bluuebunny/crossref_metadata_2025_split huggingface dataset:
Automatic LHC accelerator warm-up and cool-down experience during the Long Shutdown 2
Authors: Bradu B , Brodzinski K , Ferlin G , Pezzetti M , Tovar A , Wolak T 
Published: June 2022

Abstract
During the so-called Long Shutdown 2 (LS2), the Large Hadron Collider (LHC) has been entirely warmed-up in 2019 and cooled-down in 2020/2021 after an important maintenance period. For the first time, these complex and delicate operations have been performed in an automatic way, using a new control logic implemented in the Process Logic Controllers (PLC). This new control logic is based on similar experiences that occurred in 2008, 2013 and 2014 where many manual operations were still needed to ensure all the constraints around the machine. After a short presentation of the general LHC warm-up and cool-down principles and constraints, this paper details the global control logic that has been chosen to fulfil all requirements. This new approach is using thermodynamic considerations to spread efficiently the available helium massflows and refrigeration capacity along a LHC sector of 3.3 km (the accelerator totalizing eight cryogenic sectors), optimizing the transient time and respecting the constraints. Finally, the warm-up and cool-down achieved on the eight LHC sectors between 2019 and 2021 are presented and discussed, validating this new approach.
Optimal absorption of distributed and conductive heat loads with cryocooler regenerators
Authors: Snodgrass Ryan , Ullom Joel , Backhaus Scott 
Published: June 2022

Abstract
The second-stage regenerators of pulse tube refrigerators are routinely used to intercept heat in cryogenic systems; however, optimal methods for heat sinking to the regenerator have not been studied in detail. We investigated intermediate cooling methods by densely instrumenting a commercial, two-stage pulse tube refrigerator with thermometers and heaters. We then experimentally emulated heat loads from common sources such as arrays of electrical cables (a single-point conductive load) and 3He return gas for dilution refrigerators (a distributed load). Optimal methods to absorb these heat loads, whether applied independently or simultaneously, are presented. Our study reveals the importance of understanding the response of the regenerator temperature profle for optimal thermal integration of heat loads along the regenerator, i.e., temperatures and heat fows at all heat sink locations. With optimal utilization of regenerator intermediate cooling, 3He fow rates of up to 2 mmol/s can be cooled from 50 K to 3 K and fully condensed using this pulse tube refrigerator; alternatively, the heat leak from over 100 electrical cables can be cooled across that same temperature span while simultaneously condensing 1.4 mmol/s of 3He.
Investigation of regenerator mesh characteristics for a pulse tube cryocooler
Authors: Abraham Derick , Kuzhiveli Biju T 
Published: June 2022

Abstract
An investigation of regenerator mesh characteristics on a Pulse tube cryocooler’s performance is conducted using Sage V11 software. The cryocooler operates between temperatures of 300 K and 80 K. The components of the cryocooler are free piston linear compressor, aftercooler, regenerator, pulse tube, warm heat exchanger, and inertance tube- bounce space as the phase shifter. The performance of the regenerative cryocoolers depends on the regenerator. The regenerator of this cryocooler consists of a stack of stainless steel meshes. In this paper, a comparison of regenerator stainless steel meshes with mesh number #200, #300, #400, #500 and its combinations were analysed. To choose the best multi mesh combination, the length of the individual meshes is varied so that the total length of the regenerator is unchanged. The performance was analysed based on the Coeffcient of Performance of cryocooler for single mesh type and mesh combinations (combination two) at acceptor temperature of 80 K. The maximum performance with single mesh was with #400 mesh with COP of 6.12%. The cryocooler’s maximum Coeffcient of Performance was with the combination of #400 and #500 meshes in the regenerator. The best multi mesh combination gave 4.071 W cooling power with an input power of 61.92 W with a COP of 6.57%. There was an improvement of 7.26% with the use of multiple mesh regenerator.
Application of Stirling pulse tube cryocoolers in high temperature superconducting filters subsystems
Authors: Duan Y B , Wang J , Wu S S , Wang W , Huang R J , Li L F , Zhou Y 
Published: June 2022

