# ICEC/ICMC 2014 Conference

Europe/Amsterdam
, ,
Description
The joint

ICEC 25,  the 25th International Cryogenics Engineering Conference

and

ICMC 2014,  the 2014 International Cryogenics Materials Conference.

• Monday, July 7
• Registration: Registration starts on Monday morning at 10:00, ends at 17:00 in the conference center Registration desk (Entry Hall)

### Registration desk

#### Entry Hall

• Monday Courses
• 1
Course 1: Cryo-Coolers 2L (2nd floor building Carre)

### 2L

#### 2nd floor building Carre

Speaker: Fons De Waele (Eindhoven University of Technology)
• 2
Course 2: Cryostat Design WA3 (First floor building Waaier)

### WA3

#### First floor building Waaier

Speaker: John Weisand (European Spallation Source)
• 3
Course 3: Superconducting Materials for Power Applications WA4 (2nd floor building Waaier)

### WA4

#### 2nd floor building Waaier

Speaker: Pascal Tixador (CNRS - Grenoble)
• Registration: Registration desk open Registration desk (Entry Hall)

### Registration desk

#### Entry Hall

• 5:00 PM
Break
• Registration: Registration Open during Welcome Reception Registration Desk (Faculty Club)

### Registration Desk

#### Faculty Club

• 6:00 PM
Welcome Reception and Continued Registration (free drinks and a buffet-type meal will be served) Faculty Club Garden (buiding 42 on Campus Map, at a short walk from the conference center)

#### Faculty Club Garden (buiding 42 on Campus Map, at a short walk from the conference center)

• 9:00 PM
Shuttle service to hotels
• Tuesday, July 8
• 8:00 AM
Registration desk open Entry hall

### Entry hall

Open from 8:00-18:30

• Tue-Mo-Plenary Session 1: Opening of the Conference, Introduction to the Day and 2 Plenary Orals WA1

### WA1

Conveners: Philippe Lebrun (CERN) , Steven Van Sciver (Florida State University)
• 4
Opening of the Conference
• 5
SPACE CRYOCOOLER DEVELOPMENTS
The need for cryogenic cooling in space has become of increasing importance with time. In many space sciences projects cryogenic detectors are essential for the accomplishment of the scientific objectives. Several other components such as the optics can benefit from a cryogenic cooling which reduces the radiative loading on the detectors. The current trend in space cryogenic is to develop cryogen free satellite, ie suppress the liquid reservoir for mechanical coolers. Although liquid cryostat is a straightforward technique, it leads to heavy reservoirs and structures and by essence limits the mission duration. For low temperature, several systems must be chained together to cover the temperature range, which now extends to 50 mK for some future space missions. Obviously the overall performance of the cryogenic chain depends on the performance of each links, on their ability to operate together and finally on the compatibility with the detectors. The use of mechanical coolers can require dedicated devices to distribute the cooling effect far from the cooler cold head and/or to deal with the temperature stability and limited instant cooling power. For decades development programs have been carried out to produce space cryocoolers able to provide net heat lifts at various temperature. At the European level, the laboratories and industries involved in space cryogenics are now in a position to propose full cryogenic chains from ambient temperature down to 20 mK. In this paper we will give an overview through selected examples, and a particular focus on European developments will be made.
Speaker: Lionel DUBAND (C)
• 6
Study on Introduction of CO2 Free Energy to Japan with Liquid Hydrogen
In Japan, both attainments of CO2 emission reduction and energy security are the very important social issues after Fukushima Daiichi accident. On the other hand, fuel cell vehicles utilizing pure hydrogen will be on the market in 2015. It is anticipated that hydrogen consumption in Japan will exceed domestic production capability in the next decade. From these backgrounds, Japanese government has been making a road map on the introduction of hydrogen energy supply chain. Under these circumstances, imported CO2 free hydrogen will be one of the solutions for energy security and CO2 reduction, if the hydrogen price is affordable. Accordingly, realization of low cost hydrogen production is of importance. To achieve this, Kawasaki Heavy Industries, Ltd. (KHI) performed a feasibility study on CO2-free hydrogen energy supply chain utilizing Australian brown coal linked with CCS (Carbon dioxide Capture and Storage). In the study, brown coal gasification hydrogen production systems, transportation methods etc. are examined. The supply chain with liquid hydrogen transportation shows the lowest CIF (Cost Insurance and Freight) of hydrogen for the first commercial chain. The CIF of hydrogen is 1.5 times higher than that of natural gas imported to Japan today. The imported hydrogen linked with CCS is virtually CO2 free and thus will become competitive to price rising conventional fossil fuels when CO2 penalties, e.g. taxes, is imposed. This paper presents structure of the CO2 free hydrogen supply chain, and cost breakdown of the CIF. Based on the evaluated hydrogen cost, fuel economy is compared between fuel cell and gasoline engine hybrid electric vehicles. Also, cost of power (electricity: yen/kWh) is compared amongst hydrogen gas turbine combined cycle and existing power generations.
Speaker: Dr Shoji KAMIYA (Kawasaki Heavy Industries, Ltd.)
• 7
Gustav and Ingrid Klipping Award ceremony
• 10:35 AM
Coffee Break Exhibition and Posters Area

### Exhibition and Posters Area

• Tue-Mo-Orals Session 1: Magnet Design and Quench Protection WA1

### WA1

Convener: Rainer Wesche (Ecole Polytechnique Fédérale de Lausanne (EPFL))
• 8
[Invited Oral] Design Options of the Superconducting Detector Magnets for a very large 100 TeV Hadron Collider
Early 2014 a new design study has started at CERN for a future 100 TeV circular proton-proton collider, a factor 7 more than in the present LHC. A new 100 km tunnel for the collider magnets is foreseen as well as two new general purpose detectors. A conceptual design report is to be issued in 2018 for consideration by CERN and collaborating institutes. The new 100 TeV collider may be operational earliest medio 2040. The increase in collision energy from 7 to 100 TeV implies a scaling up of the detector magnets as well in size and magnetic field for maintaining particle detection resolution. Options for the new detector magnet systems are being explored. Option one is a scaling up of the ATLAS magnet system layout based on using toroids for muon tracking and a solenoid for the inner detector. Also two dipole magnets are incorporated for covering the low angle forward directions. In a similar way the second option features a scaled-up CMS solenoid but also in combination with two dipole magnets. The outer dimensions of the magnet systems show a diameter of 20-30 m and an overall length of 40 to 50 m. The magnetic field in the bores of the large toroid and solenoid will go up to some 2.5 and 6 tesla, respectively, with peak magnetic fields in the 7-8 tesla range, still possible with NbTi technology. The magnetic stored energies are in the record range of 50-100 GJ.
Speaker: Herman Ten Kate (CERN)
• 9
Reduction of screening current-induced magnetic field for REBCO coils by the use of multi-filamentary conductors
A screening current induced in REBCO superconducting layers during coil charging and causes several problems such as hysteresis effect of the central magnetic field and reduction in the central magnetic field intensity. These are critical problems for superconducting coil systems such as NMR. The present work systematically investigated reduction effect of the screening current-induced field by the use of multi-filamentary conductors based on coil experiments and numerical simulation. 4 mm-width REBCO conductors were divided into three filaments along the longitudinal direction using a cutter. A coil which comprises three double pancake coils was wound with the conductors. The inner diameter, outer diameter, and length of the coil are 30 mm, 37 mm, and 28 mm, respectively. The number of total turns and the total length of the conductors are 162, and 16.8 m, respectively. The coil was charged to the coil critical current for both positive and negative polarities in liquid nitrogen and the central magnetic field was measured by a Hall sensor. The same measurement was made for another coil wound with mono-filamentary REBCO conductors, which had the same configuration as the multi-filamentary coil. The screening current-induced field, Bs, for the multi-filamentary coil at a loading factor of 80%, was 38% of that for the mono-filamentary coil. Simulation showed a similar result. Thus, Bs was reduced to ~1/3 by dividing the REBCO layers into three filaments. And we found the reduction effect of the multi-filamentary conductors on the screening field is notably effective for high-loading factor operations.
Speaker: Yi XU (RIKEN,Yokohama,Japan;Chiba University,Chiba,Japan)
• 10
Construction and test of a non-insulated insert coil using coated conductor tape
An insert coil was constructed using coated conductor tape without electrical insulation. The coil inner diameter, outer diameter and height are 43 mm, 56 mm and 120 mm respectively; the coil constant is 16.7 mT/A. The coil is composed of 13 double pancakes (270 m of tape in total) with insulating disks placed in between the pancakes; the coil was impregnated with beeswax. The reason for choosing a coil without turn to turn insulation is to obtain a better tolerance to over-current. Indeed, at 77 K it was possible to apply twice the critical current, without any thermal run-away, because of the current sharing between tapes in adjacent turns; of course at such high currents the magnetic field generated in coil centre is lower than the expected value, the current flowing radially instead that azimutally (along the superconducting ceramic). The quench protection is a simple circuit which switches the power supply off when the voltage exceeds a threshold value that can be set between 50 mV and 200 mV. After the power supply is switched off the energy stored in the coil is dissipated in the coli itself, with the contact resistance between turns replacing the dump resistor usually found in standard insulated coils. Quench tests at 4.2 K in self field and in background field (up to 12 T) were also carried out.
Speaker: Davide Uglietti (EPFL)
• 11
Quench detection and protection for high-temperature superconducting magnets: lessons from Bi-2212
High temperature superconducting magnets may enable applications ranging from high field magnets generating magnetic fields of >20 T and highly efficient electric power devices such as superconducting magnetic energy storage systems and wind generators. A critical roadblock, however, is to detect a normal zone propagating only at a speed of 1-10 cm/s, while the maximum temperature of the normal zone rises quickly at 10-200 K/s, depending on the stabilizer current density, operating temperature and magnetic field. This presentation will report on the quench characteristics of a round wire Bi-2212 as well as small-scale Bi-2212 coils at 4.2 K and in a background field up to 14 T. Conductors and coils tested included those made using both 1 atmosphere melt processing, which yield an engineering current density Je of 300 A/mm2 at 20 T, 4.2 K, and an overpressure process, which was recently used to achieve Je above 700 A/mm2 at 20 T, 4.2 K in short-length round wires of Bi-2212. Based on the experimental and modeling results of quench propagation in Bi-2212, this talk will also discuss the feasibility and trial tests of using various strategies to detect quenches, including traditional voltage based method, fiber optics, acoustic emission sensors, and an innovative quench detection sensor being developed at Fermilab.
Speaker: Tengming Shen (Fermilab)
• 12
Study of quench behaviors of REBCO impregnated pancake coil with 75-um-thick copper stabilizer under conduction-cooled condition
Recently, high performance REBa2Cu3Ox (REBCO) coated conductors such as over 250 A per 5 mm in width at 77 K have become in commercial. The REBCO coated conductors are expected to show high performance for the superconducting applications because of their high current density and high mechanical strength. The quench behaviors, particularly the normal-zone propagation and increase in hot-spot temperature, of REBCO pancake coils are important issues for safe operation in the superconducting applications. Although the experimental data on the quench characteristics of REBCO coated conductors have been reported, there is insufficient data of REBCO impregnated pancake coils. In this work, a REBCO impregnated pancake coil was fabricated using REBCO coated conductors laminated with 75 um-thick copper stabilizer. The inner diameter of the REBCO coil was 50 mm and outer diameter was approximately 73 mm. The measured longitudinal normal-zone propagation velocities (NZPV) in the REBCO coil were 3-8 mm/s at 50, 40 and 30 K.We also confirmed that the REBCO coil was shut down from 240 A at 40 K without degradation after the detected normal transition.
Speaker: Masanori Daibo (F)
• 13
The Roebel Assembled Coated Conductor (RACC) cable, status of performance and prospects for further upgrades
The high temperature REBCO coated conductor development is progressing in available conductor length and current capacity performance. Such conductors are available commercially and are used in an increasing number of applications. The application in large superconducting magnets (fusion) or high current windings (generators, motors) requires high current carrying conductors with low AC losses, as the RACC cable. In contrast to most of the alternative cable concepts, the RACC cable shows a comparable current anisotropy in background fields as the REBCO tape. This gives the opportunity to take advantage of nearly the maximum possible current aligning the cable in the favourable field orientation. The consequence is an advantage of up to approximately the 4-fold current compared to alternative cable concepts where the tapes are twisted and are experiencing all field directions. This is important for the costs and the optimum in engineering current density. The RACC cable is assembled from Roebel strands punched out from tapes. The absence of defects in particular along the tape is a crucial quality feature of the strand since the current flows in a meander like trace. An option for further reduced AC losses are filament structures in the strands, cut by a laser. A filament structure is extraordinary sensitive to defects, in particular if their size approaches the filament width. With reduced width an increasing influence on the transport current is observed. We present data on REBCO tapes and results achieved on Roebel strands with up to 20 filaments. A systematic work on filamentarized RACC conductors will be shown. Summarizing the different contributions affecting the currents, the potential of the current carrying capability of RACC cables will be discussed and evaluated.
Speaker: Dr Wilfried Goldacker (Institute for Technical Physics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany)
• 14
Self-healing effect from thermal runaway for uninsulated REBCO coils
The major advantage of REBCO coils is their capability for high current density operation, typically >250 A/mm2. However, if a thermal runaway happens at such a high current density, a hot spot quickly exceeds hazardous temperatures, >300 K, resulting in permanent damage to the coil winding. This is the most serious problem for high-current density REBCO coils and a protection method is required. The uninsulated winding method (Hahn et. al. IEEE Trans. Appl. Supercond. 212, 1592-1595, 2010) is promising for protection of high current density REBCO coils. We have demonstrated that thermal runaway is self-healed due to the current mode transition; i.e. thermal runaway triggers a transition of current flow patterns from the usual “multi-turn” mode to the “single-turn” mode, resulting in dissipation of the thermal runaway. For much higher overcurrents, the coil goes into “terminal-to-terminal current” mode, resulting in an overheated region between the electrodes. This paper investigated (i) the effect of cooling conditions and (ii) the effect of the local Joule heating in uninsulated REBCO coils, to clarify the basic behavior of the current mode transition. For a dry-wound uninsulated coil, the transitions between the three modes are clearly observed and the transitions are reversible for charging and discharging processes. On the other hand, a paraffin impregnated uninsulated coil in a quasi-adiabatic condition showed a complicated behavior. After the transition from multi-turn mode to single-turn mode, the coil showed “terminal-to-terminal current” immediately. Then, during the discharging process, the coil did not return to multi-turn mode from single-turn mode. The behavior of current mode transition and the effect of cooling condition for layer-wound REBCO coils and pancake-stacked REBCO coils will be also investigated.
Speaker: Ms Kyoko Yanagisawa (RIKEN,Chiba Uneversity)
• Tue-Mo-Orals Session 2: Joule-Thomson cryocoolers WA2

### WA2

Convener: John WEISEND (SLAC)
• 15
[Invited Oral] Separator of 3He isotope from liquid 4He
Nowadays the worldwide market of He3 isotope is under strong crisis. The new technologies of radiological and nuclear materials detectors as well as science, industrial and medicine applications required a large amount of this helium isotope. On the other hand, a production of the nuclear weapon, which 3He is a by-product, is successively reduced last decades. Therefore to meet the 3He market demands an exploration of new sources of this isotope need to be considered. One of alternative 3He isotope source is liquid 4He. Unfortunately, its natural concentration in 4He varies from a few tenths to a few ppm only. Moreover, last years a drastic increase of liquid 4He price is observed, what can cause the 3He separation cost extremely high. The places where the 3He separator installation can still provide financial profit are large liquid helium production plants. PGNiG SA branch Odolanow in Poland, with of about 100 kg/h LHe production, makes an attractive place for such installation. Therefore, Wroclaw University of Technology, PGNiG SA and Institute of Molecular Physics of Polish Academy of Sciences in Poznan, Poland, lunch a pilot program to design and run a prototype separator of 3He from 4He. Paper presents description and conceptual design of the 3He from 4He separation cryostat. The separator consists the J-T scheme based cooling loop with external warm compressor for helium vapor pressure lowering, the recuperative heat exchanger working between 4.2K and 1.5K as well as the separation vessel with so call “entropy filter”. The advantage of the separator is that the LHe stream leaving device after separation will still under the liquid form, which remains its marked value, what keeps the cost of 3He separation on the low level.
Speaker: Dr Jaroslaw POLINSKI (PWR)
• 16
Study on a miniature mixed-gases Joule-Thomson cooler driven by an oil-lubricated mini-compressor for 120 K temperature ranges WA2

### WA2

The mixed-gases Joule-Thomson (J-T) refrigerator driven by oil-lubricated compressor has many merits, such as high reliability, low cost, high efficiency with optimized design. For many applications, the size and weight are crucial factors for the system design. Miniature J-T coolers, especially those open cycle coolers using high-pressure pure nitrogen for infrared devices cooling, have already been used for decades, in which the size of the cold figure is quite small with Linde-Hampson heat exchanger. With the progress of miniaturization technologies, oil-lubricated mini-compressors are available for individual cooling or electronic devices applications. So in this paper, a miniature J-T cooler using multicomponent mixtures was developed and tested, in which an oil-lubricated mini-compressor was used to drive the cooler. A plate-fin type heat exchanger with micro-channel configuration was designed and fabricated with electric wire-cutting method, which is used as the recuperative heat exchanger. Experimental tests on the performance of the miniature J-T cooler were carried out. The minimum no-load temperature of 110 K and about 4 W cooling capacities at 118 K were achieved. Such miniature J-T coolers driven by oil-lubricated mini-compressors show good prospects in many applications.
Speaker: Prof. Maoqiong Gong (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)
• 17
Vibration-free cooler for the METIS instrument using sorption compressors WA2

### WA2

METIS is the ‘Mid-infrared ELT Imager and Spectrograph’ for the European Extremely Large Telescope that will cover the thermal/mid-infrared wavelength range from 3 – 14 micron. Starting from a pumped nitrogen line at 70K, it requires cryogenic cooling of detectors and optics at 40K (1.4 W), 25K (1.1 W), and 8K (0.4 W). A vibration-free cooling technology for this instrument based on sorption coolers is under development at the University of Twente in collaboration with Dutch Space. We propose a sorption-based cooler with three cascaded Joule-Thomson coolers of which the sorption compressors are all heat sunk at the 70K platform. A helium-operated cooler is used to obtain the 8K level with a cooling power of 0.4 W. Here, three pre-cooling stages are used at 40K, 25K and 15K. The latter two levels are provided by a hydrogen-based cooler, whereas the 40K level is realized by a neon-based sorption cooler. Based on our space-cooler heritage, our preliminary design used sorption compressors equipped with gas-gap heat switches. These have maximum efficiency, but the gas-gap switches add significantly to the complexity of the system. Since in METIS relatively high cooling powers are required, and thus a high number of compressor cells, manufacturability is an important issue. We, therefore, developed an alternative cylindrical compressor design that uses short-pulse heating establishing a thermal wave in radial direction. This allows to omit the gas-gap heat switch. The paper discusses modeling, validating experiments, and the consequences in the design of the METIS cooler.
Speaker: Yingzhe Wu (University of Twente)
• 18
Performance Analysis of Joule-Thomson Cooler Supplied with Gas Mixtures WA2

### WA2

Joule-Thomson (J-T) cryo-coolers working in closed cycles and supplied with gas mixtures are the subject of intensive research in different laboratories. The replacement of pure nitrogen by nitrogen-hydrocarbon mixtures allows to improve both thermodynamic parameters and economy of the refrigerators. It is possible to avoid high pressures in the heat exchanger and to use standard refrigeration compressor instead of gas bottles or high-pressure oil free compressor. Closed cycle and mixture filled Joule-Thomson cryogenic refrigerator providing 50 W of cooling power at temperature range 90-100 K has been designed and manufactured. Thermodynamic analysis including the optimization of the cryo-cooler mixture has been performed with ASPEN HYSYS software. Preliminary tests has shown instability of the cooler working parameters. The paper describes the design of the cryo-cooler and provides thermodynamic analysis of the system. The test results are presented and discussed.
Speaker: Dr Agnieszka Piotrowska (Wroclaw University of Technology)
• 19
Sensitivity of micromachined Joule-Thomson coolers to clogging due to moisture WA2

### WA2

A major issue in long-term operation of micromachined Joule-Thomson coolers is the clogging of the microchannels and/or the restriction due to the deposition of water molecules present in the working fluid. To verify which microcooler design is the least sensitive to clogging, the operating times of various microcoolers with a cold-end temperature of 120 K are compared. In these experiments, relatively low-purity nitrogen gas (5.0) is supplied from a gas bottle and led through a filter to control the concentration of water vapor. The filter consists of a tube-in-tube counter flow heat exchanger and a heat exchanger that is stabilized at a certain temperature by using a Stirling (other) cooler. The set-point temperature determines the equilibrium water partial pressure at the exit of the heat exchanger, as given by the water sublimation curve. Meanwhile, we have developed a model for predicting the deposition rate of water molecules in a previous study. An updated model is developed to investigate how the deposition rate affects the mass-flow rate of a microcooler and thus to predict the operating time of the microcooler.
Speaker: Dr Haishan Cao (University of Twente)
• 20
Demonstration of active magnetic regenerative refrigeration with pump-less system WA2

### WA2

Active magnetic regenerative (AMR) refrigeration is well established concept of magnetic refrigeration which can generate a large temperature difference between both ends of a regenerator (AMR bed) by accumulating a lot of small temperature changes on every piece of magnetocaloric materials. In the AMR cycle, the magnetocaloric material and heat transfer fluid work collaboratively to accumulate a small temperature difference in the AMR bed. Specifically, magnetocaloric materials become warm by applying a magnetic field with magnets, and then, the warm heat transfer to one side of the AMR bed by the fluid flow. After that, magnetocaloric materials become cold by removing a magnetic field, and then, the coldness transfer to the other side of the AMR bed by the fluid flow in the opposite direction. In order to operate AMR cycle, both magnetic field changing mechanism and fluid flow mechanism are necessary. In many studies, the fluid flow is executed by piston motion or pumping. In this paper, we report a new concept of the AMR cycle operation in which fluid flow requires no power. We have developed a primitive rotary AMR apparatus with the only one source of power for the motor of rotating magnets. The reciprocating fluid flow motion can be accomplished by tug of war between magnetic force and elastic force of springs. More than 10 degrees in temperature difference have demonstrated between both ends of AMR bed by cycle operation with the only input for magnetic field changing mechanism. This concept will be effective to downsize and get higher efficiency of AMR cycle system.
Speaker: Dr Akiko Saito (Toshiba corporation)
• 21
Miniature Piezoelectric Compressor for Joule-Thomson Cryocoolers WA2

### WA2

Joule-Thomson (JT) cryocoolers operate with a continuous flow of the working fluid that enters the cooler at a high pressure and leaves it at a lower pressure. Ideally, the temperature of the outgoing fluid equals the temperature of the entering fluid. JT cryocoolers that operate with pure refrigerants require high pressure of a few tens of MPa where the low pressure is usually around 0.1 MPa. Circulation of the working fluid in such cases requires high pressure ratio compressors that evidently have large dimensions. JT cryocoolers can operate with much lower pressure ratios by using mixed-refrigerants. Cooling from 300 K to about 80 K in a single stage cryocooler normally requires pressure ratio of about 1:25. In the present research a miniature compressor driven by piezoelectric elements is developed in collaboration between Rafael and the Technion. This type of compressor has the advantage of improved long life compared to other mechanical compressors, very low vibrations, and silent operation. In the current case, the design goal of the intake and discharge pressures has been 0.1 and 2.5 MPa, respectively, with a flow rate of 0.06 g/s. The compressor has two compression stages; 1:5 and 5:25. Several configurations have been considered, fabricated, and tested. The performance of the last configuration approaches the desired specification and is presented in the current paper together with the design concept.
Speaker: Sergey Riabzev (Ricor)
• Tue-Mo-Orals Session 3: High Performance RE123 Tapes and Nb3Sn Wires WA4

### WA4

Convener: Teruo Matsushita (K)
• 22
[Invited Oral] Long-length YBCO coated conductors manufactured in medium size pilot production line based on pulsed laser deposition
Pulsed laser deposition (PLD) was implemented in processing of high quality coated conductors of long length. Experimental data on YBCO coated conductor (CC) tapes with a length up to 200 m processed employing a multi-beam PLD (MB-PLD) technique with a throughput up to 40m/hour are presented. The YBCO films were deposited onto stainless steel substrate tapes preliminary coated with bi-axially textured yttria-stabilised-zirconia buffer layer and CeO2 cap layer. Possibilities for further gain of the throughput is demonstrated and discussed. Using optimized conditions we deposited a number of 4mm wide YBCO coated tapes, each with a length up to 200 m. Critical currents measured in these tapes with linear resolution of 0.3 mm were in between 200 and 400 A/cm-width (at 77K in self-field). Obviously, these tapes represent so far the longest coated conductors manufactured in Europe. Homogeneity, connectivity, local weak zones and their influence to quench behaviour are studied together with critical current densities in YBCO coated conductors. Outstanding behavior of critical current in high magnetic fields was demonstrated in tapes with artificial and “intrinsic” pining. In 18 T field by B||c and 4.2 K, the tapes are capable to carry critical currents up to 1.2 kA/cm-width. This seems to be the highest values observed so far. Acknowledgements: This work was supported in part via European Projects EUROTAPES and EUCARD-2.
Speakers: Dr Alexander Usoskin (Bruker HTS GmbH) , Mr Tim Bubelis (Bruker HTS GmbH)
• 23
Characterization of (Re)BCO conductor for development of 32T superconducting magnet
In order to successfully use (Re)BCO conductor in the 32T all-superconducting user magnet, a variety of its properties should be controlled in the required 10 km of tape within specific tolerances defined by the coil design. So far we have evaluated short samples from more than 102 conductor 60-110 m piece lengths, each manufactured by SuperPower Inc. We observe only a small variability of $\alpha$ values ($I_c(H)\propto B^{-\alpha}$ ) $<\alpha>$=0.82; $\sigma_{\alpha}$=5.2%. $I_c(4K, 17T, 18^o)$ extrapolated from data measured up to 13.5T for samples from different production runs has a mean of 290A and standard deviation $\sigma_{4K}$=17%, but $< I_c(77K, SF) >$=131A, $\sigma_{77K}$=8.4%. The normalized to the average difference between $I_c$ from each end of each tape is small ($\sigma_{r77K}$=4.8%) at 77K, SF but about twice as large for $I_c(4K, 17T, 18^o)$ where $\sigma_{r4K}$=9.3%. The highest values and lowest spread of $I_c(4K, 17T, 18^o)$ occur for tapes with smallest spread of $T_c$, larger $\alpha$ values, smaller angle between ab-planes and tape plane, and lower CuO grain density. These measurements have been performed within the context of quality assurance (QA) procedures developed for (Re)BCO conductor, which includes magnetic field dependence measurements of critical currents at 4.2K up to 13.5T at $18^o$ from the tape plane, a critical orientation for the 32T coil design, the self-field joint resistance at 77 K, residual resistivity ratio of Cu stabilizer, dimensional tolerances, and its uniformity. Optimal choice of tape and its orientation for stacking in top and bottom coil parts based on Ic statistics will be discussed.
Speaker: Dr Dmytro Abraimov (NHMFL)
• 24
Enhancement of In-field J<sub>c</sub> in GdBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-$\delta$</sub> Coated Conductor by Using Highly Oriented IBAD Substrate
For the improvement of Jc in rare-earth based superconducting coated conductor (CC), it is well established that highly oriented substrate is required because Jc across grain boundaries decreases significantly with increase of grain boundary angles. Typical value of the in-plane misalignment of Ion Beam Assisted Deposition (IBAD) substrate is around 3$^\circ$ where intra-grain Jc is almost the same level of inter-grain Jc at 77K, self-field. However, the effectiveness of highly oriented IBAD substrate on in-field Jc and its temperature dependence have not well clarified yet. In this study, we compared current transport properties in two GdBa2Cu3O7-$\delta$ CCs deposited on different quality of IBAD templates, i.e., in-plane alignment of the substrate is 1.98$^\circ$ and 2.78$^\circ$, respectively. From the comparison, Jc enhancement can be confirmed in wide temperature and magnetic field region in the sample using highly oriented IBAD substrate, whereas the irreversibility field doesn’t change much. Macroscopic pinning force density curve of these two samples are similar, however, the maximum value of the pinning force density was increased. For the further understanding of the origin of Jc enhancement, we analyzed statistical distribution of Jc from E-J curve by using the percolation transition model. From the analysis, it can be seen that the minimum value of Jc distribution was increased as the substrate texturing is improved. These results indicate that the enhancement of in-field Jc comes from the improvement of grain connectivity. It should be noted that the improvement of in-plane texturing in the substrate is still very effective even in such range of 2 to 3$^\circ$. This work was supported by the METI: Development of Fundamental Technology for HTS Coils".
Speaker: Masayoshi Inoue (Kyushu University)
• 25
Transverse, axial and torsional strain tests on ReBCO tapes
For fusion superconductors in high magnet fields with currents in the order of 50 kA, single ReBCO coated conductors must be assembled in a cable geometry where combined torsion, axial and transverse loading states are anticipated in the tapes and tape joints. Axial and transverse loading, caused by differential thermal contraction and electromagnetic forces, may affect the transport properties. The effect of pre-applied twist on degradation of current carrying capability as a function of controlled tensile stress was studied at 77 K. Initial results of the effect of transverse pressure applied to tapes and lap joints. The transport properties and irreversibility limits are compared for pure axial tensile and compressive loading tests on free standing samples and when soldered to a Ti-alloy U-spring. An overview of the facilities and present results obtained on tapes from different manufacturers is given.
Speaker: Chao Zhou (University of Twente, Faculty of Science & Technology, 7522 NB Enschede, The Netherlands)
• 26
Options for epoxy impregnation of REBCO Roebel cables
REBCO Roebel cables combine high current density with low AC loss, and as such are promising for HTS inserts in high-field accelerator magnets (up to 20 T). The Lorentz forces in these magnets accumulate over the windings and may lead to local stress concentrations in the cable structure. An appropriate impregnation of Roebel cables – and eventually coils – redistributes these forces, and thus increases the transverse cable strength. Epoxy impregnation of REBCO cables and coils is challenging: first, REBCO tapes are known to delaminate under transverse tensile stresses, which may arise due to a thermal expansion mismatch with the epoxy. The punched Roebel strands are especially susceptible to this, because the copper sheath is removed at their edges. Second, the REBCO layer can be chemically affected, since it is directly exposed to the impregnation material. Finally, impregnation may decrease the stability of the cable if the strands become thermally or electrically isolated. We report on the impregnation of Roebel cables with epoxy resins loaded with different fillers (alumina, quartz, silver, graphite) to tune their thermal conductivity, electrical resistivity and thermal expansion. The impregnation methods are first tested on single REBCO tapes and steel Roebel dummies, to ensure that the strands are not damaged and that the epoxy penetration is adequate. Impregnated cables are then subjected to thermal cycling and checked for degradation. Finally, the transverse pressure dependence of the critical current of a suitably impregnated cable is tested in conditions close to those inside an accelerator magnet (T = 4.2 K, B = 11 T).
Speaker: Anna Kario (KIT)
• 27
Developing Nb3Sn and Bi-2212 conductor s for high field magnet applications
Oxford Superconducting Technology (OST) has been continuously improving Nb3Sn and Bi-2212 round wire performance for application in high-field magnets. For particle accelerator applications the Nb3Sn development focus has been to reduce the effective filament diameter while maintaining high Jc and RRR. We will present our latest results on 169 stack distributed barrier strand designs with modified Nb, Sn and Cu ratios to maintain high values of RRR and Jc in strands having subelement diameter of less than 50 µm. We will present results on strands developed through the US Conductor Development Program with thicker diffusion barriers, modified metal ratios, and higher stack counts to improve RRR at smaller effective filament diameters. We will also present of the latest results of strand performance for strand designed specifically for laboratory research magnets, NMR magnets, and cable-in-conduit applications. Bi2212 round wire development is focused on improving the engineering critical current density (JE) by optimizing initial powder, wire configuration and filament densification. Several wire configurations have been developed to meet different wire diameters, operating current and low ac loss requirements. In order to meet the large scale application requirement, the wire piece-length has been significantly increased by improving our process. The twisting of Bi-2212 wire has been proven to significantly reduce ac loss and effective coupling filament diameter without the critical current degradation. The latest results of Bi-2212 wire development and properties will be presented in detail.
Speaker: Michael Gerace (OST)
• 28
Influence of indentations on the critical current of Nb3Sn strands
Japan Atomic Energy Agency is procuring all of theNb3Sn cable-in-conduit conductors for ITER Central Solenoid (CS). The CS conductor cable consists of 576 Nb3Sn strands of which diameter are 0.83 mm, 288 Cu strands, a central spiral and stainless steel wraps around the cable. The current sharing temperature (Tcs) of CS conductors with normal-twist-pitch cables degraded with electromagnetic (EM) cycles. On the other hand, the Tcs of short-twist-pitch (STP) conductors were stable under EM cycles because of the improvement in the bending property of STP cables. However, the short twist pitch increases the pressure between two strands at contact points, and strands become indented before the heat treatment for the reaction of Nb3Sn. Therefore, the influence of indentations on the critical current (Ic) of Nb3Sn strands need to be investigated. Ic measurements were carried out for indented bronze-route (BR) and internal-tin (IT) Nb3Sn strands. The strands were pressed and artificially indented across the longitudinal direction of the strands by an edge with a radius of 0.5 mm before the heat treatment. Then, the indented strands were wound onto ITER barrels of Ti6Al4V. The Ic were measured at 4.2 K and 12 T. When Ic decreased 5 %, the depths of the indentations were 0.26 mm and 0.37 mm for the BR and IT strands, respectively. These depths are defined as the critical indentation depths (dc). The Ic of both strand types decreased drastically with depth over dc. The degradation of Ic were probably caused by damage of the Nb filaments due to indentations. In order to maximize the superconducting properties of the Nb3Sn cable, the depth of indentation should be smaller than dc in the cable.
Speaker: Mr Tomone Suwa (Japan Atomic Enrgy Agency)
• 1:00 PM
Lunch Break (a lunch buffet will be served for all registrants) Lunch Area

