single material, still maintain the matrix and the reinforcement form that describes composites. These materials are becoming increasingly attractive to the energy industry, especially for piping applications, due to their low material cost and high-rate of production by means of tape-laying resulting in lower manufacturing costs. Their applicability to hydrogen-fuelled aircraft is also a possibility but will require comprehensive material characterisation at representative conditions to be undertaken.

In this work, tensile tests on three different fibre-reinforced polymer composite material systems (SPC, GFRP, CFRP) were carried out at room temperature, 77 K and 20 K by utilising a wet-bath cryostat to expose the specimens to a cryogenic environment. In the case of 77 K, simply submerging the test rig in liquid nitrogen is sufficient whereas for 20 K, a novel temperature control configuration was developed, operating on the principal of controllably boiling liquid helium inside the test dewar with a set of heating elements. The specimens were only loaded within their elastic region as the focus of this work was to highlight the effect of extreme low temperatures to their elastic response, namely Young’s modulus and Poisson’s ratio.

Speaker: Nassos Spetsieris (National Physical Laboratory)

478 M4Or1B-03: Piezometric properties of 3D-printed composites at cryogenic temperatures

Type-V cryogenic storage tanks, made from composite materials, have recently utilized 3D-printed composites reinforced with short carbon fibers. These materials combine lightweight design with excellent structural integrity while also exhibiting electrical conductivity and a piezometric response under applied loads. Despite these advantages, their piezometric properties remain unexplored, especially at cryogenic temperatures. This study examines the mechanical and piezometric properties (resistivity, surface conductivity) of these 3D-printed composites at cryogenic temperatures. The effects of various processing parameters—including print orientation, print temperature, and layer height—on these properties were examined and compared to their behavior at room temperature. New testing protocols have been developed to study the evolution of piezometric properties under applied strain at cryogenic temperatures. The findings reveal significant changes in piezometric characteristics at cryogenic conditions, presenting a novel approach for structural health monitoring of storage tanks without requiring additional sensors.

Speaker: Satyajit Mojumder (Washington State University)

479 M4Or1B-04: Thermal performance of common bulk-fill cryogenic insulation materials in helium and hydrogen background gasses

Maritime shipping of vast quantities of liquid hydrogen (LH2) will be necessary to facilitate a global hydrogen ecosystem; with some studies estimating volumes up to 172,000 m3 for individual tanker ships, and requiring stationary storage tanks at terminals of 50,000 m3 to 100,000 m3—ten to fifteen times larger than the current largest tank, located at launch pad B at NASA Kennedy Space Center (KSC). Such a radical scale-up will push the boundary of traditional, vacuum-insulated tank designs. Hence, a potential need exists for non-vacuum solutions, which necessitates exploring the thermal performance of insulation materials in non-condensable background gasses at LH2 temperatures, namely helium and hydrogen. Testing of two bulk-fill insulation materials common to large LH2 storage tanks, perlite and glass bubbles, in helium and hydrogen was recently conducted by the Cryogenics Test Laboratory at KSC using the Cryostat-100 liquid nitrogen boiloff calorimeter per the ASTM C1774 standard methodology. Effective thermal conductivity (ke) and heat flux (q) results for each insulation/gas combination are presented across the full vacuum range, as well as thermal profiles through the insulation thickness, and estimates of ke and q as a function of temperature between 80 K and 300 K.

Speaker: Adam Swanger (NASA)

480 M4Or1B-05: Investigating dual electrospinning as a means of enhancing passive thermal control coatings for cryogenic propellant storage in extraterrestrial environments

As space exploration becomes more prevalent, passive thermal control becomes increasingly necessary. Preserved cryogenic compressed fuels in space for exploration must be exposed to as little thermal energy as possible, and the primary objective to accomplish this task is through the reflection of incident sunlight. Current passive reflective thermal control coatings are metallic with relatively high reflectivity; however, they have some absorption, resulting in high surface temperatures on the coatings after extended exposure to sunlight. This shortcoming necessitates active cooling techniques, which are non-ideal for payload efficiency. In this regard, next-generation thermal coatings can have a significant role. Previous studies have shown that electrospun nanofibers have high solar reflectance alongside infrared emittance, resulting in a passive cooling phenomenon even when exposed to direct solar radiation. This study aims to create hybrid electrospun materials through dual-spinning by leveraging known desirable traits of different electrospun materials while minimizing undesirable traits.

