bluuebunny/crossref_metadata_2025_split huggingface dataset:
Implementation and testing of a 100 mK ADR backed by a 4He/3He sorption fridge for CMB-S4 project
Authors: Romand Thibault , Schillaci Alessandro , Soliman Ahmed , Steinbach Bryan , Fatigoni Sofia , Prouve Thomas , Durand Jean-Louis , Duval Jean-Marc , Bock James J 
Published: July 2024

Abstract
CMB-S4 is a ground-based experiment that will use large-format bolometer arrays to map Cosmic Microwave Background (CMB) polarization with unprecedented sensitivity, including the search for a B-mode polarization pattern associated with cosmic inflation. The focal planes on which the superconducting detectors are mounted weigh about 20 kg each and must be cooled at 100 mK. To reach this temperature for a first receiver fielding prototype hardware, we have developed an Adiabatic Demagnetization Refrigerator (ADR) used in conjunction with an existing 4He/3He sorption refrigerator.
The ADR unit described here is based on a Chromium Potassium Alum (CPA) salt pill. It is backed by a 3-stage (4He/3He/3He) sorption fridge, coupled through a 3He gas-gap heat switch. This heat switch is connected to a 3He stage of the sorption fridge to dissipate the heat generated by magnetization. The ADR is cycled with a 1.3 T magnetic field. The parasitic field at the detectors’ location during observations is kept below 2.5 µT thanks to a ferromagnetic shield. The pill is supported by Kevlar lines, which are doubly intercepted by the 4He and 3He stages of the sorption fridge to reduce conductive heat losses. With a total recycling time of 12 hours, this cryogenic assembly provides 2 µW of cooling power during 48 hours at 100 mK. The ADR has been designed by CEA/DSBT in France and is now implemented in a cryostat at Caltech.
Advances in Pulse Tube Cooler with Dual-opposed Ambient Temperature Displacers
Authors: Li Haibing , Zhang Yibing , Chen Shuai , Wang Xiaotao , Yang Zhaohui , Yang Mingfa , Dai Wei 
Published: July 2024

Abstract
The pulse tube cooler offers several advantages, such as low vibration, high reliability, and no moving parts at the cold end. However, its efficiency is hindered by the limited phase modulation capability and acoustic power dissipation in the phase shifter. In response to this, Lihan Cryogenics has developed a Stirling pulse tube cooler employing ambient displacers. This innovative cooler comprises a moving magnet compressor with dual-opposed pistons and a co-axial cold finger. By utilizing ambient displacers, the cooler can recover expansion work and enhance cooling efficiency. This article highlights recent advancements in this type of cooler. To simplify manufacturing and increase reliability, the displacers now adopt a rod structure, reducing the requirement for supporting spring stiffness. Additionally, the cooler incorporates dual-opposed room temperature displacers, positioned orthogonally to the compressor piston axis (referred to as “OrthoCoolTM”). This arrangement results in low vibration, reduced flow resistance, and eased assembly and production challenges. Experimental tests demonstrate that compared to the cooler employing inertance tube phase modulation, the new ambient displacer structure effectively enhance system efficiency, achieving a cooling capacity of 100W at 77K with 1455W input electric power. The corresponding relative Carnot efficiency is 20%.
Numerical study on two-stage Stirling cryocooler with a long second expansion space
Authors: Kim B , Kim J , Jeong S , Caughley A 
Published: July 2024

Abstract
Design of two-stage Stirling cryocooler with a unique long second expansion space volume is proposed to effectively reduce the displacer length and mass. The thermodynamic performance of this cooler which is similar to a pulse tube cryocooler with the warm-end expander is investigated by the numerical analysis. The long expansion space at the second stage behaves as a pulse tube with a temperature gradient along the longitudinal direction. Similar to the conventional two-stage Stirling cryocooler, the displacer simultaneously recovers the expansion work at the first stage expansion space and the warm end of the second stage expansion space. Although the long expansion space is an additional compliance volume to the second stage, the stepped displacer can still produce sufficient phase shift for both regenerators at the first and the second stages. This configuration brings the advantage of recovering the expansion work and eliminating the moving part at the coldest region of the cooler. The designed two-stage Stirling cryocooler has a cooling power of 10 W at 50 K and 30 W at 100 K with the input PV power of 352.9 W. The detailed thermal analysis presents its characteristic with the comparison to a conventional two-stage Stirling cryocooler which has the same displacer diameters.
Experimental study on a single-stage adiabatic demagnetization refrigerator with Chromium Potassium Alum
Authors: Zhao Shubao , Wang Guopeng , Wei Lingjiao , Wu Qian , Pan Zijie , Lei Yilin , Zheng Maowen , Xia Mingjun , Liang Jingtao 
Published: July 2024