### Lunch Area

• Tue-Af-Posters Session 1.1: Large Scale Cryogenics I
Convener: Minoru Takeda (Kobe University)
• 29
Cooling network design of the ITER thermal shield considering its flow distribution and thermal load
Thermal Shield (TS) in the ITER tokamak cuts off the radiation heat load from the vacuum vessel/cryostat transferring to the magnets operating at 4.5 K. The TS will be cooled down by 80 K helium gas supplied from the cryoplant. The helium goes through the cooling tubes attached on the TS. The TS consists of a lot of panels, which are to be connected by bolted joints. The panels have their own cooling tube routings and they are connected to the end of cryo-distribution lines by manifold piping. As the composed piping for the TS cooling is complex, the flow distribution is one of the major concerns for the design of TS cooling network. This paper describes the design of TS cooling tube and manifold, taking the flow distribution and the thermal load into account. The TS hydraulic network was modeled in details by a dedicated program. Frictional pressure drop in the pipes and local losses at all piping components in the TS were considered in the model. It was found that coolant flow rates in some panels were insufficient compared with their design values. Two kinds of design modifications were proposed in order to improve the flow distribution in the cooling tubes. Thermal analysis was also performed for the manifold feeder, the surface of which is partly exposed to the warm surface. The helium temperature rise through the manifold feeder due to incident radiation was obtained and its effect on the radiation shielding performance of the TS was evaluated.
Speaker: Dr Kwanwoo Nam (ITER Korea, NFRI)
• 30
Design of the Helium Purifier for IHEP-ADS Helium Purification System
With the development of superconducting accelerators, a massive increase of helium is needed for the superconducting equipment of the Accelerator Driven Sub-critical System in the Institute of High Energy Physics (IHEP-ADS). Since the cryogenic system requires a high standard of helium purity, a helium purification system will be built to use helium efficiently and circularly. The purifier is designed to work at a temperature of 77K. Oil and moisture are removed by coalescing filters and a molecular sieve bed, while nitrogen and oxygen are condensed by a phase separator and then adsorbed in several activated carbon absorbers. The purifier will work in a flow of 5 g/s at 200 bar in continuous operation for 12 hours. After purification, the purified helium has an impurity content of less than 5ppm.
Speaker: Dr Jianqin Zhang (IHEP,CAS)
• 31
Development of a divisible pressure-resistant accumulator for the cryogenic hydrogen system at J-PARC
At the J-PARC, supercritical hydrogen with a pressure of 1.5 MPa and a temperature below 20 K is used as a moderator material to provide a pulsed cold neutron beam. The J-PARC cryogenic hydrogen system provides the supercritical hydrogen to three moderators and removes total nuclear heating of 3.75 kW for a 1-MW proton beam operation. A heater and a cryogenic accumulator with bellows structure are prepared to mitigate the pressure fluctuation caused by the sudden heat load because the hydrogen loop is filled with the incompressible supercritical hydrogen. The 1st accumulator had an internal leaking from the welding bellows, which has a diameter of 520 mm and a design pressure of 2.0 MPa, due to its poor weld in February 2010. Since then, we had used a tentative accumulator, where the welding bellows diameter was reduced to 353 mm and design pressure was also reduced to 0.94 MPa to manufacture it using the existing reliable welding technology. The bellows had unexpected large hysteresis in the expansion and the contraction. We had developed the 3rd accumulator with a pressure-resistant of 2.0 MPa and a long-life operation to achieve the stable operation for higher proton beam power since 2014. A divisible structure is adopted to shorten the replacement period unlike the existing accumulators. We have installed the 3rd accumulator into the hydrogen cold box in November 2013. It has been confirmed through the cryogenic test that it meets our requirements.
Speaker: HIDEKI TATSUMOTO (Japan Atomic Energy Agency)
• 32
Enhancement of cryogenic distillation by the presence of a gradient magnetic field
The demands for industrial gases are increasing rapidly. It is of great importance to further reduce the energy consumption and cut down the unit cost for gases, in particular for the large-scale air separation systems, which mainly depends on cryogenic distillation. However, since the air separation device itself technical limitations, it is challenging to significantly improve the efficiency of cryogenic distillation. Oxygen has a relatively high magnetic susceptibility compared to other gases and displays a paramagnetic behavior. The unique property can be employed to enrich oxygen from atmospheric air by introducing magnetic field, but still hard to obtain a high efficiency at room temperature. Fortunately, the magnetic susceptibility of oxygen rises dramatically at low temperatures. We propose a novel method to realize an efficient combination of distillation and magnetic separation at cryogenic temperatures to enhance separation efficiency. In order to verify the principle, liquid flow and particle diffusion under high gradient magnetic field were investigated numerically for a wide range of magnetic flux density gradient and a series of magnetic structure. The magnetic effect on liquid oxygen-nitrogen mixture was also investigated experimentally using a laser interferometer. The concentration gradient was formed around the edge of magnetic structure. The facts demonstrate the possibility to improve the efficiency of cryogenic distillation by applying a high gradient magnetic field.
Speaker: Mr Shiran Bao (Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou, 310027, P. R. China)
• 33
Failure mechanism and consolidation of the compensation bellows of the LHC cryogenic distribution line
Beginning of year 2013, after the first three years of operation, the Large Hadron Collider (LHC) was progressively emptied from helium and warmed up to the ambient temperature in order to perform during its first long shutdown all necessary consolidation and maintenance of different technical systems. During the warm-up, six helium leaks were declared on the cryogenic distribution line (QRL). All the leaks were detected on main header supplying supercritical helium at 4.5 K during normal LHC operation. Following complex investigation based on combination of time-of-flight leak detection over 400-m long vacuum sub-sectors and X-rays, the leaks have been localized on the compensation bellows required for longitudinal thermal contraction. During the investigation, some compensation bellows were found damaged but not leaky yet, amounting to the total number of 16 bellows to be repaired. This paper will present the investigation method for the localization of damaged bellows, the failure mechanism and the applied improvements in the bellows design. The QRL repair procedures and the final leak-tightness validation campaign will be also described.
Speaker: Mr Laurent Jean Tavian (CERN)
• 34
Modeling and Dynamic Simulation of a Large Scale Helium Refrigerator
In order to simulate the transient behaviors of a newly developed 2kW helium refrigerator, numerical models of the critical equipments, including a screw compressor with variable-frequency drive, plate-fin heat exchangers, a turbine expander, and pneumatic valves were developed. Meanwhile the related control strategies were involved. To validate these models, dynamic simulation was set to reproduce the start-up process of warm compressor station with gas management system and the cool-down process of cold box in actual operation. The calculation of helium thermodynamic properties was based on 32-parameter modified Benedict-Webb-Rubin (MBWR) state equations in the simulation. Furthermore dynamic response and stability of the simulation system were analyzed and discussed under different disturbances. The reliability of the developed models was verified by comparing the simulation results with the experimental data.
Speaker: Prof. Xiujuan Xie (1Key Lab of Cryogenics, Technical nstitute of Physics and Chemistry Chinese Academny of Science)
• 35
Simulations for a Novel Single-Column Cryogenic Air Separation Process Using LNG Cold Energy
In this paper, a novel single-column air separation process is proposed to reduce energy consumption through the implementation of thermal pump technique and introduction of LNG cold-energy. Compared with conventional double-column cryogenic process, the new single-column distillation utilizes a nitrogen compressor acting as a thermal pump, which recuperates both the latent and sensible heat in the system, thereby lowers down the column operating pressure to 0.12 MPa. Meanwhile, an LNG cold energy recovery thermal recycle system is also set up to achieve further energy saving. Nitrogen, which is chemically inert, is used as the cyclic working medium to protect the highly inflammable natural gas from concentrated oxygen for operation safety. To optimize the parameters of the proposed process, several single-column processes are constructed and simulated on the Aspen Hysys® platform under the operation conditions: air flow rate at 50,000 Nm3/h, inlet quality of feed air to the distillation column at 0.98. The proposed processe provides standard liquid products of LIN (99.999%) and LOX (99.6%) at 12,368 Nm3/h and 10,250 Nm3/h, respectively. Simulation results reveal a unit power consumption of liquid products around 0.3 kWh•mol-1, and an energy saving over 25% is achieved compared with those of conventional double-column air separation unites with LNG cold energy recovery system from the latest literatures. In the end of the paper, several other sets of thermal recycle system are demonstrated for future studies and the criterion to select between systems based on varied cyclic pressure is also discussed.
Speaker: Prof. Yanzhong Li (Xi'an Jiaotong University)
• Tue-Af-Posters Session 1.2: Cryocoolers I
Convener: Naiho Song
• 36
CFD simulation and optimization of a 10K VM refrigerator
The VM refrigerator with power being supplied by liquid nitrogen shows great potential for development below 10K. The 2D axisymmetric model refers to actual geometry under oscillating flow conditions is carried out using FLUENT software. The coldest temperature, the pressure in three cavities, the temperature profile along the regenerator, and the overall cooling power are present. The simulation results show good agreement with available data. Then the regenerator between cold with middle cavity is optimize to obtain the coldest temperature, it is filled with stainless steel screens and lead shot. It is found that there exists the best ratio of stainless steel screens and lead in the same length regenerator.
Speaker: Prof. Junjie Wang (Key Laboratory of Cryogenics, TIPC, Chinese Academy of Sciences, Beijing 100190, China)
• 37
Development of compact 2K GM cryocoolers
A compact 2K Gifford-McMahon (GM) cryocooler has been developed for cooling electronic devices, such as Superconducting Single Photo Detectors. The heat exchangers, regenerators are optimized with the simulation method developed for 4K GM cryocoolers. After optimizing, the cylinder length is reduced by about 80 mm compared with a commercial 0.1W 4K GM cryocooler. With no load on the second stage, a temperature of about 2.2K has been achieved. And also, it is found that the temperature oscillation decreases as the average temperature decreases. A temperature oscillation displacement of less than ±20 mK has been achieved. The object of the project, target specification, and a summary of experiment results will also be introduced in this paper. The research results have been achieved by "Development of a Compact Superconducting Single Photon Detector System for Photon-Quantum Information and Communication", the National Institute of Information and Communications Technology (NICT), JAPAN.
Speaker: Dr Mingyao Xu (Sumitomo Heavy Industries, Ltd.)
• 38
Development of High Capacity Split Stirling Cryocooler for HTS
Abstract. Sumitomo Heavy Industries, Ltd. (SHI) developed a high power stirling type pulse tube cryocooler for the purpose of cooling high-temperature superconductor (HTS) devices, such as superconductor motor, SMES and current fault limiter. The experimental results of a prototype pulse tube cryocooler were reported in September 2014. For a U type expander, the cooling capacity was 151 W at 70 K with a compressor input power of 4 kW. Accordingly, COP was about 0.038. However, the efficiency of the cryocooler is required to be COP > 0.1 and it is found that, theoretically, it is difficult to further improve the efficiency of a pulse tube cryocooler because the work-flow generated from the hot-end of the pulse tube cannot be recovered. Therefore, it is decided to change the expander to a free-piston type from a pulse tube type. A prototype has been developed and preliminary experiments have been performed, as the results, the cooling capacity was 120 W at 70 K with a compressor input power of 2.15 kW, COP was about 0.056.The detailed results are reported in this paper.
Speaker: Mr Yumoto Kenta (Sumitomo Heavy Industries, Ltd.,)
• 39
Experimental Investigation of Cooling Capacity of 4K GM Cryocoolers in Magnetic Fields
4 K GM cryocoolers have been widely used for cooling superconducting magnets, such as, magnets in MRI systems. When an MRI system is operated, superconducting magnets generate a high magnetic field. Accordingly, 4K GM cryocoolers, which are installed in the MRI system, are inevitably exposed to the magnetic field. Especially, the heat capacity of the magnetic regenerator materials and the torque of the coldhead driving motors in the 4K GM cryocoolers will be affected by the magnetic field. In general, the cooling capacity of a 4K GM cryocooler is strongly dependent on the heat capacity of the magnetic regenerator materials, such as HoCu2, ErNi3 and Gd2O2S(GOS). In order to clarify the effect, we measured the cooling capacity of a Sumitomo Heavy Industry, Ltd. (SHI) 1W 4K GM cryocooler in magnetic fields up to 2.0 T. It is found that the impact of a magnetic field on the cooling capacity with a HoCu2/GOS hybrid regenerator is much smaller than that with a HoCu2 regenerator. The detail experimental results will be reported in this paper.
Speaker: Mr Takaaki Morie (Sumitomo Heavy Industries, Ltd.)
• 40
Performance study of hybrid space cryocoolers working at liquid helium temperature
The hybrid space cryocooler consists of a Stirling or pulse tube cryocooler, serving as a precooler, and a J-T loop. With the high efficiency, compact structure, long service life, and remote cold head which can be isolated from vibration or electromagnetic interference, it has been employed by several space missions to provide the liquid helium temperature environment for the detectors. These space missions are briefly reviewed and the performance comparison of the hybrid cryocoolers is given. It is shown that the cryocooler for SPICA mission has the highest COP and lowest precooling power needed in the J-T loop per unit mass flow. Further analysis, based on the cryocooler for SPICA mission, shows that the appropriate lower precooling temperature, higher pressure ratio and higher recuperator effectiveness are the keys to improve the performance of the J-T loop. According to the current performance level of the precoolers and the linear compressors of the J-T loops, the precooling temperatures and pressures of the J-T loop are discussed to optimize the overall efficiency of the hybrid cryocooler. The results show that a better performance of the cryocooler can be obtained with the optimized parameters.
Speaker: Mr Dongli Liu (Institute of Refrigeration and Cryogenics, Department of Energy Engineering, Zhejiang University)
• 41
Study on Minor Losses around the Thermoacoustic Parallel Stack in the Oscillatory Flow Conditions
Minor losses around the thermoacoustic parallel stack in the oscillatory flow conditions are one of the main factors influencing on the efficiency of the thermoacoustic systems. In this paper, a two-dimension model of a single stack in a standing wave thermoacoustic refrigerator is setup. The acoustic characteristics including oscillating pressure, volume flow rate and impedance of the oscillatory flow at the thermoacoustic parallel stacks and its adjacent areas are simulated and compared under different driving conditions. Meanwhile based on the principle of two-microphone method and the above simulation result, the minor loss coefficient of oscillatory flow through a sudden area change are analyzed. The result shows that the acoustic impedance is inversely proportional to the ratio of traveling wave. The real part of minor loss coefficient exponentially increased with the ratio of hydraulic radius and displacement amplitude of oscillatory flow. Furthermore, a close agreement between simulation and experimental results is found, thus providing support for the applicability of the model.
Speaker: Prof. Xiujuan Xie (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China)
• 42
Theoretical Study on Standing Wave Thermoacoustic Engine
Applications of thermoacoustic engine are not limited to driving the pulse tube cryocooler. Performance of thermoscousitc engine is governed by various design parameters like type of resonator, stack geometry, frequency, type of working gas etc. and various operating parameters like heat input, charging pressure etc. It is very important to arrive at an optimum configuration of the engine for which a theoretical model is required. In the present work, a theoretical analysis, based on linear acoustic theory of a standing wave type half wavelength thermoacoustic engine is carried out using DeltaEC software. The system dimensions like length of resonator, stack, hot and cold heat exchangers are fixed with helium-argon mixture as a working gas and assuming parallel plate type stack. Later on, two plate spacings, corresponding to helium-argon mixture and nitrogen gas, is used for carrying out analysis with helium, argon, nitrogen, carbon dioxide and helium-argon mixture as working gases of the system. Effect of charging pressure on performance of the system is studied in terms of resonating frequency, onset temperature, pressure amplitude, acoustic power and efficiency. The conclusions derived from the analysis are reported in the paper. Key words: Thermoacoustic, Standing Wave, Engine, Frequency.
Speaker: Prof. NAIK HEMANT (MECHANICAL ENGINEERING DEAPRTMENT, SARDAR VALLABHBHAI NATIONAL INSTITUTE OF TECHNOLOGY, SURAT, GUJARAT, INDIA, 395007)
• Tue-Af-Posters Session 1.3: Cryogenics for Power Applications, Other Applications, LNG and H2
Convener: Mr Serge Claudet (CERN)
• 43
A cooling system for practical HTS applications
The cooling system is a key component for realizing practical HTS applications. Even if the HTS application is ready for commercial use today, its cooling system is still experimental stage. There are several test sites of HTS cables but these cooling systems are not suited for practical applications. It is the same case with other HTS applications such as motors, generators and power systems. Because of this situation, HTS applications are still primitive up to now. There are several types of refrigerators selected in HTS cooling systems such as a G-M cryocooler, a Stirling refrigerator and a Turbo Brayton refrigerator. In order to realize a practical cooling system, the best-fit refrigerators to a HTS cooling system must be chosen. In this paper the characteristics and the structure of refrigerators are explained and the cooling system with those refrigerators are shown and proposed. In a HTS cable cooling system for example, a turbo Brayton refrigerator, heat exchangers and a liquid nitrogen pump are the essential components. However, suitable refrigerators and pumps do not exist. Also this paper describes how a refrigerator cools an HTS system and what kind of cooling capacity is required for HTS applications.
Speaker: Dr Yasuharu Kamioka (ColdTech Associates)
• 44
Advantages, design and manufacturing of vacuum insulated transfer lines for LNG
In February 2013 Demaco was awarded with the contract for the design, manufacture and delivery of 1800 meter vacuum insulated transfer lines for the Skangass LNG terminal Lysekil, Sweden. Besides delivery of LNG to Preem’s refinery, a truck loading facility is built in connection to the terminal. The terminal will also become an important hub for distribution of LNG as fuel for ships. A shift to LNG as fuel is one of the most effective ways to reduce CO2 emissions and meet stricter environmental requirements. Vacuum insulated transfer lines (VIP) are proven technology in the industrial gas market. For the emerging market of LNG it must be proved again that VIP is superior comparing to conventional insulated pipes. The total cost of ownership are substantial lower due to much less Boil-Off Gas and the absence of maintenance costs. Although the CAPEX is slightly higher, VIP lines will lead to the lowest possible Total Cost of Ownership (TCO). Next to the cost savings VIP lines offer some unique safety issues and are very sustainable. The conceptual design and calculations led to the detailed design and manufacturing of the transfer lines. Successful factory acceptance tests shows the results in praxis.
Speaker: Sjoerd Van der Putte (Demaco Holland bv)
• 45
Commercial Electronic Components and Silicon-on-Sapphire ICs at Extreme Cryogenic Temperatures
Electronic circuits generally perform well at moderately cold temperatures, but can show interesting and negative behaviors as extreme cryogenic regimes are reached. This paper looks at the performance of Silicon-on-Sapphire (SOS) and selected commercial silicon devices operating to temperatures at and below the freezing point of nitrogen. While expected freeze-out behavior is observed clearly in a commercial silicon device (1N4001 rectifier), SOS resistors and transistors tested using the same setup did not experience this effect, and in some cases stayed reasonably well-behaved to 5 Kelvin. However, unlike other reported investigations of SOS devices operating at extreme cryogenic temperatures, strong kink-effects were observed, especially for devices operating at low Vgs overdrives (weak inversion). These results point out both problems and promises of developing electronics in an RF and mixed-signal IC process suitable for use in exploring the surface of outer-planets and their moons.
Speaker: Dr Andrew Rys (Kansas State University)
• 46
Conceptual Design of the Cooling System for a Superconducting Wind Turbine Generator
The wind energy sector is one of the main energy sources concerned with environment and energy. However a particular trend is increasing turbine ratings, this trend causes the increase of the nacelle weigh. To solve this problem, superconducting wind turbine generators have the potential to provide a compact and light weight drive train. Nevertheless of these advantages, the cryogenic system has some problems. Because the use of a stationary refrigerator requires that a means be provided for the transfer of cooled helium gas from the stationary supply to the rotating field winding and for return of the gas from the rotor to a stationary reference frame. It was possible by using the centrifugal force due to high speed rotation, so-called self -pumping effect that causes the refrigerant circulation. However, the wind turbine speed is lower by two orders of magnitude than in normal generators or motors, the superconductors of the rotor must be force-cooled by cooling channel. Moreover, it is necessary to supply a high pressure helium gas. However, the sealing technology of high pressure cryogenic refrigerant has not been established yet. Therefore, we propose a method of supplying a coolant in the cooling channel of the superconducting rotor by circulation pumps built in the rotor and a rotating-stationary heat exchanger placed in the rotor to separate the refrigerant of the stationary system and the rotational one.
Speaker: Dr Shuichiro Fuchino (National Institute of Industrial Science and Technology)
• 47
Counterflow cooling tests of superconducting cables for railway systems
DC electric railway systems are widely used in Japan, including in the metropolitan areas. However, they have some problems, such as limited use of regenerative brakes and energy loss. In order to solve those problems and in the aim of streamlining and saving of energy of power system in DC electric railway systems, Railway Technical Research Institute (RTRI) has developed superconducting cables for railway systems. It has consistently tackled various issues including technologies and applications, such as basic property of HTS wires, optimization of introductory configuration by simulation, and system design with high reliability. Based on such various inquests and examination results, the prototype of the superconducting cable(30 meters, DC1.5 kV, 5 kA) ,where the counterflow circulation system (Go-Return system) was adopted, was produced and installed in railway test track of RTRI. Results of counterflow cooling tests by controlling the number of cryocoolers in the opposed terminal will be discussed. Acknowledgement This research was supported by the Japan Science and Technology Agency, JST, as part of the Strategic Promotion of Innovative Research and Development Problem.
Speaker: Masaru Tomita (Railway Technical Research Institute)
• 48
Developing progress of critical equipment in the CSNS cryogenic hydrogen system
Construction of the China Spallation Neutron Source (CSNS) started in October 2011 and is expected to last 6.5 years. Supercritical hydrogen is used as moderator for coupled and decoupled moderators of CSNS. Cryogenic system provides ~20 K cryogenic hydrogen (at 1.5 MPa) to neutron moderating system, and nuclear heating load is transfer to the helium refrigerator by the circulation of hydrogen. Cryogenic hydrogen system is a closed circulation, which consists of key equipments including hydrogen-helium heat exchanger, cryogenic hydrogen heater, accumulator, cryogenic hydrogen pump, ortho-para hydrogen convertor and cryogenic valves. Most of these apparatuses are non-standard equipment, and will be developed independently. This study introduces the latest research progress. Manufacturing of the accumulator has been completed this February. A prototype of the hydrogen-helium heat exchanger has been manufactured and tested for sealing. Engineering design of the cryogenic hydrogen heater and the ortho-para hydrogen convertor have been finished, and the prototypes will be manufactured this April. Besides, cryogenic valves produced by STOHR arrived, and the cryogenic hydrogen pump is under manufacturing at Barber-Nichols Inc, and will be delivered in the middle of 2014. Finally, all these cryogenic devices will be integrated into two cold boxes, i.e. a hydrogen cold box and an accumulator cold box. The engineering design of the cold boxes will be completed soon. Developing these critical equipments will help to accumulate valuable engineering experience for the construction of the CSNS cryogenic system.
Speaker: Dr Guoping Wang (Institute of High Energy Physics, CAS)
• 49
Development and test of a cooling system for a 154 kV superconducting fault current limiter
The superconducting fault current limiter (SFCL) is an electric power device which limits the fault current immediately in a power grid. Korea Electric Power Corporation (KEPCO) has been developing a 154 kV, 2 kA SFCL since 2011 to protect power grids from increasing fault current and improve stability and quality of electric power. This SFCL adopts 2G YBCO wires and operates at 71 K and 5 bars. In this paper, a cooling system for the 154 kV SFCL and its test results are reported. This cooling system uses a Stirling-type cooler to make subcooled liquid nitrogen (LN2), which cools superconductor modules of the SFCL. LN2 is circulated between the cooler and the cryostat that contains modules by a cryo-circulating pump. LN2 also plays a role of a high voltage insulator between the modules and the cryostat, so it was determined to be kept at 5 bars for high insulation performance. This cooling system had been made, installed on a test site, and tested without superconductor modules. In this operation test, some important data were measured such as temperature distribution in LN2, pressure change, performance of a heat exchanger and cooling capacity of the total system. The results showed this cooling system operates well as originally designed.
Speaker: Ms Kim Heesun (Korea electric power corporation)
• 50
Evaluation of a Two-Stage Mixed Refrigerant Cascade for HTS Cooling below 60 K
High temperature superconducting devices are currently tested worldwide in many pilot projects for the efficient transportation of electrical energy. Primary cooling down to 65 – 70 K is mostly achieved by either subatmospheric liquid nitrogen, by closed cycle turbo-Brayton plants or by batteries of Stirling cryocoolers. In order to increase the current density in the superconductors, a further reduction of operating temperatures to below 60 K is desirable. This work examines the potential of two-stage mixed refrigerant cascades as an efficient and reliable alternative for cooling in this temperature range. The envisioned process consists of a low-temperature stage operating between about 55 and 120 K with a refrigerant mixture consisting of neon, nitrogen and oxygen at high pressure (100/45 bars at pressure/suction side, respectively) . The inclusion of oxygen lowers the freezing temperature of the mixture to about 52 K. Precooling to 110 – 120 K is achieved with a high temperature stage consisting of a conventional mixed refrigerant cycle. The concept was evaluated by simulation of the low temperature stage with Aspen Plus. First results predict an overall efficiency of 7.1 % of Carnot. The influence of the fluid property models on calculated cycle efficiency and optimum composition is discussed.
Speaker: Mr Thomas M. Kochenburger (Institute of Technical Thermodynamics and Refrigeration, Karlsruhe Institute of Technology, Germany)
• 51
Integration challenges of an Air Separation Unit with a thermal power plant
Development of oxy-combustion technology requires relatively low purity oxygen (90 - 95% O2) in quantities exceeding the present oxygen production by orders of magnitude. Oxygen of the required purity level can be produced in cryogenic or sorption plants. Both technologies can be coupled with thermal power plants electrically or thermally. The exemplary coupling methods include use of cogeneration heat for sorbent bed regeneration or lignite drying with heat recovered from the air compressors. It is also possible to combine the PSA method with a swing of temperature by using waste heat from combined heat-power generation (cogeneration) processes, leading to pressure temperature swing adsorption (PTSA). The paper shows a thermodynamic and economy analysis of different couplings of ASU with thermal power plant. A concept of energy storage in liquid gases in order to smooth the oxygen production independently of the power plant load is discussed.
Speaker: Prof. Maciej Chorowski (Wroclaw University of Technology)
• 52
Optimum design of the outer shield layer in an innovative superconducting DC cable
The structure of the inner conductor of the innovative superconducting DC cable has been discussed and we proposed the optimum structure in which superconducting tapes were arranged to decrease the Lorentz force in local magnetic field. However, the design of the outer shield conductor of the cable that applies the axial magnetic field to the inner conductor by the back current has not been argued. It is needed to optimize the structure, the angle distribution of the superconducting tapes, of the outer shield conductor under the required conditions of the capacity of the back current and the axial field strength. In this study the optimum condition is investigated to provide the maximum longitudinal magnetic field to the inner part of the cable under the condition of the same current as the inner part. The total efficiency of the proposed innovative cable will be discussed based on the obtained results. Acknowledgements: This work is supported by Advanced Low Carbon Technology Research and Development Program (ALCA) of Japan Science and Technology Agency (JST). References: [1] V.S. Vyatkin, K. Tanabe, J. Wada, M. Kiuchi, E.S. Otabe and T. Matsushita, Physica C 494 (2013) 135. [2] T. Matsushita, V.S. Vyatkin, M. Kiuchi and E.S. Otabe, to be published in Adv. Cryog. Eng. Mater. 60 (2014).
Speaker: Dr Vladimir Vyatkin (Kyushu Institute of Technology)
• 53
Plate-Fin Heat-Exchangers for a 10 kW Brayton Cryocooler and a 1 km HTS Cable
Plate-fin heat exchangers are designed and fabricated for an integrated cryogenic system, serving for a 10 kW Brayton cryocooler and a 1 km HTS cable under development in Korea. The main heat exchanger is a counter-flow recuperator between high-pressure and low-pressure helium of the Brayton cooler, and the second heat exchanger is a sub-cooler of liquid nitrogen that circulates through the 3-phase cable in transmission class. The heat transfer coefficient and friction coefficient are calculated with real fluid properties and engineering correlations to determine the physical dimension of two compact heat exchangers. A key feature is the coldest part of sub-cooler, where the streams of liquid nitrogen and gaseous helium are arranged as cross-flows in order to reduce the risk of freeze-out of liquid nitrogen. Our recent experimental works showed that the cross-flow heat exchanger is less vulnerable to the freeze-out, since the temperature distribution is basically two-dimensional. Details of fabricated hardware are presented and discussed towards an immediate application to the HTS cable system. This work was supported by a grant of the Power Generation & Electricity Delivery Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), funded by the Ministry of Industry, Trade, and Energy, Korea (No. 2011101050002B).
Speaker: Mr Kyung Hyun Gwak (Hong Ik University)
• 54
Radiant cooling of the rotator in a superconducting induction motor
We have been developing a cryogen-free superconducting induction motor, which is thermally insulated in a single vacuum vessel, which ensures a high thermal insulation and a short distance between stator and rotator. High temperature superconducting coils are embedded in both the stator and the rotator, and the stator is cooled below the critical temperature Tc with a compact cryocooler through solid state thermal conduction. On the other hand, the rotator is cooled below Tc by radiation. This radiant cooling is enabled by the structure that the stator and the rotator have a lot of coaxial fines whose surfaces are coated with ceramics to enlarge emissivity. In this work the efficiency and the validity of the radiant cooling which enables to produce closed superconducting currents on a rotator without current leads are reported.
Speaker: Mr Koichi Omachi (Graduate School of Engineering, Okayama University of Science)
• 55
Study of the thermo-syphon cooling system with a vessel in the sea states
A thermosyphon application is considered to be a choice to cool down superconducting rotating machines. The thermosyphon cooling system by using neon gas in the temperature range of 25 K to 40 K has been tested in laboratories, since it possesses advantages of large capacity of heat transport, less complicated construction, and smaller volume. Applying the thermosyphon cooling system to HTS rotating machine in the ship propulsion system, we need to study the effect of both pitching and rolling motions caused by the sea states on the cooling performance such as stability and allowable thermal load. In this study, we equipped the “SHIOJI MARU”, a 425 ton vessel with the thermo-syphon cooling system. Great attention has been paid to the heat load, which is applied to the evaporator, under the influence of the pitching and rolling of the vessel. The gradual and rapid heat loading tests have been conducted. In addition, we investigated the effect of the neon quantity on the cooling performance at sea. These on-board testing results for cooling with the thermosyphon are comparatively discussed with those obtained in the laboratories. The pitching and rolling of the ship encouraged heat exchange. The obtained result is caused by an increased thermal exchange on the surface originating from the ship motions. 1)B. Felder, M. Miki, K. Tsuzuki, N. Shinohara, H. Hayakawa, and M. Izumi, “A 100-W grade closed-cycle thermosyphon cooling system used in HTS rotating machines”, in AIP Conf. Proc., vol. 1434, pp. 417–424 (2012). 2)R. Sato, B. Felder, M. Miki, K. Tsuzuki, H. Hayakawa, and M. Izumi “Helium-Neon Gas Mixture Thermosyphon Cooling and Stability for Large Scale HTS Synchronous Motors”,IEEE Trans. appl. Supercond., vol. 23, no. 3, 5200704 (2013).
Speaker: Mr Kota Yamaguchi (Tokyo University of Marine Science and Technology)
• 56
Study on Magnetic Field Distribution of Superconducting Magnets in Magnetic Separation
Since the 1980s, superconducting magnets have been adopted in the high-gradient magnet separation (HGMS) systems. In recent years, the use of HGMS has become widespread in diverse industries ranging from waste water purification of steel production to coal desulfurization. Here, we introduce basic concepts of magnetic separation and design parameters of the magnetic coils. The analysis of the magnetic field distribution of superconducting magnets is an essential process in the HGMS systems, and a high magnetic field gradient is of great benefit to efficient separation. Thus in this work, we also analyze the influence of relevant parameters of the coils on the magnetic field distribution in the key area. Finally, we discuss how stainless steel orifice plates affect the magnetic field gradient.
Speaker: Mr Laifeng Li (Technical Institute of Physics and Chemistry,CAS (P.R. China))
• 57
Thermal insulation test of newly designed cryogenic pipes for the superconducting DC power transmission system in Ishikari, Japan
Superconducting power transmission systems have been developed intensively and applied to actual power grids at several places in the world in recent years. This is because the system is recognized as one of the most efficient ways of power transmission in the world. In Japan a DC superconducting power transmission project, which consists of construction and operation of two DC superconducting power transmission lines of 500 m and 2000 m, was launched in 2013 in the Ishikari area as one of the national projects of Japan. This project is called Ishikari project. Firstly, the power transmission by the 500 m transmission line, which will connect a solar power plant and an Internet data center, will be started by the end of FY 2014. In the case of superconducting power transmission, heat leak along a cryogenic pipe is one of the main sources of the transmission loss, in particular, for long transmission lines. Therefore, the development of cryogenic pipes with efficient thermal insulation performance is crucial to make the efficiency of the system higher. We have developed a new cryogenic pipe for the Ishikari project, which comprises of two inner pipes, one for installation of a cable and the other for return of the liquid nitrogen, respectively. The pipe in which the cable is installed is surrounded by a thermal shield, which is thermally anchored to the pipe for the liquid nitrogen return. This makes reduction of the heat leak to the pipe in which the cable is installed possible. We have tested the efficiency of the thermal insulation of cryogenic pipes with different structures design. The result of the test will be reported in the conference. This work was supported in part by the Japanese Ministry of Economy, Trade and Industry (METI).
Speaker: Dr Hirofumi Watanabe (Chubu University, R&D partnership for Ishikari Superconducting DC Power Transmission System (i-SPOT))
• Tue-Af-Posters Session 1.4: Instrumentation and Process Controls
Convener: Christine Darve (European Spallation Source)
• 58
An optimal control approach for an overall cryogenic plant under pulsed heat loads
This work deals with the optimal management of a cryogenic plant composed by refrigeration plants in parallel, which provide supercritical helium to pulsed heat loads. First, different strategies to estimate the efficiency of each refrigerator are analyzed. Then, taking into account these efficiencies, an optimal operation of the cryoplant is proposed and studied. It ensures a long and stable operation of the cryoplant during a typical pulsed heat load sequence minimizing the power consumption of the refrigerators. The management of the refrigerators is carried out by an upper control layer, which balances the relative production of helium in each refrigerator. In addition, this upper control layer deals with the mitigation of malfunctions and faults in the system, such as a compressor stop or a turbine stop. The proposed approach has been validated using a dynamic model of the refrigerators and of the distribution system developed with the software EcosimPro based on first principles modelling and thermo-hydraulic equations.
Speaker: Mr Luis Gomez Palacin (CERN)
• 59
Building a thinner gap in a Gas Gap Heat Switch
A gas gap heat switch (GGHS) reaches its highest conductance state when the gap between two exchange surfaces is filled with a conducting gas in a viscous regime. The broader the surface and the thinner the gap, the higher the ON conductance achieved. In this presentation we describe a very thin cold gas gap heat switch based upon the use of the differential thermal expansion of the construction materials. Such a technique overcomes the intricacies of the manufacturing process of the switch. We designed, built and tested a prototype of a very thin gap heat switch using our new methodology. The high conductance was measured with both helium and nitrogen, at temperatures ranging from 20 K (He) or 75 K (N2) up to room temperature. The inferred gap opening at low temperature (≈ 17 μm) showed up to be slightly above the expected, which allowed us to reinterpret the design calculations performed. The switch was also characterized along its extreme conductance states while using a sorption pump, and its performance was compared with a previously developed model. Lessons learned from first prototype led us to build up a second one with better performances. Our experiments suggest that the proposed design allows the development of a customized cryogenic switch with improved ON conductance while keeping the assembly very simple and sturdy, hence widening the scope of the applicability of these devices.
Speaker: Prof. Isabel Catarino (CEFITEC, Departamento de Física, FCT - Universidade Nova de Lisboa, 2829-516 Caparica, Portugal)
• 60
Calibration of an HTS based LOX 400mm level sensor
The cryogen level measurement for space missions is very crucial. At the same time, the weight of the sensor should be less because the payload fraction would be reduced; resulting in increase in the mission cost. An attempt was made to develop HTS based level sensor of 400 mm for LOX measurement. In the initial phase of testing, the sensor goes to normal state due to increase in temperature as a result of the pressurization of the LOX cryostat. In order to maintain the sensor in the superconducting state, a test cryostat with minimum heat transfer from ambient was designed to have stable LOX level to provide thermal stability to HTS based LOX sensor. The calibration of developed sensor is carried against diode array to verify its linearity and performance under different pressures. The sensor consists of HTS wire with nichrome heater wire tapes. The calibrations are carried out with and without heating. The automatic data logging is done by using the program developed in LabVIEW 11.0.
Speaker: Prof. Karunanithi Rangasamy (Indian Institute of Science)
• 61
Commissioning of temperatue sensors for the XFEL AMTF
Demaco was awarded with the contract for the design, manufacturing and installation of the Accelerator Module Test Facility (AMTF) for XFEL at DESY, Hamburg. The scope consisted of a Sub-cooler Box XASB, a Valve Box XAVB and all interconnecting multiple Helium Transfer Lines. The instrumentation was part of the responsibility and based on the specifications of DESY. For Temperature measurement suitable thermo sensors of resistive type had to be installed at the locations where the lowest temperature could drop below 40 K. Calibration of the thermo sensors has been held on a certified calibration set-up based on International Temperature Scale 1990 (ITS-90). The number of calibration points are adequate to the required accuracy of the thermo sensor. The low temperature thermo sensors are calibrated between 300 K down to 4 K. Specification of thermo sensors: Nominal resistance at 300 K: 40 ≤ R ≤ 1100 Ohms. Temperature coefficient: Negative. Self-heating effect: ≤ 2 mK for temperature range 1.6 - 5 K. Dimensionless sensitivity | (T/R)•( dR/dT) |: ≥ 0.15. Accuracy dT/T (calibration and fitting): better than ± 0.5 % for the whole T - range. Thermal cycles before calibration: ≥ 25 times in the range from 80 K to 300 K. Long term stability δ after 150 thermal cycles from 300 to 80 K, and after 5 years: -0.5 % ≤ δ ≤ 0.5 % for the whole T - range. Temperature shift β caused by gamma radiation of 1x106 Gy total dose: -0.5 % ≤ β ≤ 0.5 % for the whole T - range. Electrical insulation resistance: > 3000 MΩ. Physical size: less than 10mm long and 3mm diameter. The specification of the temperature sensors has been tested, validated and accepted by the customer.
Speaker: Ruud Van der Woude (Demaco Holland bv)
• 62
Corrections of reducing the uncertainty of the self-heating in cryogenic temperature measurements of the highest accuracy
Self-heating of resistance thermometers is a well-known phenomenon, which occurs when the measuring current additionally heats up the sensing element.The temperature difference caused by the self-heating can be corrected by basic two-current method. However, in measurements of the highest accuracy, uncertainty of the self-heating correction, achieved by basic two-current method, may not be sufficient. More advanced methods for self-heating correction are proposed, based on the use of more than two different currents. Uncertainty of the self-heating for four methods (basic two-current method, three-current method, four-current method and five-current method) at different cryogenic temperatures is studied in this paper. The results show that the three-current method can decrease the uncertainty from 0.7 to 0.5 mK in 8 K, and from 0.84 to 0.64 mK in 10 K, compared with the two-current method. However,there is no remarkable difference between the three-current method and four-current method. In order to balance the computing time and precision,we should choose three-current method to correct the uncertainty of the self-heating.
Speaker: Prof. Zhengyu Li (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, CAS)
• 63
Cryodiagnostics of SC-accelerators with fast cycling superferric magnets
This report presents long-term experience in cryodiagnostics of superconducting accelerators cooled with two-phase helium flows. It concerns: resistive temperature (T) sensors for wide applications including the magnetic field and irradiation environments, their calibration system and features to mount these sensors; RF-void fraction (VF) sensors and set-up to calibrate them; a discrete level-meter (L) based on a resistive temperature sensor suitable for all cryogens; the two-phase helium flow-meters (G) which are able to operate in the VF-range from 0 to 100 %. A measuring system based on a modular industrial computer to find values of T, VF, L, G and pressure, P, is also described. A way to produce a multi-channel measuring system is proposed which can be applied for superconducting accelerators like SIS100-FAIR and NICA. Separate sensors and measuring devices can be used in nitrogen, hydrogen and LNG systems. It is also shown that the experience gained in cryodiagnostics allows separationless flow-meters to be produced for the three-phase oil-salty water-gas flows that are typical in the oil production industry.
Speaker: Yury Filippov (J)
• 64
Deep Cryogenic Low Power 24 bits Analog to Digital Converter with Active Reverse Cryostat Package
LBNL has developed an innovative data acquisition module for superconductive magnets where the front-end electronics and digitizer resides inside the cryostat. Currently, in most cases, the digitization of signals internal to the cryostat containing the superconducting magnet is done outside the cryostat. This kind of setup can degrade the performance of the data acquisition in several ways, and add complexity to the system that increases with the number of monitored signals. The system described in this work allows conventional electronic technologies such as enhanced metal–oxide–semiconductors to work inside cryostats at temperatures as low as 4.2K. This is achieved by a combination of careful active management of heat inside the module that keeps the electronic package at approximately 77K, and the use of very low power active components. This approach avoids all difficulties that arise from changes in carrier mobility that occurs in semiconductors at deep cryogenic temperature. A significant reduction in electrical noise from signals captured inside the cryostat occurs due to the low temperature environment that the electronics is immersed in, reducing the thermal noise. The shorter distance that signals are transmitted before digitization reduces pickup, and cross-talk between channels. Another important advantage is the simplification of the feedthrough interface on the magnet head. All lines coming out of the cryostat are digital and low voltage, reducing the possibility of discharges inside the cryostat. This paper will explain in details the architecture, and inner workings of this electronic system. It will also show results on the performance of the Analog to Digital Converter (ADC) when the system is immersed in a cryostat at 4.2K, and at 77K. Parameters such as power dissipation, integral non-linearity, effective number of bits, signal-to-noise and distortion, will all be presented for both temperatures.
Speaker: Dr Marcos Turqueti (L)
• 65
Development of a Measurement and Control System for a 40L/h Helium Liquefier Based on the Siemens PLC S7-300
Abstract. A 40L/h Helium Liquefier is established at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences. A measurement and control system based on Siemens PLC S7-300 for this Helium Liquefier is developed. Proper sensors are selected, for example, three types of transmitters are adopted respectively according to detailed temperature measurement requirements. Siemens S7-300 PLC CPU315-2PN/DP is as master station and two sets of ET200M DP remote expand I/O is as slave station. Profibus-DP field communication is established between the master station and the slave stations. The upper computer Human Machine Interface (HMI) is compiled using Siemens configuration software WinCC V7.0. The upper computer communicates with PLC by means of industrial Ethernet. A specific control logic for this Helium Liquefier is developed. The control of the inlet and outlet pressures for the compressor and the control of the turbine loop are discussed in this paper. After several months’ commissioning, the temperature before the throttle valve has reached to conversion temperature. Keywords: 40L/h Helium Liquefier, Measurement and control system, PLC, control logic ACKNOWLEDGMENTS: This work is supported by the Key Laboratory of Cryogenics, TIPC, CAS(CRYOQN201307).
Speaker: Dr Tao Yan (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, China)
• 66
Fiber Bragg grating sensors for a mass flow determination in a rotating liquid neon cooling channel
The use of High Temperature Superconducting (HTS) magnets has increased in recent years in many applications due to its chances of achieving high current carrying capacity and the possibility of avoiding the HTS cooling by costly, less available liquid helium. While most of the applications aimed at liquid nitrogen coolant, some special applications like HTS Generator, for example, use liquid neon for cooling its rotor. The operational characteristics of such a rotor could be greatly improved by optimized cooling channel, mass flow rate of the coolant and its interaction with the magnet under given thermodynamic conditions. To understand and to optimize the cooling efficiency, a model has been developed in which the thermodynamic parameters have been varied and analyzed. The calculated mass flow rate of the optimized cooling channel has to be validated by a real time measurement system. The commercially available sensing systems may not be suitable for this purpose, because of the various practical difficulties in sensor installation, wiring and signal tapping in a high speed rotating cooling channel. In order to overcome these issues, a Fiber Bragg grating based sensing system with multiplexing capability has been considered. The measured temperature distribution along a cooling channel could be used to determine the mass flow rate. In this work, an outline of the simulated model and the initial test studies of FBG sensors will be reported.
Speaker: Mr Thomas Richter (Karlsruhe Institute of Technology ( campus North))
• 67
Fundamental study of a liquid hydrogen tank for transportation using MgB2 level sensor
Hydrogen energy is attracting attention as an alternative energy source to fossil fuels and nuclear power. In the storage and transport of a huge quantity of hydrogen on the sea, liquid hydrogen (LH2) is very effective because its density is about 788 times that of gaseous hydrogen ( 273 K, 1 atm). We are currently developing an external-heating-type superconducting magnesium diboride (MgB2) level sensor for a liquid hydrogen tank. Our purpose in this study is to elucidate sloshing phenomenon in the LH2 tank during transportation by truck and ship using MgB2 level sensor because of the good response. As a preliminary test to clarify the sloshing phenomenon in the LH2 tank, synchronous measurements of liquid level, temperature, pressure and acceleration inside the tank were successfully carried out on board of the training ship. Experimental results including sloshing phenomenon by means of simultaneous measurements using several MgB2 level sensors are reported.
Speaker: Mr Kazuma Maekawa (Kobe University)
• 68
Heat load estimator for smoothing pulsed heat loads on supercritical helium loops
Speaker: Christine Hoa (CEA SBT)
• 69
Improved software production for the LHC tunnel cryogenics control system
The control system of the cryogenic in the LHC tunnel is based on an automatic approach for the control software production process due to its overall complexity. Consequently, an extensive use of various IT technologies - databases, repositories, commercial engineering software, CERN frameworks and dedicated tools are required. The software development is partially automatized, however, every single modification of the control software requires a sequence of consecutive and interdependent tasks to be executed manually by software developers. A large number of control system consolidations performed during the first LHC run and long shutdown as well as a frequent evolution of used IT technologies lead to a review of the development environment and software production methodology. As a result, an open-source continuous integration server has been employed integrating all development task, tools and technologies in a predefined time and event triggers. All changes triggered are combined into the project and the resulting work is automatically built and tested. This paper describes the software production chain, the main improvements that have been made to fully automate the process of software production for the cryogenics control system for the LHC tunnel.
Speaker: Mr Czeslaw Fluder (CERN)
• 70
Improvement of the operational settings of a helium purifier, leading to a higher purity of the recovered gas
The operating conditions of internal purifiers of commercial helium liquefiers are determined by the adjustment of the cold end temperature, the cold flow, the regeneration completion temperature and the heater temperature. By changing the cold end temperature of the purifier from 32.5 K to 22 K, the purity of the recovered gas is improved from 33% to 99%, The current regulation values for this purification process are now set as follows: cold end temperature 22.0 K, cold flow rate 180 ℓ / min and complete regeneration temperature 145 K. This paper describes how the improvement in the purification system internal to the helium liquefier has been achieved.
Speaker: Prof. Hiroshi Ikeda (University of Tsukuba)
• 71
The ESS superconducting RF cavity and cryomodule cryogenic processes
The European Spallation Source (ESS) is one of Europe's largest research infrastructures, to bring new insights to the grand challenges of science and innovation in fields as diverse as material and life sciences, energy, environmental technology, cultural heritage, solid-state and fundamental physics by the end of the decade. The collaborative project is funded by a collaboration of 17 European countries and is under design and construction in Lund, Sweden. A 5 MW, long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms and the repetition frequency is 14 Hz (4 % duty cycle). The choice of SRF technology is a key element in the development of the ESS linear accelerator (linac). The superconducting linac is composed of one section of spoke cavity cryomodules (352.21 MHz) and two sections of elliptical cavity cryomodules (704.42 MHz). These cryomodules contain niobium SRF cavities operating at 2 K, using the accelerator cryoplant and the cryogenic distribution system. This paper presents the superconducting RF cavity and cryomodule cryogenic processes, which are developed for the technology demonstrators and to be ultimately integrated for the ESS tunnel operation.
Speaker: Dr Christine Darve (European Spallation Source)
• 72
Validation of a new method for flow measurement in cryogenic systems
A new thermal method for flow measurement in cryogenic systems was recently published, featuring the capability for intrinsic calibration. The new method minimizes the differences between two physically exact evaluation functions for the flow rate, which are based on the same input parameters, i.e. the measurement readings of temperature differences and heater power of a heat exchanger. The minimization removes all systematic errors from the measurement, yielding uncertainties of typically less than ±1 % with regard to the actual flow rate. A proof-of-principle based both on experimental data and a closed analytical model was presented earlier, but comparative measurements against a second standard were not available at the time. This paper presents the results of room-temperature experiments taken with a first prototype sensor, designed with a tube diameter of 4 mm. The experiments were carried out with nitrogen flowing from gas cylinders against atmospheric pressure, and with flow rates ranging from 0.04 to 0.4 g/s. A gallery with 4 calibrated sonic nozzles was used as a reference, having measurement uncertainties of ±0.33 % with regard to their measurement range.
Speaker: Mr Andreas Janzen (Karlsruher Institut of Technology - Institute of Technical Thermodynamics and Refrigeration (ITTK))
• Tue-Af-Posters Sessions 1.5: NbTi and Nb3Sn Superconductors and Stability
Convener: Arnaud Foussat (CERN)
• 73
Analysis of the Nb3Sn strand microstructure after full-size «SULTAN» test of an ITER TF conductor sample
The study of defects generated in superconducting filaments of Nb3Sn strands under electromagnetic and thermal cycling was carried out for the TFRF3 cable-in-conduit-conductor (CICC) sample passed final testing at the SULTAN test facility. The TFRF3 sample was manufactured from the qualification RF toroidal field CICC. The strand samples were taken from different locations in cross–section of TFRF3 and different positions along its axis in relation to background magnetic field. Qualitative and quantitative analysis of defects were carried out using metallographic images obtained by Laser Scanning Microscope. We analyze number, types, and distribution of defects in filaments of Nb3Sn strand samples extracted from different petals of TFRF3 in dependence on a strand location in cross–section (the center of petal, nearby the spiral, nearby the outer jacket) and also a strand position in relation to background field (high field zone or low field zone). The results about the defects distribution are presented and discussed.
Speaker: Dr Liudmila Potanina (Russia Scientific R&D Cable Institute (JSC VNIIKP))
• 74
CICC performance evaluation by numerical modelling of electromagnetic-mechanical properties in ITER Nb3Sn strand
Aiming for a better quantitative description of superconducting strand degradation in large ITER Cable In Conduit Conductors (CICC), the electromagnetic-mechanical modeling of strain-sensitive Nb3Sn strands and full-size CICCs is essential. A numerical strand model is built based on accurate intra-strand resistance data, computed spatial filament strain distribution and experimentally obtained filament crack allocation. It consists of a 3D network of resistors including superconducting filaments, normal matrix elements, and an outer stabilising shell or inner core when present. With the ITER-Twente Nb3Sn strain scaling law based on measured strand data, the model calculates the corresponding spatial electrical potential distribution. The critical current and n-value of a strand element in a CICC varies with the local magnet field, temperature, uniform axial strain, peak bending strain and crack density. Implementation of the local strand properties in the cable model JackPot remains manageable in terms of computation time by the use of simplified analytical functions produced with the strand model. The relations allow an accurate description of the electromagnetic-mechanical properties of each strand element subjected to the complex axial and bending strain pattern, even with cracks, in CICCs with the Twente cable model JackPot for cable performance analysis and predictions.
Speaker: Chao Zhou (University of Twente, Faculty of Science & Technology, 7522 NB Enschede, The Netherlands)
• 75
Deformation behaviour and critical temperature of NbTi superconductor processed by cold rolling with a pulsed current
NbTi superconductors are traditionally produced by a process, which comprises many stages. It is characterized by large true strain, as well as high energy, labor and time consumption. A combining severe plastic deformation by rolling (SPDR) with pulse current for various kinds of materials leads to a decrease in flow stresses and microstructure refinement, as well as to improvement of the deformability, microhardness, and other mechanical characteristics of the material. It is assumed that these effects are due to the interaction of conduction electrons with lattice defects during material deformation. The aim of this study is to investigate specific features of SPDR with pulse current in NbTi superconductive wire. The influence of SPDR and pulse current combined effect on composite, which includes electrical and thermal Cu-stabilizer, Nb-diffusion barrier and Nb–47wt.%Ti core, has been investigated. Specimens were rods by size of ∅7 ×120 mm. SPDR with pulse current was carried out using a setup that included a rolling mill with 1 to 7 mm rolls, a pulse current generator, and an oscillograph. The rolling was performed at room temperature without heating. The current density was j =100 A/mm2. It was shown that pulse current during the SPDR enhances the strength and microhardness and retains the superconductivity effect. It was found that tension with pulse current displays the electroplastic effect in the NbTi superconductor. *The reported study was supported by RFBR, research project No.14-08-31390 and No.13-08-12222.*
Speaker: Ms Anna Frolova (Mechanical Engineering Research Institute of the Russian Academy of Sciences)
• 76
Properties of Nb3Al wires processed by Double Rapid Heating and Quenching
We have been developing Nb3Al wires processed by a rapid heating and quenching for a number of years as a promising candidate for use in future high-field accelerator magnets. These wires have better strain and stress tolerance than Nb3Sn wires. However, to meet the demands for future accelerator magnet designs, it is necessary to enhance the performance of Nb3Al wires, particularly their non-copper critical current density in the field range of 12-20 T. To pursue this goal, we introduced double rapid heating quenching (DRHQ) treatment into the fabrication process of Nb3Al wires and studied the various properties (mechanical and/or superconducting properties) of the resulting DRHQ-processed wires. This paper briefly reports the results of the study.
Speaker: Kiyosumi Tsuchiya (K)
• 77
Status of AC loss verification tests on ITER conductors with transverse load cycling
Speaker: Kostyantyn Yagotyntsev (University of Twente, Faculty of Science & Technology, 7522 NB Enschede, The Netherlands)
• 78
Transverse pressure dependence of the critical current in Nb3Sn Rutherford cables up to 200 MPa
The transverse pressure dependence of the critical current in various Nb3Sn Rutherford cables is reported. CERN has prepared for the 11 T so-called Dispersion Suppression (DS) dipole magnets constructed in the frame of the LHC luminosity upgrade, cables from different types of strand either with or without AC-loss suppressing central core. Since Nb3Sn is a brittle material and the Lorentz forces in dipole magnets lead to sizeable transverse pressures in their winding pack, it is essential that the cyclic transverse stress response of the cables and especially their irreversible stress limit are well characterized under magnet-relevant conditions. Three DS cables, one prepared with RRP-type strands and two with PIT-type strands and the latter two with and without steel core, were impregnated on a U-shaped holder and mounted in a superconducting transformer set-up equipped with a cryogenic press. The transverse pressure dependence of the critical current was measured at 4.2 K in a magnetic field up to 11 T and a maximum applied force of 240 kN, equivalent to some 200 MPa mean transverse stress on the cable. Additionally, RRR-values and critical current of witness- and extracted strands were investigated in order to understand the influence of cabling process on the critical current.
Speaker: Mr Peng Gao (University of Twente)
• 3:30 PM
Coffee Break Exhibition and Posters Area