Individually, different materials show promise as reflective insulators but with distinct fallbacks. Polymer-based nanofibers made from PVDF-HFP are extremely effective insulators with very high reflectivity, with average solar reflectances around 99.5%. It has satisfactory adherence to its substrate material - an aluminum foil, and is resistant to delamination and tearing. However, it experiences minor degradation in the presence of atomic oxygen. Silica-based nanofibers, on the other hand, are highly resistant to temperature fluctuations and atomic oxygen but are brittle and exhibit minimal adherence to their substrate material. It also has very good reflectivity but less so than its polymer-based counterparts, with a reflectance value averaging around 97%. This research aims to, through dual electrospinning, interweave the silica nanofibers with the polymer nanofibers (PVDF-HFP), with the goal of maintaining the reflective performance of the polymers while adopting the temperature and atomic oxygen resistance of the silica. The resultant composite electrospun material is expected to have a reflectivity value of approximately 98-99%, which is more resilient to atomic oxygen and thermal cycling than the component materials.

Speaker: Adrien Neveu (Rensselaer Polytechnic Institute)

481 M4Or1B-06: Design and cryogenic mechanics finite element analysis of a novel sandwich structure mouth for Type V storage vessels

Liquid hydrogen (LH2), recognized as a sustainable green fuel, has garnered significant attention in the field of unmanned aerial vehicles (UAVs) owing to its high energy density and hydrogen purity. However, storing LH2 imposes stringent requirements on the cryogenic temperature mechanical properties of hydrogen storage vessels. Existing hydrogen storage vessels are susceptible to inner liner failure at cryogenic temperatures due to the thermodynamic mismatch between the liner material and the external carbon fiber reinforced polymer (CFRP). In response, a linerless hydrogen storage vessel (Type V vessel) has been proposed as a potential solution. However, the thermal mismatch between the metal material of the BOSS structure and CFRP at cryogenic temperatures presents a significant challenge to the further development of the Type V vessel.
This study employs CFRP with added polyethylene (PE/CFRP) as the inner layer for the Type V vessel. A CFRP-BOSS-PE/CFRP sandwich structure is proposed to mitigate the thermal mismatch between the BOSS structure and the carbon fiber composite at cryogenic temperatures. The sandwich structure consists of a CFRP outer layer, a 6061-T6 aluminum alloy BOSS intermediate layer, and a PE/CFRP inner layer, with adhesive bonding facilitated by a 7 wt.% polyethylene glycol (PEG)-modified polyurethane (PU) resin. The dome of the PE/CFRP liner is designed with a standard ellipsoidal profile. The inner surface of the BOSS is shaped to conform to the ellipsoidal profile of the PE/CFRP liner, with its maximum inner diameter equal to half the outer diameter of the PE/CFRP liner. The outer surface of the BOSS is also designed with an ellipsoidal profile. The CFRP layer is tailored to match the shape of the BOSS structure.
A finite element model of the sandwich structure for cryogenic mechanics was developed to assess the structural reliability under LH2 storage conditions. Based on a PE/CFRP liner with a body length of 390 mm, an outer diameter of 160 mm, and an ellipsoidal head ratio of 2, BOSS structures with outer surface ellipsoidal ratios of 1.2, 1.3, 1.4, 1.5, and 1.6 were designed. Using these structures, 1/8-scale finite element models of the Type V vessels were developed. Cohesive zone model was employed to simulate the bonding between the different material layers. Static structural simulations were conducted on these models under LH2 storage conditions (20 K, 2 MPa). The simulation results demonstrate that the interface stress in all models remains below 60 MPa, which is within the elastic limit of the modified PU resin at the specified temperature. These results confirm that the adhesive material in all models remains within the elastic phase. The BOSS with an outer surface ellipsoidal ratio of 1.4 exhibited the lowest maximum interface stress, thereby making it the optimal design.
Therefore, the proposed CFRP-BOSS-PE/CFRP sandwich structure represents a viable design for Type V vessels. The BOSS with an outer surface ellipsoidal ratio of 1.4 demonstrates optimal mechanical performance under LH2 storage conditions. The vessel mouth sandwich structure and BOSS design offer significant potential for application in the manufacturing of Type V LH2 storage vessels.