Abstract
As an excellent paramagnetic material with low Curie temperature, Chromium Potassium Alum (CPA) is commonly used in the adiabatic demagnetization refrigerator (ADR) to achieve extremely low temperatures. A typical ADR consists of many components, such as a salt pill, a superconducting magnet, a heat switch, etc. An experimental system was built to test the performance of a single-stage ADR we designed. A two-stage GM refrigerator was used to provide ADR with a low-temperature environment of less than 4 K. A superfluid helium bath was connected to the ADR, via a mechanical heat switch. In the experiment, the CPA salt pill can be pre-cooled to 1.35 K by the superfluid helium bath. A superconductor power supply is used to magnetize and demagnetize the crystal. After applying a 1 T magnetic field, the single-stage ADR can obtain a minimum temperature of 318.5 mK.
Optimal Leveraging of a Gifford-McMahon Cryocooler’s Regenerative Cooling Power for SNSPD Applications
Authors: Cooper B. E. , Chase S. , Namburi D. , Morozov D. , Parker J. T. , Hadfield R. H. 
Published: July 2024

Abstract
Superconducting nanowire single photon detectors (SNSPDs) offer unparalleled efficiency, minimal dark count rates, and picosecond jitter, making them ideal for single photon detector applications across the visible to mid-IR spectrum. A common cryogenic system used to reach these detectors’ optimal operating temperatures (>1 K) consists of Sumitomo’s compact RDK101 Gifford McMahon Cryocooler (GMC) running on an Zephyr air cooled compressor, coupled with a helium four (4He) adsorption stage. In this work, our aim is to provide measurements of the RDK101 GMC second stage regenerator tube cooling power at several locations along its length. We then characterise the performance of the adsorption cooler with heat loads applied to the regenerator tube. Our measurements demonstrate that heat loads of 1.2 W can be intercepted at the tube’s section near the GMC’s first cooling stage, with a negligible effect on the performance of the adsorption cooler. The thermal conductivity of yellow brass coaxial was characterised from 4 K to 40 K. Here we show that the heat load from 64 coaxial cable can be optimally intercepted with the defined regenerator cooling power. These results indicate that a 1024-pixel SNSPD array using a 32x32 row column multiplexing architecture could be successfully implemented in this cryogenic platform.
Energy of Fluid (EOF) Simulation of Large-Scale Densification and Solidification of Hydrogen
Authors: Mahony C , Marchetta J G , Swanger A M 
Published: July 2024

Abstract
The current research develops a finite volume-based Computation Fluid Dynamic (CFD) model utilizing an Energy of Fluid (EOF) approach to generate a simulation of the densification of liquid hydrogen (LH2) in the Integrated Refrigeration and Storage (IRAS) experimental tank for the Ground Operations Demonstration Unit for Liquid Hydrogen Project (GODU-LH2) at the Kennedy Space Center (KSC). The computational code will integrate a commercial software pressure-based model with User Defined Functions (UDF) generated and added to the model. The modified model will solve the energy equation in terms of internal energy and provide temperature and pressure calculations for a given tank geometry. This method will decrease computational time when compared to the built-in commercially available Enthalpy solvers. Currently the research focused on utilizing User Defined Scalars (UDS) compared to the enthalpy model and a lumped node analysis to show the written UDS is as accurate as the built-in solvers, and the models will be verified using known solutions for solidification and validated with the experimental results from the Cryogenics Test Laboratory (CTL) at KSC for the IRAS densification process.
Thermomechanical optimization of actively cooled thermal shield in PIP II Cryogenic Distribution System
Authors: Banaszkiewicz T , Chorowski M , Dhuley R C , Duda P , Martinez A , Poliński J , Soyars W M , Stanclik M 
Published: July 2024