### Exhibition and Posters Area

• Tue-Af-Orals Session 4: Large Scale Refrigeration and Liquefaction WA1

### WA1

Convener: Christoph Haberstroh
• 79
ITER Cryoplant Status and Economics of the LHe Plants
The ITER Cryoplant is composed of helium and nitrogen refrigerators and generator combined with 80K helium loop plants and external purification systems. Storage and recovery of the helium inventory is provided in warm and cold (4.5K and 80K) helium tanks. The conceptual design of the ITER Cryoplant has been completed, the technical requirements defined for industrial procurement and contracts signed with industry. Each contract covers the design, manufacturing, installation and commissioning. Design is under finalization and manufacturing has started. First deliveries are scheduled by end of 2015. The various Cryoplant systems are designed based on recognized Codes and international Standards to meet the availability, the reliability and the time between maintenance imposed by the long-term uninterrupted operation of the ITER Tokamak. In addition, ITER has to consider the constraint of a nuclear installation. ITER Organization is responsible for the Liquid Helium (LHe) Plants contract signed end of 2012 with industry. It is composed of three LHe Plants, working in parallel and able to provide a total average cooling capacity of 75kW at 4.5K. Based on concept designed developed with industries and the procurement phase, ITER has accumulated data to broaden the scaling laws for costing such systems. After describing the status of ITER Cryoplant part of the cryogenic system, we shall present the economics of the ITER LHe Plants based on key design requirements, choice and challenges of this ITER Organization procurement.
Speaker: Emmanuel Monneret (I)
• 80
ITER LHe Plants parallel operation
The cooling power required to maintain the nominal operation condition of the ITER superconducting magnets and cryopumps is produced by three identical liquid helium (LHe) Plants, each capable to deliver an average cooling capacity equivalent to 25 kW at 4.5 K. The cold ends of these three LHe Plants are connected to the so called Cryoplant Termination Cold Box (CTCB). In the CTCB, the cold streams from the plants are collected and distributed to the clients (magnets and cryopumps) as requested. The streams returning from the clients are recollected in the CTCB and withdrawn by each LHe Plant at mass flow rates proper to maintain their internal thermal balance. Due to the time dependent heat load of the clients, the cooling capacity generated by the LHe Plants has to vary from 40 to 110 kW resulting in alternating liquefaction and refrigeration modes. In addition, the operation of one of the plants in fail soft (or degraded) mode, corresponding to equipment (compressors and turbines) failures has to be considered. Consequently, the simultaneous operation of the three LHe Plants in parallel compliant with the client requirements and the internal thermal balance is far more complex than simple helium stream redistribution inside the CTCB, and a robust process control scheme is essential. This proceeding we will present the basic principles and control strategies for a stable operation of the three LHe Plants in parallel. Also the latest status of the LHe plant project will be introduced.
Speaker: Eric FAUVE (ITER)
• 81
Acceptance plan and performance measurement methodology for the ITER cryoline system
The cryoline (CL) system of ITER consists of a complex network of vacuum insulated multi and single process lines distributed over three different areas with a total length of about 5 km. With the imminent award of the manufacturing contract for a prototype, the CL project will soon enter into the construction phase. Acceptance tests after on-site installation are critical for the validation of the design, fabrication, quality control procedures and to demonstrate that the CL system will fulfill the expected thermo-mechanical requirements. The acceptance itself will be performed in two phases, namely provisional and final. The strategy for each phase is based on the availability of the final connection of the CLs to their interfacing equipment and will be refined during the execution of the project. The thermal performance of the CL system will be measured during the final acceptance tests using the ITER cryoplant and cryodistribution (CD) infrastructure. The method proposed is based on temperature measurements of a small calibrated cryogenic helium flow through the lines. The cryoplant will be set to establish constant pressure and temperature whereas dedicated heater and valves in the CD will be used to generate the stable mass flow rate. Fluid inserted well-type temperature sensors may be foreseen to minimize the external influences for best accuracy. In this proceeding we will briefly introduce the ITER CL system and describe in detail the acceptance tests planned. A methodology for heat in-leak measurements using the available infrastructure while maintaining a small stable flow will also be discussed.
Speakers: Mr Biswanath Sarkar (ITER-India, Institute for Plasma Research) , Mr Nitin Shah (ITER-India, Institute for Plasma Research) , SATISH BADGUJAR (ITER Organization)
• 82
Experimental and numerical investigations for the operation of large scale helium supercritical loops subjected to pulsed heat loads in tokamaks
Strategies for smoothing pulsed heat loads are of great interest for future operation of large refrigeration systems for tokamaks, such as JT-60SA or ITER as their superconducting magnets are cooled by independent supercritical helium loops. Numerical and experimental process studies have been conducted at CEA Grenoble to validate and optimize the control of such large scale refrigeration circuits. At the cryo-distribution level, in the auxiliary cold box, pulsed heat loads effects have been analysed on a scaled down loop of supercritical helium driven by a cold circulator. Variation of pressure and mass flow can be significant is depending on the pulsed load scenario and on the volume distribution between the heat sources and extractions along the loops. Extensive experimental tests have been performed on the HELIOS test facility during the past three years and the present article aims at summarizing the pulsed load strategies and the understanding of the thermodynamics along the supercritical loop. Dynamics modelling on EcosimPro and the CRYOLIB library is a relevant tool to validate and to compare possible future process controls. The HELIOS loop has offered the possibility to test several configurations: the supercritical loop can be either completely closed (isochoric) or regulated in pressure (isobaric). The article addresses a comparative study of the two configurations. The observations and outcomes of this study can be used for preparing the operation of future cryogenic installations, which main new feature will be the pulsed heat load control resulting from the cycling operation of the tokamak.
Speaker: Christine Hoa (CEA SBT)
• 83
Conceptual design of the cryogenic system for the high-luminosity upgrade of the Large Hadron Collider (LHC)
The discovery in 2012 of a Higgs boson at CERN is the start of a major program of work to measure this particle’s properties with the highest possible precision for testing the validity of the Standard Model and to search for further new physics at the energy frontier. The LHC is in a unique position to pursue this program. Europe’s top priority is the exploitation of the full potential of the LHC, including the high-luminosity upgrade of the machine and detectors with an objective to collect ten times more data than in the initial design, by around 2030. To reach this objective, the LHC cryogenic system must be upgraded to withstand higher beam current and higher luminosity at top energy while keeping the same operation availability by improving the collimation system and the protection of electronics sensitive to radiation. This paper will present the conceptual design of the cryogenic system upgrade with recent updates in performance requirements, the corresponding layout and architecture of the system as well as the main technical challenges which have to be met in the coming years.
Speaker: Mr Laurent Jean Tavian (CERN)
• 84
Helium inventory management and losses for LHC Cryogenics: strategy and results for Run 1
The Large Hadron Collider (LHC) cryogenic system requires an unprecedented helium inventory of 136 tons. If the operational availability for physics was clearly set first priority for run 1 (from first cool-down to long shut-down 1), specific measures were taken from the beginning towards the best rational use of helium during this period. Additional storage capacity was installed to match schedule constraints. Tools were developed to monitor the inventory. Operational achievements were analysed and corrections applied. After recalling the strategy defined for managing the helium inventory and associated infrastructure, tools and methods developed, the achieved results and perspectives will be presented.
Speaker: Mr Serge Claudet (CERN)
• 85
Rotating machinery for LHC Cryogenics: first analysis of reliability and origins of downtime
The Large Hadron Collider (LHC) is cooled by eight independent helium cryogenic plants. Each cryogenic plant combines an 18kW at 4.5K refrigerator and a 2.4kW at 1.8K refrigeration unit totaling 64 oil lubricated screw compressors, 74 expansion turbines and 28 cold hydrodynamic compressors. Since the first cool-down of LHC in 2007, the large number of running hours and start-stop sequences accumulated allow to draw some tendency for reliability of such key components for present refrigeration technology. Statistics and origins of downtime will be presented, with possible typical failure rates.
Speaker: Mr Serge Claudet (CERN)
• 86
Renewal of the control system and reliable long term operation of the LHD cryogenic system
The Large Helical Device (LHD) is a heliotron-type fusion plasma experimental machine which consists of a fully superconducting magnet system cooled by a helium refrigerator having the total equivalent cooling capacity of 9.2 kW@4.4 K. 17 times of plasma experimental campaigns have been performed successfully from 1997 with high reliability. However, 17 years have passed from the beginning of the system operation. The improvements are being done to prevent serious failures and to pursue further reliability. The LHD cryogenic control system was designed and developed as an open system utilizing latest control equipment of VME controllers and UNIX workstations at the construction time. However the generation change of control equipment has been advanced. Down-sizing of control devices has been planned from VME controllers to compact PCI controllers in order to simplify the system configuration and to improve the system reliability. The new system is composed of compact PCI controller and remote I/O connected with EtherNet/IP. Making the system redundant becomes possible by doubling CPU, LAN, and Remote I/O respectively. The system is aiming to increase availability by facilitating diagnosing the system failure. The smooth renewal of the LHD cryogenic control system and the further improvement of the cryogenic system reliability are reported.
Speaker: Toshiyuki Mito (National Institute for Fusion Science (NIFS))
• 87
Final Acceptance Tests of the Helium Refrigerator for Wendelstein 7-X
The cryogenic systems of the stellarator fusion experiment Wendelstein 7-X (W7-X) consisting of superconducting coils, coil-casings and supports will be operated at 3.4K in peak power and 3.9K in standard mode. Radiation shield (80K) protects these components against ambient loads. The refrigerator supplied by Linde Kryotechnik AG has an equivalent refrigeration power of 7kW at 4.5K. It comprises compressor system, cold boxes including cold compressors, subcooler box with cold circulators, distribution valve box and test boxes. Cooling of divertor cryo-vacuum pumps (CVP) is also included in the refrigerator. Following the successful installation and commissioning, the final acceptance tests were carried out on the refrigerator for the normal operating modes i.e. peak power (3.4K), standard (3.9K), short standby (<10K) and long standby (<100K) modes and purification mode. Also, the transient operating modes were included in the test procedure i.e. cool-down and warm-up and interchanging of the operating modes. In addition the handling of quench and emergency signals such as vacuum failure and forced shut-downs and the failure conditions were checked. During standby modes besides cooling the applications, liquid helium is produced which is then supplemented for the additional cooling power required during peak power and standard modes. During these two operating modes the cooling conditions were achieved using four cold circulators and two cold compressors. The short standby mode contained various tests on different components. The test results shall be presented in the paper.
Speaker: Chandra Prakash Dhard (M)
• Tue-Af-Orals Session 5: New Devices and Novel Concepts WA2

### WA2

Convener: Prof. Zhihua GAN
• 88
[Invited Oral] Solid-State Optical Cryocoolers
Compact, vibration-free solid-state refrigerators, are ideal for cooling infrared sensors, gamma-ray spectrometers and other cryogenic electronics. Such coolers could be integrated into these devices, eliminating the need for liquid cryogens or bulky, noisy mechanical coolers. Currently, the dominant solid-state cooling technology is thermoelectric cooling, which uses the Peltier effect. Despite decades of effort, the lowest achievable temperature for multi-stage thermoelectric coolers (TECs) is around 170 K. Programs at ThermoDynamic Films, LLC, the University of New Mexico and Los Alamos National Laboratory have made important strides developing an entirely different solid-state cooling technology, optical refrigeration. Optical refrigeration removes heat by anti-Stokes fluorescence in which a cooling material absorbs photons at one energy and then remits them at a higher average energy; the energy difference extracts heat from the material. This approach has advanced to the stage where it now cools to temperatures that are much colder than those TECs can currently achieve. Laboratory measurements have demonstrated optical refrigeration cooling from near room temperature to 93 K. This talk will describe the physical principles and current status of optical refrigeration and our goals for the near future. One immediate goal is building lightweight, compact optical refrigerators that can be easily integrated with cryogenic electronics. In parallel, we are developing improved cooling materials that can allow optical refrigeration to cool below the 80 K, enabling it to be used with high-temperature-superconductor electronics. The talk will also describe our longer-term goals and approaches for improving the cooling efficiency to make optical refrigerator at least as efficient as the current generation of mechanical cryocoolers.
Speaker: Dr Richard Epstein (ThermoDynamic Films, LLC)
• 89
Prospective solid-state photonic cryocooler based on the “phonon-deficit effect”
In this design microwave photons are propagating in a sapphire rod, and are being absorbed by a superconductor deposited on the surface of the rod. The frequency of the radiation is tuned to be less than the energy gap in the superconductor, so that the pair breaking is not taking place. The photon pumping redistributes the electron-hole quasiparticles, so that their distribution function is non-equilibrium, and the “phonon-deficit effect” takes place. There is a dielectric material deposited on top of superconductors, which is an “object to cool”. Its “acoustical density” is supposed to be smaller than that of the superconducting material, so phonons are being “rectified” to propagate from, but not toward it. Thus, the energy flows from this “object to cool” into the superconductor. The best rectification achieved as of today is about factor of five. This is marginal in view of the positive/negative heat flux ratio. To amplify the rectification, one can use the acoustical filtering, which we describe. Filtering can be arranged between the superconductor and the “object to cool”. Having a remarkably high heat conductivity and high acoustic density, the sapphire rod serves not only as a photonic wave-guide, but also as a thermal heat sink. It is thermally anchored to the bigger external heat-bath. If necessary, one can arrange spectral filters between sapphire and superconducting film, so that sapphire would only admit phonons without supplying them to the superconductor in the range of the absorption spectrum of the superconductor. We performed the calculations using parameters of existing materials. The results still can be further enhanced to take into account subtle effects characterizing the design. Our firm belief is that this cooling opportunity is “cool” enough to be pursued experimentally.
Speaker: Dr Armen Gulian (Chapman University)
• 90
40 K liquid Neon Energy Storage Unit
To attenuate temperature fluctuations, inherent to the cryocooler working or due to sudden heat bursts, a thermal Energy Storage Unit (ESU) could be used. The ESU directly coupled to the cold source actuates as a thermal buffer increasing temporarily its cooling capacity and providing a better thermal stability of the cold finger (“Power Booster mode”). The energy storage units presented here uses an enthalpy reservoir based on the high latent heat of the liquid to vapour transition of neon (38 K- 44 K) to store up to 900 J and a 6-liter expansion volume at RT in order to work as a closed system. Experimental results in the power booster mode will be described: the low temperature cell was directly coupled to the cold finger, its volume (≈12 cm3 of liquid neon) allowing to store 450 J around 40 K. 10 W heat bursts were applied, leading to liquid evaporation, with reduced temperature changes. The liquid neon reservoir can also provide a temporary cold source to be used after stopping the cryocooler allowing a vibration-free environment. In this case the enthalpy reservoir implemented (≈24 cm3) was linked to the cryocooler cold finger through a gas gap heat switch for thermal coupling/decoupling of the cold finger. We will show that, by controlling the enthalpy reservoir’s pressure, 900 J is stored at a constant temperature of 40 K as in a triple-point ESU.
Speaker: Mr Daniel Martins (CEFITEC, Departamento de Física, FCT - Universidade Nova de Lisboa, 2829-516 Caparica, Portuga)
• 91
Activated Carbon-Hydrogen based continuous sorption cooling in a single adsorbent bed with a LN2 heat sink
The use of vibration-free solid-sorption based cooling in space cryogenics has a long successful history. In a typical Linde-Hampson cycle based liquefaction process, periodically adsorbed (or desorbed) gas to (or from) a solid adsorbent plays the role of ‘thermal compressor’. Alternatively, adsorbent beds can be used as ‘condenser’ or ‘evaporator’, while a mechanical compressor generates the required pressure swing. Unlike the heat-driven system where evaporation of the refrigerant produces cooling, in a ‘mechanical compressor’ driven system, cooling is generated by desorption of the gases from adsorbent. The second type of cooling process is rarely used in cryogenics is. Recently, a new concept has been proposed for creating a temperature difference between the two ends of a single adsorbent column with the quick and sequential inflow and outflow of adsorbate through the bed. This sorption cycle can be fundamentally differentiated from pulse tube operation in terms of their operating frequencies and the origin of cooling. In an empty pulse tube, the operating frequency is typically few Hertz. Conversely, the same in the new cycle is in the order of mili-Hertz. The cooling in a ‘single bed’ is due to the heat of desorption, whereas, the expansion of gaseous helium produces cryogenic refrigeration in a pulse tube. While, different adsorbent-adsorbate combinations are suitable for different temperature zones, theoretical investigations involving activated carbon-hydrogen have been made for generating refrigeration around liquid nitrogen boiling point.
Speaker: Susmita Koley (Cryogenic Engineering Centre, IIT Kharagpur)
• 92
Development of a passive, adaptive and autonomous heat switch
We report on the development of a heat switch for autonomous temperature control of electronic components in a satellite. A heat switch can modulate when needed between roles of a good thermal conductor and a good thermal insulator. Electronic boxes on a satellite should be maintained within a typical optimum temperature range of 260 to 310 K. The heat sinking is usually by means of a radiator. When the operating temperature of the electronic box increases beyond 310 K, a good contact to the radiator is desired for maximum cooling. On the other hand, when the satellite is in a cold dormant state, the electronics box should be heated by the onboard batteries. In this state a weak thermal contact is desired between the electronic box and the heat sink. In the present study, we are developing a gas gap heat switch in which the sorber material is thermally anchored to the electronic box. A temperature change of the electronic box triggers the (de-)sorption of gas from the sorber material and subsequently the gas pressure in the gas gap. This talk will describe the physical principles and current status of this technology and our goals for the near future. One immediate goal is selecting a suitable sorber material with the appropriate pressure and temperature characteristics. The talk will also describe our approaches in developing a technology to improve the ON-OFF conductance ratio of the gas gap.
Speaker: Srinivas Vanapalli (University of Twente)
• 93
Superconducting antenna concept for gravitational waves
The most advanced contemporary efforts and concepts for registering gravitational waves are focused on measuring tiny deviations in large arm (kilometers in case of LIGO and thousands of kilometers in case of LISA) interferometers via photons. In this presentation we discuss a concept for the detection of gravitational waves using an antenna comprised of superconducting electrons (Cooper pairs) moving in an ionic lattice. The major challenge in this approach is that the tidal action of the gravitational waves is extremely weak compared with electromagnetic forces. Any motion caused by gravitational waves, which violates charge neutrality, will be impeded by Coulomb forces acting on the charge carriers (Coulomb blockade) in superconductors, as well as in normal metals. We started with a design, which avoids the effects of Coulomb blockade. It exploits two different superconducting materials used in a form of thin wires — ”spaghetti.” The spaghetti will have a diameter comparable to the London penetration depth, and length of about 1-10 meters. To achieve competitive sensitivity, the antenna would require billions of spaghetti, which calls for a challenging manufacturing technology. If successfully materialized, the response of the antenna to the known highly periodic sources of gravitational radiation, such as the Pulsar in Crab Nebula will result in an output current, detectable by superconducting electronics. The antenna will require deep (0.3K) cryogenic cooling and magnetic shielding. This design may be a viable successor to LISA and LIGO missions, having the prospect of higher sensitivity, much smaller size and directional selectivity. We further simplified the bimetallic antenna design into a monometallic one, which should be easier to implement. This concept of compact antenna may be of benefit also in terrestrial applications since gravitational wave detectors may serve as gravity gradiometers.
Speaker: Dr Armen Gulian (Chapman university)
• 94
A compact remote heat transfer device for space cryocoolers
In this paper a compact remote heat transfer device (CRHD) for cryocoolers is proposed. This device is especially attractive in cases where cryocoolers are not easy to set near the heat source, generally the infrared sensor. The CRHD is designed on basis of the conception of loop heat pipes, while the primary evaporator is located near the cryocooler cold head and a simple tube-in-tube secondary evaporator is remotely located and thermally connected with the heat source for cooling. With such a device a cooling power of 1 W is achieved across a heat transfer distance of about 2 m. The major problem of this device is the low heat transfer efficiency (1 W of net cooling power at the cost of about 7 W of cooling power from the cryocooler), and in the future a secondary wicked evaporator will be used instead of the tube-in-tube evaporator in order to improve the efficiency.
Speaker: Dr Tao YAN (Technical Institute of Physical and Institute, Chinese Academy of Science)
• Tue-Af-Orals Session 6: Metals and Insulators WA4

