bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a space irradiance simulator for advanced studies and materials research
Authors: Swanger A M , Krenn A , Youngquist R , Gibson T L
Published: June 2022

A lab-scale experimental apparatus that mimics the solar-thermal environment of space has recently been developed and tested at NASA Kennedy Space Center in support of novel materials research for future space science and exploration applications. The Space Irradiance Simulator (SIRS) apparatus exposes specimens up to roughly 61 mm in diameter to a similar thermal environment that exists at distances as close as 0.4 AU from the Sun. This includes a high vacuum environment, access to a deep cryogenic background temperature with optical properties that closely imitate a blackbody, and irradiance from a broadband solar “point” source at fluxes as high as 9300 W/m2. Cooling is provided by a Gifford-McMahon cryocooler capable of 25 W of cooling power at 20 K, with a base temperature of 14 K. A commercially available Xenon lamp acts as the solar source, creating broadband electromagnetic radiation with a spectrum similar to that of the Sun. Light is beamed through the vacuum chamber and onto a sample suspended within the cold-mass via a flexible quartz fiber bundle in conjunction with a custom vacuum feedthrough. The system design, fabrication, and operation are discussed; and results from the initial checkout testing of the system are presented.
The effect of external heat inflow to the cryogenic liquid pressurized discharge process
Authors: Baek Seungwhan , Jung Youngsuk , Cho Kiejoo
Published: June 2022

The launch vehicle with a liquid propulsion system requires pressurization during the propellant discharge. While the launch vehicle is flying through the air layer, a process in which frictional heat is generated between the liquid propellant tank and the air layer can be assumed. External heat inflow occurs during the liquid discharging process, and it is necessary to investigate how the external heat influx affects the liquid pressurized discharge process. A test device was constructed to determine the effect of pressurization of external heat inflow. The test device consisted of a liquid tank located in a vacuum chamber and a heating device to simulate external heat inflow. The heating device is a halogen lamp. The cryogenic liquid discharge with and without external heat inflow was compared. It was confirmed that the amount of pressurant gas used was decreased when there was external heat inflow. External heat inflow contributes to the evaporation of the liquid, and the evaporated gas increases the pressure of the ullage.
Helium gas-gap heat switch for Sub-Kelvin refrigeration system
Authors: Xi Xiaotong , Yang Biao , Gao Zhaozhao , Chen Liubiao , Zhou Yuan , Wang Junjie
Published: June 2022

The heat switch is an indispensable thermal control device in the low-temperature system. The helium gas-gap heat switch plays a key role in Sub-Kelvin sorption coolers and adiabatic demagnetization refrigerators, and its effective switching between thermal conducting (ON state) and insulating (OFF state) is achieved by changing the pressure of the gas in the gap. In this paper, a4He gas-gap heat switch was designed. And the thermal characteristics at different cold block temperatures were experimentally tested, which provides a reference for the development of high-efficiency gas-gap heat switches.
Numerical study on pressure variation of marine liquefied natural gas (LNG) fuel tanks under sinusoidal sloshing excitation
Authors: Wu Sixian , Ju Yonglin
Published: June 2022

In this paper, a numerical model considering phase change and external heat leakage is established to study the pressure variation and temperature distribution of marine Liquefied Natural Gas (LNG) fuel tanks under sinusoidal sloshing excitation. The Volume of Fluid (VOF) method, coupled with the mesh motion treatment, is adopted to predict the movement of the vapor-liquid interface. The sinusoidal sloshing excitation is realized by a User-Defined Function (UDF). The feasibility of the numerical model is verified by comparisons with related fluid sloshing experiments. The thermal physical process in the LNG fuel tank under sloshing conditions and the static condition are compared, and the effects of sloshing amplitude and frequency on the pressure and temperature distribution of the tank are also studied. The results show that when the external sloshing excitation frequency is close to the first natural frequency of the LNG fuel tank, the tank pressure will drop rapidly in a short time, resulting in the shutdown of Natural Gas (NG) engine. Meanwhile, the influence of the sloshing excitation on the mass transfer is theoretically analyzed by the definition of the sloshing Nusselt number.
Thermodynamic analysis of ideal thermocompressor based on Euler view
Authors: Wu S S , Wang J , Zhang H C , Huang C J , Li L F , Zhou Y
Published: June 2022