Abstract
The PIP-II Cryogenic Distribution System (CDS) connects the cryogenic plant to the superconducting linac consisting of 23 modules. The helium stream flow through the PIP-II CDS is regulated by means of control valves located in the Distribution Valve Box. The cryomodules are supplied with helium from individual Bayonet Cans. The entire CDS process lines are shielded from the thermal radiation from the ambient vacuum jacket by actively cooled thermal shields. High efficiency of the thermal shield has been achieved by state-of-the-art optimization of its thermalization system consisting of thermal bridges connecting the shield to the high temperature helium return pipe nominally at 80 K. The temperature and stress analyses of the thermal shield have been performed numerically. The results obtained for the thermal shield of the PIP-II CDS Distribution Valve Box are compared with the solutions applied in other large science machines.
Parametric analysis of the Charge-Hold-Vent method for cryogenic propellant tank chilldown
Authors: Mercado M , Hartwig J 
Published: July 2024

Abstract
In the absence of external heat exchangers, the on-orbit transfer of cryogenic propellants requires the receiver tank to first be quenched to a sufficiently low energy state to allow for a continuous no-vent fill to avoid unnecessary venting of liquid. One proposed method for tank chilldown that minimizes the potential for venting liquid is the charge hold vent (CHV) method. CHV follows a cyclic process that gradually removes thermal energy from the receiver tank by injecting liquid with the vent valve closed and allowing the fluid and wall to reach near-thermal equilibrium before venting the superheated vapor. However, the CHV method must be optimized to minimize complexity, mass, and time. This paper presents a modular CHV analytical model used to quantify the number of cycles and propellant mass consumed based on first principles. The model is used to examine the effect of eight parameters: receiver tank material, volume, mass, maximum expected operating pressure, and initial pressure, liquid injection pressure and temperature, and the target temperature. The model is validated against the only two available CHV datasets. Based on results, the tank mass-to-volume ratio is the most important factor in determining the number of CHV cycles and thus degree of difficulty in tank chilldown. The model can easily be used for early-stage design, sizing, and analysis of cryogenic propellant transfer systems.
Modified 3ω conductivity technique for measurements of thermal conductivity in cryogenic fluids
Authors: Hamilton Ben , Brisson J G 
Published: July 2024

AbstractAn instrument based on a modification to the 3-omega thermal conductivity technique that allows precise measurement of thermal properties in fluids is presented. Existing hot-wire techniques have difficulty measuring thermal conductivity because of the effects of natural convection distorting the measurement, however the standard 3-omega technique has been used extensively in the measurement of the properties of solids with great success. To address the challenge posed by natural convection in fluids, we modify the boundary condition of the 3-omega device configuration to be finite in extent, thereby restricting fluid motion and enabling a direct high-precision measurement of a fluid’s thermal conductivity. This modified scenario also presents an opportunity for a simultaneous measurement of the thermal diffusivity of the fluid. The behavior of the device is described with the reformed boundary conditions to show how a simultaneous measurement is made. By applying a constant temperature finite boundary condition, the solution characteristic in the frequency domain gains features that allow for simultaneous measurements of the fluid thermal conductivity and diffusivity. Given the density of the fluid, measured separately, the specific heat of the fluid can be calculated. The effects of the thermal properties of the measurement wire influence the measurement characteristic, and only when the wire thermal properties are sufficiently small compared to those of the fluid can a simultaneous measurement be made. Due to limitations in the dynamic reserve of the measurement devices, a setup is described that allows the signal of interest to be extracted and a precise measurement to be made with minimal distortion. Initial data on the thermal conductivity of helium is presented in the 4-300K temperature range. Preliminary specific heat data is also presented. Limitations on the device’s thermal properties prevent a specific heat measurement above 70K. This data is compared with reference fluid properties databases to validate the device performance.
High-cycle fatigue strength of 22Cr-12Ni austenitic stainless steel at 77 K
Authors: Bratasena M E , Kato T , Umezawa O , Ono Y , Komatsu M 
Published: July 2024