### WA4

Convener: Tripti Sekhar Datta (Inter- University Accelerator Centre. New Delhi. India)
• 95
[Invited Oral] High-cycle fatigue properties of Alloy718 base metal and electron beam welded joint
Tensile and high-cycle fatigue properties of Alloy 718 10 mm-thickness plate and its welded joint were investigated at 293 K and 77 K in this study. The welded joint for the plate was manufactured using electron beam welding (EBW) and followed by a solution treatment and a conventional double aging. After these heat treatments, the hardness of the welded zone became about HV470 same as that of the base metal. The 0.2% proof stress ($σ_{0.2}$) and the tensile strength ($σ_{B}$) of the base metal and the EBW joint increased with a decrease in temperature, without decreasing elongation. The $σ_{0.2}$ and the $σ_{B}$ of the EBW joint reached about 94% of those of the base metal at both temperatures. Fatigue tests were carried out under uniaxial loading for up to $10^{7}$ cycles at stress ratio of R=-1. The base metal and the EBW joint exhibited the similar high-cycle fatigue properties at 293 K. The fatigue strengths of these samples increased at 77 K. However, the EBW joint specimens fractured in longer life region, resulting in the same fatigue strength at $10^{7}$ cycles as that at 293 K. SEM observations of the fractured EBW joint specimens revealed that fatigue crack initiated from specimen surface at 293 K, and often from blow holes formed in the welded zone at 77 K. Thus, it could be concluded that fatigue crack initiation from blow holes tend to be caused more frequently at low temperatures and degrades high-cycle fatigue strength of the EBW joint.
Speaker: Yoshinori Ono (N)
• 96
TENSILE AND FATIGUE QUALIFICATION TESTING of ITER-CS CONDUIT ALLOY JK2LB
The ITER Central Solenoid (CS) coils utilize cable-in-conduit conductor (CICC) and the conduit alloy is JK2LB. The production grade conduit alloy (and it’s welds) must meet strict requirements for strength, toughness, fatigue crack resistance, and fabricability. The conduit alloy must retain good mechanical properties after additional fabrication steps such as welding, coil winding strain and exposure to the Nb3Sn superconductor’s reaction heat treatment. Here we present data from cryogenic tensile, fracture toughness, fatigue crack growth rate, and axial fatigue tests of JK2LB alloy and conduit butt welds, before and after the exposure to the reaction heat treatment. The tests of specimens removed directly from the conduit provide confirmation of the materials properties and its resistance to the effect of the cold work and aging. 4 K fatigue performance is extremely important to the reliability of the CS is covered both by axial cyclic fatigue tests and the fatigue crack growth rate measurements.
Speaker: Robert Walsh (Florida State University)
• 97
Extensive Characterisation of Copper-clad plates, Bonded by the Explosive Technique, for ITER Electrical Joints.
Cable-in-conduit conductors will be extensively implemented in the large superconducting magnet coils foreseen to confine the plasma in the ITER experiment. The design of the various magnet systems imposes the use of electrical joints to connect unit lengths of superconducting coils, by inter-pancake coupling. The design is based on a twin-box lap type joint. By fabrication of twin terminals at both conductor ends, soldered together, the concept allows for the joints to be dismountable. Each terminal is manufactured by compacting the stripped cable end into a bimetallic box, machined from a copper-clad plate, bonded by the explosive technique. Various characteristics, amongst which electrical resistance and mechanical strength, have to be addressed to obtain satisfactory joint operation while avoiding degradation of conductor performance. The joints are submitted to fast varying magnetic fields, inducing locally high stresses, requiring for the bimetallic material to exhibit sufficient mechanical strength at 4.2 K. As a result of operating conditions involving transient magnetic fields during coil operation in certain magnet systems, eddy currents are induced in the copper sole, leading to Joule-heating, hence a reduced superconductor stability. The use of a low purity copper cladding, featuring a low residual resistivity ratio (RRR) will be efficient to increase loop resistance and reduce induced currents. However, the joint must also comply with a low DC resistance requirement to prevent excessive energy loss. To validate technical joint solutions for the various magnet systems, non-destructive, micro-optical and mechanical examinations were conducted to assess the performance of numerous copper-clad plates. These tests confirmed the suitability of such copper-clad plates for an overall joint application. Additionally a discussion is presented concerning the compatibility of certain copper purity grades, aiming at identifying the most suitable copper grades for the different joints types.
Speaker: Stefanie Agnes Elisabeth Langeslag (CERN)
• 98
Cryogenic fatigue and stress-strain behaviour of fibre metal laminates
This paper reports on the cryogenic fatigue life of Al2024 / Stycast 2850ft composite sandwiches loaded under cyclic strain, as well as on the strength of their constituent materials at 77 K. These Fibre Metal Laminate (FML) specimen serve as a model for an alternative class of materials to be used in downstream LNG applications. FMLs, such as the GLARE ™, are already used in the aeronautic industry, where they provide better damage tolerance, corrosion resistance and lower specific weight. Their cryogenic performance however, is yet to be understood. In contrast to the FML used in aeronautic industry, preliminary results show that the metal/filled-epoxy combination presented here, withstands repeated cool-down to 77 K. Moreover, its cryogenic fatigue life is at least 20 times longer than at room temperature. These observations are consistent with the measured stress-strain behaviour of the metal and the epoxy, as well as with the shear strength of the bond between them. The Young’s modulus, yield strength and tensile strength of the Stycast 2850ft roughly double when cooled down to 77 K. In addition to this, the bond strength with the GLARE-type coated Al increases significantly. These preliminary experiments indicate that cryogenic FML are technically feasible.
Speaker: Wilco van de Camp (Energy, Materials and Systems, University of Twente, The Netherlands)
• 99
Winding Pack Height Management during Fabrication of the ITER CS Module
The Central Solenoid stack consists of 6 modules, 2.1 m tall each. In order to verify good impregnation, we performed a VPI (vacuum-pressure impregnation) test of a full cross section of the CS module, 14 conductors wide and 40 conductors tall. It was discovered that after preparation of the full cross section stack till completion of the VPI the stack shrunk in height by 20-25 mm. Our study of the literature and discussions with the leading experts in VPI did not reveal obvious reasons for this change of height. We launched a study to address this issue. We assembled two 12x1 arrays and several 7x1 arrays in order to study characteristics of the dry winding pack under compressive force and effects of different fabrication steps. Then we impregnated these arrays in different conditions under compressive force and studied change of height as a result of compression, impregnation, gelling and curing of the stack of insulated conductors. We showed that by controlling the application of the compressive force, before closing the mold and during impregnation, one can reduce the height uncertainty. The most of the height reduction takes place while the glass is dry under the dead weight and the applied compressive force. Reduction of height during injection of the resin and during gelling, curing and cooling of the coil is noticeable, reproducible and relatively small. The paper presents results of our studies and recommendations for assembly and VPI of tall windings.
Speaker: Dr Nicolai Martovetsky (LLNL)
• 100
Fatigue and fracture toughness of cryogenic-grade epoxy resin at low temperature
Thermosetting epoxy resins are commonly used as adhesives, sealants, and matrices of insulation material of superconducting magnets. In the present work, fatigue and fracture toughness of a cryogenic-grade epoxy resin were investigated at room and liquid nitrogen temperatures to establish sound data bases for practical applications. The fatigue testing of the epoxy was conducted with strain and stress-controlled modes with various strain and stress amplitudes. The fracture toughness, KIC, was tested with a compact tension specimen according to standard ASTM D 5045. The results of fatigue and fracture toughness testing will be useful in engineering designs.
Speaker: Prof. Laifeng Li (Technical Institute of Physics and Chemistry)
• 101
A calorimeter for measurements of multilayer insulation at variable cold temperature
An improved calorimeter cryostat for MLI thermal performance measurements has been designed and put into operation at the TU Dresden. Based on a liquid helium cooled flow cryostat, it allows the setting of any cold level temperature between approx. 30 K and ambient temperature. Thermal shields and all-embracing radiation guards at both ends can be kept at nearly identical temperature. This is done by means of two separate cooling circuits. Both the actual cold test surface temperature and the cooling of the mechanical support and radiation shields can be independently controlled. Insulation specimens are wrapped around a test cylinder with a surface of 0.9 m². The heat transfer through the MLI is measured by recording the mass flow, the inlet and outlet temperature of the cooling fluid. Measurements both in horizontal and vertical orientation can be performed or compared, respectively. Moreover the effect of an additional vacuum degradation – as it might occur by decreasing getter material performance in real systems at elevated temperatures – can be studied by controlled inlet of an elective gas. It is reported about the design and the equipment of this cryostat and comparative measurments of a 10 layer MLI specimen at different cold temperatures.
Speaker: Mr Thomas Funke (TU Dresden)
• 102
Effect of matrix modification on the interlaminar shear strength of glass fiber reinforced epoxy composites at cryogenic temperature
In order to investigate the effect of the matrix variability on the interlaminar shear strength (ILSS) of the glass fiber reinforced composites at 77K, three kinds of modifiers were employed to modify the diethyl toluene diamine (DETD) cured diglycidyl ether of bisphenol F (DGEBF) epoxy resin system in this study. The woven glass fiber reinforced composites were fabricated by vacuum pressure impregnation (VPI) process. The ILSS at 77K was studied and the results indicated that introduction of modifiers used in this study can enhance the ILSS of composite at 77K and a maximum of 14.87% increase was obtained by addition of 10wt% IPBE into the epoxy matrix. Furthermore, scanning electron microscopy (SEM) was used to investigate the fracture mechanism and strengthening effect.
Speaker: Prof. Laifeng Li (State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)
• 6:15 PM
Exhibitors Reception (free drinks and a buffet-meal will be served). Exhibition Area

### Exhibition Area

• 9:00 PM
Shuttle service to hotels
• Wednesday, July 9
• 8:00 AM
Registration desk open Entry hall

### Entry hall

Open from 8:00-18:30

• Wed-Mo-Plenary Session 2: Introduction to the Day and 2 Plenary Orals WA1

### WA1

Conveners: Ho-Myung Chang (Hong Ik University) , Takanobu Kiss (Kyushu University)
• 103
Introduction Wednesday
• 104
ICMC Award for Excellence ceremony
• 105
ICEC Mendelssohn Award ceremony
• 106
The Future with Cryogenic Fluid Dynamics
The applications of cryogenic systems have expanded over the past 50 years into many areas of our lives. During this time, the impact of the common features of Cryogenic Fluid Dynamics, CFD, on the economic design of these cryogenic systems, has grown out of a long series of experimental studies carried out by teams of postgraduate students at Southampton University. These studies have sought to understand the heat transfer and convective behaviour of cryogenic liquids and vapours, but they have only skimmed over the many findings made, on the strong convective motions of fluids at low temperatures. The convection takes place in temperature gradients up to 10,000 degrees K/meter, and density gradients of 1000% per meter and more, with rapid temperature and spacially dependent changes in physical properties like viscosity, surface tension, etc, making computer modelling almost impossible without experimental data. These temperature and density gradients are far larger than those met in other convecting systems at ambient temperatures, and there is little similarity. The paper will discuss the likely impact of CFD on future cryogenic systems, and hopefully inspire further research to support and expand the use of existing findings, and to improve the economy of present-day systems even more effectively. Particular examples to be mentioned include the following. Doubling the cooling power of cryo-coolers by a simple use of CFD. Reducing the boil-off rate of liquid helium stored at the South Pole, such that liquid helium availability is now all-the-year-round. Helping to develop the 15 kA current leads for the LHC superconducting magnets at CERN, with much reduced refrigeration loads. Improving the heat transfer capability of boiling heat transfer surfaces by 10 to 100 fold.
Speaker: Dr Ralph G. Scurlock (Emeritus Professor of Cryogenic Engineering University of Southampton, UK)
• 107
Engineering and Materials Challenges in ITER Toroidal Magnet system
The ITER Tokamak magnet composed of 4 superconducting coils (toroidal field (TF), poloidal field (PF), central solenoid (CS) and correction coils (CC)) is now well under procurement. Concerning the Toroidal Field Coils (TFC), the first windings and structures components are being fabricated by industries through large contracts managed by European Fusion For Energy (F4E) and Japanese Domestic Agency (JADA) since last mid 2010. Those large magnets with 41GJ magnetic total stored energy are used to contain plasma and consist of eighteen toroidal field coil windings, utlizing Nb3Sn Cable in conduit conductor, electrically connected in series and operated with nominal transport current of 68kA, supplied through HTS current leads. The coils are cooled by supercritical helium at about 4.5K, and experience a peak field of 11.4 T. One of the key challenges of ITER coils design is the development of high strength class, fatigue-resistant structural 316LN stainless steel material in forging and welded form compatible with high operating stress at liquid helium temperature. Composite materials used in magnet insulation system and the large precompression rings require specific qualifications and manufacture processes to guarantee final properties over lifetime. Some important coil features such as helium supply inlets, electrical joints require dedicated qualification to confirm the design choices and the utilized manufacturing routes. At each stage of manufacture of those components, proper allocation of tolerances to the different manufacture steps of winding, assembled encased coils has been defined in order to guarantee the final mechanical integrity of assembled coils under operating loads. The resulting position of the magnetic center line datum installed in the cryostat allows to control plasma interactive errors of magnetic fields. This paper will present an overview of the key development on material related to ITER TF fusion magnets and their main challenges on integration engineering.
Speaker: Dr Arnaud Foussat (ITER Organisation)
• 10:30 AM
Coffe Break Exhibition and Posters Area

### Exhibition and Posters Area

• Wed-Mo-Orals Session 7: Safety, Standards, Instrumentation and Current Leads WA1

### WA1

Convener: Johan Bremer (CERN)
• 108
[Invited Oral] Controlled Cold Helium Spill Test in the LHC Tunnel at CERN
The helium cooled magnets of the LHC particle accelerator are installed in a confined space, formed by a 27 km circumference 3.8 m diameter underground tunnel. The vacuum enclosures of the superconducting LHC magnets are protected by a lift plate against excessive overpressure created by eventual leaks from the magnet helium bath, or from the helium supply headers. A three-meter long no stay zone has been defined, based on earlier scale model studies, on both sides of these plates, protecting the personnel against the consequences of an eventual opening of such a lifting plate. More recently several simulation studies have been carried out modelling the propagation of the resulting helium/air mixture along the tunnel in case of such a cold helium release at a rate in the range of 1 kg/s. To validate the different scale models and simulation studies, real life mock-up tests have been performed in the LHC, releasing about 1000 liters of liquid helium under standard operational tunnel conditions. Data recorded during these tests include oxygen level, temperature and flow speed measurements as well as video recordings, taken up- and downstream of the spill point (-100 m to +200 m) with respect to the ventilation direction in the LHC tunnel. The experimental set-up and measurement results will be presented enriched with recorded video. Generic effects found during the tests will be discussed to allow the transposal to possible cold helium release cases in similar facilities.
Speaker: Torsten Koettig (CERN)
• 109
Modelling and experimental verification of the pressure wave following a gaseous helium storage tank rupture
Helium inventory in high energy accelerators, tokamaks and free electron lasers may exceed tens of tons. The gaseous helium is stored in steel tanks under the pressure of 20 bar and at environment temperature. Accidental rupture of any of the tanks filled with the gaseous helium will create a rapid energy release in form of physical blast. An estimation of pressure wave distribution following the tank rupture and potential consequences especially to ITER tokamak adjacent infrastructure and buildings is a very important task critical in the safety aspect of the whole cryogenic system. A special test stand was designed and built in order to verify experimentally the blast effects in controlled conditions. In order to obtain such a shock wave a pressurized plastic tank was used. The tank was ruptured and the resulting pressure wave was recorded using an spatially-distributed array of pressure sensors connected to a high-speed data acquisition device. The results of the experiments and the comparison with theoretical values were presented. A good agreement between the simulated and measured data was obtained.
Speaker: Mr Maciej Grabowski (Wroclaw University of Technology)
• 110
SQUID-based noise thermometer for sub-millikelvin refrigerators
The magnetic-field fluctuation thermometer (MFFT) is a high-accuracy SQUID-based noise thermometer suitable for sub-Kelvin thermometry. It consists of a highly sensitive low-Tc SQUID magnetometer and a metal body in contact with the temperature stage to be measured. The SQUID is used to inductively detect magnetic field fluctuations that arise from the thermal motion of electrical charges in the metal body. For fixed geometry and constant electrical conductivity of the metal the spectral shape of the magnetic flux noise sensed by the SQUID is temperature independent, and the detected “magnetic” Johnson noise is directly proportional to the temperature. Hence, a reference measurement at one known temperature suffices for calibration. A complete MFFT thermometer system for the temperature range of ca. 4 K down to <10 mK is commercially available [1]. We have now developed an integrated MFFT with an extended range of operation down to <1 mK. For this purpose the sensitivity of the SQUID sensor has been increased, the metal body geometry modified and the magnetic shielding of the MFFT module improved. These modifications make it possible to obtain a thermometer noise temperature of <10 µK. We discuss the rationale for our MFFT configuration for ultra-low temperatures and present details of numerical simulations and experimental results. [1] http://www.magnicon.com/fileadmin/download/datasheets/Magnicon_MFFT-1.pdf
Speaker: Mr Marco Schmidt (Physikalisch-Technische Bundesanstalt)
• 111
Standardization in Cryogenic Thermal Insulation Systems
The close relationship between industrial energy use and cryogenics drives the need for optimized thermal insulation systems. Emerging cryofuels usage is enabled by adequate isolation of the liquid hydrogen or liquefied natural gas from the ambient environment. Thermal performance data for the total insulation system, as rendered, are essential for both engineering designs and cost-benefit decisions involving comparisons among alternatives. These data are obtained through rigorous testing with suitable apparatus and repeatable methods. Properly defined terminology, analysis, and reporting are also vital. Advances in cryogenic insulation test apparatus and methods have led to the recent addition of two new technical standards of ASTM International: C1774 - Standard Guide for Thermal Performance Testing of Cryogenic Insulation Systems and C740 - Standard Guide for Evacuated Reflective Cryogenic Insulation. Among the different techniques described in the new standards is the cylindrical boiloff calorimeter for absolute heat measurement over the full range of vacuum pressure conditions. The details of this apparatus, test method, and data analysis are given. Benchmark thermal performance data, including effective thermal conductivity and heat flux for the boundary temperatures of 293 K and 77 K, are given for a number of different multilayer insulation (MLI) systems in comparison with data for other evacuated insulation systems including perlite powder, fiberglass, and aerogel composite.
Speaker: Mr James Fesmire (NASA)
• 112
Cryogenic commissioning of the new Current Lead Test Facility CuLTKa
The Current Lead Test facility Karlsruhe (CuLTKa) has been constructed to optimize the capabilities for current lead testing at the Karlsruhe Institute of Technology (KIT). The facility comprises five cryostat vessels including two test cryostats connected by transfer lines to the 2 kW refrigerator. Each test cryostat holds two current leads with a superconducting short circuit connector. The new facility is integrated into a setting of several experimental setups for which the 2 kW refrigerator provides helium of two different temperature levels at overcritical pressures. The maximum current of 30 kA is fed to the current leads by water cooled flexible cables. The aim of the setup is a flexible, efficient and reliable testing of current leads. In a first step the cryogenic commissioning of the facility without current leads was performed in the beginning of 2014, followed by a commissioning with current leads installed including current tests. Towards the end of the first half of the year the test campaign of 26 current leads for the JT-60 SA tokamak will start. The paper will give an overview of technical details of the facility and its performance during the cryogenic commissioning phase.
Speaker: Mr Thomas Richter (Karlsruhe Institute of Technology (KIT))
• Wed-Mo-Orals Session 8: Cryogenics for Power and Other Applications WA2

### WA2

Convener: Guenter Thummes
• 113
Air Liquide cryogenic solutions for HTS refrigeration
Air Liquide started the development of Turbo-Brayton cryogenic refrigerators in 2007. The goal was to design refrigerators with high efficiency and reliability, which are key issues when talking about HTS systems refrigeration. The innovation consists in the assembly of all active elements on the same shaft. The recovery of the expander mechanical power, the centrifugal compressors and the direct drive high speed motor lead to a high overall efficiency. The operation is very flexible, and the cold power can be adapted from 0 to 100% by changing the rotation speed of the motor, keeping high efficiency on a large range of operation. A standard range of industrial Turbo-Brayton refrigerators (5-23kW at 77K) is now available. A first industrial refrigerator has been manufactured and tested in-house in 2012, and a second has been commissioned end of 2013, demonstrating the reliability of the refrigerators. The developments continue, in order to increase the cold power up to 40kW. The use of cryogenic pumps is necessary to transfer the heat from the refrigerator to the HTS device to be cooled. Air Liquide has developed a range of cryogenic circulators on active magnetic bearings in order to ensure a Mean Time Before Failure of 105 000 hours of the global system (refrigerator + pump).
Speaker: Cecile Gondrand (A)
• 114
Cryogenic tests of 30 m flexible hybrid energy transfer line with liquid hydrogen and superconducting MgB2 cable
Recently we reported about first in the world test of 10 m hybrid energy transfer line with liquid hydrogen and MgB2 superconducting cable [1]. In this paper we present the new development of hybrid energy transfer line with 30 m length. The flexible 30 m hydrogen cryostat has three sections with different types of thermal insulation in each section: simple vacuum superinsulation, vacuum superinsulation with liquid nitrogen precooling and active evaporating cryostatting (AEC) system. We performed thermo-hydraulic tests of the cryostat to compare three thermo-insulating methods. The tests were made at temperatures from 20 to 26 K, hydrogen flow from 70 to 450 g/s and pressure from 0.25 to 0.5 MPa. It was found that AEC thermal insulation practically eliminated completely heat transfer from room temperature to liquid hydrogen. AEC thermal insulation method can be used for long superconducting power cables. High voltage current leads were developed as well. The current leads and superconducting MgB2 cable were passed high voltage DC test up to 50 kV DC. Critical current of the cable at ~21 K was 3500 A. It means that the 30 m hybrid energy system developed is able to deliver ~ 50 MW of chemical power and ~ 75 MW of electrical power (at 25 kV and 3000 A), i.e.~125 MW in total. [1] V. S. Vysotsky,et al., IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 23, NO. 3, JUNE 2013, 5400906
Speaker: Vitaly Vysotsky (R)
• 115
Innovative Superconducting DC Cable Using the Longitudinal Magnetic Field Effect
We have proposed the innovative superconducting DC cable using the longitudinal magnetic field effect. That is, the current-carrying capacity of the cable can be enhanced under a axial magnetic field produced by the current itself flowing in the inner conductor and outer shielding conductor. Because of the weak link properties in coated conductor that disturb a uniform current flow, the enhancement of the critical current density is limited. However, it was found that the current-carrying capacity can be enhanced appreciably in comparison with conventional cables by designing the structure of the cable so as to reduce the Lorentz force. This scheme can also be applied to BISCCO tapes. The optimal design for a cable with commercial BISCCO tapes will be discussed. One of the merits of this innovative cable is that the cable itself has a limiting function of fault currents. The current-carrying capacity can be enhanced by the longitudinal magnetic field. It means that, if the longitudinal magnetic field is reduced, the critical current density in the superconducting tapes is appreciably degraded, resulting in a smooth transition to the resistive state with reduction in the current. Such situation can be realized by arranging the copper conductor layers in a suitable structure that transport the current when the superconductors are in the resistive state. The possibility of the fault-current limiting function will also be discussed.
Speaker: Prof. Teruo Matsushita (Kyushu Institute of Technology)
• 116
Towards an Optimized Coupling-Loss-Induced Quench Protection System (CLIQ)
The recently developed Coupling Loss Induced Quench (CLIQ) protection system is a new method for initiating a fast and voluminous transition to the normal state for protecting high energy density superconducting magnets. Upon quench detection, CLIQ is triggered to generate an oscillating current in the magnet coil by means of a capacitive discharge. This in turn introduces high coupling loss in the superconductor which provokes a quick transition to normal state of the coil windings. CLIQ is now implemented for the protection of a two meter long superconducting quadrupole magnet and characterized in the CERN magnet test facility. Various CLIQ configurations with different current injection points are tested and the results compared to similar transients lately measured with a not optimized configuration. Test results convincingly show that the newly tested design allows for a more global quench initiation and thus a faster discharge of the magnet energy. Moreover, the performance of CLIQ for reducing the hotspot temperature after a quench is compared to that of conventional quench heaters. In addition, measured transients are reproduced using a lumped element dynamic electrothermal model developed with Simulink©. After its validation, the model is now used for simulating various discharges in order to find the optimum CLIQ configuration and operating parameters for the most homogeneous transition to the normal state of the coil windings and hence the lowest hotspot temperature. Finally, the integration of the new CLIQ with conventional protection systems like quench heaters and energy extraction is thoroughly discussed for incompatibilities and synergies.
Speaker: Mr Emmanuele Ravaioli (Twente Technical University (NL))
• 117
Evaluation of Warm and Cold Shaft Designs for Large Multi-megawatt Direct Drive Offshore Superconducting Wind Generators
For offshore wind power generation applications, multi-megawatts rated direct drive generators are believed to provide an opportunity to convert the abundant wind energy into electricity. Because of its ability to generate high flux fields, superconducting (SC) technology can offer significant size and mass reduction over traditional technologies. However, many challenges still exist, and cryogenic cooling design is one of the major obstacles. Many current SC designs use cold shaft designs, which enclose the rotor inside a single cryostat and cool it to the cryogenic temperatures. Such approach may not be practical for large generators because of the large rotor mass that requires long cool down time during startup. Instead of cooling the entire rotor, a warm shaft design offers an alternative to the SC cold shaft rotor design. Each pole has its own separate cryostat and keeps the rest of the rotor at room temperature. This provides faster cool down time. Another major advantage is lower maintenance time and cost, which can be very expensive when considering the costs associated with troubleshooting in offshore wind turbines. For warm shaft design, it is possible to replace a cryostat pole onsite resulting in minimum downtime. Warm rotor design, however, does present a significant challenge as the cryostat design is so compact, it is more difficult to minimize heat leak and it requires special design concepts for structural integrity. This paper presents the investigations on the advantages and disadvantages of both rotor designs for large SC generators from manufacturability and service perspectives.
Speaker: Edward Chen (TECO Westinghouse Motor Company)
• 118
Cryogenic Thermal Modeling and Experimental Validation of Termination System for Helium Gas Cooled Superconducting DC Cable
The Florida State University has recently completed a successful demonstration of a helium gas cooled superconducting DC cable system. Terminations are critical elements of a superconducting cable system. The terminations for the gas cooled superconducting cable are particularly challenging due to lower dielectric strength and heat capacity of helium gas compared to those of liquid nitrogen. The termination system used in the demonstration contained some novel design concepts to mitigate the challenges. Thermal models were used to assess the heat loads from the terminations. Experiments were carried out and thermal map of the system was obtained at various helium gas mass flow rates. Experimental results were compared with those of the model. It was observed that the model describes the heat loads from various sections. The paper will describe the design of the terminations and comparison of the results of the thermal models and experiments. This work was supported by the Office of Naval Research (ONR).
Speaker: Sastry Pamidi (The Florida State University)
• 119
Simulation of liquid level, temperature and pressure inside a 2000 liter liquid hydrogen tank during a truck transportation
Hydrogen is an ultimate energy source because only water is produced after the chemical reaction of hydrogen and oxygen. In the near future, a large amount of hydrogen, produced using sustainable/renewable energy, is expected to be consumed. Since liquid hydrogen (LH2) has the advantage of high storage efficiency, it is greatly attractive as the ultimate medium for the worldwide storage and transport of large amount of hydrogen. Recently, development of LH2 tanks and carriers as well as liquefied natural gas tanks and carriers are ongoing. It is important to elucidate the sloshing condition inside an LH2 tank during transportation by truck and ship. To make a calculation model of the sloshing of LH2 inside a tank, simulation of LH2 level, temperature and pressure inside the tank during transportation were carried out using a multipurpose software ANSYS CFX. Calculated results are discussed in comparison with experimental results of a 2000 liter tank during transportation by truck.
Speaker: Prof. Minoru Takeda (Kobe University)
• Wed-Mo-Orals Session 9: BSCCO, MgB2, Fe-pnictides and New Superconducting Materials WA4

### WA4

Convener: Dmytro Abraimov (NHMFL)
• 120
[Special Invited Oral: 2014 ICMC Award for Excellence Winner] Key microstructural features of Bi2212 and Bi2223: why is the Jc of highly textured Bi2223 smaller than that of isotropic high Jc Bi2212 round wires?
By utilizing the over pressure technique, Bi2Sr2CaCu2Ox (Bi2212) round wires without macroscopic texture recently achieved Jc of 4000 A/mm2 at 4.2 K, 5T, despite the presence of many universally-assumed obstructing high angle grain boundaries (HAGBs). We sought to understand the nature of more local scale texture, in particular to better understand the apparent disagreement between Bi2212 and its sibling Bi2Sr2Ca2Cu3Ox (Bi2223). In order to understand whether HAGBs in Bi2212 are superior to those in Bi2Sr2Ca2Cu3Ox or REBa2Cu3O7-δ, or whether other mechanisms compensate for obstructing HAGBs, we extensively compared the grain and GB structure in a Bi2212 round wire to those in a uniaxially textured Bi2223 flat tape by using the electron backscatter diffraction orientation image analysis (EBSD-OIM). It turned out that, compared with the Bi2223 tape in which the in-plane orientations of grains are basically random in spite of small out-of-plane GB misorientations, the Bi2212 round wire possesses the quasi-biaxial texture in which large basal-plane-faced GBs are formed as a result of large grain formation in the constraint of narrow filament cavities. It is strongly suggested that the major current paths in the high Jc Bi2212 round wire are ~10-15° basal-plane-faced, c-axis twist GBs which are strongly coupled due to their large area and force-free configuration in current flow and magnetic fields. These unique features of the Bi2212 grain structure may help explain the strong grain-to-grain coupling that we have found and lead to further improvements in performance.
Speaker: Dr Fumitake Kametani (National High Magnetic Field Laboratory)
• 121
Design and development of high current density, oxide based superconductors with mechanical properties enabling their use in very high field magnets
Superconducting oxide (HTS) – based conductors must support large stresses and strains in demanding next-generation high field applications without current density and structural degradation. This paper describes recent advances in the mechanical properties of HTS-based commercial and development stage conductors. A comprehensive design model has been established and applied to the development of very high stress and strain tolerant, reinforced HTS wires, tapes and cables with minimal added material, and consequent current density reduction. The analysis incorporates the properties of constituent materials, architecture, method of fabrication and operating conditions, to calculate axial stress, strain, bend, twist and surface indent tolerance. The method was applied to identify superior classes of reinforcement materials in comparison to the currently used stainless steels and superalloys. Conductors with mechanical properties tailored for key applications have been designed for YBCO and Bi2223 oxide based HTS tapes, as well as for Bi2212 based round wires. Based on the analysis and new reinforcement material options, prototype long lengths of reinforced Bi2223-based superconducting tapes were produced that exhibit up to 540 MPa axial stress tolerance, a 1.5 fold improvement that exceeds threshold levels required for use in a broad range of very high field magnet applications. In a second application of this approach, a scalable low cost test bed is built and applied to demonstrate the practical reinforcement of round Bi2212/silver wire, in its fully developed form allowing the much lower cost and more versatile react-and-wind fabrication of Bi2212 based coils for very high field magnets.
Speaker: Dr Alexander Otto (Solid Material Solutions, LLC)
• 122
5T class superconducting bulk magnet using MgB2 bulk doped with Ti
MgB2 superconductors have mainly been studied for the practical application of tapes and thin films owing to its high Tc of about 39 K and a high upper critical field among metallic superconductors. We have studied that the trapped field properties of MgB2 bulk samples fabricated by the capsule and hot isostatic pressing (HIP) methods and succeeded in producing the 2-3 T class bulk magnet. Recently, a trapped field of 5.4 T was reported for the hot-pressed MgB2 bulk using the mechanical alloyed precursor powder [1]. In this paper, to obtain the higher trapped field we studied the doping effect of Ti on the trapped field in MgB2 bulk samples fabricated by the HIP method. The Mg(1-x)TixB2 bulk samples were magnetized by the field cooling magnetization (FCM) in a magnetic field of 10 T using a 10 T cryogen-free superconducting magnet. The highest trapped field at the top surface of the single bulk (x=0.1) was 3.6 T and that at the center between the doubly stacked bulks (x=0.05 and 0.1) was 4.6 T. We discuss precisely the effect of Ti on the enhancement of the vortex pinning from the analysis of the micro structure. [1] G. Fuchs et al, Supercond. Sci. Technol. 26 (2013) 122002.
Speaker: Dr Tomoyuki Naito (Iwate University)
• 123
Novel Critical Current Estimation Method for Internal-Mg-diffusion-processed MgB2 Wires Based on Magnetic Microscopy
We have succeeded in characterizing critical current properties of recent high-performance MgB2 wires at very high critical current conditions. Generally, critical currents of a wire are measured by four-probe transport measurements. However, for high critical current conditions, e.g., at relatively low magnetic fields, it is difficult to perform the measurement due to heat generation and/or the limitation of experimental system. This is one reason why the performances of the wires are often reported for high external magnetic field conditions, e.g., at higher than 5 T. On the other hand, one of the most promising applications for MgB2 wires is MRI where the wire experiences much lower external magnetic field. This means that some characterization method for such conditions is indispensable for MgB2 wire development and for MRI magnet design. As a complementary method, magnetization measurement is often used to estimate critical current densities. However, we cannot apply this method to recent high-performance MgB2 wires because a simple magnetization pattern cannot be assumed due to their magnetic sheath materials and spatial inhomogeneity. In this study, we established a characterization method of critical current properties for the MgB2 wires based on scanning Hall-probe microscopy. Magnetic field distribution on a magnetized wire was measured, and then the value of critical current which could express it quantitatively was estimated. As a result, we successfully evaluated critical current values as hundreds to a thousand amperes without a transport current. Furthermore, it was confirmed that the results agreed very well with the extrapolation from the properties obtained by the four-probe transport method. We will show critical current properties of internal-Mg-diffusion-processed wires where the performances have been dramatically improved recently as the second generation wires. This work was partly supported by JST as ALCA.
Speaker: Prof. Kohei Higashikawa (Kyushu University)
• 124
Low Temperature- High Field performances of Iron calchogenides thin films
Among the various families of Fe-based superconductors, iron chalcogenides, although presenting a not particularly high transition temperature, show great advantages for potential applications in high field, albeit at liquid helium temperature . The critical temperature in thin films can be increased by applying stress up to 21 K, but the stress can push the critical field up to more than 50 T (and the irreversibility field close to this value). Also critical currents up to 1 MA/cm2 in self-field at liquid helium temperature can be reached with a very weak dependence on the magnetic field. Interestingly the anisotropy depends on the mode of growth and the substrate used and the high values of critical current can be achieved without appreciable anisotropy. In this work, STM and TEM techniques will be used to characterize pinning centers that are effective in different types of films. It was shown that Fe-chalcogenide films can be deposited on technical oxide substrates. Interesting would be to develop metal technical polycrystalline substrates. Our preliminary measurements reported here, show that the critical current at the grain boundary is not severely depressed.
Speaker: carlo ferdeghini (C)
• 125
Engineering room-temperature superconductors via ab-initio calculations
The BCS, or bosonic model of superconductivity, as Little and Ginzburg have argued, can in the case of high-enough frequency of bosonic mode bring in superconductivity at room temperatures. It was further elucidated by Kirzhnits et al., that the condition for existence of the high-temperature superconductivity is closely related with negative values of the real part of dielectric function at finite values of the reciprocal lattice vectors. In view of these findings, the task is to calculate the dielectric function for real materials. Then the poles of this function will indicate existence of bosonic excitations which can serve as a “glue” for Cooper pairing, and if the frequency is high enough, and the dielectric matrix is simultaneously negative this material is a good candidate for very high-Tc superconductivity. Thus, our approach is to elaborate a methodology of ab-initio calculation of the dielectric function of various materials, and then point out appropriate candidates. We used the powerful codes (TDDF with the DP package, used in conjunction with ABINIT) for computing dielectric responses at finite values of the wave vectors in the reciprocal lattice space. Though our report is concerned with the particular problem of superconductivity, the application range of the data processing methodology is much wider. The ability to compute dielectric function of existing and still non-existing (-though being predicted!) materials will have many more repercussions not only in fundamental sciences but also in technology and industry.
Speaker: Dr Armen Gulian (Chapman University)
• 1:00 PM
Lunch Break (a lunch buffet will be served for all registrants) Lunch Area