The thermocompressor is the driving source and the core heat-work conversion part of Vuilleumier (VM) refrigerator, which cause pressure fluctuation of the gas by converting the thermal energy at a constant volume. The thermocompressor is consists of cylinder, heater, generator, cooler, displacer, driving mechanism, load, hot cavity and cold cavity. Therefore, the ideal thermocompressor was introduced for thermal analysis to simplify the thermodynamic process and components. In order to better understand the principle of heat-work conversion in the ideal thermocompressor, firstly, the thermodynamic concept of the variable mass system that can be used in the ideal thermocompressor was introduced. Secondly, the thermodynamic process of the ideal thermocompressor under the Euler view was analyzed. Thirdly, the internal operation characteristics of the thermocompressor without load and driving displacer type refrigerator were discussed. At last, the distributions of enthalpy flow, entropy flow and exergy flow in all parts of the ideal thermocompressor were carried out. The results show that the thermocompressor does not output the net entropy flow to the load in one cycle and the flow exergy output by thermocompressor is equal in quantity to the acoustic power output by thermocompressor.
Study on reducing the impact to EAST cryogenic system caused by the failure of load devices
Authors: Yu Q , Lu X F , Zhou Z W , Zhuang M , Zhang Q Y
Published: June 2022

EAST tokamak has complicated supercritical helium loops for cooling the superconducting magnets and other thermal loads. When failures occur in these load devices, such as magnet quench or vacuum failure, a large amount of helium evaporated in the cryogenic circuits returns to the cryogenic distribution system, which makes the pressures rise and the helium returning to the refrigerator increases. The refrigerator will run in a supercooling state and the turbine protection shutdown will be triggered with probability, which further affects the operation of the cryogenic system. This paper analyzes the archive data of this undesired phenomenon, the EAST cryogenic system model based on EcosimPro is used to simulate the dynamic process during the failure. A split-range control scheme to stabilize the pressures in the distribution system under failure state is proposed. the control module is developed in EcosimPro, simulation results show that it could achieve a satisfactory control performance and reduce the impact caused by the failure.
Liquid helium level regulation improvement in the LHC electrical distribution feedboxes
Authors: Bradu B , Coppier H , Gery J , Pezzetti M , Tovar A
Published: June 2022

An important cryogenic equipment of the Large Hadron Collider (LHC) consists in the electrical distribution feedboxes (DFBs) which are used to power the superconducting magnets of the accelerator. These feedboxes contain the current leads achieving the electrical transition between the copper cables at ambient temperature to the Niobium-Titanium wires at cryogenic temperature, immersed in a liquid helium bath at 4.5 K. This liquid helium bath must be regulated at a defined level to allow the powering of the LHC, and this regulation often caused non-availabilities in the past. This paper presents the development of a new control scheme, coupled to the existing PID level controller, significantly improving this regulation, and rejecting disturbances in a highly efficient manner. First, a dynamic model of the DFBs was developed in the EcosimPro software using the CRYOLIB library to reproduce in simulation the regulation issues. In a second step, the new proposed regulation modes were tested and validated in simulation. Finally, the paper will present the results obtained in 2021 on a real DFBs operation in the LHC, validating the new control approach prior its massive deployment all around the LHC cryogenics.
Experimental study of different structural parameters on gas lubricated spiral groove thrust bearing for cryogenic turbo expander
Authors: Zhang X H , Li K R , Yan H , Zheng L W , Ke C L , Dong B , Peng N , Liu L Q , Gong L H
Published: June 2022