Abstract
The application of high temperature superconducting(HTS)filter has penetrated into various fields. In recent decades, GM-type pulse tube cryocooler and Stirling-type pulse tube cryocooler (SPTC) are two common cryocoolers. Due to the advantages of PTCs, such as no moving parts at the cold end, simple structure, small mechanical vibration and longer lifetime, pulse tube cryocoolers is gradually replacing oil-lubricated Stirling-coolers and G-M cryocoolers to cool down HTS magnets. In this paper, the development of PTC in HTS magnet cooling in the past 20 years is summarized firstly. Secondly, the development of HTS cooling system in our lab are reported. At last, the further development direction of HTS’s cooling system is discussed.
Comparative study on HTS magnet coil design approach for 1.0 T @ 65 K with 10 ppm field homogeneity at 80 mm DSV
Authors: Chand S K , Gour A S , Datta T S 
Published: June 2022

Abstract
A comparative study is carried out between two distinct coil design approaches (Multi-coil and Compensated solenoid) for the development of 1.0 T REBCO main magnet coil suitable for Extremity Magnetic Resonance Imaging (E-MRI). The design includes a operating temperature of 65 K, for the enhancement of Ic
with field anisotropy of REBCO tape. Each magnet design consists of HTS tape wound in the form of double pancake coils, having the inner winding diameter as 200 mm, whereas both outer diameter and magnet length are restricted to less than 400 mm. The two coils configurations are compared by keeping the bore inner diameter, outer diameter, length and fixed HTS tape length constant. Thereafter the parameters such as peak flux density, maximum radial field, stray field distribution, coil stress and field homogeneity for 80 mm diameter of spherical volume (DSV) are analyzed. Multi-coil design gives a better field homogeneity (315 ppm) as compared to Compensated solenoid.
Design of injectors and stay-alone cryostats with superconducting cavities for high RF powers applications
Authors: Putselyk S 
Published: June 2022

Abstract
Injectors and stay-alone cryostats with superconducting (sc) cavities are sometimes applied at modern particle accelerators. Typically, very stringent requirements on beam quality are foreseen at injectors, and application of sc cavities is advantageous, particularly if operation at high current densities and high accelerating gradients is foreseen. Stay-alone cryostats with one or few sc cavities also find applications, e.g. at ELBE, DIAMOND, S-DALINAC accelerators, and accelerate particle beams in High Frequency fields. In the future, very high RF fields will be needed, and improvement of the cooling of cavity surfaces will improve cavity performance. Application of a sub-cooled superfluid helium gives several advantages, e.g. higher heat flux densities, longer time for onset of a film boiling regime and shorter recovery time, reduced Kapitza resistances, etc [2]. In the present paper, an application of sub-cooled superfluid helium for injector and stay alone cryostats is considered. Design of the cryogenic system is presented in some details and possibility of adapting of such injector for future applications is also discussed.
Heat and mass transfer during levitation of a liquid nitrogen Leidenfrost droplet on a water pool
Authors: Zhang Z , Spijkers RMA , Schremb M , Vanapalli S 
Published: June 2022

Abstract
The understanding of cryogenic droplets evaporating on a liquid surface is of great interest in many industrial applications such as the Dearman engine, or food and beverage processing. However, due to the complexity of the physics involved, the entire process is far from being fully understood. Therefore, in the present study, the dynamics of a liquid nitrogen droplet deposited on a water surface is experimentally studied and theoretically modeled. During continuous cooling through the floating nitrogen droplet, the liquid at the pool surface may eventually solidify, which may significantly alters the situation for the evaporating droplet compared to the situation in which the pool remains liquid for the entire time. A crude theoretical model for the evaporation process of a floating nitrogen droplet is developed to calculate the vaporization rate of the droplet and the vapor layer thickness as a function of the radius of the droplet. The predictions from the model are compared to the experimental results, showing the lifetime predicted by the model is in good agreement with the experimental results.
Numerical study on the flow and heat transfer characteristics of natural convection in CFETR cryostat
Authors: Huang J H , Wei J J , Liu S M , Ge J , Song Y T , Jin T 
Published: June 2022

