The J-PARC accelerator has been jointly operated by JAEA and KEK since 2007 and a variety of experiments has been carried out using secondary beams of pions, muons, neutrinos and other particles generated by proton beam with a power of several hundreds of kilowatts from 3 GeV Rapid Cycle Synchrotron and 30 GeV Main Ring. Superconducting (SC) magnets have been widely utilized in J-PARC. In...
Superconducting magnets have been used for more than fifteen years in protontherapy systems, starting with NbTi (Varian, IBA) and Nb3Sn (Mevion). These magnets, designed with large temperature, field and current margins, proved to be reliable and show no sign of conductor performance degradation.
The development of HTS presents opportunities and triggers questions about their suitability for...
During operation, ITER superconductive (SC) magnets are subjected to significant thermal loads which mostly result from the deposition of energy by plasma-generated neutrons, as well as from secondary gamma radiation produced when neutrons interact with matter. In addition to thermal loads, total neutron fluence and absorbed dose in key magnets components like the magnet’s insulators should be...
The first part of the talk will summarize the physics behind the changes of the superconducting properties upon radiation. The introduced defects enhance flux pinning and scattering of the charge carriers. The implications of these two effects on metallic and high-temperature superconductors will be compared. While the change in pinning is currently difficult to predict, the influence of the...
It is crucial to immobilize magnetic vortices threading the superconductors. Capturing vortex pinning from microscopic interactions with defects poses a very difficult yet insightful task. The theory of strong vortex pinning provides the necessary starting point. We revisit the different regimes of strong-pinning theory and investigate them using large-scale numerical solutions of the...
The superconducting properties of rare-earth barium cuprates (REBCOs) are extremely sensitive to the presence of crystal defects. Irradiation of REBCOs with energetic particles produces a plethora of defects, difficult to characterize thoroughly with experimental investigations alone, in particular at the expected working conditions. Atomistic simulations can assist in the understanding of the...
Understanding irradiation damage in high-temperature superconductors is important as new compact fusion reactors rely on these materials to generate the high magnetic fields needed to confine the plasma. The superconductor of choice is (RE)Ba2Cu3O7-δ (RE = rare earth element), REBCO. We have used high-energy-resolution X-ray absorption spectroscopy (XAS) to probe the local environment around...
High temperature superconducting (HTS) materials, such as YBa2Cu3O7-δ, will be exposed to high energy neutrons that may impact the superconducting properties and ultimately lead to degradation of the magnetic field strength. Density functional theory (DFT) calculations have been used to investigate the energetics of point defects in YBa2Cu3O7. The formation energies of point defects indicate...
High-temperature superconductors (HTS) are promising materials for next-generation fusion reactors and particle accelerators, owing to their remarkable field strengths at elevated temperatures. In these environments, radiation will impinge on the HTS, causing damage. Assessing the extent and nature of this damage is essential for determining the material's lifespan and any necessary shielding...
Atomic collision processes are fundamental to numerous advanced materials technologies, such as electron microscopy, semiconductor processing and nuclear power generation. Understanding the atomistic scale phenomena happening during the primary damage production has been a research topic for many decades, both computationally and experimentally. The standard measurement of quantifying the...
FLUKA is a general-purpose code for the Monte Carlo simulation of coupled hadronic and electromagnetic radiation showers in complex aterial geometries, accounting for the transport, interaction, and decay (where applicable) of over 60 particle species (photons, leptons, hadrons, and ions) at energies up to the PeV and down to the keV (down to 0.01 eV for neutrons). A wide range of...
To predict the operating lifetime of materials in radiation environments, the displacement per atom(dpa) value, which is the average number of displaced atoms per atom of a material based on the Norgett-Robinson-Torrens (NRT) model, is widely used as an exposure unit and is defined by elastic energy transfer to Primary Knock on Atoms (PKAs), as well as high-energy effects (e.g., nuclear...
Irradiation studies on high-temperature superconductors (HTS), particularly REBCO (Rare-Earth Barium Copper Oxide), are critical for understanding their performance in high-radiation environments, such as those found in particle accelerators and fusion reactors. This work focuses on neutron irradiation experiments conducted in Japan, which investigate the effects of neutron fluences of up to...
On 2024, J-PARC achieved the goal of high-power beam operation of 1 MW for the spallation neutron source. The allowable beam power can be said to be determined by the beam intercept materials for the high-power accelerator. J-PARC plans to build a Proton Beam Irradiation facility using 400 MeV protons to study materials, especially beam intercept ones used for the high-intensity proton beam....