### Lunch Area

• Wed-Af-Posters Session 2.1: Large Scale Cryogenics II
Convener: Philippe Lebrun (CERN)
• 126
Conceptual Design of the Liquid Hydrogen Moderator Cooling Circuit for the European Spallation Source
The European Spallation Source in Lund, Sweden, is planned to be a spallation neutron research center of 5 MW beam power. As subsystem of the target station the moderators play a vital role in decelerating high energy neutrons which were set free during the spallation process. To provide maximum neutron flux intensities with high availability for scattering experiments a proposal for a liquid hydrogen moderator cooling circuit was developed. Circulating supercritical Hydrogen at approximately 17 K and 1.5 MPa will be utilized to absorb energy of the penetrating neutrons in two parallel moderator vessels. A helium refrigerator provides the necessary cooling. Strategies for the mitigation of rapid pressure and temperature changes due to beam interruptions are being presented. Solutions in form of accumulator or expansion vessels are evaluated. Different supercritical hydrogen circulator implementation scenarios are compared to indicate the most reliable setup. For an efficient moderation process a parahydrogen concentration of more than 99 % has to be guaranteed at the moderator inlet. A possible irradiation impact on the apparent parahydrogen concentration, the positioning of a catalyst bed and methods for a continuous concentration measurement will be pointed out. The proposed arrangement and interactions of all major components will be discussed in the paper.
Speaker: Marcel Klaus (TU Dresden)
• 127
Cool-down Experiences with the SST-1 Helium Cryo System Before and after Current Feeder System Modifications
The SST-1 machine comprises of superconducting magnets system (SCMS) which includes TF and PF magnets. In order to charge the SCMS, we need superconducting current feeder system consisting of sc feeders and vapor cooled current leads (VCCLs). We have installed all (+/-) 10 pairs of vapor cooled current leads for the TF and PF systems. While conducting initial engineering validation of SST-1 machine, our prime objective was to produce circular plasma using only the TF system. During SST-1 campaign I to VI, We have to close the PF magnets cooling in order to get the cryo stable conditions for current charging of the TF magnet system. In that case, the cooling of the PF current leads is not essential. It has been also observed that after closing of the PF system cooling, there was a limited experimental window of TF operation. Therefore, in recent SST-1 campaign-VII, we removed the PF current leads (9 pairs) and kept only one (+/-) pair of the 10 kA rated VCCLs to realize the charging of the TF system for extended window of operation. We have observed better cryogenic stability in TF magnets after modifications in CFS. In this paper, we report the comparison of the cool down performance for SST-1 machine operation before and after modifications of the current feeder system.
Speaker: Mr Rakeshkumar Patel (Institute For Plasma Research)
• 128
Cryogenic Infrastructure for the Serial Magnet Test Facility for FAIR
In order to test the fast-ramped superconducting magnets for FAIR (Facility for Antiproton and Ion Research), a cryogenic test facility was designed and is currently under construction at GSI. The overall capacity of the cryo plant is about 1.5 kW @ 4.4 K equivalent and can be distributed to four test benches individually. In total 108 dipoles for the SIS100 will be tested at cold. The capacity of the cryogenic system is designed in order to simultaneously cool down one magnet while the other one is operated at cold state for the measurements. The other two test benches serve for warming up and for magnet exchange, respectively. Beyond the dipoles, the high flexibility of the set-up allows also the testing of other FAIR magnets, like the SIS100 quadrupole modules or the operation of a string configuration. The design of the cryogenic infrastructure, including an advanced feed box and magnet support system, will be presented and an overview of the time schedule will be given.
Speaker: Mr Claus Schroeder (GSI)
• 129
Cryogenic System Preparation for the Test of Superconducting Cavities and Cryomodules
The Rare Isotope Science Project (RISP) is building the RAON, which is a heavy ion accelerator. The cryogenic system of the SRF (Superconducting Radio Frequency) test facility is designed to perform the test of superconducting cavities and cryomodules. The test benches consist of the vertical cryostats for the cavity test and the cryomodule test benches. The cryogenic system supplies 4.5 K supercritical helium and 4.5 K liquid helium for superconducting cavities, as well as gas helium between 80 K and 300 K. This paper presents our current design status of the cryogenic system. The flow scheme, the overall layout and acceptance test procedures were considered for the design. The engineering design of cryogenic system is currently ongoing and will be fabricated soon.
Speaker: Shin Jaehee (I)
• 130
Cryogenic Systems Control Migration and Developments towards the UNICOS CERN Standard at INFN
The UNICOS (Unified Industrial Control System) developed at CERN, and widely adopted for all existing cryogenic plants there, has been chosen at INFN (Istituto Nazionale di Fisica Nucleare) LNL (Laboratori Nazionali di Legnaro) for the revamping of the local cryogenic facilities. The cryogenic systems at INFN-LNL comprise a 1500 W @4.5 K refrigerator for the ALPI superconducting accelerator, which includes 22 cryostats housing the superconducting cavities, a TCF50 refrigerator for the superconducting RFQ injector, and a TCF20 helium liquefier for local experiments needs. INFN-LNL has signed an agreement with TE-CRG @CERN for the transfer of the necessary knowledge in order to realize the new cryogenic control. Furthermore the collaboration has been extended to INFN Genova and LNGS (Laboratori Nazionali del Gran Sasso) for similar UNICOS applications. At INFN-LNL after the new control successfully realized with the TCF20 liquefier, the new UNICOS control migration is in progress to be applied to the distribution of helium in the complete superconducting accelerator, its relevant refrigerator, and in the close future to the injector and its related refrigerator. In the paper details will be described, which include the use of the Schneider PLC’s and PVSS (WinCC OA) supervision. The progress in the communication with EPICS supervision will be also outlined. The goal of the project is to propose UNICOS as the control system for all INFN cryoplants and cryosystems, as done for other important European research laboratories.
Speaker: Paolo Modanese (INFN, Laboratori nazionali di Legnaro, 35020 Legnaro -Padova, Italy)
• 131
Design of Cryogenic Distribution System for RAON
The helium distribution system of RAON is being developed by the Rare Isotope Science Project (RISP) in South Korea. The Helium Distribution System (HDS) consists of a distribution box, helium transfer line, and valve box to supply 4.5 K super-critical helium to each cryogenic component reliably and efficiently. The helium transfer line will be installed in the linac tunnel with a total length of 700 m. Five service lines will be used; super-critical helium supply (4.5 K, 3 bar), gas helium return (5~8 K, 1.05 bar), gas helium shield supply and return (40~70 K), and sub-atmospheric gas helium return (3 K, 0.03 bar) lines. The heat loads and pressure drops at each line are the most important factors for the pipe design of the helium transfer line. This work shows the results of the thermal analysis and flow dynamics of RAON’s HDS.
Speaker: Mr Ki Woong Lee (Institution for Basic Science)
• 132
Design of Vertical Test System for Superconducting Cavities at 2K and 4K
The superconducting accelerating segment in injectorⅡ of the Accelerator Driven Sub-critical System(ADS) uses superconducting cavities operating at a frequency of 162.5MHz. The vertical performance of the superconducting cavity devices must be tested at liquid helium temperature(2K, 4.2K) before being the assembly intp their cryostat. This paper describes the constructed test station.
Speaker: Feng Bai (Institute of Modern Physics, Lanzou, Gansu China)
• 133
Design, optimization and operational parameters of multichannel cryogenic transfer line for XFEL AMTF
The cryogenic transfer line for XFEL/AMTF is dedicated for transferring cryogenic cooling power from helium refrigerators to a cryogenic test facility by means of the constant flows of supercritical and cold gaseous helium. The external envelope of this cryoline contains 4 cold process lines and a common radiation shield, as well as the system of supports and thermal contraction compensators. The line was designed and manufactured within the scope of Polish in-kind contribution to the XFEL project. The line has been in operation since 2012. The paper presents exergetic analysis of the line. Working parameters of the line have been measured and compared with the thermodynamic model. Entropy minimization approach towards multichannel cryogenic transfer lines optimization is presented.
Speaker: Mr Paweł Duda (Wroclaw University of Technology)
• 134
Helium contamination through plastic walls
The concentration of impurities in Helium gas is an important parameter for a recovery and liquefaction plant. A low level of impurities is necessary to maintain an optimum liquefaction rate in any kind of liquefier. The main origin of the impurities is the contamination with air that enters the helium mainstream at some point in the recovery cycle. In this work we study the main sources for impurities in a helium recovery plant, and propose the way to reduce it. Experimental measurements of the change in oxygen content, with sensitivity below 1ppm, have been performed for helium gas before and after circulating through metal and plastic hoses. Also, the dependence of the impurities concentration with the time of permanence of helium inside a recovery gasbag has been measured, and a model has been developed. This model is useful to estimate the helium impurities concentration in a helium recovery plant. Finally, an analysis of the impurities composition reveals a different Nitrogen/Oxygen ratio in the helium contaminated through plastic walls compared with the one existing in air (approximately 80/20). This difference is due by the difference of the nitrogen and oxygen diffusivity through plastic walls and should be taken into account in the design of the helium recovery plants.
Speakers: Dr Maria Pilar Lozano (University of Zaragoza) , Mr Miguel Gabal (University of Zaragoza)
• 135
Helium Recovery and Purification System for the ADS program
In order to reduce the waste of helium during the testing of superconducting cavities (RFQ + HWR) for the Accelerator Driven Sub-critical (ADS) program, a new cryogenic helium recovery and purification system has been built by the Institute of Modern Physics (IMP). It can store 8000m3 helium gas, and can improve helium purity from 98% to 99.999%.
Speaker: Xiaofei Niu (Institute of Modern Physics, Lanzou, Gansu, China)
• 136
Multivariable Pressure Control in the Compression Station of Large–cale Helium Refrigerators by Quasi-Newton Methods
Large–scale Helium Refrigeration is widely used in the fields of superconducting, nuclear fusion energy and high-energy physics. However, the present PID controlling system of the compression station is not well able to keep the high pressure and low pressure both in the expected range. In this paper, a multivariable model-based non-linear predictive controller for a Compression Station is proposed. The compression station is a non-linear system, so we use Quasi-Newton Methods to find PID gains. The Quasi-Newton Methods solution model and the simulation result is introduced and presented.
Speaker: Dr zhengyu li (Technical Institute of Physics and Chemistry, China Academy of Sciences)
• 137
Nelium – a Refrigerant with High Potential for the Temperature Range between 27 and 70 K
In the search for the optimum process for the liquefaction of hydrogen, it was found that mixtures of Helium and Neon, called “Nelium”, allow processes with very high efficiency compared with pure Helium or pure Neon in the temperature range between 27 and 70 K. A mixture with e.g. 75 % Helium and 25 % Neon has a molecular weight of 8 kg/kmol. In contrast to pure helium the ambient temperature compression can be performed with turbo compressors, and a direct recovery of the expansion turbine power is feasible. Compared to pure Neon, the heat transfer is better and the pressure drop is lower. Suitable components for such processes have been identified. The primary use of this refrigerant is in the gaseous state. But there are also interesting options for the partial separation of Neon and Helium at the cold end, where the Neon-rich liquid could be used for the storage of refrigeration power and later peak shaving, and the Helium-rich gaseous phase could be used to obtain somewhat lower temperatures.
Speaker: Prof. Hans Quack (TU Dresden)
• 138
Numerical Study on Unsteady Flow in Centrifugal Cold Compressors
In helium refrigeration systems, high-speed centrifugal cold compressors are utilized to pump gaseous helium from a saturated liquid helium tank at low temperature and pressure to produce superfluid helium or sub-cooled helium. Stall and surge are common unsteady flow phenomena in centrifugal cold compressors severely limiting the operation range and the impact efficiency reliability. In order to obtain the installed range of cold compressor, unsteady flow at lower inlet pressures and higher speeds are investigated with CFD. It provides a numerical foundation of analysing the effect of an unsteady flow field and reducing the flow loss, and it is helpful for the further study and able to instruct the designing.
Speaker: Mr Qing Li (IPC)
• 139
Purification of recovered Helium with low level of impurities: evaluation of two different methods
Helium gas coming from low temperature experimental systems is recovered to avoid losses of this scarce gas on Earth. Once this Helium gas has been recovered and before its liquefaction, the impurities contained should be removed. It is possible to achieve a low level of impurities by using the proper materials and procedures on the road to Helium recovery. A comparison of two different methods applied for the purification of recovered Helium with low level of impurities is reported in this paper. One method is the use of liquid nitrogen traps and the other one is the application of a purification system based on getter materials. The cleaning efficiency has been probed experimentally for both methods through the analysis of the purified He gas. The evaluation covers the life time between regenerations, the everyday care as well as the long term, the energy consumption, the initial investment besides the cost of maintenance of both methods.
Speakers: Dr Maria Pilar Lozano Bernal (University of Zaragoza) , Miguel Gabal (Universidad de Zaragoza)
• 140
The Commissioning of the Helium Cryogenic System and LN2 Transfer System in the TPS Ring
Because of the delay of civil construction, one refrigerator/liquefier test area (R/L area) was constructed for the assembly and test of a 700 W cryogenic system in year 2012. The 700 W cryogenic system was installed in March 2012 and tested in the test area with a non-vacuum jacket liquid nitrogen (LN2) transfer line in October 2012. The Civil construction of the TPS ring was completed, which is available for installing the system in mid of 2013. The cryogenic system for R/L area was thus dissembles and relocated from the R/L test area to the TPS ring. The vacuum jacketed LN2 transfer line with a phase separator was installed in November 2013. This paper is aimed to present the disassembly, reinstallation and re-commissioning results of cryogenic system. The function test and heat load test of the LN2 transfer line and phase separator is also presented and discussed.
Speaker: Dr Huang-Hsiu Tsai (NSRRC)
• Wed-Af-Posters Session 2.2: Cryo-Coolers II
Convener: Mingyao Do Xu
• 141
An inter-phasing Stirling pulse tube cryocooler without reservoirs
A substantial fraction of the volume of a traditional pulse tube cryocooler is occupied by a reservoir, which greatly reduces the specific power of the cryocooler. This is undesirable for applications that require a small size and weight. This paper presents an inter-phasing pulse tube cryocooler conjoining two or more cold fingers via their inertance tubes. Because the volume flow in the cold fingers are elaborately adjusted to make the total volume flow into the junction of the inertance tubes zero, the reservoirs are allowed to be removed. Experiments demonstrated that, with a 1 kW electric power input, the cooling power at 77 K reached 59.8 W, corresponding to a relative Carnot efficiency of 16.8%. Compared with a traditional pulse tube cryocooler, this cryocooler can achieve the same cooling performance.
Speaker: Dr Jianying Hu (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)
• 142
Design and Testing of a Two-Stage High Capacity Stirling Cryocooler Operating below 30K
The high capacity cryocooler working below 30K can be applied in many applications in many fields such as superconducting motors, superconducting power and cryopump. Compared to the GM cryocooler, the Stirling cryocooler can achieve higher efficiency and more compact structure. Because of its obvious advantages, we have designed a two stage free piston Stirling cryocooler system in our laboratory, which is driven by a moving magnet linear compressor with an operating frequency of 40 Hz and a maximum 5 kW input electric power. The first stage of the cryocooler is designed to operate in the liguid nitrogen temperature and output a cooling power of 100 W. And the second stage is expected to simultaneously provide a cooling power of 50 W below the temperature of 30 K. In order to achieve the best system efficiency, a numerical model based on the thermoacoustic model was developed to optimize the system operating and structure parameters. At the same time, the finite element analysis software FLUENT was used to study the heat transfer and flow characteristics. Some preliminary testing results is also given in this paper.
Speaker: Dr Xiaotao Wang (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry of CAS)
• 143
Experimental investigation on regenerator materials of Stirling-type pulse tube refrigerator working at 20 K
Regenerator, a most important part of pulse tube refrigerator (PTR), must be carefully designed especially when working at high frequency and ultra-low temperature. In process of selecting regenerator materials, much attention is paid on the heat capacity of regenerator materials, while thermal conductivity is always omitted. In this paper, an effort will be made on explaining how thermal conductivity makes a difference on the performance of PTR. Experimentally, we will report on a detailed study in the various kinds of regenerator materials working at liquid hydrogen temperature, such as lead spheres, Er3Ni, HoCu2, and high-mesh number stainless steel, which are of different heat capacity and thermal conductivity. A systematical performance of the refrigerator with different regenerator materials will be presented. We will make a possible interpretation to clarify the results. Combined with experimental results, a theoretical analysis will be made to explain how thermal conductivity will impact the performance of the refrigerator. Finally, to sum up a guide line for future experiments, a parameter will be proposed, according to which one can select the most promising kind of regenerator materials.
Speakers: Prof. Junjie wang (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, CAS) , Mr Liubiao Chen (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, CAS) , Dr Qiang Zhou (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, CAS)
• 144
Experimental Investigations on Stirling type Thermally Coupled Three Stage Pulse tube Cryocoolers with ‘U’ type Configuration
Research on Stirling type Pulse Tube Cryocooler(PTC) is focused on achieving lower temperatures by cascading the stages or by multi-staging. Multi-staging can be done either by gas coupling or by thermal coupling of the stages. In the thermal coupling option, either a two stage cooler can precool a single stage PTC to reach lower temperatures or a single stage PTC can cool a two stage PTC. In the present work, both these configurations are tested experimentally keeping the same two stage PTC. In case-1, the two stage PTC is used as a precooling stage while in case-2, the single stage PTC is used as a precooling stage. Length of the single stage is required to be increased to match the two stages PTC for effective thermal coupling in case-1. The lowest temperature achieved in case-1 is 50.07 K where as in case-2 the lowest temperature achieved is 19.61 K at 17 bar charge pressure and 68 Hz frequency. The pressure drop in both the PTCs is compared to analyze the difference in performance.
Speaker: Prof. H.B. Naik (Sardar Vallbhbhai National Institute of Technology Surat, Gujarat, India)
• 145
Experimental Study on a Cascade Pulse Tube Cooler
With no moving parts at the cold head, a pulse tube cooler can in principle not not achieve the Carnot efficciency since the acoustic power is finally dissipated in phase shifters. Based on our previous study, a cascade pulse tube cooler working at 233 K with 200 W class cooling power is designed, fabricated and tested, in which the secondary stage is driven by the recovered acoustic power from the first stage via a long transmission tube. Experiments are carried out and feasibility is demonstrated with the efficiency significantly increased. Effects of charging pressure, pressure ratio, matrix type and the transmission line size on the cooling performance are investigated. This is a new exploration for high power pulse tube coolers working at lower temperatures.
Speaker: Ms Mei Wu (Institute of Refrigeration and Cryogenics)
• 146
Investigation of Inertance Phase Shifting Characteristics in Small Scale Pulse Tube Cryocooler
Phase shifting characteristics of inertance tube in small scale pulse tube cryocooler are investigated experimentally. It was found that the length of inertance tube whose diameter is 1mm has a more significant influence on the optimal frequency of the pulse tube cryocooler than the inertance tube with diameter 3mm. The performances of the pulse tube at each optimal frequency is not significantly affected when the length of inertance tubes with 1mm diameter and 3mm diameter is changed . The compressor dynamic behavior as influenced by the inertance tube is investigated too. It was found that in the case of the best performance of the cryocooler dynamic behavior of the compressor is more sensitive to the length of the inertance tube.
Speaker: Dr Houlei Chen (Technical Institute of Physics and Chemistry, CAS, China)
• 147
Investigation on a High-Power Stirling Cryocooler working at 77 K
Stirling cryocoolers are promising in high temperature superconductivity application and small scale gas liquefaction, due to their high efficiency, wide operating temperature range and fast cool-down process. A high-power Stirling cryocooler driven by a crank-rod mechanism was studied systematically. A numerical model built upon Sage-software was used to show the detailed characteristics of mass flow, pressure oscillation, temperature profile along the regenerator, acoustic power distribution and enthalpy flow in the cryocooler. The cooling performance of the cryocooler was tested and analyzed under various operating conditions. A cooling power of 700 W at 77 K with an electrical input power of 11.2 kW has been achieved up to now. The comparison analysis between the simulation results and experimental results shows the direction for further design optimization of the high-power Stirling cryocooler.
Speaker: Ms Ya XU (Institute of Refrigeration and Cryogenics, Zhejiang University)
• 148
Low Frequency Linear Compressors For GM and Pulse Tube Cryocoolers
Pressure Wave Systems GmbH is developing low frequency linear compressors to directly drive GM or pulse tube cryocoolers without the need for a rotary valve. Since the rotary valve can be identified to account for substantial efficiency losses in conventional arrangements there is a large potential for increased energy efficiency. We have built a low frequency linear compressor that shows that pV-efficiencies of >70% can be reached with this concept. We will discuss our set-up and measurements.
Speaker: Mr Jens Hoehne (Pressure Wave Systems GmbH, Haeberlstr. 8, 80337 Munich, Germany)
• 149
Thermodynamic analysis of the cold-end connection tube influence in U-shape pulse tube cooler
The objective of this paper was to demonstrate and analyze the influence of cold-end connection tube in U-shape pulse tube cooler (UPTC). A UPTC was constructed and experimented and the performance was undesirable. According to the experimental results, the temperature difference between the cold-end heat exchangers of the pulse tube and regenerator always existed. This phenomenon was explained by the gas parcel thermodynamic analysis. Through thermodynamic analysis about UPTC and linear pulse tube cooler (LPTC), the influence of the cold-end connection tube was verified. According to the research, the periodical movement of the gas parcel in connection tube experienced a thermodynamic process like pumping heat from pulse tube to regenerator. This kind of heat-pumping process leads to the loss of cooling power of UPTC. The further research showed the quantity of the loss was influenced by the size of connection tube, frequency, the phase angle between mass flow rate and dynamic pressure.
Speaker: Prof. Houlei Chen (Technical Institute of Physics and Chemistry ,CAS)
• Wed-Af-Posters Session 2.3: Heat Transfer I
Convener: Holger Kollmus (GSI Helmholtzzentrum für Schwerionenforschung GmbH)
• 150
Design of a heater for the CSNS cryogenic hydrogen system
The China Spallation Neutron Source consists of a pulsed neutron source with ~20 K and 1.5 MPa supercritical hydrogen used as moderator. The dynamic heat load due to the neutron moderating is removed by the circulation of cryogenic hydrogen. A pulsed dynamic heat load is induced by the intense pulsed proton beam injection and trip, and a large pressure fluctuation in supercritical hydrogen loop was brought out simultaneously. Hybrid control by the heater and accumulator is adopted, in order to mitigate the pressure fluctuation in the hydrogen loop. The CSNS cryogenic system is under construction now, and most of the critical equipment will be developed independently. This study shows the physical design of a cryogenic hydrogen heater. Theoretical analysis was conducted through changing structural parameters of the heater, and numerical analysis was carried out on the typical case. Flow and heat transfer performance were analyzed, according to the simulation results. In order to improve the heat transfer performance, optimal structure of the hydrogen heater was proposed. Theoretical analysis on the hydrogen heater, will lay a foundation for the research and development of a cryogenic hydrogen heater independently, and promote the actively construction of CSNS cryogenic system.
Speaker: Ms Yu Zhang (Institute of High Energy Physics, CAS)
• 151
Effective Temperature of Non-uniform Temperature Distribution and Size Effects of Effective Temperature
The thermal radiation properties from a non-uniform temperature distribution are investigated and the effective temperature for non-uniform distribution is defined. The thermal radiation spectra for non-uniform temperature distributions are shown as a function of frequency and are compared to the effective temperature. The thermal radiation from arbitrary size of particle is derived and the effective temperature of the body is shown as a function of the particle size.
Speaker: Dr Woo Kang Kim (Institute for Basic Science)
• 152
Heat transfer simulation to liquid nitrogen from HTS tapes at current overloads
Knowledge of HTS materials behavior at overload currents is important to design fault current limiters or fault protection systems of electro-technical devices. Recently we observed sharp voltage peaks during rectangular current pulses on HTS tapes cooled by boiling liquid nitrogen. We explain these peaks by analysis of transient cooling regimes in liquid nitrogen. It is common knowledge that a homogeneous liquid can withstand certain amount of superheat before switch to the boiling phase. In the transient regimes even inhomogeneous nitrogen can withstand a certain overheating. Basing on the measurements of voltages and temperatures of the HTS tapes during current overload and numerical analysis of the process we estimated the transient heat-transfer characteristics from the HTS tapes into liquid nitrogen. We also obtained important information about limiting superheating of the liquid nitrogen. Influence of covers of the HTS tapes on superheating of the nitrogen is discussed also.
Speaker: Dr Vasilii zubko (VNIIKP)
• 153
Investigation on the thermal equilibrium around a cryogenic accidental event and the impact on the possibly enclosed surrounding environment
Complex and large cryogenic distribution systems are an integral part of a fusion machine having superconducting magnets, cryopumps etc. The various equipment of the cryogenic distribution system are interconnected via notably large cryogenic transfer lines (CTL) to distribute the cold helium to the end users. During the nominal operation of the fusion machine, the helium inventory in the CTLs could be in the order of several tons. In the worst possible accidental scenario, the cold helium present in CTLs could be released in the surrounding volume due to complete breakage of process pipe and outer vacuum jacket. This disruption can significantly reduce the temperature of the ambient including the equipment/systems existing in the area of vicinity of ruptured CTLs. Such a study on thermal equilibrium between the process fluid of CTLs and finite surrounding, possibly enclosed volume in case of accidental scenario is necessary considering the safety aspects of a fusion plant. The simulation study of such a scenario has been performed for two possible practical cases; (i) effect on temperature of outer vacuum jacket due to loss of insulation vacuum (ii) effect on temperature of the ambient including surrounding systems due to rupture of process pipe as well as breakage of outer vacuum jacket of CTLs. A detailed mathematical model has been developed to evaluate the propagation of the thermal wave train between the process fluid of CTLs and the surrounding environment. The present analysis, based on certain assumptions, aims to estimate the lowest possible temperature in the surrounding environment due to the possible accidental scenario. A test plan in the simulated condition also has been conceptualized. The paper will describe the simulation results and basis of the test plan to obtain the near possible realization.
Speaker: Mr Ketan CHOUKEKAR (ITER-India (Institute for Plasma Research))
• Wed-Af-Posters Session 2.4: Accelerator and Detector Magnets
Conveners: Subhash Jakob, Triptisekhar Datta
• 154
A structured approach to analyze the influence of channel dimensions on heat extraction via superfluid helium
When the luminosity of the LHC at CERN is upgraded, the final focusing quadrupole magnets will receive a much higher energy deposition in their coil windings. To better understand the thermal behavior of coil windings at temperatures below -and some kelvin above- the helium lambda transition point, several numerical models have been developed. These models have been partially validated with experimentally obtained results, but none of them have been used to analyze the various designs in a structured way. The main reason for the missing analyses is that setting up and varying the several free parameters is very laborious in the existing models. Here we present a new model, based on an earlier presented FEM model, which makes use of coupling - and integration variables. By making use of coupling variables, a full 3D model can be made 2.5D, which allows changing the insulation width, thickness and angle, as well as the number of layers in a straightforward way, without any loss of generality. The user can easily and quickly change the parameters of interest, giving the possibility to analyze new ideas effectively. By changing boundary conditions, analyses show clearly which thermal paths are favorable over others and where improvements can be made. The thermal path along the wide side of the Rutherford cable is longer than from the small side, but more heat is extracted via here since the contact surface with the cable is larger.
Speaker: Erwin Roland Bielert (CERN)
• 155
Advances in the Principal Design of The Superconducting Toroid for the new International AXion Observatory (IAXO)
Axions are amongst the most promising dark matter candidates in modern cosmology. IAXO, the International AXion Observatory, once established, will operate the most ambitious solar axions detector to date. The sensitivity of the IAXO detector to the axion-photon coupling is one order of magnitude beyond the limits of the current detector, the CERN Axion Solar Telescope (CAST). Although having low mass and zero electric charge, axions can be detected by their conversion to observable photons when passing through a channel with a high magnetic field. Thus, the IAXO detector incorporates a high-magnetic field distributed over large volume to increase the conversion probability. Inspired by the ATLAS barrel and end-cap toroids, a new large superconducting toroid is being designed to provide the required magnetic-field. The new toroid comprises eight, one meter wide and twenty one meters long, racetrack coils and its outer diameter is 4.1 m. The toroid produces a useful magnetic field of 2.5 T, while the peak field is 5.4 T, for an operating current of 12 kA. The stored energy is 660 MJ. The coils are wound with Al-0.1wt%Ni stabilized NbTi/Cu cables. The anticipated cryogenic load at the operating temperature of 4.5 K is 250 W. Here, we describe the principal design of the toroid, including concepts for the cold mass, cryostat, supporting structure and the movement system. Recent developments, such as new cold mass supports design and induced forces, are reported as well. Conductor design and stability analysis are presented. The quench analysis confirms the safe quench protection scheme. The challenges and constraints on the cryogenics system are explained. Thermal loads are evaluated to assess the necessary cryogenic power. Lastly, a concept of a forced flow supercritical helium based cryogenic system is presented.
Speaker: Idan Shilon (CERN)
• 156
Analysis of the Cryogenic Operating Scheme for SIS100
The upcoming Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany will provide high current anti proton, heavy ion and rare isotopic beams using an accelerator system of synchrotrons, production targets and storage rings. The first machine in the chain after the booster is the synchrotron SIS100 which will be equipped with superconducting iron dominated magnets. Always one sixth of the ring will be supplied by one common header with all magnets in parallel operation. The helium flow in this common supply header has to be subcooled with a pressure below 2 bar. As there are no active control elements foreseen to adjust the requested helium mass flows through the parallel supplied magnets, the hydraulic adjustment between the different components for all possible operating points has to be invested. The results of the numerical analysis of this system are presented and the results for the design parameters in the cryogenic infrastructure such as subcoolers and phase separators are given.
Speaker: Dr Marion Kauschke (GSI Helmholtzzentrum für Schwerionenforschung GmbH)
• 157
Cryogenic Distribution System for the ESS Superconducting Proton Linac
The European Spallation Source is a 5 MW, 2.0 GeV long pulse proton machine, currently under construction in Lund, Sweden. Its superconducting linear accelerator will use three types of cavities, i.e. double-spoke resonator cavities, medium-β and high-β elliptical cavities. The superconducting section of the ESS linac will be composed of 13 spoke cryomodules (each with 2 spoke cavities), 9 medium-β cryomodules and 21 high-β cryomodules (each with 4 elliptical cavities). The nominal operation temperature for the cavities is 2 K, with 40/50 K thermal shielding. The total heat loads to both the cavity cooling loops and thermal shields are estimated as 2.3 kW and 8.5 kW, respectively. The required cooling powers will be provided by the linac cryoplant and delivered in two temperature levels: 4.5 K and 40/50 K. Then, the 2 K temperature level will be produced in each cryomodule by precooling and throttling the 4.5 K helium. The linac cryomodules will be connected with the cryoplant by a dedicated cryogenic distribution system. The system will include a number of valve boxes, which will allow for warming up and cooling down one or more cryomodules without affecting the others. The installation and commissioning are scheduled for the beginning of 2017 and mid of 2018. This paper describes the functional requirements, general layouts and the in-house conceptual design of the cryogenic distribution system.
Speaker: Jaroslaw Fydrych (European Spallation Source ESS AB)
• 158
Cryogenic Operation on the R3B-Glad Large Acceptance Superconducting Dipole Spectrometer at CEA Saclay.
The R3B-Glad superconducting Magnet is a large acceptance dipole dedicated to the analysis of Reactions with Relativistic Radioactive ions Beams on the future FAIR facility at GSI Darmstadt. The original shape of the cryogenic tank and fluid distribution was imposed by the compact design of the six tilted and trapezoidal racetrack coils. The coils, electrically connected in series in a butterfly-like magnet, provide the field integral of 4.8 T.m required for the experiments while ensuring the active shielding. They are imbedded into the coil casings with their covers as in sarcophagi, and are indirectly cooled by means of copper braids fixed to the casings made of aluminium alloy. The very efficient two-phase helium tw thermosiphon keeps the magnet cold mass under 4.8 K. Its original features lie in the low slope (5°) of the heat exchanger tubes glued directly to the casings as well as in its compact geometry. The whole magnet cold mass, weighing 21 tons, is thermally protected by a stainless steel screen superinsulated and cooled down thanks to 50 K helium flowing in pipes brazed thereon. It is supported by three cold-to-warm feet, each one being thermalized at 60 K, half-height, with dedicated cryogenic circuits. For the operation during the cryogenic test at CEA Saclay, the cold mass was adapted and connected at the W7X Test Facility in order to get close to the real conditions in its final configuration at GSI. The cooling down to liquid helium temperature, as well as the rise of the current up to the nominal value of 3584 amperes were successfully achieved in December 2013. This paper presents the cryogenic fluid distribution process, and shows the more relevant cooling results.
Speaker: Mrs Roser Vallcorba (CEA-Saclay)
• 159
Accelerator driven sub-critical system in China (CADS) is a kind of transmutation machine to minimize the nuclear wastes. As one of the important parts in ADS, InjectorⅠwill be built in IHEP, CAS needingtwo cryomodules operating at 2K cryogenic environment to realize 10MeV proton beam energy. Each cryomodule includes seven Spoke cavities and seven superconducting magnets. This paper describes the design and progress of the cryogenic system, which includes flow chart analysis, key equipment, heat load analysis and the current state.
Speaker: Prof. Shaopeng Li (IHEP, CAS)
• 160
Cryogenics for Super-FRS at FAIR
The challenge of cooldown the huge cold mass up to 1400 tons (dominated by iron) to 4.5 K is addressed as one of the most important features for Super-FRS cryogenics at FAIR. For such large cold mass the precooling with LN2 is necessary due to the reason that approximately ~80% of the cool down load is from 300K to 80K. The capacity of the LN2 precooler at 80 K as well as the 4.5 K cooling power have been specified in order to reach reasonable cooldown time of 3 to 4 weeks. In the presentation we will also discuss the technical specification for Super-FRS magnet testing at CERN in terms of the limitations of cooldown / warmup rate on magnets, operation conditions, interface definition, and the magnet cryostat protection against over-pressure under worst-case scenarios, i.e., quench and insulation vacuum loss to air, which are the key issues for the cryogenic test facility planning. In addition the important features of the refrigerator and the cryogenic distribution system for the Super-FRS at FAIR will be presented.
Speakers: Claus Schroeder (CrYogenic group in Common System - CSCY, GSI Helmholtzzentrum für Schwerionenforschung GmbH) , Dr Holger Kollmus (GSI Helmholtzzentrum für Schwerionenforschung GmbH) , Dr Marion Kauschke (CrYogenic group in Common System - CSCY, GSI Helmholtzzentrum für Schwerionenforschung GmbH) , Dr Yu Xiang (CrYogenic group in Common System - CSCY, GSI Helmholtzzentrum für Schwerionenforschung GmbH)
• 161
Current-biased transition-edge sensors based on re-entrant superconductors
Transition-edge sensors are widely recognized as one of the most sensitive tools for the photon and particles detection in many areas – from astrophysics to quantum computing. Their application became practical after understanding that rather than being biased in a constant current mode, they should be biased in a constant voltage mode. Despite the methods of voltage biasing of these sensors are well developed since then, the current biasing generally is more convenient for superconducting circuits. Thus transition-edge sensors designed inherently to operate in the current-biased mode are desirable. We developed a design for such detectors based on the re-entrant superconductivity. In this case constant current biasing takes place in the normal state, below the superconducting transition, so that it does not yield a latching following the absorption of a photon. Rather, the sensor gains energy and shifts towards the lower resistant (e.g., superconducting) state, and then cools down fast (since Joule heating is now reduced), and resets in a natural way to be able to detect the next photon. We prototyped this kind of transition edge sensors and tested them operational in accordance with the outlined physics. The samples used in experiments were modified compositions of YBCO-superconductors in a ceramic form, which reproducibly demonstrated pronounced re-entrant superconductivity. In this presentation we report their composition, methods of preparation, and the detection results. This approach, in some areas, may have practical advantage over the traditional voltage-biased devices.
Speaker: Dr Armen Gulian (Chapman University)
• 162
Design of the conduction-cooled HTS coils for rotating gantry
The carbon ion cancer therapy is widely spreading because of its high curative effects and low burdens on patients. The carbon ions are delivered to patients through some electromagnets on the rotating gantry.　A rotating gantry is an attractive irradiation equipment, because the carbon ions can be irradiated to a tumor from any direction without changing the posture of the patient. On the other hand, because of the high magnetic rigidity of carbon ions, the weight of the rotating gantry for the carbon cancer therapy is about 3 times heavier than one for the proton cancer therapy, according to our estimation. Downsizing the rotating gantry for the carbon cancer therapy is considered by applying high temperature superconducting (HTS) magnets. The weight target is less than 200 t that is equivalent to the weight of the disseminated rotating gantry for the proton cancer therapy.　In this study, magnet constitutions of the rotating gantry and superconducting magnets were designed from beam optics.　When applying the high temperature superconductors to accelerator magnets, some problems should be considered, for example, influence of tape magnetization and manufacturing accuracy on the field quality, the thermal stability of the conduction-cooled HTS coils under alternating magnetic field, and the coil protection methods from thermal runaway caused by anomaly thermal input such as beam loss. Firstly, the thermal stability of conduction-cooled HTS coils was simulated numerically, and the thermal runaway current was calculated in static situation. The calculated results will be presented.
Speaker: Shigeki Takayama (Toshiba Corporation)
• 163
Integration and Commissioning of the ARIEL e-Linac Cryogenic System
The Advanced Rare IsotopE Laboratory (ARIEL) is a major expansion of the Isotope Separation and Acceleration (ISAC) facility at TRIUMF. The key part of the ARIEL project is a superconducting radiofrequency (SRF) electron linear accelerator (E linac). E-linac helium cryogenic system was designed to meet the ARIEL specifications. The HELIAL LL helium liquefier by Air Liquide Advanced Technologies supplies 4 K liquid helium (LHe) to cryomodules via LHe distribution system. The cryomodules have a top-loaded design. The 4 K – 2 K temperature conversion is achieved by a counter flow heat exchanger and a JT-valve installed onboard of each cryomodule. The temperature in 2K volume of cryomodules is controlled by the pressure control in sub-atmospheric line. Sub-atmospheric helium is warmed up in a custom-designed heat exchanger and after passing sub-atmospheric pumps goes to the helium compressor suction line. LN2 system supplies liquid nitrogen to the liquefier, 80K shielding of the cryomodules and LHe distribution system, as well as to freeze-out helium purifier. The installation of the E-linac cryogenic system components started in February 2013 while the corresponding subsystems tests started in November 2013. This paper describes the E linac cryogenic system components integration and presents the results of the acceptance tests and commissioning activities performed at TRIUMF since November 2013.
Speaker: Alexey Koveshnikov (TRIUMF)
• 164
Mathematical simulation of the unclosed 2-G HTS shield
The mathematical model based upon the authors’ previously introduced unclosed shield physical conception was developed. This model allows calculation of the magnetic field radial and longitudinal components in shield systems. One-dimensional problem of a thin-wall coil with the unclosed shield for the various relative positions of the shield and the solenoid was solved. Evaluation of magnetic field homogeneity was carried out. Verification of the model was made on the small-size shields. The developed model makes it possible to calculate shield parameters subject to solenoid magnetic field characteristics and shield material. The obtained results are necessary to construct systems with the high magnetic field homogeneity, in particular, for the electron cooling system of charged particle beams at the new accelerator complex which is being developed at JINR in Dubna, Russia.
Speaker: Mr Evgeny Kulikov (JINR)
• 165
On the Mystery of using Helium’s Second Sound for Quench Detection of a Superconducting Cavity
The detection of a second sound wave, excited by a quench, has become a valuable tool in diagnosing hot spots and performance limitations of superconducting cavity. Several years ago, Cornell developed a convenient detectors (OSTs) for these waves that nowadays are used world-wide. In a usual set-up, many OSTs surround the cavity and the quench location is determined by triangulation of the different OST signals. Convenient as the method is there is a small remaining mystery: taking the well-known velocity of the second sound wave, the quench seems to come from a place slightly beyond the cavity’s outer surface. We will present a model that might help explaining the discrepancy.
Speaker: Prof. Ralf Eichhorn (Cornell University)
• 166
Operation of the SKS magnet at K1.8 beamline in J-PARC Hadron Hall
After 18 years operation in KEK Tsukuba, the SKS (Superconducting Kaon Spectrometer) magnet was modified and moved to the K1.8 beamline of the J-PARC Hadron Hall in 2009. The SKS magnet has a structure cooled by pool boiling method. During this relocation, the cooling scheme of the SKS magnet was changed to use three GM-JT cryocoolers from the previous 300-W helium refrigerator. Since this relocation, SKS has maintained a steady state of 4.5 K as long as possible in order to avoid repetitions of long precooling. The SKS magnet has been used for nuclear physics experiments. The SKS magnet has two long term suspensions. One is damage by the 2011 Pacific coast of Tohoku Earthquake and the other is broken down by the radioactive material leak accident at the Hadron Hall which occurred in May 23, 2013. The SKS magnet is foreseen to be moved to another K1.1 beamline in the Hadron Hall to complete the repair of the damage caused by the 2011 earthquake. The preparation had begun before the radioactive material leak accident. A new SKS base structure has been fabricated. The base structure was designed based on the experience of the earthquake. Five year operational experiences of the SKS magnet at K1.8 beamline will be summarized in this report.
Speaker: Ms Kanae Aoki (KEK)
• 167
Quench Modeling in High-Field Nb3Sn Accelerator Magnets
In the framework of the LHC luminosity upgrade, the development of high field superconducting magnets is under way. The resulting peak field of about 12 T requires the use Nb3Sn as superconductor. Due to the high stored energy density and the low stabilizer fraction, quench protection becomes a challenging problem. Accurate simulation of quench transients in these magnets is crucial to the design choices, definition of priority R&D and to prove that the magnets are fit for operation. In this paper we focus on the modelling of quench initiation and propagation, comparing numerical results with available experimental data.
Speaker: Susana Izquierdo Bermudez (CERN)
• 168
SSR1 and SSR2 cryomodules for the heavy ion accelerator RAON
The driver linac of the heavy ion accelerator called RAON will be built in Korea and it utilizes four types of superconducting cavities. The SCL1 (Superconducting Linac 1) consists of the QWR (Quarter Wave Resonator, β=0.047, 81.25 MHz) cavities and dedicated cryomodules each hosting one cavity. Furthermore, the HWR (Half Wave Regenerator, β=0.21, 162.5 MHz) cavities and cryomodules hosting two and four cavities. The SCL2 (Superconducting Linac 2) consists of the SSR1 (Single Spoke Resonator1, β=0.3, 325 MHz) and the SSR2 (β=0.51, 325 MHz) cavities and the dedicated cryomodules host three and six cavities, respectively. The manufacturing of the prototypes of the SSR1 and SSR2 cryomodules is on-going and the current status is reported. The issues included are the estimation of the thermal load, the P&ID of the cryomodules, as well as the results of the thermal and structural designs of the cryomodule’s components such as the two phase pipe, support posts and flow pipes.
Speaker: Dr WooKang Kim (Institute for Basic Science)
• 169
Test sequence for superconducting XFEL Cavities in the Accelerator Module Test Facility (AMTF) at DESY
The European XFEL is a new research facility currently under construction at DESY in the Hamburg area in Germany. From 2016 on, it will generate extremely intense X-ray flashes that will be used by researchers from all over the world. The main part of the superconducting European XFEL linear accelerator consists of 100 accelerator modules with 800 RF-cavities inside. The accelerator modules, superconducting magnets and cavities will be tested in the accelerator module test facility (AMTF) at DESY. This paper gives an overview of the test sequences for the superconducting cavities, applied in the preparation area and at the two cryostats (XATC) of the AMTF-hall, and describes the complete area. In addition it summarizes the tests and lessons learnt until the middle of 2014.
Speaker: Joern Schaffran (DESY)
• 170
XFEL Injector-1 cryogenic equipment
Two accelerator cryomodules will be delivered for the XFEL Injector-1. This injector consists of an end cap, two accelerator modules, a feed cap, a feed box and a transfer line connecting the feed cap with a feed box. The feed box is connected to a valve box. The valve box is connected to XLVB by a transfer line. First injector will be located at the -7th level of XTIN. At this level the end cap, two accelerator cryomodules and the feed cap are placed. The feed box and the injector valve box will locate at the -4th level. The feed caps will be connected to the feed boxes by the corresponding transfer lines running through the XTIN shaft. The injector valve box will be connected to XLVB by an injector transfer line running through a transfer line shaft of XSE. The cryogenic supply of the injector accelerator cryomodules is separated from the supply of the cryomodules in the main tunnel.
Speaker: Mr Evgeniy Pyata (BINP)
• Wed-Af-Posters Session 2.5: Current Leads and Links; Safety, Reliability and Standards
Convener: Wilfried Goldacker
• 171
14 kA HTS Current Leads with one 4.8 K Helium Stream for the Prototype Test Facility at GSI
The key part of the international FAIR project in Darmstadt, Germany, is the synchrotron SIS100, for which superconducting magnets are employed. For the First of Series Dipole a pair of HTS current leads with a nominal current of 14 kA DC were specified, manufactured and successfully tested. The motivation for these current leads was a high operation current and the liquefaction limit of 1 g/s of the cooling plant. In the design it has to be taken into account that per lead only one helium stream is available for the entirely inner cooling. For I=0 (8 kA DC) only 0.25 g/s/lead (0.38) were necessary to be compared to 0.365 (0.51) specified. Slow ramping with 50 A/s up to 17 kA was accomplished. Triangular cycles with 27 kA/s up to 14 kA were achieved. The current leads withstood the test voltage of 3 kV between two leads and between lead and ground. The one stream helium flow is regulated by the temperature at the warm end of the HTS to be 50 K. The reliability of the first pair, especially of the cold terminal, is a clear go for the series of HTS current leads needed for the Series Test Facility, the String Test and the SIS100 ring. There is a separate 50 K helium gas supply which allows a significant reduction of cooling requirements. These 19 pairs in total shall have a common design which will be slightly different to that of the first pair for the Prototype Test Facility.
Speaker: Mr Alexander Bleile (GSI Helmholtzzentrum)
• 172
Current lead system of the SuperKEKB final focus SC magnet cryostats
The SuperKEKB is being constructed at KEK, based on the nano-scheme. The final focus superconducting (SC) magnets to squeeze the beams, were designed with 8 quadrupoles, 4 compensation solenoids and 43 correctors, contained in two cryostats at the left and right sides of the interaction point (IP). The cooling power for each cryostat is supplied with an independent refrigerator and the dominant heat leak into the cryostat is from the current lead system. For the main quadrupoles and solenoids the current leads were rated at 2000 A, 1800 A, 1350 A, 1000 A and 450 A and were commercially supplied with the self vaporized helium gas cooled mode. The leads for the correctors with the maximum current of about 70 A were developed at KEK with the high temperature SC (HTS) tape at their cold ends. To qualify the current leads prior to installation into the service cryostat, a dedicated measurement cryostat was designed and fabricated. The cryostat consists of two liquid helium (LHe) vessels, which allow the leads to work under real operating conditions with the self cooling mode. This paper presents the electrical and thermal results of the full cryogenic tests on the leads. The current lead system will be analyzed for the coming commissioning and the future normal operation.
Speaker: Zhanguo ZONG (kek)
• 173
Electrical Integrity and its Protection for Reliable Operation of Superconducting Machines
The long term operation of such a complex facility as the superconducting SIS100 accelerator of the FAIR project requires adequate Electrical Integrity (EI). Issues related to EI shall be taken into account at the design, production and commissioning stage respectively. In order to assure the safe and reliable operation of the superconducting magnets at cryogenic conditions, the facility shall be equipped with active protection systems. When using superconducting technology, quench detection and magnet protection are the most essential systems. Their design has a strong influence on the coordination of electrical insulation systems. This paper focuses on the correlation between EI and active protection systems. The presented study provides the basis for the development of adequate electrical integrity tests (including acceptance criteria) that should be performed at both the production and test stage. The case of SIS100 synchrotron is considered as an example.
Speaker: Mr Piotr Szwangruber (GSI)
• 174
Numerical simulation of cold helium safety discharges into a long recovery line
Helium cryogenics is currently the most developed technology for the thermal conditioning of large superconducting particle accelerators. The extremely elongated structures of these accelerators require long-distance transport of cold helium from the helium refrigeration units to the users of cryogenic cooling powers (mainly magnet cryostats and cavity cryomodules). The design and operation of the superconducting accelerators must fulfill requirements of high reliability and operating cost minimization. These strongly influence the baseline design choices for cryogenic gas management and pressure equipment safety strategies. As helium accidental discharges from the cryostats and cryomodules cannot be excluded, some possibilities of recovering helium releases from safety devices are taken into consideration. Collecting of discharged helium and transferring it back to the cryoplant via a long recovery line is an option. However, rapid and fast discharges of cold helium into warm recovery lines can result in significantly unsteady, compressible and thermal flows. Therefore the proper designing and sizing of the recovery lines have to be supported by detailed analyses of all expected fluid dynamics and thermodynamics phenomena. This paper describes the numerical simulations of cold helium discharges into a long warm recovery line that have been used for sizing the recovery line of the ESS linac cryogenic system. The paper discusses the model assumptions and presents some exemplary results.
Speakers: Jaroslaw Fydrych (European Spallation Source ESS AB) , Mr Riccard Andersson (European Spallation Source ESS AB)
• 175
Preliminary Study on Air in Liquid Hydrogen
The accumulated oxygen in liquid hydrogen is a big risk for storage. The oxygen and nitrogen molecules will be cooled down from gas to solid when air enters the liquid hydrogen. The intermolecular attractive force can influence the accumulation of oxygen and nitrogen molecules. The contents of molecule clusters can be different from each other. This paper studies the accumulation of air in liquid hydrogen by experiment and shows some initial results.
Speakers: Mr Aihua LI (State Key Laboratory in Technologies of Space Cryogenic Propellants) , Dr Gang LEI (State Key Laboratory in Technologies of Space Cryogenic Propellants) , Mr Haisheng LIU (Beijing Institute of Aerospace Testing Technology) , Dr Tianxiang WANG (State Key Laboratory in Technologies of Space Cryogenic Propellants) , Dr Wenqing LIANG (Southeast University)
• 176
Reliable longtime operation of the superconducting current-feeder system for the LHD
A superconducting (SC) current feeder system is used as the current transmission lines for the experimental fusion device, LHD. It consists of nine flexible SC bus-lines with total length of 497 m, and nine pairs of gas-cooled current leads. The rated current and withstand voltage of each SC bus-line are 32 kA and dc 5 kV, respectively. The first experimental campaign for the plasma confinement study on LHD started in 1998. Cryostable condition of the SC coils and SC current-feeder system have been kept for more than four months every year. Five-corrugated stainless-steel tubes with a thermal shielding channel were used for the SC bus-line. Liquid helium consumption of the innermost tube of the SC bus-line is negligible, because the liquid helium in the second inner channel absorbed the heat load of about 0.3 W/m. The cooling process is automatically switched from forced-flow of two-phase helium to pool boiling, when the faults happen. The allowable current carrying time on the fault protection mode is expected to be longer than 30 minutes of the design value. The total time of the coil excitations exceeds 10,000 hours. Total number of the plasma production exceeds 120,000 shots. We have demonstrated successfully that the SC current feeder system was stable and easy for handling, and was useful for the SC experimental fusion device.
Speaker: Dr Shuichi Yamada (National Institute for Fusion Science)
• Wed-Af-Posters Session 2.6: ReBCO, BSCCO and Flux Pinning
Convener: Kohei Higashikawa (Kyushu University)
• 177
Critical Current Density in GdBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-$\delta$</sub> Coated Conductor under the Influence of Flux Creep
Critical current density, *J*$_c$, of Gd1Ba2Cu3O7-$\delta$ (GdBCO) coated conductor (CC) under the influence of flux creep is one of the most important issues for the design of superconducting magnet applications because the flux creep affects field homogeneity and stability in the magnet. Namely, magnetic moment induced in the tape strands becomes much larger than the case of conventional round wire because of its flat and wide surface. We should also take into account angular dependence against external magnetic fields. In this study, we have carried out magnetic moment, *m*, measurements at 77 K for GdBCO CC under external magnetic field conditions including inclined external field by use of vector SQUID MPMS. From the relaxation of *m*, electric field (*E*) vs. current density (*J*) characteristics at low electric field ranges from $10^{-10}$ to $10^{-9}$ V/m have been estimated. Combining these results with the four-probe transport measurements, we have successfully obtained wide-range *E-J* characteristics from $10^{-10}$ to $10^{-2}$ V/m. Extending the analysis of transport measurements in the range of $10^{-4}$ to $10^{-2}$ V/m within a framework of the percolation transition model, we also obtained analytical expression for the *E-J* characteristics which can cover both flux creep and flux flow regime. From the comparison between the experimental data and the analytical expression, it is clarified that the flux creep can be estimated from flux flow property measured by the transport measurements. *J*$_c$ in inclined external magnetic field will also be discussed. A part of this work is supported by the Ministry of Economy, Trade and Industry (METI) as “Development of Fundamental Technologies for HTS Coils”.
Speaker: Yuta Onodera (Kyushu University)
• 178
Current Density Distribution in 2G HTS Tape in an External Magnetic Field
Our recent measurements of critical currents Ic of 2-G HTS tapes in an external magnetic field B demonstrated the difference in Ic(B) depending on mutual directions of transport currents and magnetic fields. Depending on Lorenz force direction the difference of Ic was about 10%. This phenomenon could be explained by suggestion about non-uniformity of Ic across a width of a tape. In this paper we had a goal to study critical current density distribution across a tape in a background magnetic field. The most often method to study current distribution in a cross-section of a superconducting tape is the measuring magnetic field distribution across a tape and then recalculation of fields measurements to current density [1]. Without external field this method could be realized by moving of a single Hall probe across a tape. But this method is difficult to use inside a magnet due to size of a moving mechanism. We suggested the combined method. First, we measured current distribution by use of a single Hall probe with moving mechanism. Then we measured field across a tape by sequence of several Hall probes placed on a single substrate. By comparison of data from these two experiments we could verify data obtained from the sequence of Hall probes and precisely determine its position at a tape. Then we can to measure current distribution of current density across a tape inside a magnet. We did such measurements in magnetic field up to 0.6T at different orientation of magnetic field to surface of a tape. The details of measuring method and results of Ic measurements across 2G HTS tapes are presented. [1] Pavol Ušák, The measurement of current distribution in superconducting tape. Comparison of destructive and non-destructive methods, Physica C 384 (2003) 93–101
Speaker: Dmitry Sotnikov (Russian Scientific R&D Cable Institute)
• 179
Flux pinning and dynamics in pnictide superconductors
First and third harmonics of ac susceptibility along with resistivity of Ba0.56 K0.44 Fe2As2 (Tc=37.6 K) and Ba(Fe0.91Co0.09)2As2 (Tc=25.3 K) polycrystalline samples are measured as a function of excitation ac field amplitude (0.1-10 Oe), frequency (10-2000 Hz), and applied dc magnetic field (0-18 T) in a detailed study. The excitation frequency f influence on flux dynamics is studied. The shift of Tp, temperature of the peak of the imaginary part χ” of ac susceptibility, does not show the single linear ln f vs 1/Tp fit, predicted by the Arrhenius Anderson-Kim model of thermally activated flux flow. The ln f vs 1/Tp plot has 2 separate lines with different slopes, showing that the selected excitation ac field frequency range impacts the size of the measured flux pinning energy. The pinning energy is measured as a function of the applied dc and ac magnetic fields, driving ac frequency, and temperature. The results are compared with energies extracted from resistivity measurements. Peaks, troughs and inflection points in the third harmonic of ac susceptibility are analyzed to get additional insight into the flux behavior. Ac losses and flux penetration, visible even in a zero resistivity state, are examined.
Speaker: Martin Nikolo (St. Louis University)
• 180
Long-length HTS coated conductors processed via PLD/ABAD
Employing a newly developed compact pilot pulsed laser deposition (PLD) machine that is based on 308nm-excimer laser we manufactured 40-80 m long coated conductors (CCs) aimed for demonstration and prototyping. Both a single beam and a double beam deposition PLD regimes were tested. The PLD installation was substantially based on “helical” technology of tape translation, “black-cavity” tape heating, and smoothed target ablation developed earlier by Bruker and improved further in the present equipment. Stainless steel tapes buffered via alternating-beam-assisted deposition (ABAD) of yttria stabilized zirconia layer were implemented as a substrate material. The polished substrate tapes and ABAD buffers were also manufactured in the pilot line of "compact" class. CeO2 buffer cap layer was deposited onto the tape in situ, via PLD prior to HTS layer. A silver protection layer and thick Cu layer were deposited by vacuum thermal evaporation and galvanic plating, respectively. Above 100A (or >250A/cm-width) critical currents were measured in 4mm wide coated conductors at 77K and self-field. Maximal critical current achieved in the best quality tape was 410 A/cm-width. Inhomogeneity of critical current detected using a magneto-scan did not exceed 5%. At optimized conditions, the Ic-inhomogeneity may be suppressed further, down to 2%. A possibility to increase PLD throughput above 30 m/hour in multi-beam modus was demonstrated. Advantages and feasibility of compact-scale equipment in process/ device prototyping and flexible pilot production are discussed in terms of processing costs and processing yield.
Speakers: Dr Alexander Usoskin (Bruker HTS GmbH) , Mr Tim Bubelis (Bruker HTS)
• 181
Measurement and Analysis of Normal Zone Propagation in a YBCO coated conductor at temperatures below 50 K
Measurements of the quasi-adiabatic normal zone propagation velocity and quench energies of a Superpower SCS4050 copper stabilized YBCO superconducting tape are presented over a temperature range of 23-47 K; in parallel magnetic fields of 6, 10 and 14 T; and over a current range from 50% to 100% of Ic. These data are compared to analytical predictions and to one-dimensional numerical simulations. The availability of long lengths of ReBCO coated conductor makes the material interesting for many HTS applications operating well below the boiling point of liquid nitrogen, such as magnets and motors. One of the main issues in the design of such devices is quench detection and protection. At higher temperatures, the quench velocities in these materials are known to be about two orders of magnitude lower compared to LTS, resulting in significantly smaller normal zones and the risk of higher peak temperatures. To investigate whether the same also holds for lower temperatures more extended data sets are needed, both as input and as validation for numerical design tools.
Speaker: Jeroen Van Nugteren (Twente Technical University (NL))
• 182
Reversible Ic degradation behavior in REBCO coated conductor tapes with different configuration under transverse stress
Second generation (2G) coated conductor (CC tapes) with rare-earth barium copper oxide (REBCO) gained its popularity in electrical field applications such as motor and generators, power cables, and especially coils. This is due to its superiority in characteristics and performance compared to the first generation (1G) CC tapes. However, in coil applications, the CC tapes might experience several factors that might limit its optimum performance or worst, possibly damage its integrity through the delamination of its layers. Such factors include excessive transverse stresses produced by large Lorentz force, coefficient of thermal expansion (CTE) mismatch of each constituent layers, screening current and other fabrication related reasons. As reported elsewhere, the critical current, Ic of impregnated coil was completely degraded due to the delamination of the CC tape’s layer. Therefore, in coil designs, mechanical and electromechanical delamination strength of the CC tape should be enough to withstand these threatening factors for the optimum design. In this study, mechanical and electromechanical properties of CC tapes with high critical current were investigated under transverse load using the popular anvil test. Especially, reversible critical current degradation behaviors under transverse stress were examined. Damination mechanism of the CC tape under transverse loading was thoroughly investigated. Lastly, the effects of brass and copper lamination regarding their thickness and properties on the reversible Ic behavior and the delamination mechanism were investigated. This work was supported by a Grant from the Power Generation & Electricity Delivery Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) funded by the Ministry of Trade, Industry and Energy, Republic of Korea.
Speaker: Hyung-Seop Shin (Andong National University)
• 183
Unconventional pinning in iron based superconductors of 122 family
Based on our results of critical current measurements and data published by other groups, we report on comparative analysis of vortex pinning in Fe-based superconductors (FBS) of the 122 family with different type of doping within the models proposed by R. Griessen et al [*Phys. Rev. Let.* **72** (1994) ] and Dew-Hughes [*Phil. Mag.* **30** (1974) 293]. The first one describes behavior of the temperature dependence of the critical current density in the framework of $\delta T$-pinning (fluctuation of the critical temperature, extended pinning centers) and $\delta l$-pinning (random deviations of the mean free path charge carriers, point like pinning centers). The second one evaluates the strength of pinning force depending on the position of the peak maximum ($h_{peak}$) on the curve of normalized pinning force versus reduced field. The location of the $h_{peak}<0.5$ indicates strong pinning centers, while the position of the $h_{peak} >0.5$ suggests weak pinning centers. In accordance with Dew-Hughes model, our analysis shows that FBS 122 superconductors with electron and hole-doping demonstrate strong pinning ($h_{peak}\sim 0.3-0.45$), whereas isovalent doping (i.e. substitution As for P) shows $h_{peak}\sim 0.7$ indicating weak pinning. We argue that pinning in FBS with isovalent doping can be successfully described by $\delta T$ and $\delta l$ models, while pinning in FBS 122 superconductors with electron and hole-doping shows behavior significantly different from the $\delta T$ or $\delta l$ model predictions.
• 3:30 PM
Coffee Break Exhibition and Posters Area