Abstract
The cryostat in the China Fusion Engineering Testing Reactor (CFETR) provides vacuum and low temperature operating conditions for the superconducting magnet system. A high pressure in the cryostat can increase the Rayleigh number (Ra) and cause the natural convection within the continuous hypothesis. A three-dimensional model, using incompressible ideal gas model and realizable k-ε model, is built to simulate the natural convection between the superconducting magnet system and the thermal shield within the temperature range of 4.5-80 K. The distributions of velocity field and heat flux on different surfaces of superconducting magnet system are obtained under different Rayleigh number conditions. The results show that the areas with large natural convection velocity mainly locate near the Central Solenoid (CS) coils and at the bottom of vacuum chamber. When the Rayleigh number ranges from 104 to 1010, the maximum velocity of helium gas decreases, while the heat flux on walls of superconducting magnets increases rapidly, and the heat flux on walls of PF-1, CS and TF coils is more affected by pressure, which needs to be considered in designing the safety system.
Vapor-liquid equilibrium of the nitrogen-argon system at 100 K
Authors: Tamson J , Mair M , Grohmann S 
Published: June 2022

Abstract
Mixed-refrigerant cycles (MRC) are state-of-the-art for efficient LNG production. The development of cryogenic mixed-refrigerant cycles (CMRC) at temperatures below 100 K relies on physical property data of cryogenic mixtures such as vapor-liquid equilibria and enthalpies. This data is insufficient for some binary mixtures and unavailable for most multi-component systems. The cryogenic phase equilibria test stand CryoPHAEQTS provides precise physical property data of cryogenic fluid mixtures at temperatures from 15 K to 300K and at pressures up to 150 bar. Contrary to previous apparatus in the literature, CryoPHAEQTS uses cooling of the equilibrium cell by a pulse-tube cryocooler. Temperature is measured by two CERNOX® sensors directly immersed in the liquid/vapor phase. Pressure is measured through a capillary and a differential pressure sensor connected to a secondary system containing three high precision sensors. Up to three occurring phases can be sampled directly from the cell and analyzed by gas chromatography. Measurement uncertainties are ±13mK in temperature, ±1 mbar in pressure and ±1% in composition. Prior to publishing new phase equilibrium data, the test stand is benchmarked against available vapor-liquid equilibrium data of the widely investigated nitrogen-argon system. In this paper, we report on the first measurement results of cryogenic mixtures in CryoPHAEQTS and compare them against the literature data.
Effects of grain size and strain rate on the low-temperature tensile properties of ferrite-austenite duplex stainless steel
Authors: Koga N , Nameki T , Umezawa O 
Published: June 2022

Abstract
The effects of grain size and strain rate on the low-temperature tensile properties of ferrite-austenite duplex stainless steel were investigated. The coarse- and fine-grain specimens exhibited a grain size of approximately 20 and 8 μm, respectively. At 77 K, the fine-grain specimen exhibited a higher strength and elongation than the coarse-grain specimen. The work-hardening rate at 77 K in both specimens leveled off or increased slightly at late stage of deformation although the work-hardening rate was lower than the true stress. This characteristic work-hardening behavior is caused by the deformation-induced martensitic transformation of metastable austenite. Grain refinement stabilized austenite phase and enhanced the elongation of the material, resulting in the better low-temperature tensile properties of fine grain. The elongation decreased remarkably with an increasing strain rate at 77 K independent of grain size. The characteristic work-hardening was not detected at a high strain rate, indicating that the deformation-induced martensitic transformation did not occur. The strain rate affects the frequency of deformation-induced martensitic transformation, resulting in a change in elongation. Grain refinement effectively improves the low-temperature tensile properties of duplex stainless steels; however, these properties are strongly influenced by the strain rate, where a high strain rate causes a low elongation.
Fiber bragg grating sensors to monitor strain response of epoxy resin during curing and cryogenic temperature
Authors: Dong H Y , Liu H M , Fang C S , Huang C J , Li L F 
Published: June 2022