Abstract
The high-cycle fatigue strength of 22Cr-12Ni austenitic stainless steel was evaluated at 77 K for three types of materials with partially recrystallized (PR), finely recrystallized (FR), and solution-treated (ST) microstructures. Subsurface crack initiation was detected at the lower stress level and/or higher cycles in the materials, such that the fatigue crack initiation sites were shifted from the specimen surface to the interior of the specimen with increasing cycles. The ST showed a significant decrease in fatigue strength over 106 cycles due to subsurface crack initiation. Both PR and FR showed a significant improvement in their high-cycle fatigue strength in the high-cycle regime, although the increase in fatigue strength in the low-cycle regime was approximately equal to the increase in tensile strength.
Strength and Fracture Toughness of Type 304 and 316 Austenitic Stainless Steels at 4.2 K
Authors: Sakurai Takeru , Umezawa Osamu , Ono Yoshinori 
Published: July 2024

Abstract
The tensile properties and fracture toughness of type 304L, 316L and 316LN austenitic stainless steels and their weldments at cryogenic temperatures have been summarized in the literature. Rolled plates showed a trade-off relationship between 0.2% proof stress and planestrain fracture toughness with those at 4.2 K. The 0.2% proof stress increases with increasing C+N content, and the fracture toughness depends on their austenite stability to α’-martensitic transformation at the crack tip. The formation of shear bands at low strains is directly related to fracture toughness. The stacking fault energy represents the shear-band formation as well as slip deformation manner, so alloy design with higher Ni, Mn, and Mo contents in the chemical composition range of 316LN would be desirable to improve fracture toughness due to higher stacking fault energy.
Magnetic Laminates for Motor Slot Wedges and Other Applications
Authors: Krzak A. , Matula G. , Nowak A.J , Ebbing C. , Haugan T. , Sumption M. 
Published: July 2024

Abstract
We have examined the properties of G-10-Fe, a commercially manufactured fiber-reinforced epoxy with a 70 wt% inclusion of Fe powder, and the advantages of this material in motor slot wedges are presented. The microstructure of G-10-Fe was observed by SEM/EDS and its magnetic properties were measured in terms of magnetization, saturation magnetization and AC loss. The saturation magnetization was 150 Am2/kg, as determined by vibrating sample magnetometry (VSM). Core losses were measured by spinning magnet calorimetry (SMC). In loss measurements made at applied field frequencies of 10 to 120 Hz essentially only hysteretic loss was present, the per cycle loss was ≅ 19 mJ/cm3. The absence of eddy current loss made G-10-Fe more suitable than bulk Fe for use as motor slot wedge material.
Tuned Windings: the window of opportunity for the implementation of solid conductors in high frequency cryogenic electric machines
Authors: Bruj Olivia-Ramona , Majoros Milan , Sumption Michael , Cantemir Codrin-Gruie (CG) 
Published: July 2024

Abstract
Optimization techniques can significantly improve the performance of electrical machines. The analysis and the optimization algorithms focus on computational efficiency. In this paper, the optimization of a high frequency electrical machine in cryogenic conditions is proposed. The losses introduced by AC current in a conductor are directly proportional with the applied frequency in terms of skin effect and proximity effect. The stator coil, made from two aluminium (Al) turns, in the presence of cryogenic coolants has been analysed at frequencies up to 1000 Hz. In order to reduce the AC losses introduced by the magnetic fields, Nonlinear Conjugate Gradient (NCG) method has been applied for the stator coil thickness optimization. Frequency dependence is observed in most simulations. In the presence of Liquid Hydrogen (LH2) coolant, Al 1100 conductor presents the minimum power loss.
Scanning Raman Spectroscopy Characterization of 1 Meter Long REBCO Coated Conductor
Authors: Castaneda N , Majkic G , Goel C , Robles F C , Selvamanickam V 
Published: July 2024