### Exhibition and Posters Area

• Wed-Af-Orals Session 10: Large Scale Refrigeration and Liquefaction WA1

### WA1

Convener: Ho-Myung Chang (Hong Ik University)
• 184
Specification of ESS Accelerator Cryoplant
The European Spallation Source (ESS) is a neutron-scattering facility being built with extensive international collaboration at Lund, Sweden. The ESS accelerator will deliver protons with 5 MW of power to the target at 2.0 GeV, with a nominal current of 62.5 mA. The superconducting part of the accelerator is about 300 meters long and contains 43 cryomodules. The ESS accelerator cryoplant will provide the cooling for the cryomodules and the cryogenic distribution system that delivers the helium to the cryomodules. The cryoplant will cover three cryogenic circuits: bath cooling for the cavities at 2 K, the thermal shields at around 40-50 K and the power couplers thermalization with 4.5 K liquid helium. This paper describes the cryogenic architecture and reference process solution of the cryoplant. The design basis including the staging, cooling capacity, operation modes, process constraints, availability and interfaces are given. The important design choices comprising one integrated cold box, optimized design parameters, spare part and process control system overview and strategy are presented. The milestones and the selection and award criteria also are presented.
Speaker: Dr xilong wang (European Spallation Source ESS AB)
• 185
Ras Laffan Helium Recovery Unit HeRUII Project
Helium plays a critical role in a wide array of product. It is used for a number of industrial and medical applications, including MRI scanners, semiconductors, fiber optic cable. The helium market is expected to grow steadily, by an average of +4% a year. With the largest proven helium reserves, Qatar decided to meet the world helium rising demand by building a second Helium Recovery Unit HeRUII. In this context and after the successful Helium I Project Commissioned in 2005, Air Liquide was awarded for this second project. The Helium Recovery Unit II is the largest facility in the world that was designed, manufactured, installed and commissioned by Air Liquide in Qatar. It is located adjacent to Helium I plant, operated by Rasgas. It includes a purification unit and the world’s largest helium liquefier ever designed and manufactured. The plant capacity is more than the double of Helium I (20Tons/day of liquid Helium). It is designed to recover 98% of the helium from the feed gas entering the plant. HeRUII produced its first drop of liquid helium end of June 2013 and achieved the full capacity by October 2013. The project was completed with an exceptional safety record of 5 million man hours Lost Time Incident free. With this start-up, Qatar becomes the largest helium exporter in the world and the second producer with 25% of worldwide production.
Speakers: CIndy DESCHILDRE (airliquide) , David GRILLOT (airliquide) , Delphine PICHOT (airliquide) , Franck DELCAYRE (airliquide) , Frédéric ANDRIEU (airliquide) , Mrs Rawia ALI SAID (Air Liquide) , Vincent HELOIN (airliquide) , Véronique GRABIE (airliquide)
• 186
ENGINEERING, PROCUREMENT, AND COMMISSIONING OF THE NEW HELIUM LIQUEFACTION FACILITY FOR GAZPROM GAZENERGOSET IN ORENBURG, RUSSIA
In 2012, Linde Kryotechnik AG, Switzerland, received the contract for supply of a helium liquefaction plant with a capacity of 500 l/h for Gazprom Gazenergoset’s Orenburg facility in Russia. The plant will deliver liquid helium mainly to the Russian market and replaces existing helium liquefaction plants which have been operated by Cryor. Whereas Linde Kryotechnik AG was in charge of the engineering and supply of the key components, the Russian company Cryogastech covered local activities including civil works, installation, and commissioning under supervision of Linde experts. The presentation will outline the design basis of the plant, provide insights into the execution of the project, and will particularly focus on specific requirements imposed by Russian regulations and climatic conditions.
Speaker: Mr Klaus Ohlig (Linde Kryotechnik AG)
• 187
Development of a Ground Operations Demonstration Unit for Liquid Hydrogen at Kennedy Space Center
NASA operations for handling cryogens in ground support equipment have not changed substantially in 50 years, despite major technology advances in the field of cryogenics. NASA loses approximately 50% of the hydrogen purchased because of a continuous heat leak into ground and flight vessels, transient chilldown of warm cryogenic equipment, liquid bleeds, and vent losses. NASA KSC needs to develop energy-efficient cryogenic ground systems to minimize propellant losses, simplify operations, and reduce cost associated with hydrogen usage. The GODU LH2 project will design, assemble, and test a prototype storage and distribution system for liquid hydrogen that represents an advanced end-to-end cryogenic propellant system for a ground launch complex. The project has multiple objectives and will culminate with an operational demonstration of the loading of a simulated flight tank with densified propellants. The system will be unique because it uses an integrated refrigeration and storage system (IRAS) to control the state of the fluid. The integrated refrigerator is the critical feature enabling the testing of the following three functions: zero-loss storage and transfer, propellant densification/conditioning, and on-site liquefaction. This paper will discuss the design of the system, the current status of the installation, and the test objectives.
Speaker: Dr William Notardonato (NASA KSC)
• 188
Overview on AL.AT cryogenic solutions under 4.5K
Through its history from 70’s, Air Liquide Advanced Technologies developed various cryogenic solutions (cold machines and cryogenic refrigeration) to support superconductivity applications. Thanks to a proven reliability pointed out in particular by the huge refrigeration architecture at LHC, CERN, very cold cryogenics has become “usual”. Reach very cold temperature more favorable to superconductivity (~ 2K) is then becoming widespread. Consequently, in recent years, all over the world, many experiences and projects of various size requiring very low temperatures were carried out. The aim of this paper is to present an overview of Air Liquide past and recent contributions to Very Low temperature Superconductivity, focusing on the current project for the Turkish accelerator (TARLA).
Speaker: Simon CRISPEL (Air Liquide Advanced Technologies)
• 189
Cryogenic cooling of the cold neutron source at ESS
The European Spallation Source (ESS) neutron spallation project currently being designed will be built outside of Lund, Sweden. The ESS design includes three helium cryogenic plants, providing cryogenic cooling for the proton accelerator superconducting cavities, for the target cold neutron source, and for the ESS instrument suite. Supercritical hydrogen circulates through and cools the target cold neutron source, and is in turn cooled from the target helium cryogenic plant. This report describes the unique cooling requirements for the cold source supercritical hydrogen cooling system, defines the operating parameters for the target helium cryogenic plant based on expected heat loads, and explores design options for the target cryogenic plant to optimize its performance.
Speaker: Mr John Jurns (European Spallation Source ESS AB)
• 190
JT-60SA: status of Cryogenic System and focus on Cryogenic Rotating Machines
The Cryogenic System for JT-60SA must provide cold power to 5 circuits of the Tokamak: Toroidal Field coils (TF) and structures at 4.4K, Central Solenoid and Equilibrium Field coils (CS+EF) at 4.4K, cryopumps at 3.7K, thermal shields (TS) at 80K and current leads at 50K. The process choice was driven by the decision to feed the first two circuits (TF and CS+EF) using two supercritical helium independent loops equipped with cryogenic circulators, and the third circuit (cryopumps) is directly supplied with the process flow. The two cryogenic circulators are identical and have been designed in order to supply the helium flow rates to the circuits. Another important feature of the refrigerator is to deal with pulsed heat loads. Thanks to the allowable temperature increase during recovery period between plasma pulses, a thermal damper has been implemented to reduce the size of the plant. A cold compressor, located at the outlet of this damper, is used to lower the pressure (initial pressure about 1.1 bar abs) in order to meet the final temperature requirement and to keep a constant flow during pulse mode while letting the damper pressure increase. After reaching the “Detailed Design” milestone, the JT-60SA Cryogenic System is currently under assembly in Air Liquide Advanced Technologies workshops. The Refrigeration Cold Box and the Auxiliary Cold Box (12m long and 3m diameter each) are assembled in the manufacturing hall with a Factory Acceptance Test scheduled in September 2014.
Speaker: Cecile Gondrand (Air Liquide Advanced Technologies)
• 191
CURRENT STATUS OF THE MODIFICATIONS OF THE FORMER HERA CRYOGENIC PLANT FOR THE XFEL FACILITY
The Hadron-Electron-Ring-Accelerator (HERA) at the German Electron Synchrotron (DESY) in Hamburg, Germany, was in operation between 1990 and 2007. The required cooling capacity for the superconducting magnets was provided by a cryogenic system consisting of three identical helium refrigeration plants. Due to the implementation of the X-ray free electron laser European XFEL, the existing HERA refrigeration plants have been adapted to the new heat load requirements. To provide the required cooling power for the XFEL, two of the three HERA refrigerator plants have been modified and will serve as the XFEL cryoplant. A 2 K cooling loop of approximately 2.6 kW comprising a string of four cold compressors has been included into the XFEL cryoplant. The 2 K cooling loop features a full flow recooling bypass across the cold compressors, providing high turn down ability during part load. Since the cryoplant is designed for 17.5 GeV beam load operation and already prepared for further upgrade options, efficient operation at future project stages is ensured. The revamp of the existing plant components, the installation of new equipment and the commissioning of the XFEL cryoplant will be completed during continuous operation of the third cryoplant, which is still providing refrigeration power for other consumers. Beside the main features of the XFEL cryoplant, the current status of the project is presented.
Speaker: Mr Hanspeter Wilhelm (Linde Kryotechnik AG)
• 192
DESIGN, PROJECT EXECUTION, CONSTRUCTION AND COMMISSIONING OF THE 1.8K SUPERFLUID HELIUM REFRIGERATION SYSTEM FOR SRF CRYOMODULE TESTING
The Fermilab Cryomodule Test Facility (CMTF) provides a test bed to measure the performance of superconducting radiofrequency (SRF) cryomodules (CM). These SRF components form the basic building blocks of future high intensity accelerators such as Project X, International Linear Collider (ILC), and a Muon Collider. Linde Kryotechnik AG and Linde Cryogenics have designed, constructed and commissioned the superfluid helium refrigerator needed to support SRF component testing at the CMTF Facility. The hybrid refrigerator is designed to operate in a variety of modes under a wide range of boundary conditions down to 1.8 Kelvin set by CM design. Special features of the refrigerator include the use of warm and cold compression and high efficiency turbo expanders. This paper gives an overview on the wide range of the challenging cooling requirements, the design, fabrication and the commissioning of the installed cryogenic system.
Speaker: Mr Philipp Treite (Linde Kryotechnik AG)
• Wed-Af-Orals Session 11: Regenerative Cryocoolers WA2