Abstract
The epoxy resin is one of the critical components of large-scale superconducting magnets which find wide applications in magnetic confinement fusion, high energy accelerator and magnetic resonance imaging. In general, magnetic confinement fusion, high energy accelerator and magnetic resonance will be used at cryogenic temperatures. An approach with respect to real-time monitor of epoxy curing and cryogenic process is practically significant for magnetic reliability, maintainability as well as future mass production. Fiber Bragg Grating (FBG) sensors are excellent candidates of this measurement for their anti-electromagnetic interference characteristics and high sensitivity. The aim of this work is to use the embedded Fiber Bragg Gratings (FBG) to obtain real-time strain response of curing epoxy, and the strain change of the epoxy at cryogenic temperature from 4.2K to 300K. An FBG pre-tensioning device was designed to keep the FBG embedded in the epoxy in a stretched state during the epoxy curing process. Moreover, strain gauge sensors were also embedded to monitor the curing process at the same time. There are subtle differences in strain values obtained by the two sensors, which illustrate higher sensitivity of FBGs. This work verifies the reliability of FBG monitoring the strain response of epoxy during curing process as well as the cryogenic service.
Development of multi-filament textured-powder Bi-2212/Ag wire with enhanced local area ratio
Authors: May G D , Coats C , Elliott T , McIntyre P M , Ratcliff C T , Rogers J S , Besser M 
Published: June 2022

Abstract
The performance and cost of Bi-2212/Ag wire is limited by the large area fraction of Ag matrix (∼3:1) that is required in the conventional oxide-powder-in-tube fabrication process. An alternative process is being developed in which fine-powder Bi-2212 is uniaxially compressed to form a bar tetrahedral bar with a Ag-alloy foil cladding. The fine powder naturally textures under compression (aligns the a-b planes perpendicular to the direction of compaction). Earlier work demonstrated that a symmetric billet of trapezoidal-cross-section textured-powder (TP) bars draws conformally so that the local area ratio is preserved.
Temperature dependent pinning efficiency in multilayer and single layer BZO/YBCO nanocomposite films
Authors: Panth M , Ogunjimi V , Sebastian M A , Zhang D , Gautam B , Jian J , Huang J , Zhang Y , Haugan T , Wang H , Wu J 
Published: June 2022

AbstractThe BaZrO3/YBa2Cu3O7(BZO/YBCO) interface has been found to affect the vortex pinning efficiency of one-dimensional artificial pinning centers (1D-APC) of BZO. A defective BZO/YBCO interface due to a lattice mismatch of ∼7.7% has been blamed for the reduced pinning efficiency. Recently, we have shown incorporating Ca0.3Y0.7Ba2Cu3O7-xspacer layers in BZO/YBCO nanocomposite film in multilayer (ML) format can lead to a reduced lattice mismatch ∼1.4% through the enlargement of lattice constant of YBCO via Ca diffusion and partial Ca/Cu replacement on Cu-O planes. In this work, the effect of this interface engineering on the BZO 1D-APC pinning efficiency is investigated at temperatures of 65-81 K through a comparison between 2 and 6 vol.% BZO/YBCO ML samples with their single-layer (SL) counterparts. An overall higher pinning force (Fp) density has been observed on the ML samples as compared to their SL counterparts. Specifically, the peak value ofFp(Fp,max) for the 6% BZO/YBCO ML film is about ∼ 4 times of that of its SL counterpart at 65 K. In addition, the location of theFp,max(Bmax) in the ML samples shifts to higher values as a consequence of enhanced pinning. For the 6% BZO/YBCO ML sample, a much smaller “plateau-like” decrease of theBmaxwith increasing temperature was observed, which is in contrast to approximately linear decrease ofBmaxwith increasing temperature in the 6% SL film. This result indicates the importance of restoring the BZO/YBCO interface quality for better pinning efficiency of BZO 1D-APCs especially at higher BZO doping concentration.
ASCEND: The first step towards cryogenic electric propulsion
Authors: Ybanez L , Colle A , Nilsson E , Berg F , Galla G , Tassisto M , Rivenc J , Kapaun F , Steiner G 
Published: June 2022

Abstract
If a cold source such as liquid H2 or cryogenic fuel is available, cryogenic and high-temperature superconductivity technologies are promising to significantly increase performance of electric propulsion systems. A first study for aeronautic applications shows that the power density of electrical components could be multiplied 2 to 3 times to reach more than 30kW/kg for electric motors and power electronics, the weight of cables can be considerably reduced, and the efficiency increased by more than 50% with a voltage between below 500 V for multi-megawatt applications. With ASCEND, AIRBUS intends to demonstrate the potential and feasibility of a cryogenic and superconducting powertrain to breakthrough aircraft electric propulsion performance.
Test of a DC-HTS Busbar Demonstrator for Power Distribution in Hybrid-Electric Propulsion Systems for Aircraft
Authors: Schlachter S I , Brand J , Elschner S , Fink S , Holzapfel B , Kudymow A , Willms J 
Published: June 2022