With the development of high speed and miniaturization of turbo expander, the gas-lubricated spiral groove dynamic pressure gas bearing plays an important role. An experimental study on the gas-lubricated spiral groove gas thrust bearing is carried out to research the relationship between the bearing loading capacity and the structural parameters such as the spiral angle, the groove length ratio, the groove width ratio and the rotating speed. The contrast experiment of spiral groove structure on thrust disc and bearing end face was also carried out. The experimental results show that the optimum spiral angle is 20°, the optimum groove length ratio is 0.61∼0.68, the optimum groove width ratio is 0.5∼0.55, and the new structure of the spiral groove on the thrust disc will increase the bearing loading capacity by 7.6% than the traditional structure.
Analysis of the effect of friction of hybrid ball bearings on grease evaporation in cold compressors
Authors: Su H , Shang J , Lv C , Wu J H
Published: June 2022

Bearings are the essential part of the cold compressor rotor system, which has a great influence on the operation of cold compressor. Hybrid ball bearing has been successfully applied in cold compressors with the lubrication of grease. With the high-speed rotation of the cold compressor, the bearing will be affected by the axial thrust of the impeller, which will cause friction, and the grease will be impacted by the frictional heat. To understand the influence of frictional heat on grease evaporation, it is important to study the bearing heat generation. In this article, the application of grease-lubricated hybrid ball bearings in cold compressors was introduced. Based on the parameters of a successfully applied impeller and a ball bearing of the cold compressor, the axial thrust of impeller was calculated, and a bearing frictional heat generation model was proposed, which considered the dynamic change of the axial thrust of the cold compressor impeller. The heat generation and temperature of the bearing was analyzed and calculated using the proposed model. According to the results of the calculation and practical experience, a test was performed on high-speed greases, and the adding amount of grease was estimated with reference to the bearing temperature.
Process analysis and control flow design of the 1kW @ 4.5K helium refrigerator for NNBI
Authors: Li J Q , Zhou Z W , Zhang Q Y , Zhu Z G
Published: June 2022

A helium cryogenic system with a cooling capacity of 1kW@4.5K was designed in order to support the NNBI(Negative ion based Neutral Beam Injection system) test facility, cryopumping test facility and beam source test facility, which consists of a helium compressor with its storage and recovery system, 1kW@4.5K helium refrigerator, a cryogenic distribution valve box, cryogenic transfer lines and a helium Dewar, etc. Based on the SIMATIC S7-1500H PLC, the cryogenic control system can realize seven major operational modes, including the independent refrigeration mode and independent liquefaction mode, etc. On the basis of process analysis, the control flow of the NNBI helium cryogenic system in each operational modes was designed and will be presented in this paper. It will direct the control system to realize automatic control in multiple operational modes.
Experimental investigation of vertical neon pulsating heat pipe for superconducting magnet cooling application
Authors: Dixit T , Authelet G , Mailleret C , Gouit F , Baudouy B
Published: June 2022

Pulsating heat pipes (PHPs) are two-phase flow, thermal transport carriers characterized by ease of fabrication, flexibility of compactness and variable heat transfer capability. Conventionally, cooling of superconducting magnets is realized by using cryogen cooling system. Cryogenic PHPs are emerging as the new-age economical alternative that can passively contribute in efficient transport of generated heat to active cryocoolers. Nevertheless, a number of challenges must be addressed to materialize this union. For this objective, a multipurpose experimental test-rig has been developed which will allow different critical parameters of cryogenic PHPs to be investigated. The preliminary tests are conducted using neon as the working fluid. The PHP capillaries, made of SS304, have an outer diameter of 2.5 mm and a projected length of 400 mm with the adiabatic part having twice the length as compared to that in the condenser and evaporator. It consists of 20 parallel tubes forming a closed-loop and are tested in gravity-assisted environment. Employing the Sumitomo RDE-418D4 4K Cryocooler, the condenser temperature is controlled at the neon saturation temperature, around 27 K. The thermal performance of this cryogenic PHP is recorded at different evaporator heat load conditions. We report here the temperature evolution of PHP evaporator, and condenser as well as the pressure oscillations with time.
Overview and status of the Long-Baseline Neutrino Facility Far Site cryogenics system
Authors: Montanari D , Adamowski M , Bremer J , Delaney M , Doubnik R , Freitag J , Haaf K , Nichols T , Parchet A , Young I
Published: June 2022