Acknowledge:
This work was supported by the Frontier Technology R&D Program of Jiangsu Province (granted number, BF2024020).

Speaker: LianJi Li (Southeast University)

482 M4Or1B-07: Study on cryogenic mechanical and gas-barrier properties of graphene oxide modified epoxy resin

As a renewable and clean energy, hydrogen energy plays a crucial role in constructing the low-carbon and efficient modern energy infrastructure. Hydrogen storage is a key link in the hydrogen energy application chain. The common vessels with metal or plastic inner liners are prone to defects such as hydrogen embrittlement, collapse, and delamination. All-composite vessel (Type V vessel) is a new type of cryogenic liquid hydrogen vessel. Its composite layers serve both as a pressure-bearing and gas-barrier function. However, the resin matrix of composite materials, which tends to become brittle in cryogenic environments, experiences a decline in mechanical properties. In addition, since the polymer contains a large amount of free volume, gas molecules are easy to escape in the free volume. Therefore, the resin matrix must be modified to improve its cryogenic mechanical strength and gas barrier properties simultaneously.
In this study, KH550 silane coupling agent was used to modify graphene oxide (GO) through a one-step hydrothermal method. The surface modification of GO by KH550 silane coupling agent enhanced the interfacial bonding between GO and the resin matrix. In this case, agglomeration of particles occurred less often at cryogenic temperatures. The product was named k-GO (functionalized graphene oxide). The modification effect was analyzed using infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The results of structural analysis revealed changes in the functional groups, interlayer spacing and surface morphology of the modified GO. The outcome confirms the successful grafting of KH550. Then, the k-GO/epoxy resin composite was prepared by blending method. The mechanical and gas barrier properties of composites with different k-GO contents were investigated. The results demonstrated that when k-GO content was 0.1 wt.%, the k-GO/epoxy resin composite achieved its maximum mechanical strength. Compared to pure epoxy resin, the tensile strength increased by 7.7% and 16.3% at room and cryogenic temperature, respectively. When k-GO content was 0.2 wt.%, the k-GO/epoxy resin composite achieved its maximum gas-barrier properties. The gas permeability coefficient decreased by 15.8%, compared to pure epoxy resin. Although this method enhanced both mechanical strength and gas barrier properties, the peak values occurred at different k-GO concentrations. This prevented the simultaneous improvement of the two attributes required for the Type V vessels. Therefore, to meet the requirements of all-composite vessels under cryogenic conditions, k-GO and PEG (polyethylene glycol) were used to modify the resin, which enhanced the cryogenic mechanical strength while maintaining its gas barrier properties. The results gave that when the incorporation of k-GO was 0.2 wt.% and PEG was 5 wt.%, the cryogenic tensile strength of the composites was increased from 79.73 MPa to 98.55 MPa, which was increased by 28.8%, compared with pure epoxy resin. At the same time, the gas permeability coefficient only increased by 0.3% compared to the case without PEG.
In this paper, the epoxy resins with high cryogenic strength and high gas barrier performance are prepared by the cooperative modification of k-GO and PEG. It is expected to be used in the manufacturing of Type V all-composite vessels, and promote the application of liquid hydrogen energy supply technology.

Acknowledge:
This work was supported by the Frontier Technology R&D Program of Jiangsu Province (granted number, BF2024020).

Speaker: Mr Junjie Chai (School of Mechanical Engineering, Southeast University, Nanjing 211189, China)