Abstract
In the framework of the German project TELOS (Thermo-Electrically Optimised Aircraft Propulsion Systems) a high-temperature superconducting 40 MVA DC demonstrator busbar for hybrid-electric propulsion systems for aircraft has been developed. The design current for a temperature below 25 K is 13.3 kA and the rated voltage is 3 kV. The 2-pole busbar contains 2 stacks of REBCO coated conductors which are supported by a 3D-printed structure allowing compensation of thermal length changes of the superconductor. It fits in a cryostat tube with an inner diameter of 25 mm. A special focus has been put on low-resistive joints that are necessary to connect single elements of the busbar system. The special layout of the joints allows an effective current redistribution between the different tapes in a stack. We present results for the test of the DC busbar demonstrator in liquid nitrogen at 77 K. The design current for this temperature is 3.3 kA which corresponds to a rated power of 10 MW. We applied currents up to 3.5 kA and measured the I-V characteristics and contact resistances of 90° and 180° joints in a virgin and in a strained state thus simulating thermal length changes. We also present results of Lorentz-Force tests with short AC current pulses up to 20 kA to demonstrate the viability of the design for application with currents up to 13.3 kA.
Numerical Studies on Two-Phase Flow of Liquid Nitrogen to Cool HTS Power Cables
Authors: de Souza I , Hassan H K , Anand A , Chand S K , Gour A S , Rao V V 
Published: June 2022

Abstract
Liquid nitrogen is the foremost coolant when it comes to cooling HTS power devices due to its abundance and since it is more economical than other cryogens. Sub-cooled LN2 is preferred over saturated LN2 as it ofers substantial advantages in terms of performance. However, in the cases where it is not possible to cool HTS power cables using sub-cooled LN2, saturated LN2 is the only option. Additionally, even when sub-cooled LN2 is used for long length cables, the heat-in-leaks along with other core losses result in rise in temperature and an unavoidable two-phase fow afects the cooling characteristics of the cryogen. This paper deals with the modeling and numerical analysis of a two-phase fow through an HTS power cable cryostat to understand the temperature profle, the pressure drop per unit length, and required pumping power for circulation of cryogen.
Cryogenic Performances Comparisons Among Si MOSFET, SiC MOSFET, Cascode GaN, and GaN Devices
Authors: Wei Yuqi , Hossain Md Maksudul , Alan Mantooth H. 
Published: June 2022

Abstract
Cryogenic power electronics is an emerging technology to achieve high efficiency and high power density. As the key element of the power electronics system, the device performance should be evaluated under cryogenic temperatures. To demonstrate the differences between different materials and technologies, cryogenic temperature performance comparisons among silicon (Si) metal–oxide–semiconductor field-effect transistor (MOSFET), Si insulated-gate bipolar transistor (IGBT), silicon carbide (SiC) MOSFET, Cascode gallium nitride (GaN), and GaN high-electron-mobility transistor (HEMT) from different perspectives are made, which includes on-state resistance, threshold voltage, turn-on and turn-off times, turn-on and turn-off switching losses. The normalized values are adopted and results are drawn in the same pictures to demonstrate the differences. The results demonstrate that traditional Si devices have better performances under low temperatures. The SiC MOSFET is not suitable for cryogenic applications due to its increased on-state resistance and switching loss. Cascode GaN and GaN HEMT are promising candidates for cryogenic applications with reduced conduction loss and switching loss.
A large millikelvin platform at Fermilab for quantum computing applications
Authors: Hollister Matthew I , Dhuley Ram C , Tatkowski Grzegorz L 
Published: June 2022

Abstract
The need for larger mK cooling platforms is being driven by the desire to host ever growing numbers of cryogenic qubits in quantum computing platforms. As part of the Superconducting Quantum Materials and Systems Center at Fermilab funded through the Department of Energy under the National Quantum Initiative, we are developing a cryogenic platform capable of reaching millikelvin temperatures in an experimental volume of 2 meters diameter by approximately 1.5 meters in height. The platform is intended to host a three-dimensional qubit architecture based on superconducting radiofrequency accelerator cavity technologies. This paper describes the baseline design of the platform, along with the expected key performance parameters.