### WA2

Convener: Fons De Waele
• 193
[Invited Oral] Low-loss damping of the intrinsic temperature oscillations of 4 K pulse tube coolers
The absence of moving parts inside their cold head, which results in low vibration level and high reliability, distinguishes pulse tube coolers (PTC) from other regenerative cryocoolers. However, residual disturbances originating from the periodic pressure oscillation remain for PTCs just like for Gifford-McMahon coolers. One of these effects is the variation of the cold flange temperature with the periodic pressure cycles. Depending on the application, this variation in temperature can disturb the cooling of detectors or superconducting voltage standards where stable temperatures are mandatory. Here, a concept for damping the intrinsic temperature variations of PTCs suitable for high cooling powers is presented. As a key component, a small pot made of copper (volume approx. 0.2 liters) located at the cold flange of a two stage 4 K PTC. From an outer tank (e.g. 4 l gas bottle), helium can be liquefied into the pot by use of precooling heat exchangers at the two cooling stages. The high specific heat of the liquid helium together with the heat transfer through two-phase-flow (“thermosyphon”) stabilizes the temperature without notable losses of cooling power over a temperature range from 2.2 K to 5.0 K. An amount of 35 cm³ of liquid helium dampens the peak-to-peak temperature oscillation from 240 mK down to 15 mK near 4.2 K with 0.7 W of heat load on the cold stage. The unit can be included in a 4 K PTC as a closed cycle system and is maintenance free.
Speaker: Dr Jens Falter (TransMIT GmbH, Center for Adaptive Cryotechnology and Sensors, Heinrich-Buff-Ring 16, D-35392 Gießen (Germany))
• 194
Experimental investigation of compact 2K GM cryocoolers
On the base of a conventional 4K Gifford-Mcmahon (GM) cryocooler, we developed a new 2K GM crycooler system which can provide considerable cooling capacity and yet being highly compact in physical size. A series of experiments were operated to confirm and show the cooling characteristic and cooling capability of this new system. It will be shown that under no-load condition the lowest temperature reached about 2.2K on the exterior surface of the second stage and temperature oscillation displacement was less than ±20mK. Detailed cooling load-map and cooling-down curve will also be introduced in this paper. The research results have been achieved by "Development of a Compact Superconducting Single Photon Detector System for Photon-Quantum Infomation and Communication", the National Institute of Information and Communications Technology(NICT), Japan.
Speaker: Mr qian bao (Sumitomo Heavy Industries, Ltd.)
• 195
Improved performance of an indigenous Stirling type pulse tube cooler and pressure wave generator
Sustained efforts have been made in our laboratory to improve the performance of an indigenously developed pressure wave generator by reducing the mechanical losses and current required to drive the piston. Currently, a matching pulse tube cooler targeted for 0.5 W @ 80 K was designed using Sage and the experience gained from previous studies. A no load temperature of 74 K was achieved. The mass flow rate at different points of the pulse tube cooler was experimentally measured using a hot wire anemometer. The experimental results including the pressure amplitude and mass flow rate at different locations of the pulse tube cooler are compared with Sage predictions, thus validating the design. In order to further improve the no load temperature and the efficiency, the effect of regenerator material configurations on the cooling power is studied. The total parasitic heat loads are measured using the rate the rise of temperature of cold heat exchanger. Also the effect of the regenerator wall thickness on the no load temperature is experimentally studied and the achieved performance level of the cooler has been reported.
Speaker: Prof. Subhash Jacob (Center for Cryogenic Technology, Indian Institute of Science)
• 196
Performance test of a G-M cooler in magnetic field.
The cryostat with a commercial Gifford-McMahon cryocooler (RDK-415 from SHI)with a cooling power of 1.5 W at 4.2 K is installed in the room temperature bore of the 10 T conduction cooled superconducting magnet. The magnet consists of NbTi and Nb3Sn coils which are connected in series and charged with a single power supply. Magnetic field uniformity is 0.25% over the axial length of 30 mm. The magnet is cooled by a commercial two-stage 4 K Gifford-McMahon cryocooler (RDK-408 from SHI) with a cooling power of 1 W at 4.2 K. The total cold mass is 71 kg. Clear room temperature bore of the magnet is 80 mm. The magnetic system design and performance test results of a G-M cooler in magnetic field are presented.
Speaker: Dr Evgeny Kostrov (Lebedev Physical Intitute RAS)
• 197
The Experimental Study of Acoustically Resonant Cooling System
Thermoacoustic engines (TEs) and pulse tube cryocoolers (PTCs) have attracted more and more attentions in recent years for their high reliability, high potential efficiency and use of environmentally-friendly working gas. Utilizing a TE to drive a PTC can produce a heat-driven cryocooler with no moving parts. However, the cooling capacity of the most existent heat-driven cryocoolers at the temperature bellow 150K is very low. This is an obstacle to the practice application in the field such as natural gas liquefaction. A novel heat-driven cryocooler named multi-stage acoustically resonant cooling system is presented in this paper. A 3-stage experimental prototype is built, which consists of three identical travelling-wave thermoacoustic heat engine units. The three heat engine units form a closed loop through resonant tubes. At the end of each heat engine units there is a branch to a PTC. Experimental results show that with the mean pressure of 3.5MPa and the heating temperature of 923K, the cooling system reaches the minimum temperature of 76K, and obtains total cooling capacity of 100W at 130K. In addition, the performance of the cooling system is tested under different working conditions, which indicates that the system will performs better as the mean pressure and heating temperature increase. The preliminary experimental results inspire us so much. As the matching mechanism further improved and the dimensions further enlarged with more stages, the acoustically resonant cooling system will obtain much larger cooling capacity with higher efficiency. It shows great application future in the field of nature gas liquefaction.
Speaker: Jianying Hu
• 198
Cold inertance tube for 4 K Stirling type pulse tube cryocoolers
The losses in the regenerator are minimized when the amplitude of the mass flow is minimized for a given acoustic power which requires that the mass flow lags the pressure by about 30° at the cold end of regenerator. The phase shift provided by an inertance tube is strongly influenced by the temperature of the inertance tube and the acoustic power at the cold end of the regenerator. For a 4 K Stirling type pulse tube cryocooler, the acoustic power at the cold end of the regenerator decreases significantly with the temperature thereby it’s difficult to achieve ideal phase relationship with ambient inertance tube as phase shifter. While cold inertance tube provide a larger phase shift in that the viscosity of the working fluid decreases and the density increases as the temperature decreases. However, use of cold inertance tube increases additional heat load to the regenerator. Therefore it’s of great significance to determine when a cold inertance tube should be used. In this paper effect of temperature of inertance tube is calculated for a 4 K Stirling type pulse tube cryocooler with different acoustic powers at the cold end. A comparison of ambient temperature inertance tube and cold inertance tube is made and the results are presented.
Speaker: ZhuoPei Li (Nanjing University of Aeronautics and Astronautics)
• Wed-Af-Orals Session 12: Heat Transfer WA4

### WA4

Convener: Mr Laurent Jean Tavian (CERN)
• 199
[Invited Oral] A deeper look into the thermodynamic perfection of the Debye equation of state for helium-3
A new form of a state equation for helium-3 in wide range of temperature and pressure, based on a conceptual extrapolation from the Debye equation for the specific heat of solid materials was previously developed. A deeper look into the performance of the state equation for helium-3 was recently considered necessary and valuable, due to some feedback from cryogenic applications, such as the observations of an unusual change in enthalpies during designing a J-T cooler with helium-3 as the working substance at pressure varying from 2 kPa to 200 kPa. A comprehensive evaluation of the state equation has been conducted with the Gruneisen parameter along isochores, cubic sound velocity – pressure linearity, Cv / T^3 – density relation, and virial coefficients as the benchmarks. The same analysis was applied to helium-4 for the sake of analogizing the common behavior in reduced forms for these isotopes in wide range of temperature and density, particularly in the critical region. The results were then checked with physics known for quantum fluids as well as general fluids, which confirms the good thermodynamic perfection of the Debye state equation for helium-3 in most areas on the phase diagram as declared before, except a narrow strip at low pressures. A revision of the equation is conducted to fix the located problem.
Speaker: Yonghua HUANG (Shanghai Jiao Tong University)
• 200
Experimental study on helium heat transfer in a small natural circulation loop above the supercritical pressure
We present here the first results on helium heat transfer in a small natural circulation loop above the supercritical pressure. The circulation loop is composed of a condenser, a uniformly heated test section and a return loop. The inner diameter of the tubes constituting the loop is 4 mm and the height of the test section is 23 cm. The condenser is thermally coupled to the second-stage of a Gifford-McMahon type cryocooler (1.5 W at 4.2 K) and is basically a phase separator with a heat exchanger. With this set-up, the helium heated in the test tube can be re-cooled in the condenser, where the pressure is held above the critical pressure and constant during the experiment. Thus, it is a self-sustaining cooling system. Data presented here correspond to the steady-state regime of the loop and gather the evolutions of the wall temperature at various heights of the test section. The temperature in the condenser was not controlled and increased as the heat flux on the test section was raised. The measurement covers a wall temperature from below the critical temperature up to 30 K for a constant pressure of 2.3 bars. The heat transfer coefficients are also presented and compared to ad-hoc correlations.
Speaker: Bertrand Baudouy (CEA Saclay)
• 201
Visualization study of the growth of a spherical bubble in He II boiling under microgravity condition
Under microgravity, the heat transfer is considered to be different from that under normal gravity condition because of zero subcooling due to zero hydrodynamic pressure in saturated He II. Thus the heat transfer in He II under microgravity is an interesting research target. Microgravity experiments are expected to reveal some hidden mechanism of boiling heat transfer across vapor-liquid interface because a stable large-scale vapor bubble is formed. In the present study, the behavior of a single spherical bubble generated by a micro heater was observed under microgravity condition created with a drop tower for about 1.3 second. The visualized images taken by a high-speed camera were analyzed to obtain the time variation of a large vapor bubble in the order of 10 mm. It was seen that the sizes of single bubbles increased with decreasing He II temperature for fixed heat input. The bubble size near lambda temperature was smaller than that at 1.9 K though the effective thermal conductivity is quite small. The heat transfer function on the basis of the Gorter –Millink’s law was found not to be significant in the prediction of the bubble dynamics of He II under microgravity.
Speaker: Dr Suguru Takada (National Institute for Fusion Science)
• 202
PIV Measurement of the Flow Field around Film Boiling in He II
Film boiling phenomena in He II were studied on the basis of the flow field measured with a PIV (Particle Image Velocimetry). Noisy and silent film boiling modes together with a non-boiling state were generated on/around horizontal planar and cylindrical heaters. For PIV tracer particles, H2-D2 micro solid particles that were neutrally buoyant in He II were used. The flow field was illuminated by a light sheet of which the light source was a 5W CW-YAG laser, and a high-speed video camera was used as PIV camera. Video images showing the development and crush of vapor bubble or film and the motions of tracer particles dragged by the normal fluid component were PIV-analyzed. The PIV result of the boiling velocity field was composed of AC and DC velocity components of the normal fluid. The AC component follows the dynamic behavior of vapor phase, and the DC results primarily from the thermal counter flow and secondarily is induced by the rising vapor bubbles due to buoyancy. The time-averaged PIV velocity field where the AC component is nearly eliminated provides with the flow field characteristics of film boiling modes of He II, noisy, silent and He I boiling modes as well as of the non-boiling state.
Speaker: Prof. Masahide Murakami (University of Tsukuba)
• 203
Development of a Novel Method for Exploration of the Thermal Response of Superconducting Cables to Pulse Heat Loads in Superfluid Helium
Management of transient heat deposition and extraction in superconducting magnets is becoming increasingly important for the purpose of bringing high energy particle accelerator performance to the limits of beam energy and intensity. Precise knowledge of transient heat deposition phenomena in the magnet cables will permit to push the operation of these magnets as close as possible to their current sharing limit, without unduly provoking magnet quenches. With the prospect of operating the LHC collider at CERN at higher beam energies and intensities an investigation into the response to transient heat loads of LHC magnets, operating in pressurized superfluid helium, is being performed. The more frequently used approach mimics the cable geometry by resistive wires and uses Joule-heating to deposit energy. Instead, to approximate as close as possible the real magnet conditions, a novel method to deposit heat in cable stacks made out of superconducting magnet-cables has been developed. The goal is to measure the temperature evolution with time between the cable stack and the superfluid helium bath depending on heat load and pulse length. Heat generation and precise measurement of small temperature differences are major challenges. The functional principle and experimental setup are presented together with proof of principle measurements.
Speaker: Tiemo Winkler (Technology Department, CERN, Geneva 23, CH-1211, Switzerland)
• 204
Transient heat transfer to He II due to a sudden loss of insulating vacuum
We report on a quantitative study of the heat flux deposited into a He II bath consequent to a failure of its insulating vacuum jacket. Failure of this vacuum is often referred to as THE worst-case scenario seriously endangering the low temperature equipment and its surroundings. In the case of a vacuum break, air floods into the vacuum jacket and carries with it a significant amount of energy (~500 J/g for air) that must impinge on the inner vacuum wall and ultimately be absorbed by the He II coolant. For the present study, an experimental rig was designed, built, and successfully operated to simulate such a sudden loss of insulating vacuum incident confined to a one-dimension space. The rig consists of an evacuated tube that dead-ends to a He II-cooled disk, beneath which is a column of He II near 1.8 K, open to its bath. A wide range of mass flow rates are studied for warm gas flooding into the evacuated tube, causing the gas to cryodeposit and transfer its internal energy through the disk to the He II. Thermometry in the disk and axially through the He II column is used to quantify the heat transport generated by the cryodeposition process. In general, it is found that the heat flux to the He II is indeed limited by the peak heat flux theory. It is further confirmed that noisy film boiling, though mechanically violent, reduces the heat transfer to the He II. The cryodeposition behavior of warm gas onto a He II-cooled surface is also shown to be somewhat stochastic. In summary, an accurate conceptual model is developed to fundamentally describe and predict the coupled mass and heat transport phenomena that result after such a vacuum failure.
Speaker: Steven Van Sciver (Florida State University)
• 205
Computational Prediction of Cryogenic Micro-Nano Solid Nitrogen Particle Production Using Laval Nozzle for Physical Photo Resist Removal-Cleaning Technology
The fundamental characteristics of the cryogenic single-component micro-nano solid nitrogen (SN2) particle production using super adiabatic Laval nozzle and its application to the physical photo resist removal-cleaning technology are investigated by a new type of integrated measurement coupled computational technique. To elucidate the detailed mechanism of micro-nano SN2 particle generation, an integrated CFD (Computational Fluid Dynamics) analysis was carried out to clarify the cryogenic particle heat transfer mechanism that is difficult to obtain by conventional measurement. For the formulation of governing equations, the single micro-nano SN2 particle’s thermohydrodynamic behavior with phase change is governed by Navier-Stokes equations, continuity equations and energy equations. The defining feature of this phenomenon is the intense evaporation (and later condensation, solidification) that takes place at the interface of the SN2 particle and surrounding gas-phase. The originality to be noted in the present study is that the continuous production of micro-nano SN2 particle is achieved by using single component gas-liquid two-phase flow of subcooled nitrogen through a Laval nozzle (converging-diverging nozzle). As a result of the present computation, it is found that high-speed ultra-fine SN2 particles are continuously generated due to the freezing of liquid nitrogen (LN2) droplet induced by rapid adiabatic expansion of subsonic subcooled two-phase nitrogen flow passing through the Laval nozzle. Furthermore, the effect of the SN2 particle diameter, injection velocity, and attack angle to the wafer substrate on resist removal-cleaning performance is investigated in detail by integrated measurement coupled computational technique. This study is not only characterized by the advanced cryogenic cooling technology for high thermal emission device, but also contributes to different academic fields closely related to the semiconductor wafer cleaning technology.
Speaker: Jun Ishimoto (Tohoku University)
• 6:15 PM
Break Exhibition and Posters Area

### Exhibition and Posters Area

• 6:30 PM
Bus shuttles to Museum
• 7:00 PM
Evening Party at the Museum Twentse Welle (museum tour, free drinks and a walking dinner will be served). Museum Twentse Welle, town of Enschede

#### Museum Twentse Welle, town of Enschede

• 9:30 PM
Bus shuttles to conference hotels
• Thursday, July 10
• 8:00 AM
Registration desk open Entry hall

### Entry hall

Open from 8:00 - 18:30.