The Sanford Underground Research Facility (SURF) will host the Far Detector of the Deep Underground Neutrino Experiment (DUNE), an international multi-kiloton Long-Baseline neutrino experiment that will be installed about one and a half kilometers underground in Lead, SD. Detectors will be located inside four cryostats filled with almost 70,000 metric tons of ultrapure liquid argon, with a level of impurities lower than 100 parts per trillion of oxygen equivalent contamination. The cryogenics infrastructure supporting this experiment is provided by the Long-Baseline Neutrino Facility (LBNF). This contribution presents modes of operation, layout, and main features of the LBNF Far Site cryogenic system, which is composed of three subsystems: Infrastructure, Proximity, and Internal cryogenics. The Infrastructure cryogenics supports the needs of the cryostat and Proximity cryogenics. It includes the equipment to receive the argon in liquid phase, vaporize it and transfer it underground as a gas, the nitrogen system (composed of the refrigeration system, liquid nitrogen buffer tanks and liquid and gaseous nitrogen distribution), liquid and gaseous argon distribution and process controls. The Proximity cryogenics receives fluids from the Infrastructure cryogenics and delivers them to the Internal cryogenics at the required temperature, pressure, purity and mass flow rate. It includes the argon condensers, liquid and gaseous argon purification and regeneration systems, nitrogen and argon phase separators, piping, valves, and instrumentation. The Internal cryogenics comprises the liquid and gaseous argon distribution inside the cryostats for the commissioning, cool down, fill, and steady state operations of the cryostats and detectors. An international engineering team is designing these systems and will manufacture, install, commission, and qualify them. This contribution describes the main features, performance, functional requirements, and modes of operation of the LBNF Far Site cryogenics system. It also presents the status of the design, along with present and future needs to support the DUNE experiment.
Energy efficient large-scale storage of liquid hydrogen
Authors: Fesmire J , Swanger A , Jacobson J , Notardonato W
Published: June 2022

The world’s largest liquid hydrogen storage tanks were constructed in the mid-1960s at the NASA Kennedy Space Center. These two vacuum-jacketed, perlite powder insulated tanks, still in service today, have 3,200 m3 of useable capacity. In 2018, construction began on an additional storage tank at Launch Complex 39B. This new tank will give an additional storage capacity of 4,700 m3 for a total on-site storage capacity of roughly 8,000 m3. NASA’s new Space Launch System (SLS) heavy lift rocket for the Artemis program includes an LH2 tank that makes up the bulk of the vehicle, holding 2,033 m3 of LH2 in its 8.4-m diameter by 40-m height. The new storage tank includes two new energy-efficient technologies: a glass bubbles insulation system in lieu of perlite, and an Integrated Refrigeration and Storage (IRAS) heat exchanger for controlled storage capability. The evacuated glass bubbles insulation system is based on the prior two decades of research to prove the thermal performance benefits as well as the mechanical and vacuum integrity; and has been shown to reduce LH2 boiloff by 46% versus perlite in field demonstrations. The IRAS capability is centered on a heat exchanger system that is built within the inner vessel to reject heat from the bulk liquid through the future implementation of an external helium refrigerator. Controlled storage via IRAS, when fully implemented, will provide full control of the ullage pressure, zero boiloff, and even production of densified LH2 pending its adoption on future launch vehicles. The design basics are described along with main construction and testing processes involved. The key features of the new technology items and implications on simplified operations and long-term energy savings are addressed.
Conceptual layout of a helium cooling system for the Einstein Telescope
Authors: Busch L , Grohmann S
Published: June 2022

The Einstein Telescope (ET) is a 3rd generation gravitational-wave detector planned in triangular shape with 10 km arm lengths in an underground installation at a depth of 200m to 300 m. While 2nd generation detectors and the ET high-frequency interferometer are operated at room-temperature, the ET low-frequency (LF) interferometer shall be operated at cryogenic mirror temperatures of 10K to 20K in order to reduce the thermal noise. Considering thermal dissipation limits in the heat extraction path from the mirror to the heat sink, He-II provides ultra-low-noise cooling to allow for an interferometer sensitivity at levels below 1 × 10−20 m/

Hz

in the detection band. In order to limit particle adsorption on the cold mirror surface, the total pressure in the cryostat must be reduced to p ≤ 1 × 10−10 mbar, i.e. partial pressures of water and heavier components pi
≤ 1 × 10−14 mbar, respectively, using a cryopump/shield around the mirror that is cooled with supercritical helium to T ≈ 5K.