Abstract
In this work, we evaluate the use of scanning Raman spectroscopy for characterizing long lengths of REBCO coated conductor tapes, as it can provide detailed insight into structure, composition, and local variations arising from defects or strain. We generate 2D maps of Raman wavelength and intensity features over extended 1 meter length of conductor and correlate them to the information collected by reel-to-reel (R2R) 2D X-Ray Diffraction (2D-XRD) and R2R Scanning Hall Probe Microscopy (SHPM). The three methods are compared in terms of depth of information, detectability of variation in features of interest and the potential for evaluating critical current performance over a range of fields and temperatures.
New concept for cryogenic gaseous hydrogen-cooled lightweight electric engine
Authors: Pohl M , Grothe R , Spitzer S , Gude M , Modler N 
Published: July 2024

Abstract
This paper presents parts of the engineering design process and the resulting concept for an electric engine for aviation purpose. Based on the requirement classes mentioned in [1], the concrete requirements resulting from flight operation and the approach of cooling with cryogenic gaseous hydrogen are first compiled. Then, the selected electrical concept of a 500 kW engine is presented, which serves as a basis for identifying the required components and their arrangement. Compared to conventional electric motors, additional components are required. These include hollow coils, structures to distribute the cold gaseous hydrogen to the coils and elements to support the stator laminations with the coils. Materials are then selected for these components with the aim of minimizing weight, and their geometries are predimensioned using analytical approaches and numerical methods. Finally, the individual concepts are synthesized into an overall concept. The result is a compact design for a cryogenically cooled electric motor with a power density of more than 10 kW/kg and a mass of less than 50 kg.
Impact of cryogenic temperatures on high-power semiconductor performance
Authors: Kwon J. , Tomsic M. , Collings E.W. , Sumption M.D. 
Published: July 2024

Abstract
Power electronics is necessary for the independent control of the stator windings of electric aircraft motors. The benefit of using liquid fuel to cool conductors to utilize their high current density has enabled power electronics to be cooled by proxy. While small scale semiconductors have been found to be degraded during operation at cryogenic temperatures, results for systems rated for high power cryogenic applications have not been explored as much. In this work we test the performance of IGBT power electronics from room temperature to 77 K, with a focus on temperatures expected for electric aircraft motors using liquid natural gas (LNG, BP about 120 K) as the cooling medium. In this work, the measure of performance was taken to be the ability to be turned on and off (switched) by an input signal provided by a function generator. We also tested the cold-start ability i.e., the lowest temperature in which the power inverter will start. The lowest cold-start temperature was measured as 140 K. Experimentally, we also observed that both conduction losses and switching loss from a low-power constant current with an operational frequency of 10 kHz were sufficient to allow the inverter to work down to 105 K (below the LNG boiling point).
Graphene oxide based plasmonic nano-cavity sensor for high-performance refractive index sensing
Authors: Roy Bapita , Majumder Saikat , Chakraborty Rajib 
Published: July 2024

Abstract
In this work, a nano-cavity based metal-insulator-metal structure is proposed which can be used as a high-performance refractive index sensor. The analysis of its sensing capabilities is done by determining the transmission characteristics of light through the insulating air channel between the metal layer. The loss in transmission in this channel is indicative of light leaking out of it and portion of it getting coupled to nano-cavities considered in the metal layers on both sides of the air channel. The analyte, whose refractive index is to be sensed, is kept in these nano-cavities. The basic structure is modified by introducing graphene oxide (GO) on the inner wall of the nano-cavity, which further improves the confinement of light in the nano-cavities. It is also shown that increasing the number of nano-cavity duos enhances the transmission loss through the waveguide and as a result the light energy confinement in the cavity increases. Calculated values of sensitivities and Figure of Merit of the proposed sensor structure are much higher than similar works done previously. The uniqueness of the work is two-fold; namely use of graphene oxide as an inner layer of the nano-cavity improves the sensitivity of the sensor and secondly calculating the waveguide transmission to indirectly determine the confinement of light energy in nano-cavity simplifies the analysis of the performance of the proposed sensor. The structure is simple and can be easily fabricated using a standard fabrication process.