• Thu-Mo-Plenary Session 3: Introduction to the Day and 2 Plenary Orals
Conveners: Wilfried Goldacker, Yifeng Yang (University of Southampton)
• 206
Introduction Thursday
• 207
Cryogenics Best Paper Award ceremony
• 208
Introduction to ICEC/ICMC 2016
• 209
Cryogenics at the European Spallation Source
Cryogenics plays an important role at the European Spallation Source, a world class neutron science center, currently under construction in Lund, Sweden. Three principal applications of cryogenics are found at ESS. The SRF cryomodules of the ESS proton linac require cooling at 2 K, 4.5 K and 40 K; the LH2 moderator surrounding the target that produces neutrons, requires cooling via 16 K helium and LHe is required for many of the scientific instruments. These needs will be met by a set of three cryogenic refrigeration/liquefaction plants and an extensive cryogenic distribution system. Significant progress has been made on the ESS cryogenic system in preparation for the expected first beam on target in 2019. This work includes: funding of industry studies for the accelerator cryoplant, detailed design of the cryogenic distribution system, investigation of possible in kind contributors and most importantly, the recruitment of a team of highly qualified cryogenic engineers. This paper describes the requirements, design solutions and current status of the ESS cryogenic system. The planned recovery of waste heat from the cryogenic plants, a unique aspect of ESS, is described. The procurement of the cryogenic system, expected to be done via a combination of purchase via competitive bids and in kind contributions is also discussed.
Speaker: Dr John G. Weisend II (European Spallation Source)
• 210
The Superconducting Conductor Challenge
The dominant use of superconductors remains magnet technology, applications very well served by the low temperature superconductors (LTS), Nb-Ti and Nb3Sn, even if the dreams of large scale superconducting electrotechnology have driven huge investments in the High Temperature Superconductor (HTS) conductors, (Bi,Pb)2Sr2Ca2Cu3O10 (Bi-2223) and REBa2Cu3Ox (REBCO). But well over 95% of all superconductors are LTS round wires, while Bi-2223 and REBCO are both high aspect ratio tapes. Their potential for service well above liquid helium temperatures continues to drive their development, yet their constrained architectures and high costs pose continued challenges. Thus MgB2 with Tc of 38 K, a medium temperature superconductor (MTS) also challenges HTS applications, both because of its inexpensive raw materials and because of its round, multifilament form. But it does not yet really challenge LTS applications, because its high Tc does not compensate a low critical field. However the MTS compound (Ba0.6K0.4)Fe2As2 (K-122) is potentially capable of challenging LTS, because it is also fabricated from comparatively cheap raw materials and it has 5 times the upper critical field of MgB2 (>80 T at 4 K) and 3 times that of Nb3Sn. But Bi-2223 and REBCO suffer from weak superconducting grain boundaries (GBs) that force their fabrication with extreme crystallographic texture so as to minimize their GB density. But this old paradigm may be changing: The largely ignored Bi2Sr2CaCu2O8+x (Bi-2212) has evolved into a round, multifilament, twisted conductor with flexible architecture that has the highest Jc (at 4 K, anyway) of any HTS conductor. And K-122 in untextured, high GB density form has Jc within about a factor of 5 of that needed for applications. Thus superconducting conductor technology is at a very interesting stage: Bi-2212 and MgB2 will allow magnets in domains of H and T inaccessible to LTS conductors in the same round, multifilament, twisted architecture that magnet builders really prefer. Most intriguingly of all is the prospect of an equivalent REBCO round wire technology if only the better GB transparency now being exhibited in Bi-2212 and K-122 could be developed in REBCO too. Such a conductor could take superconducting magnet technology into totally new domains, both for small lab and for large machine magnets like those needed for DEMO or High Energy Hadron colliders. My talk will review recent progress and the nature of the challenges for new conductor technologies.
Speaker: David Larbalestier (National High Magnetic Field Laboratory)
• 10:30 AM
Coffee Break
• Thu-Mo-Posters Session 3.1: Cryogenics Components and Space Applications
Convener: John Vandore
• 211
A CTE heat switch for cryogenic space applications near 100 K using UHMW-Polyethylene as actuator material
Recently, we designed and built a proof-of-concept heat switch for space applications based on the high thermal expansion coefficient (CTE) of Ultra-High-Molecular-Weight-Polyethylene (UHMW-PE). The initial design showed a reliable switching performance [1]. A new design is proposed which is focused on lower mass and increased reliability, as well as a better understanding of the CTE material behavior at cryogenic temperatures. Measured material properties such as CTE, thermal conductivity, and Young´s modulus of UHMW-PE between 330 and 70 K are presented as well as the new switch design. [1] M. Dietrich, A. Euler, and G. Thummes, Cryogenics vol. 59, 70-75 (2014) This work is financially supported by the German Federal Ministry of Economics and Technology (BMWi), grant numbers 50EE0940 and 50EE1322.
Speaker: Mr Marc Dietrich (TransMIT GmbH)
• 212
CFD analysis of a turbo expander for cryogenic refrigeration and liquefaction cycles
The demand for low temperature operations for liquefaction and refrigeration at cryogenic temperature, for air separation, gas purification, superconductivity etc has necessitated the need for improvement in turboexpander performance in terms of isentropic efficiency. The design of turboexpander for liquefaction systems is quite critical at low temperatures due to process conditions such as lower volumetric flow rate as compared to the high temperature turbines and thermo physical properties of fluids at low temperature. In order to evolve a design that yields better isentropic efficiency, it is imperative to understand the sources of inefficiency through investigation of flow physics in the turbine designed based on existing methodology. The experimental techniques for the study of turbomachinery flows at cryogenic temperature are quite involved and expensive. Computational Fluid Dynamics (CFD) provides insight into these most complex turboexpander flow characteristics which includes secondary flows, boundary layer formation, separated flows, rotor stator interactions etc. In the present work, 3D turbulent flow analysis of a cryogenic turboexpander for small scale air separation was performed using Ansys CFX. The turboexpander has been designed based on design methodologies proposed by Balje, Kun and Sentz and Hasselgruber. The different models adopted for the simulation such as that for turbulence and modelling technique for rotor have been discussed. The data obtained from simulations have been used to analyse the aerothermodynamic performance of the different components of the machine like nozzle, vaneless space, wheel and diffuser. Attempts have been made to identify the different sources of losses in these components.
Speaker: Prof. Parthasarathi Ghosh (Cryogenic Engineering Centre, Indian Institute of Technology Kharagpur, India-721302)
• 213
Characteristics of a cryogenic supercritical hydrogen pump with dynamic gas bearings at J-PARC
At the J-PARC spallation neutron source, supercritical hydrogen with a pressure of 1.5 MPa and a temperature below 20 K is used as a moderator material. The total nuclear heating at the moderators is estimated to be 3.8 kW for 1-MW proton beam operation. The temperature rise at the moderators should be reduced below 3.0 K to provide a pulsed cold neutron beam. A centrifugal pump with dynamic gas bearings was developed to circulate the supercritical hydrogen with the flow rate of more than 0.16 kg/s. The characteristics such as the pump head and the adiabatic efficiency were measured at the hydrogen temperature of 95 K, 45 K and 20 K for various flow rates as parameters. The pump performances that are estimated using dimensionless parameters of pressure and flow coefficient exist on an identical curve, which almost agree with the design values. The adiabatic efficiency has an outstanding peak at the flow coefficient of 0.046. However, it decreases down to 0.2 for flow coefficients higher and lower than 0.046 where the pump casing flange is cooled from 20 oC to a few oC by the supercritical hydrogen. As the first step, the numerical analysis of fluid flow in the hydrogen pump were carried out at the temperature of 95 K using a CFD code, STAR-CCM+. The simulation results agree well with the experimental data. It was clarified that the excess cooling phenomenon was caused by a circulation flow along the sides of the pump casing.
Speaker: HIDEKI TATSUMOTO (Japan Atomic Energy Agency)
• 214
Design and fabrication of the 2K-module for the SRF test facility of Raon
The first Korean heavy-ion linac, Raon, is based on superconducting radio frequency (SRF) cavities. These cavities will be operated at sub-atmospheric pressures, 2 K. For performance tests of cavities and cryomodules, the SRF test facility of the Raon needs a dedicated heat recuperating system, the 2K-module. Similar to the system of other institutes, the 2K-module of Raon consists of a heat exchanger, a warm pump system, and Joule-Thomson valves. The heat exchanger, which increases the efficiency of the helium refrigeration system, was made by Korea Aerospace University and its performance was verified. The warm pumping system is setting up sub-atmospheric pressure and its pumping speed is 4000 m3/hr for the gas helium. The size of J-T valves is DN 2 which needs filters and heaters. Leak tests will be performed to check the superleaks. The 2K-module will be used for many cryogenic experiments in the test facility.
Speaker: Sungwoon Yoon (Institute for basic science)
• 215
Finite element analysis and optimization of a flexure bearing for a linear motor compressor
Nowadays linear compressors are commonly used in miniature cryocoolers instead of rotary compressors because rotary compressors apply large radial forces to piston, which provide no useful work, cause large amount of wear and usually require lubrication. Recent trends however favour flexure supported configuration for long life. The present work aims at design and geometrical optimization of flexure bearing using finite element analysis and the development of design charts for selection of flexure bearing. The work also covers the manufacturing of flexures using different materials and validation of finite element analysis results experimentally. Keywords: cryocooler, linear compressor, flexure bearing, FE analysis, strain and stress measurement
Speaker: Prof. Maruti Khot (Mechanical Engineering Department, Walchand College of Engineering Sangli)
• 216
Investigation of a Stirling cryocooler driven by a moving magnet linear motor
The attention is focused on the Stirling cryocooler driven by a moving magnet linear motor because of its advantages of high efficiency, small vibration, and long life. In order to find the parameters influencing the efficiency of the compact Stirling cryocooler, a linear motor structure was proposed and designed, the performance of the cooler is experimentally optimized. The relationship between diameter of the coil and the motor constant and the performance of the cooler was experimentally explored. The stiffness and assembly structure of the flexure bearings, the filling pressure and operating frequency were optimized by comparing the performance of the cryocooler. In the experiment, the maximum cooling power of the cryocooler is 2.3W@80K, with input power less than 50W. The investigation provides reference to the development of the compact and high-efficient Stirling cryocooler.
Speaker: Mrs Zhenzhen ZHENG (Institude of Cryogenics and Electronics, Hefei, 230043, PR China)
• 217
Numerical investigation of the thermal distribution and pressurization behavior in a helium pressurized cryogenic tank with a multi-component model
Heat and mass transfer process at gas-liquid interface exerts significant influence on pressurization performance of cryogenic storage tank. In this paper, an improved CFD model adapted to multi-component and two-phase is constructed to describe the heat and mass transfer effect within the propellant tank considering the existence of pressurizing helium. In the model, the temperature difference between real fluid temperature and its saturation temperature Tsat corresponding to vapor partial pressure is taken as the phase change driving force. The wall together with fluid region is simultaneously considered as the computational domain, and low-Re k–ε approach is selected to account for the fluid-wall heat transfer. Hydrogen and oxygen tanks with helium pressurization are respectively computed, by which the pressure curves and temperature distribution are obtained and analyzed. The computation results show that the interfacial temperature is reaching consistency with Tsat under the action of driving force over the whole process. Heat transfer between gas-wall, gas-liquid and liquid-wall is well presented, higher ullage temperature and pressure and a lower wall temperature are obtained than those without multi-component consideration. It is also found that the representation of the field distribution for hydrogen and oxygen are obviously different. The oxygen gas, with larger density than pressurizing helium, mainly locates under the helium region during the pressurization process. While for the hydrogen tank, hydrogen gas experiences an upward diffusion process derived by hydrogen-helium density difference. The difference of gas concentration distribution in propellant tank may produce different effect on the temperature distribution. On the whole, the new model can provide more reasonable field distribution and description while the existence of pressurizing helium.
Speaker: Dr Lei Wang (Xi'an Jiaotong University)
• 218
Simulation studies on cooling of cryogenic propellant by gas bubbling
Injection cooling was proposed to store cryogenic liquids (1,2). When a non-condensable gas is injected through a liquid, the liquid component would evaporate into the bubble if its partial pressure in the bubble is lower than its vapor pressure. This would tend to cool the liquid. Earlier works on injection cooling (1,2,3) analysed the cooling process by considering instantaneous mass transfer and finite heat transfer between gas bubble and liquid. Based on the discrepancy between the experimental and simulated data in these works, it is felt that bubble dynamics (break up, coalescence, deformation, trajectory etc.) should also play a significant role in liquid cooling. Hence in this work, we propose a lumped parameter model assuming single bubble and considering both heat and mass interactions between bubble, liquid and the surroundings. This model can be used to study the effects of injection temperature, injection flow rate, orifice diameter, and gas and liquid properties on cooling performance. References: 1. Larsen P. S., Randolph W. O., Vaniman J. L., and Clark J. A., Cooling of cryogenic liquids by gas injection. Advances in Cryogenic Engineering. Vol. 8. K. D. Timmerhaus, ed., Plenum Press, p 507, 1962. 2. Schmidt A. F., Experimental Investigation of liquid-hydrogen cooling by helium gas injection. Advances in cryogenic Engineering. Vol. 8. K. D. Timmerhaus, ed., Plenum Press, p 521, 1962. 3. Cho N., Kwon O., Kim Y., Jeong S., Investigation of Helium Injection cooling to liquid oxygen propellant chamber, Cryogenics, vol. 46, p 132, 2006.
Speaker: Pavitra Sandilya (Indian Institute of Technology Kharagpur)
• 219
Study on a Low-Temperature Refrigerator
A single-stage coaxial pulse tube cryocooler (PTC) has been designed, manufactured and tested at Shanghai Institute of Technical Physics (SITP), Chinese Academy of Sciences (CAS) for cooling an aerospace low temperature refrigerator (LTR) whose cooling volume is 20 liters. An experimental setup has been designed and fabricated and some experimental investigations have been carried out and analyzed after the PTC is coupled with the LTR. The results show that the PTC is capable of cooling the LTR down to173K around in a few hours and the input power is only 135W DC. The LTR system and the PTC are introduced respectively. In addition, the LTR cooling curve has also been presented and investigated in detail for a thorough understanding of this cooling system. KEYWORDS: Low Temperature Refrigerator; Pulse Tube Cryocooler; Experimental Study
Speaker: Prof. yinong Wu (Shanghai Institute of Technical Physics, CAS)
• Thu-Mo-Posters Session 3.2: Cryostats
Convener: Prof. Maciej Chorowski
• 220
A Cryogen-free Cryostat for Neutron Scattering Experiments
Most ultra-low temperature (below 1K) sample environment experiments at advanced neutron facilities are based on dilution and 3He refrigerator inserts used with Orange cryostats, or similar systems. However recent liquid helium cost increases, caused by global helium supply problems, have raised significant concern about the affordability of such cryostats. Here we present design and test results of a cryogen free top-loading cryostat which provides neutron scattering sample environment in the temperature range 1.25 – 300 K. The high cooling power of the cryostat which is 0.23 W at a temperature of less than 2K enables the operation of a dilution refrigerator insert in a continuous regime. The cooling time of a dilution refrigerator insert is similar to one operated in the Orange cryostat. The main performance criteria such as base temperature, cooling power, and circulation rate are compatible with the technical specification of a standard dilution refrigerator. In fact the system offers operating parameters very similar to those of an Orange cryostat, but without the complication of cryogens. The first scientific results obtained in neutron scattering experiments with this system are also going to be discussed.
Speaker: Mr Richard Down (ISIS STFC)
• 221
A cryogenic treatment system for treating large rolls
Cryogenic treatment is a supplementary process of traditional heat treatment which has been acknowledged for many decades as an effective method for increasing wear life, dimensional stability and mechanical properties such as yield strength, hardness et al. A customized cryogenic treatment system for treating large rolls has been designed, built and tested. Liquid nitrogen has been employed to provided cooling capacities; and the temperature can be controlled from -180 ℃ to the room temperature with an accuracy of ±3 ℃ by the developed temperature controller. The major problems and the efforts to overcome them in the development process will be described. The performance characteristics of this system and some experimental effects of cryogenic treatment on the large rolls will also be presented in this paper.
Speaker: Mr Jia Guo (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, CAS)
• 222
An Investigation of the Cool-Down Behavior of a Cryogenic Tank during the Filling Process
In this paper, a numerical study is performed on the filling process of a specified cryogenic tank from room temperature down to the low temperature. The cool-down behavior of the tank and the flow characteristics inside are analyzed considering the effects of the state (gas and liquid) of the filling substance and the filling rate. CFD simulations are carried out on saturated hydrogen gas filling processes and liquid hydrogen filling processes at four different mass flow rates, respectively. Numerical results show that the flow and temperature fields within the tank are controlled by the combined action between forced convection from the inlet of cold gas and natural convection near the tank wall in the gas filling process. The influence of forced convection is emerging with the filling rate increasing, especially in the initial and final stage of the filling process at higher filling rates (>2 kg/s), which results in a negative temperature gradient along the axis from the inlet (bottom) to the outlet (top) in the initial stage. The wall temperature of the tank presents different distribution patterns at different filling rates. In addition, the thermal stress distribution of the tank wall during the filling process is analyzed. The greatest stress appears in regions near the inlet and outlet due to existing constraints, and the values evidently depend on restricting conditions (rigid, elastic or free). In the liquid filling process, the cool down of the tank wall always follows the rise of the liquid level and the overall cooling rate increases with the increase of the filling rate in a rational range.
Speakers: Dr Lei Wang (Xián Jiaotong University) , Yanzhong LI (Xi'an Jiaotong University)
• 223
An optical cryostat for use in Microscopy cooled by a Stirling-type pulse tube cryocooler
The few products of optical cryostat for use in Microscopy and Spectroscopy in the market are generally cooled by liquid nitrogen, liquid helium or cryocoolers such as G-M cryocooler or G-M type pulse tube cryocooler (PTC), as sometimes it is not convenient to use G-M cryocooler or G-M type PTC because of its noise and big size; and in some places, liquid nitrogen, especially liquid helium, is not easily available. To overcome this limitation, an optical cryostat for use in Microscopy and Spectroscopy cooled by a Stirling-type pulse tube cryocooler (SPTC) has been designed, built and tested. The refrigerator system SPTC is an important component of the optical cryostat; it has the advantages of compactness, high efficiency, and low vibration. For simplification and compactness, single-stage configuration with coaxial arrangement was employed in the developed SPTC. In order to lower the vibration, the separated configuration was adopted; its compressor and pulse tube are connected with a flexible connecting tube. The effects of the length and diameter of the connecting tube on the performance of the cold head had been tested. The key sizes of the cold tip such as the length and diameter of the regenerator and pulse tube, the opening of the multi-bypass, the volume of the reservoir et al, are kept the same with the integral structure which we have reported before; and the performance difference between the separated structure and integral structure will also be described in this paper.
Speaker: Mr Liubiao Chen (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)
• 224
Check-Valve with low Cracking Pressure for Gas Recovery Systems
To prevent backflow of boil-off gas into a cryostat or any other cryogenic system, a check valve with a low cracking pressure may be installed. This check valve should be placed in the boil-off gas line at ambient temperature. Design considerations and applications of such low-cracking- pressure check valves will be described and presented.
Speaker: Fridolin Holdener (WEKA AG)
• 225
Cooldown analysis of a cryocooler based quadrupole magnet cryostat
A superconducting quadrupole doublet magnet cryostat with cold super ferric iron cover for Hybrid Recoil Mass Analyzer (HYRA) beam line has been commissioned. The total cold mass at 4.2K is 2 ton which is mainly contributed by iron yoke and pole. Two stage cryo coolers have been fitted to the cryostat to take care of various heat loads coming to the cryostat. 2nd stage of cryocooler has been used to reliquefy helium gas evaporated form the helium vessel by using a recondenser and the first stage provides cooling necessary to maintain the intermediate shield at ~55-65 K. HTS current leads have been used to reduce the head load. The 1st successful cooldown of the cryostat has been done recently, magnets have been powered and the magnetic field profiling in the beam tube has been completed. This paper will discuss the important development from the cryogenic view point and preliminary results obtained from the cooldown data.
Speaker: Anup Choudhury (IUAC, India)
• 226
Cryogenics for the SIS100 Synchrotron at FAIR
The cryogenic system for the superconducting SIS100 synchrotron is designed using three entry points with Feed Boxes (FBs). Each FB will supply two sextant sections, i.e. one third of the accelerator ring with liquid helium for magnet, beam pipe vacuum chamber and bus-bar cooling as well as gaseous helium for thermal shield cooling. Each sixth of the ring consists of one cold arc and a straight warm section with normal conducting accelerating cavities. The By-pass Lines (BPLs) have to bypass each of the six straight warm sections of SIS100 to supply helium and cold electrical connections to the quadrupole doublets within these sections. A detailed technical specification concerning the BPL System was prepared and approved at GSI in 2013. Based on this, the in-kind contract was signed between FAIR and Wroclaw University of Technology (WUT). In conjunction with the GSI cryogenic group, the WUT is currently preparing a complete technical solution of the proposed BPL System that will be presented here.
Speakers: Branislav Streicher (GSI) , Holger Kollmus (GSI Helmholtzzentrum für Schwerionenforschung GmbH)
• 227
Onset of thermoacoustic oscillations in flexible transfer lines for liquid helium
The onset of thermoacoustic oscillations (TAO) in transfer lines results in an increased evaporation rate of stored cryogen. As a consequence the re-liquefaction effort increases as well as the observed pressure rise in the storage dewar, whereas the latter may cause critical pressure levels. Therefore, the onset of TAO has to be mitigated. The onset of TAO in flexible transfer lines at liquid helium decant stations is barely regarded since TAO only occur at idle state, i. e. no liquid helium is transferred and most parts of the transfer line are near ambient temperature. The examination of prototype transfer lines with built-in pressure and temperature sensors resulted in a unique knowledge of the characteristics of TAO in liquid helium transfer systems. An extensive monitoring of the transfer line in idle state led to results over a wide parameter range. Varied parameters are the liquid level in the storage dewar, the storage pressure, and geometrical dimensions of the transfer line. The presented paper considers TAO as a common phenomenon in idle flexible transfer lines at decant stations. The conditions for the establishment and strategies for the prevention of TAO are examined. In addition, the resulting heat leak to the stored liquid helium is estimated by a thermodynamic model.
Speaker: Mr Nico Dittmar (Technische Universitaet Dresden)
• 228
Structural Design and Analysis of a 150 kJ HTS SMES Cryogenic System
A 150 kJ high temperature superconducting magnetic energy storage (HTS-SMES) system is under manufacturing in China. This paper focuses on the structural design and analysis of the SMES cryogenic system. The cryogenic system is designed and manufactured to maintain the operating temperature. The system includes a vacuum vessel, its thermal radiation shield, its supporting devices, conduction plates, and current leads. Two G-M cryocoolers are used for the system cooling, the main one is connected to the HTS coils and the other is connected to the thermal shield and the lower ends of the current leads. In this study, the 3D models of the SMES cryogenic system were created with CATIA, a 3D model design software, and the analysis of the SMES cryogenic system was done by ANSYS. The mechanical analysis results on the vacuum vessel, suspension devices and supporting devices are presented, particularly the analyses on suspenders and shelf supports are of vital importance since the finished SMES system should meet vehicle-mounted requirements in long time transport. The heat load and the temperature distribution of the thermal shield were analyzed. A cooling experiment of the cryogenic system was trialed and the thermal shield was cooled down to about 50 K.
Speaker: Dr Peng Han (Institute of Plasma Physics Chinese Academy of Sciences)
• 229
Test set-up for the controlled cooling of heavy magnets down to 77 K
In the scope of the High Field Magnets work package of the European FP7-EuCARD project, the structure of the future dipole magnet RMC and FRESCA2 has been be tested at liquid nitrogen temperature replacing the actual Nb3Sn-based coils by aluminium dummy coils. Such test aims at measuring during the cooling the evolution of the mechanical stresses and the temperatures via compensated strain gauges and carbon-ceramic sensors placed at various locations on the structure (shell, rods, yokes, dummy coils). These measurements help assess the thermo-mechanical behaviour of the assembly for different applied pre-stresses and validate the finite element simulation of the magnet cooling before including the definitive brittle Nb3Sn coils. For this purpose, a specific cool-down / warm-up nitrogen test station has been developed at CERN in order to control the required maximum temperature gradient in the magnet during the cooling and the warming. In this paper, we present in detail the test facility, the instrumentation along with the automatic process control system. An analytical approach computing the expected temperature evolution during a thermal cycle is introduced and the temperature measurements related to the magnets cooling down to 77 K and warm up to room temperature are presented.
Speaker: Hugo Bajas (CERN)
• 230
The cryogenic system for a REBCO insert coil of a cryogen-free 25 T superconducting magnet
A cryogen-free 25 T superconducting magnet is under development by using a REBCO insert coil which generates 11 T in a 14 T background field of outer low temperature superconducting (LTS) coils. The ac-loss of the insert coil during a field ramping is approximately 10 W, which is difficult to be cooled at the operating temperature of the LTS coils, 4 K. However, a REBCO coil can operate at a temperature above 4 K. Thus the REBCO insert coil is cooled to about 10 K by two GM cryocoolers while the LTS coils are independently cooled by two GM/JT cryocoolers. Two GM cryocoolers cool a circulating helium gas through heat exchangers, and the gas is transported at a long distance to another heat exchanger located on the REBCO insert coil, in order to protect the cryocoolers from the leakage field of high magnetic fields. The temperature difference of the 2nd cold stage of the GM cryocoolers and the insert coil can be reduced with an increase of the gas flow rate. However, at the same time, the heat loss of the heat exchangers increases, and the temperature of the 2nd cold stage is raised. Therefore, the gas flow rate is optimized to minimize the operating temperature of the REBCO insert coil by using a flow controller and a bypass circuit connected to a buffer-tank.
Speaker: Mr Sadanori Iwai (Toshiba Corporation)
• 231
The cryogenic system for the 45 T Hybrid magnet of the HFML-Nijmegen
The High Field Magnet Laboratory of the Radboud University Nijmegen is developing a 45 T hybrid magnet system that comprises a 12.3T, 600 mm bore Nb3Sn/Cu CICC based superconducting outsert magnet and a 32.8 T, 22 MW resistive insert magnet of the Florida-Bitter type. The cryostat holding the CICC coil should also be able to withstand significant fault forces that may result from the interaction between the superconducting coil and the resistive insert magnet. The outsert magnet, the NbTi bus-bars and the coldest part of the Cu/BSCCO current leads are cooled by a forced flow of 4.5 K, 5 bar supercritical helium, supplied by a Linde LR140 type of refrigerator. In magnet idle mode the refrigerator supplies liquid helium for laboratory experiments. The correct settings of the helium flow are controlled by a valve box between the magnet and the refrigerator. In the valve-box the helium is pre-cooled to 4.5 K by a heat exchanger submerged in a bath of liquid helium. All stainless steel pillow-plate radiation shields of valve box, magnet cryostat, current lead cryostat and connecting cryo-lines are cooled by a forced flow of 20 bar helium to about 70 K by a single stage Stirling SPC-1 cryo-cooler. Finally the Cu heat exchanger of the warm part of the current leads is cooled with evaporating liquid nitrogen that fixes an intercept temperature of 78 K at the transition from the Cu-heat exchanger to the BSCCO section. In this paper we present the final design and features of the magnet cryostat and the cryogenic system.
Speaker: Mr Chris Wulffers (High Field Magnet laboratory, Radboud University Nijmegen)
• 232
The Numerical Simulation of a LAr Thermostat
The experiment designed to search for dark matter WIMPs scattering off 1500L liquid argon(LAr) in an ultra-low background cryostat, will be located in the JINPING Mountain, China. A LAr thermosta, with a self-circulation argon liquefaction system by using two pulse tube cryocoolers (80W@80K), is developed in preparation of this experiment. Due to both the less gas bubble formation and the temperature gradient within 1.0 K in inner cylinder, which is detrimental for the functioning of the detector, an actively-cooled LAr shield is used to intercept heat radiation. In order to analysis the flow and heat transfer characteristics of LAr in the inner cylinder, which plays a role to make the detector work at both stable and efficient conditions, the numerical simulation had to be created. The paper presents an overview of modeling, simulations with the commercially software FLUENT performed on this system.
Speaker: Dr Meifen Wang (Institute of High Energy Physics, Chinese Academy of Sciences)
• 233
Thermal and Mechanical Analysis of the Radiation Shield Design of the HiLumi-LHC Crab Cavity Cryomodule
A prototype cryomodule to test the crab cavities for the HILumi-LHC is being designed and will be tested on SPS at CERN in 2016. The cryomodule design consists of a unique open access structure facilitating loading of the cavity-assembly from sides. It also provides access to internal components quickly and easily even after installation. Design of the radiation shield and the cooling scheme for introducing thermal intercepts at intermediate temperatures particularly for the high power RF couples is critical to achieve a desired stability at the operating temperature of 2K and also to keep the cooling power within the limits of the cryoplant available in the SPS test area at CERN. A detailed study has been conducted to address the cooling power requirements at intermediate temperatures. This paper describes the results of the thermal and mechanical analysis of the design for the radiation shield and thermal intercepts developed in the process
Speaker: Shrikant Pattalwar (STFC Daresbury Laboratory, UK)
• Thu-Mo-Posters Session 3.3: Heat Transfer II
Convener: Dr Bertrand Baudouy
• 234
Development of correlation for Thermophysical properties of supercritical Argon to be used futuristic HTS cables
Most of the power transmission systems are to be replaced by high temperature superconducting (HTS) cables for efficient operation. These HTS cables need to be cooled below the critical temperature of superconductors used in constructing the cable. With the advent of new superconductors whose critical temperatures having reached up to 134K (Hg based), need arises to find a suitable coolant which can accommodate the heating load on the superconductors. In order to accomplish such challenge an attempt has been made in the present work to identify suitable Thermophysical properties of supercritical argon (SCAR). The Thermophysical properties such as density, viscosity, specific heat and thermal conductivity of SCAR found to be drastically varying with respect to temperature at a particular pressure. Moreover, it is observed that with an increase in pressure density and viscosity are increasing. In addition, as the temperature increases a shift in Thermophysical properties is observed. Few correlations are developed which are applicable over a wide range of temperatures. These correlations may be useful in thermohydraulic modeling of HTS cables using numerical or computational techniques. In recent times, with the sophistication of computer technology, solving of various transport equations with temperature dependent thermophysical properties became popular and hence the developed correlations would benefit the technological community.
Speaker: Mr Mohit Kalsia (School of Mechanical Engineering)
• 235
Development of Correlations for Thermophysical Properties of Supercritical Hydrogen in HTS Generators
The storage and generation of power has been a main objective over the past decade. To accomplish such an objective, superconductors are introduced in 1978, which observed a sublime growth in power generation systems. However, electrical losses such as AC losses and thermal losses due to conduction, convection and radiation in those superconductors are inevitable. In order to overcome and reduce these losses, use of cryogenic fluids above their critical temperature is necessary. One such fluid being studied in this work is supercritical hydrogen (SCH). Various thermophysical properties such as density, viscosity, thermal conductivity and specific heat of SCH were studied. The results reveal that with the rise in temperature there is a radical change in thermophysical properties of SCH. Besides, few correlations have been developed for the same at various pressures and temperatures. The developed correlations are elaborated such that, the use of supercritical hydrogen (SCH) may be explored in the HTS generator for improving its performance. These correlations can be employed for further research and advancement in HTS generators. Due to the dynamic nature of HTS generators, unlike HTS cables, the cooling requires careful attention and precise monitoring. With the use of SCH, a uniform temperature distribution in HTS generators is expected leading to higher efficiency.
Speaker: Mr Mugilan Senguttuvan (School of Mechanical Engineering)
• 236
Development of correlations for Thermophysical properties of supercritical Nitrogen to be used in HTS cables
Improving the effectiveness of transmitting energy is a new challenge in future power applications. At present, there are 40-60% of losses in the transmission of electrical energy. In order to overcome such critical challenges a novel technology is needed to be developed. As nitrogen is main constituent in air and therefore it can be used in various applications. In this proposed work, a conceptual application (cryogenics) of supercritical nitrogen (SCN) is introduced. Also, various thermophysical properties of SCN have been studied in the critical region. Further, the results of thermophysical properties such as density, viscosity, thermal conductivity and specific heat are analyzed with respect to varying temperature (TC + 50K) and increasing pressure. The analyzed results shows that, for 0.1K rise in temperature there is drastic change in density, specific heat, viscosity and thermal conductivity with increasing pressure. Moreover, correlations have been developed for the above thermophysical properties. The obtained correlations of SCN can be used for cryogenic applications in future HTS cables.
Speaker: Mr Jeswanth Ravula (School of Mechanical Engineering)
• 237
Film Boiling Heat Transfer from a Round Wire to Liquid Hydrogen Flowing upwards in a Concentric Annulus
Knowledge of film boiling heat transfer from a heated wire to forced flow of liquid hydrogen in a narrow gap is important for conductor design and quench analysis of superconducting magnets cooled by liquid hydrogen. However there have been few experimental data as far as we know. Film boiling heat transfer coefficients were measured for when the heater surface superheats up to 400 K under pressures from 0.4 to 1.1 MPa, liquid subcoolings from 0 to 11 K and flow velocities up to 7 m/s. The test wire used was 1.2 mm in diameter and 120 mm in length made of PtCo (0.5 at. %) alloy, which was located at the center of 8 mm diameter conduit made of FRP (Fiber Reinforced Plastics). Temperature of the test wire was measured by resistance thermometry. The heating current was first gradually increased for a low flow rate up to the DNB heat flux. Flow rate was increased to a desired value and heating current was increased to the heater temperature around 400 K, after a jump to film boiling. Then the heating current was gradually decreased and film boiling heat transfer coefficients were measured. The film boiling heat transfer coefficients are higher for higher pressure, higher subcooling, and higher flow velocity. The film boiling heat transfer coefficients were compared with Shiotsu-Hama equation [1] for forced flow film boiling in a wide channel based on numerical analysis and experimental data. The film boiling heat transfer coefficients obtained were about 1.6 times higher than the predicted values by the equation, although the tendency of dependence on flow rate was similar. Discussions were made on the mechanism of difference between them. [1] M.Shiotsu and K. Hama, Nuclear Engineering and Design, 200.1, (2000), 23-38.
Speaker: Dr Masahiro Shiotsu (Kyoto University)
• 238
Film Boiling Heat Transfer Properties of Liquid Hydrogen in Natural Convection
In operating superconducting devices cooled by liquid hydrogen (LH2), joule heat caused by normal conducting transition sometimes results in film boiling which prevents the effective cooling and leads to the rapid temperature rise of superconducting devices. Knowledge of heat transfer in film boiling is important for using superconducting devices cooled by LH2 safely. In this study, film boiling heat transfer properties at pressures of 0.1, 0.4, 0.7 and 1.1 MPa for various bulk-liquid temperatures of LH2 were measured by applying electric current to give an exponential heat input (Q=Q0 exp(t/τ)) to a test wire submerged in LH2. The bulk-liquid temperature was set to 21 ~ 32 K by the sheathed heater equipped at the bottom of the cryostat. The exponential period τ was constant (τ = 10 s). The heat input was increased exponentially until the temperature of the test wire rose by about 400 K and then reduced exponentially to zero. The test wire was made of PtCo with the diameter of 1.2 mm and the length of 120 mm. The test wire was set to be vertical to gravity. The temperature of the heater was obtained by a resistance thermometry by four-terminal method. The heat transfer coefficient h in the film boiling region was higher for higher pressure and higher subcooling. The experimental results were compared with the equation of pool film boiling heat transfer presented by Sakurai et al. [1]. It was confirmed that the pool film boiling heat transfer coefficients in LH2 were expressed well by the equation. [1]A. Sakurai, M. Shiotsu, and K. Hata, 1990, “A General Correlation for Pool Film Boiling Heat Transfer from A Horizontal Cylinder to Subcooled Liquid”, Trans ASME, Series C, vol.223, pp430-440
Speaker: Mr Yuki Horie (Kyoto-University)
• 239
Forced Flow Boiling Heat Transfer Properties of Liquid Hydrogen for Manganin Plate Pasted on One Side of a Rectangular Duct
Liquid hydrogen has excellent properties such as large latent heat, low viscosity and so on. Therefore liquid hydrogen is expected to be used as a coolant for the high critical temperature superconducting devices. The larger heat is inputted to the superconducting device, the higher the temperature of it gets in film boiling phenomenon, which make it quench. In order to design superconducting devices in liquid hydrogen, it is necessary to clarify the cooling properties of liquid hydrogen and the effect of forced flow liquid hydrogen. Forced flow boiling heat transfer of liquid hydrogen from inner surface of heated tubes with several diameters and lengths have been studied under wide range of experimental conditions [1]. However there would be many shapes of liquid hydrogen flow passages and heated surfaces in actual cooling of superconducting devices. In this work, boiling heat transfer and DNB heat flux were measured for a vertical Manganin plate pasted on one side of a rectangular duct made of FRP (Fiber Reinforced Plastic) with 4.2 mm x 10 mm in cross section and 160 mm in length. The test heater plate is 10 mm wide, 120 mm long and 0.1 mm thick. Liquid hydrogen flows upward in the duct. Temperature of the test plate was measured by resistance thermometry. Nucleate boiling heat transfer and its DNB heat flux were measured for the various pressures, flow velocities, and subcoolings. The DNB heat fluxes are higher for higher flow velocities and higher subcoolings. The DNB heat fluxes were compared with the experimental data for round tube of nearly equal equivalent diameter. The DNB heat fluxes for the rectangular duct are lower than those for the round tube. [1]Shirai.Y., Tatsumoto.H., Shiotsu.M., Hata.K., 2011, “Cryogenics vol.51”, pp295-299
Speaker: Mr Kazuya Yoneda (Kyoto University)
• 240
Heat transfer correlation for flow boiling of hydrocarbon mixtures inside horizontal tubes
Hydrocarbons and their mixtures are suitable for environment-friendly refrigerant alternatives because of their good environmental criteria and high thermodynamic performances. They are not only the natural refrigerants but also the main components of natural gas. Therefore the research on flow boiling heat transfer of the hydrocarbon mixtures is extremely important in many industrial fields. Even if there are many classic correlations which could be used to calculate them, few correlations provide an acceptable agreement in open published literature. Based on the experimental results of the hydrocarbon mixtures(R170/R290), a modified correlation was developed earlier by Zou to predict saturated flow boiling heat transfer coefficients inside horizontal smooth tubes. The correlation was based on the asymptotic model and developed by introducing a new mixture factor from the research on pool boiling heat transfer of the mixtures. The correlation gave the total mean deviation of 16% for with experimental data. The correlation also shows the best accuracy in comparison with the experimental data on LNG by Yumei Shi et al. In this article, the earlier correlation is further refined to predict evaporation of the hydrocarbon mixtures of LNG(such as R50/R170) inside a horizontal smooth by expanding the data base from experimental investigations. The comparisons of the present model and other classic models with the recent data are made to evaluate the mean deviation for the mixtures. The proposed model yielded the lowest mean deviations among the tested correlations.
Speaker: Dr Zou Xin (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)
• 241
Pressure drop and heat transfer characteristics of boiling nitrogen in square pipe flow
Japan Aerospace Exploration Agency has been promoting the research and development of the hypersonic aircraft that can cruise at Mach 5 speed. The engine is equipped with a heat exchanger which uses liquid hydrogen fuel as a coolant for decreasing temperature of incoming air during hypersonic flight. The objective of the study was to elucidate the pressure drop and heat transfer coefficient of boiling nitrogen flow in a horizontal square pipe instead of using liquid hydrogen. The test section consisted of a heat transfer pipe with a heated length of 800 mm and a side length of 12 mm, a flow visualization pipe and two different capacitance-type void-fraction meters. The heat fluxes were 5, 10 and 20 kW/m2. In the experiment, seven types of flow patterns were observed such as bubbly, plug and slug flows. The correlation between the measured void fraction and the quality was compared with the homogeneous and separation flow models for the choosing of pressure drop models. Experimental pressure drops were compared with the predicted values using the homogeneous and separation flow models. The Butterworth model showed good agreement with the experimental values within ±30%. Local heat transfer coefficients were measured at three locations on the top, side and bottom of the pipe wall. Differences in heat transfer among three locations were obtained. The Gunger-Winterton equation showed good agreement with the experimental values within the accuracy of -20 to +30% regardless of any locations of the pipe wall.
Speaker: Prof. Katsuhide Ohira (Institute of Fluid Science, Tohoku University)
• 242
Pressure-drop reduction and heat-transfer deterioration of slush nitrogen in square pipe flow
Cryogenic slush fluids such as slush hydrogen and slush nitrogen are solid-liquid two-phase fluids containing solid particles in a liquid. There are high expectations as a functional thermal fluid for use of slush fluids in various applications. The presenter has proposed and has been developing a high-efficiency hydrogen energy system which uses slush hydrogen as a means of long-distance transportation and storage of hydrogen, and as a refrigerant for superconducting electrical power transmission and SMES using MgB2. Experimental tests were performed using slush nitrogen to obtain the pressure drop and heat transfer coefficient flowing in a horizontal square pipe with a heated length of 800 mm and a side length of 12 mm. The primary objective was to investigate phenomena of the pressure-drop reduction and heat-transfer deterioration according to changes in velocity, solid fraction and heat flux. The flow pattern and behavior of solid particles were also observed using a high-speed video camera and the PIV method. From experimental results, the pressure drop reduction emerged clearly at flow velocity of over 2.5 m/s and the reduction was up to 12% regardless of heated or non-heated condition. On the other hand, the heat transfer coefficient deteriorated in all the velocity range and the deterioration was up to 20% at the heat flux of 20 kW/m2. In the comparison between measured and numerical (SLUSH-3D) results of flow pattern and solid particles’ behavior, the mechanism involved in pressure-drop reduction and heat-transfer deterioration peculiar to a square pipe was obtained.
Speaker: Prof. Katsuhide Ohira (Institute of Fluid Science, Tohoku University)
• 243
Superfluid helium heat pipe
This paper reports on the development and the thermal tests of three super fluid helium heat pipes. Two of them are designed to get large transport capacity (4 mW at 1.7 K), they feature a copper braid located inside a 6 mm outer diameter stainless tube fitted with copper ends for mechanical anchoring. The other heat pipe has no copper braid and is designed to get much smaller heat transport capacity and to explore lower temperature (0.7 K – 1 K). The copper braid and/or the tube wall is the support of the Rollin super fluid helium film in which the heat is transferred. The low filling pressure makes the technology very simple without the need for any external hot reservoir and with the possibility to easily bend the tube. We present the design and discuss the thermal performance of the heat pipes tested in 0.7 K – 2.0 K temperature range. The long heat pipe (1.2 m with copper braid) and the short one (0.25 m with copper braid) have similar thermal performance in the range 1.7 K – 2.0 K. At 1.7 K the long heat pipe, 120 g in weight, reaches a heat transfer capacity of 12 mW and a thermal conductance of 600 mW/K for 4 mW transferred power. Due to pressure drop of the vapour flow, the conductance of the third heat pipe dramatically decreases when the temperature decreases. A 3.8 mW/K is obtained at 0.7 K for 0.1 mW transferred power.
Speaker: Lionel DUBAND (CEA)
• 244
The optimal flow rate for parallel flow multi-stream heat exchangers
A high performance heat exchanger is a critical component in a cryogenic system and its performance is typically very sensitive to the axial conduction, the parasitic heat loads and property variations. This paper presents a general 1-D model for multi-stream plate-fin parallel flow heat exchanger. The governing equations are solved by both analytical method and numerical method. The results show that there exists the optimal flow rate, which is corresponding to the maximum efficiency, for the same heat exchangers, the same working fluids, the same inlet temperature and the same inlet pressure for each fluid.
Speaker: Mr Weiping Zhu (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)
• 245
Transient heat transfer from a wire inserted into a vertically-mounted pipe to a forced flow of liquid hydrogen
Liquid hydrogen has been used as a fuel for a rocket engine and moderator material for cold neutron source. Recently, it is expected as a coolant for high-Tc superconducting devices because of its excellent cooling properties. The knowledge of transient heat transfer in forced flow of liquid hydrogen is necessary for the cooling design. However, there have been no experimental data on the transient heat transfer in liquid hydrogen as far as we know. In this work, transient heat transfer from a wire inserted into a vertically-mounted pipe to forced flow of liquid hydrogen was measured by exponentially increasing heat input, Q = Q0 exp (t/Τ) where t is time and Τ is period. The Pt-Co wire heater has a diameter of 1.2 mm and a length of 120 mm and is inserted into the pipe with a diameter of 8.0 mm, which is made of Fiber reinforced plastic due to thermal insulation. With increase in the heat flux up to the onset of nucleate boiling, surface temperature increases along the curve predicted by Dittus-Boelter correlation for longer period, where it can be almost regarded as steady-state. For shorter period, the heat transfer becomes higher than Dittus-Boelter correlation. In nucleate boiling regime, the heat flux steeply increases up to the transient DNB (departure from nucleate boiling) heat flux, which becomes higher for shorter period. Effect of flow velocity and period on the transient DNB heat flux was clarified.
Speaker: HIDEKI TATSUMOTO (Japan Atomic Energy Agency)
• 246
Transients in two-phase helium natural circulation loops
Some superconducting magnets, such as the CMS or R3B-GLAD, are passively cooled in helium two-phase natural circulation loop configuration. Whereas a good knowledge of steady state operation of such systems is available, transient phenomena taking place during non-stationary solicitation of such cooling systems, by sudden heat load increase, are still in course of study. We performed experiments on a liquid helium natural circulation loop. Different types of heated sections (vertical straight tubes and a horizontal spiral tube) have been used. Heat load transients were driven by piloting the electric current flowing along a wire glued to the heated section. Evolution of parietal temperature along the heated section, total mass flow rate and pressure drop were measured in order to infer the flow and heat transfer regimes taking place. We investigated the main thermo-hydraulic features of transients at different power ranges, on loops composed by the different heated sections mentioned above. We study the transient development of nucleate boiling and boiling crisis, as well as mass flow rate evolution. Furthermore, we study how initial conditions (initial heat flux or initial mass flow rate) can affect the transient boiling regimes. Moreover, we analyze the effect of the presence of a riser at the end of the ascending branch, both in steady and transient regimes. The objective is, through the analysis of the time evolution of representative physical magnitudes, to identify the most relevant phenomena in order to conceive simple dynamic models for future design and operation purposes.
Speaker: Dr Bertrand Baudouy (CEA Saclay)
• 247
Two Phase Flow Pattern Map for R290 in Horizontal Smooth Tubes
As a more efficient and environment-friendly refrigerant alternative, R290 has good environmental characteristics and high thermodynamic performances. It has been used to replace R22 and R502 in the refrigeration industry. The mechanisms of boiling heat transfer and pressure drop are intimately linked with the prevailing two phase flow regime. Therefore, it is necessary to study the two-phase flow pattern for R290, which is related to heat transfer and two-phase flow characteristics. In this paper, an experimental study of R290 two-phase flow patterns for evaporation in horizontal smooth tubes was presented. The measurements were taken in a 6mm inner diameter horizontal smooth copper tube with length of 500mm. The tests were conducted at various saturation pressure between 0.2MPa to 0.4MPa for different mass ﬂuxes between 70kg/ (m2∙s) to 250kg/ (m2∙s) in the entire range of vapor quality. The flow patterns were observed by a high speed camera. Three important flow pattern maps were used to compare with the experimental flow pattern data: Steiner, Kattan-Thome-Favrat and Wojtan. It was found that predictions with the flow pattern map of Wojtan agree best with the experimental results of R290. However, the transition curve between annular flow (A) and stratified-wavy flow (SW) was overestimated by the flow pattern map of Wojtan. An improved two phase flow pattern map was proposed for R290. The transition equations of some flow pattern regions are modified in the new flow pattern map.
Speaker: Prof. Mao Qiong Gong (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences)
• Thu-Mo-Posters Session 3.4: Fusion Magnets, Magnet Technology; Novel Devices and Concepts
Conveners: Maciej Chorowski (Wroclaw University of Technology) , Torsten Koettig (CERN)
• 248
A 3He cryostat for scientific measurement in a pulsed high-magnetic field
A top loading 3He cryostat has been developed for scientific experiments with a 60 T pulsed magnetic field facility at Wuhan National High Magnetic Field Center. The cryostat consists of a 4He bath cryostat, a 3He insert and a closed circulation system for 3He gas handling. To eliminate the eddy current heating during the pulse, the tail of the 3He insert with a death vacuum at the bottom is made from fiberglass tubing coated with epoxy. The 3He bath is separated from the 4He bath with the death vacuum. The 4He bath cryostat provides cooling power to condense 3He gas by a neck tube on top of the tail. Experimental results have shown that the sample temperature can be cooled down to 385 mK and kept for more than 150 second by one-shot cooling, which is sufficiently long for an experiment in a pulsed high magnetic field.
Speaker: Dr Shaoliang Wang (Huazhong University of Science & Technology)
• 249
A cryogen-free cryostat for scientific experiment in a pulsed high-magnetic field
Traditional cryostat for scientific experiment in the pulsed high magnetic field uses liquid helium as the cooling source. To reduce the running cost and to increase the operational efficiency, a cryogen-free cryostat based on a GM cryocooler has been developed for a 60 T pulsed field measurement cell at Wuhan National High Magnetic Field Center. The lowest temperature of the cryostat is 1.4 K. A double layer temperature-control insert was designed to obtain a stable temperature in the sample chamber of the cryostat. In order to eliminate the sample temperature fluctuation caused by the eddy current heating during the pulse, the inner layer of the insert is made from fiberglass tubing with epoxy coating. Different from the traditional cryostat, the sample and the temperature controller are not immerged in the 4He bath. Instead, they are separated by helium gas with negative pressure, which makes the heat transfer smoother. At the sample position, a resistance heater wound with antiparallel wires is mounted on the inner layer of the insert to heat the sample. Using the temperature-control insert, the temperature can be controlled with the accuracy of ±0.01K in the range of 1.4 K-5 K, and ±0.05K from 5 K to 300 K.
Speaker: Dr Shaoliang Wang (Huazhong University of Science & Technology)
• 250
A Novel Pre-cooling System for Cryogenic Pulsating Heat Pipe
As a highly effective two-phase cooling technique, a cryogenic heat pipe can transport several orders of magnitude larger heat loads than heat conduction of solids such as copper, and it has been used widely for cooling of superconducting magnets, electronic devices and harvesting energy. Among the different types of heat pipes, the cryogenic pulsating heat pipe is a new-type heat pipe which has several outstanding features, such as great heat transport ability, strong adjustability, small in size and simple construction. To reduce the effect of the material of the pipe on the effective thermal conductivity, the pipe of the cryogenic pulsating heat pipe is generally made of stainless steel. Because the thermal conductivity of stainless steel is low and there is no wick in the pipe, the pre-cooling of the evaporator in cryogenic pulsating heat pipes using helium as working fluid to 4.2 K is a problem. In order to solve this problem, we designed a mechanical thermal switch between the cryocooler and the evaporator as a pre-cooling system. The mechanical thermal switch is on during the pre-cooling process, and off during the test process which will not affect the measurement. By using the pre-cooling system to achieve pre-cooling, the cool down time of the cryogenic pulsating heat pipe is reduced significantly.
Speakers: Prof. laifeng LI (Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences) , Prof. linghui gong (Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences) , Mr rongjin huang (Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences)
• 251
Cold & Black Environment Design of Large Space Simulator
**Abstract:** The environment for a thermal vacuum test is created by a space simulator, of which cold & black is the important technical specification for spacecrafts’ thermal test. The objects of the paper are shrouds and nitrogen system to simulate the cold & black environment with the effective volume ⌀ 8500mm×9000mm. As for the shroud design of a large horizontal space simulator, not only the heat transfer and temperature uniformity should be considered, but also the feasibility of manufacture, transportation and installation. Based on the computation model of shrouds’ distribution, numerical simulation is conducted for flow and heat transfer in shrouds. The nitrogen system adopts a single-phase loop cycling to provide a cold source for shrouds. Sub-cooling cycling is driven by a liquid nitrogen pump in single-phase closed cycling which can absorb more heat load and sustain a stable working pressure. Given above characteristics of single-phase closed cycling, it has a common application in space simulator. The results of thermal tests show that the test data is the same as the numerical simulation, of which the shroud temperature is in the range of -191℃ to -194℃. Hence, the temperature and temperature uniformity of shrouds meet the requirement of thermal vacuum test.
Speaker: Min Liu (BISEE)
• 252
Cryogenic Design and Thermal Stability Analysis of a HTS Magnet for a Radiation Blackout Mitigation Experiment
Radiation blackout is a communication interruption phenomenon during hypersonic or reentry flight, caused by a plasma layer around a vehicle attenuating or reflecting radio waves. A vehicle in the radiation blackout phase will lose all contact with ground stations or satellites including GPS signals, data telemetry and voice communication. A method proposed to reduce the plasma density around senders and antennas is the use of crossed electric and magnetic fields. The Helmholtz-Russia Joint Research Group COMBIT will demonstrate this method at flight relevant conditions in an arc-heated wind tunnel (L2K facility) at the German Aerospace Center in Cologne. A conduction cooled HTS magnet produced by KIT is applied to generate the required magnetic field in the experiment, which is larger than 2 T outside the cryostat. Meanwhile it must satisfy the very strict space and environment conditions of L2K and will be exposed to the plasma beam with a temperature around 450 K. The special design of COMBIT cryogenic system is presented in detail in this contribution. The thermal stability of COMBIT magnet is analyzed, considering the influences from AC losses during current ramping and the heat exposure of the vacuum vessel due to the plasma beam. At last, this paper presents the test result of the COMBIT HTS magnet, which confirms the design of its cryogenic system and the thermal stability analysis.
Speaker: Hong Wu (Karlsruhe Institute of Technology)
• 253
Cryogenic design of the 43 T LNCMI Grenoble hybrid magnet
The association of two inner copper alloy resistive coils (polyhelix and Bitter) producing 34.5 T with an outer NbTi superconducting coil producing 8.5 T to obtain a 43 T hybrid magnet is a technical challenge. Accidental failure modes leading to complex electromagnetics behaviors and large transient dynamical forces should be anticipated. These considerations lead to a reinforced design of the SC coil, of the cryostat and of the coil protection system. To reduce the probability of quench occurrence of the SC coil in case of the disruption of the resistive inserts, the eddy current shield already developed for the last project is reused between the SC coil and the Bitter coils. The cryostat has been designed with sophisticated thermo-mechanical supports sustaining the coil at 1.8 K and the eddy current shield at 30 K, both being possibly overloaded by high dynamic forces in the worst accidental failure case. The 1100 liters superfluid helium pressurized bath at 1.8 K atmospheric pressure is produced in an external cryogenic satellite located in a limited magnetic stray field area. The CEA-CNRS French collaboration for the LNCMI 43 T hybrid test facility project works actively to finalize the last studies recently reviewed by an external committee.
Speakers: Bertrand Hervieu (CEA-Saclay Irfu) , Luc Ronayette (CNRS-LNCMI Grenoble)
• 254
Cryogenic High Voltage Insulation Breaks for ITER
Insulation breaks are used in cryogenic lines with gas or liquid (helium, hydrogen, nitrogen, etc.) at a temperature range of 4.2-300 K and pressure up to 30 MPa to isolate the parts of an electrophysical facility with different electrical potentials. In 2013 NIIEFA delivered 95 insulation breaks to the IO ITER, i.e. 65 spiral-type breaks and 30 uniflow-type breaks. These insulators were designed, manufactured and tested in accordance with the ITER Technical Specifications: Axial Insulating Breaks for the Qualification Phase of ITER Coils and Feeders. The insulation breaks consist of the glass-reinforced plastic cylinder equipped with channels for cryoagent and stainless steel end fittings. The operating voltage is 30 kV for the spiral-type breaks and 4 kV for the uniflow-type breaks. The main design feature of the spiral-type insulation break is the spiral channel instead of a linear one. This approach has enabled us to increase the breakdown voltage and decrease the overall dimensions of the insulation breaks. In 2013 the manufacturing technique was developed to produce the insulation breaks with the spiral and uniflow channels that made it possible to proceed to serial production. To provide the acceptance tests of the breaks the special test facility was prepared. The helium tightness test at 10-11 m3∙Pa/s under the pressure up to 30 MPa, the high voltage test up to 135 kV and different types of mechanical tests were carried out at the room and liquid nitrogen temperatures.
Speaker: Mr Oleg Kovalchuk (NIIEFA)
• 255
Design of a PF1 coil helium inlet and dummy joint samples for fatigue tests at 77 K
Helium inlet (HI) and electrical joint (EJ) between conductors are critical elements of double pancakes (DP) of ITER PF-1 coil. HI is a part of the PF-1 coil used to inject the liquid helium into PF1 conductor channel. The full-scale sample of HI and mechanical loading facility have been designed and manufactured to perform a fatigue tests at 77K under required strain and to check leak tightness of the HI sample. Thermocycling (296-77K) and leak tightness test of HI were carried out before and after fatigue tests. The low ohm EJ is used to connect two lengths of NbTI CICC into a single electric circuit, To qualify the technique and equipment for EJ manufacturing the dummy joint (DJ) qualification sample has been designed to simulate required strain of fatigue test. The main feature of the sample design is the symmetric combination of two DJs to compensate the bending moment. The HI sample passed fatigue test successfully in 2013 year. Fatigue tests of DJ sample will be carried out in 2014. The article includes the results of the HI and DJ design stress analyses under required test conditions, the facility description for fatigue tests at 77K, HI sample fatigue and leak tightness tests results.
Speaker: Sergey Nasluzov (JSC NIIEFA)
• 256
Discussion of regenerator for cryogenic energy storage
Developing and utilizing energy storage technologies means a significant push for the “Smart Grid”. Pumped hydro storage and compressed air energy storage have been proved useful in the field of large scale energy storage, however, to adopt liquid gas, e.g., air, as a storage medium could provide much higher energy density, reduce the cost and need for space considerably. In such storage system, the key device that builds the thermal equilibrium of the whole system is regenerator, which is designed for low temperature usage, and thus, influences the global efficiency markedly. Generators for large-scale cold energy storage commonly employ packed columns that consist of hollow tanks and fillers within these tanks, and the characteristics of such packed columns mainly determined by the fillers’ density, specific heat, flow resistance, etc., as well as the shape of such hollow tanks. Based on the discussion of former researches, the factors that influence the efficiency was analyzed in this paper.
Speaker: junjie Wang (Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China;)