The results of two decades of neutron irradiation experiments on high temperature superconducting tapes (coated conductors) will be summarized. The change of the critical current is determined by a competition of improved pinning by the introduction of nanometre sized defects and a reduction of superfluid density by pair-breaking scattering on point-like defects. The latter is directly...
Understanding the effect of irradiation with fast neutrons at cryogenic operating temperature on the properties of REBCO HTS is crucial for the design of magnets for fusion tokamaks. However, suitable high flux neutron sources such as fission reactors are not widely available, performing in situ cryogenic measurements in these reactors is challenging, and neutron irradiation activates the...
The deuterium-tritium reaction is the most promising source of fusion energy for power plants but generates high-energy neutrons that compromise reactor components - from the plasma-facing walls to fusion magnets. In compact, high-field REBCO-based fusion devices, radiation damage will limit the lifespan. Simulating the fusion environment in test facilities is challenging but essential to...
HTS magnets employed in fusion plants and high-energy physics experiments will be subjected to significant gamma ray fluxes. Gamma rays ($E_γ$ > 100 keV) have energies orders of magnitude more than the binding energies of REBCO lattice ions ($E_b$ ~ 10s eV) and Cooper-pairs ($E_b$ ~ 10s meV) and are, in principle, therefore capable of altering REBCO microstructure and suppressing...
The degradation in critical temperature of REBCO coated conductors has been attributed to the generation of point defects, particularly on the oxygen sublattice. This introduces substantial challenges for observing the defects directly because the low mass oxygen atoms are not visible in the most widely used atomic resolution electron microscopy technique, high angle annular dark field...
In order to operate reliable beam-intercepting devices in the framework of energy and intensity increase for next generation accelerators, the RaDIATE collaboration (Radiation Damage In Accelerator Target Environment) managed by Fermilab, brings together existing expertise in nuclear material and accelerator targets from 20 international institutions to execute a coordinated strategy for high...
An extensive experience has been gained throughout the last decades in the characterization of the radiation field impacting the magnets of existing and envisaged high-energy particle colliders. Detailed spatial distributions of the dose absorbed by the most exposed coils have been calculated by means of Monte Carlo simulation codes, through the description of the relevant radiation sources...
In superconducting magnets of particle accelerators like HL-LHC, FCC-hh and a muon collider, shielding is required to reduce the dose absorbed by the magnet materials. A goal of the CERN Polymer Laboratory irradiation study is to increase the acceptable dose limit of the insulation systems beyond the limit of about 30-50 MGy that is presently assumed for shielding design.
Irradiations are...
The talk summarizes the results of the combined neutron and gamma irradiation studies on polymers performed for the development of the insulation system of the ITER PF coils. The ultimate tensile stress (UTS) and the interlaminar shear strength of epoxy raisins and cyanate ester based polymers were determined as a function of the neutron fluence or dose rate. The fatigue behaviour of the UTS...
This contribution aims to review basic dosimetry principles, give examples for dose calculations as well as a brief overview of the available irradiation facilities for material irradiation studies and their associated dosimetric means. Their interest, limitations and some practical aspects involving the organization of irradiation campaigns for total ionizing dose testing will be also...
Low temperature environments are vital for radiation testing of materials used in accelerator components. The cryogenic environment can either be established by immersion in a cryogenic fluid like Helium or in a dry manner by using cryocoolers as cooling source. The operation of helium cryostats requires frequent refill via long distance transfer lines. A direct cooling with cryocooler...
Magnet shielding design in high-energy particle colliders is a multidisciplinary challenge, requiring consideration of diverse constraints to ensure both performance and longevity of components. An integrated design shall address key factors such as power load management in relation to quench and cryogenic limits, dose tolerance for organic materials, displacement per atom (DPA) thresholds for...
Designing magnet systems for fusion devices, including tokamaks, stellarators, and mirror machines, requires careful consideration of the intense radiation environments in which these systems operate. This study focuses on the conceptual design and optimization of magnet systems for DEMO and VNS machines, with particular attention to achieving a balance between compactness, durability, and...
Recent progress in high temperature superconducting (HTS) magnets has greatly enhanced the potential of spherical tokamaks (ST) for harnessing fusion energy. Given the compactness of an ST and high plasma density, the centre column shield is subjected to challenges such as high neutron load, volumetric heating from neutrons and gamma radiation, and a limited amount of available space. The...
Commonwealth Fusion Systems (CFS) is building the world’s first compact net energy fusion device, SPARC, by utilizing recent advances in the commercial production of 2G REBCO coated conductors. SPARC’s delivery and operation will inform the design of ARC, the world’s first fusion power plant, scheduled to come online in the early 2030s. The design, safe operation, and quench protection of high...