We present the conceptual layout of a helium cooling system that can provide cooling power for several ET-LF cryostats and their corresponding cryotraps, including mirror cooling at 2K as well as thermal shielding at 5K and at 50K to 80K. A process flow diagram focuses on the cooling system’s key components with their locations and their interconnections. On the diagram’s basis, we explain the cooldown process and steady-state operation, ranging from outer shield and cryotrap cooling to the formation of He-II in the mirror heat extraction path.
Dynamic simulation of the cool down process of double-pressure helium liquefaction cycle
Authors: Su H K , Li Z Y , Gong L H , Zhu W P , Zhang M M , Jia Q M
Published: June 2022

A double-pressure helium liquefaction cycle, which consists of two compressors, six heat exchangers, two expanders and several valves, was proposed in this paper. The thermodynamic parameters of the process were calculated and analyzed. The mathematical models of the above-mentioned key equipment are established, and the cool down process of the helium refrigerator is dynamically simulated. By adjusting the parameters of each valve in the process, the working process of the compressor was simulated, and the cool-down process of heat exchangers and the expanders was obtained and analyzed. Finally the stable refrigeration capacity was obtained. The simulation of the dynamic process has a great guiding role for the actual experimental process afterwards.
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

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

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

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

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

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

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

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

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

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

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

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

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

The 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

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

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

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

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

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.
The experimental measurement of the thermal emissivity of a black coating from 50 K to 300 K
Authors: Zhang S Y , Shen F Z , Liu H M , Huang C J , Li L F
Published: June 2022

High-emissivity coatings are commonly applied in satellite detectors and large-scale cryogenic systems. Accurate and quick measurement of emissivity is in high demand for practical applications at cryogenic temperatures. In this paper, a method for the measurement of the total hemispherical emissivity from 50 K to 300 K was presented based on the static calorimetric method. A two-stage GM cryocooler was used as a cooling source in the measuring device without assumption of cryogenic liquids. The thermal emissivity of a black carbon coating was measured by monitoring temperatures timely in the device. The tested results exhibited good accordance with previous reports. This cryogenic measurement device has made it a strong candidate for the radiative heat dissipation at cryogenic temperatures. Design details of the experiment and measurement results will be presented.
Superconducting-like and magnetic transitions in oxygen-implanted diamond-like and amorphous carbon films, and in highly oriented pyrolytic graphite
Authors: Gheorghiu N , Ebbing C R , Murphy J P , Pierce B T , Haugan T J
Published: June 2022

In our previously published work, we have reported colossal magnetoresistance, Andreev oscillations, ferromagnetism, and granular superconductivity in oxygen-implanted carbon fibers, graphite foils, and highly oriented pyrolytic graphite (HOPG). In this follow-up research, more results on these oxygen-implanted graphite samples are presented. We show results from transport measurements on oxygen-implanted diamond-like carbon thin coatings, amorphous carbon films, and HOPG. Significantly, a three-order magnitude drop in the electrical resistance of the oxygen-implanted diamond-like carbon films is observed at the 50 K temperature that we have previously reported for the transition to the superconducting state. Below 50 K, the films’ resistance oscillates between the high and low resistance states, less when the sample is under a transverse magnetic field. This metastability between the insulating and superconducting-like states possibly reflects the evolution of the amplitude for the superconducting order parameter also known as the longitudinal Higgs mode. Transitions to low resistance state and metastability are also observed for amorphous carbon films. Finally, the HOPG samples’ resistance have a thermally activated term that can be understood on the basis of the Langer–Ambegaokar–McCumber–Halperin model applied to narrow SC channels in which thermal fluctuations can cause phase slips. We also find that in oxygen-implanted carbon materials, the electron charge and spin correlations do not compete and their interplay rather facilitates the emergence of high-temperature superconductivity, and thus, additional unexpected effects like Heisenberg spin waves and magneto-structural transitions are observed.