bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Design of the High-Resolution Volatiles and Minerals Moon Mapper (HVM3) Instrument on the Lunar Trailblazer Mission (LTB)
Authors: McKinley I M , Rodriguez J I , Allen G D , Keller J , Mok M A , Chan L
Published: July 2024

The Lunar Trailblazer (LTB) Mission consists of a spacecraft that hosts two science instruments, the High-resolution Volatiles and Minerals Moon Mapper (HVM3) and the Lunar Thermal Mapper. Flight system delivery is scheduled for the Fall of 2022. The purpose of the mission is to understand the form, abundance and distribution of water on the Moon as well as the lunar water cycle. HVM3 is a pushbroom shortwave infrared (SWIR) Offner imaging spectrometer that is optimized for the detection of volatiles to map OH, bound H2O and water ice. It has a spatial resolution of 70 m/pixel over a 20 km swath width and a spectral resolution of 10 nm over a spectral range of 0.6 µm to 3.6 µm. The spacecraft will deploy from an ESPA Grande and enter a 100±30 km lunar polar orbit where it may operate over all beta angles. The HVM3 thermal control architecture consists of active and passive elements. It leverages the passive cryogenic cooler design developed for the Moon Minerology Mapper (M3) that underwent a similar orbit. The first stage of the passive cooler is used to reject the heat of a Lockheed Martin Micro1-2 cryocooler that is used to actively cool the focal plane array (FPA). The second stage of the passive cooler is used to passively cool the optics. An overview of the overall thermal control design approach is presented.
Superconducting heat switch made from a transition metal
Authors: Gunderson C , Miller F , Jahromi A , Holmes W
Published: July 2024

High sensitivity astrophysics detectors such as transition edge sensor (TES) bolometers or microwave kinetic inductance detectors (MKIDs) require sub-Kelvin operating temperatures for observing low energy photons in infrared and x-ray ranges. Continuous Adiabatic Demagnetization Refrigerators (CADRs) are presently the state of the art solution for providing cooling to these detectors below as low as 50 mK. The CADR shuttles heat through a series of paramagnetic stages from a 50 mK heat load to a 1-6+ K heat sink, using heat switches between stages to “switch” between thermal isolation and thermal communication. A superconducting heat switch is required between the two lowest temperature stages and is considered a critical system component as it determines recycling time and cooling power of the lowest temperature stage. A figure of merit for this technology is the “switching ratio”: the ratio of the thermal conductivity in the on and off states. This ratio is a function of temperature, fixed material properties, and the purity and anneal state of the metal. Lead is most commonly used in this type of thermal switch because it is readily available as a high purity material. However, an analysis of the material properties of other superconducting material suggests that transition metals such as tantalum and vanadium could achieve a significantly higher switching ratio – as high as 5-10 times that of lead. Increasing the switching ratio could allow for shorter recycling times and reduce the parasitic load on the lowest temperature stage. This work discusses relevant properties of various potential heat switch material and compares predicted performance in the CADR against the presently used lead switch.
Experimental performance of a modified Collins cycle cryocooler for in-space applications
Authors: Bunge C D , Siahvashi A , Hannon C L , Brisson J G
Published: July 2024

This paper presents initial experimental results of a modified-Collins-cycle cryocooler designed for space cooling applications. A high efficiency and lightweight single-stage cryocooler design to provide 100 W of cooling at temperatures at 90 K is discussed. With multi-staging, cooling to 4 K is possible. A single-stage room-temperature floating piston-machine is experimentally demonstrated with helium as the working fluid. Cryocooler construction materials and control system methodologies are discussed.
Ball Modular Advanced Cryocooler Control Electronics (MACCE)
Authors: Taylor Ryan , Mock Cameron , Glaister D. , Simons James , Duval David , Kristof Dave
Published: July 2024

To support the application of heritage aerospace coolers and modern tactical coolers to future mission architectures, Ball has developed the Modular Advanced Cryocooler Control Electronics (MACCE). This entirely new cryocooler electronics architecture is based on modularity and scalability in performance supporting a wide range of cryocoolers including 4K Hybrid Systems (J-T + Pre-Cooler), Pulse Tube Cryocoolers, and Stirling Cryocoolers. The MACCE design includes the primary CCE box and an Accelerometer Pre-Amp (APA) box that can be remote mounted. The MACCE architecture includes four high power drive channels and two low power channels supporting >500W of output power, three independent accelerometer feedback control loops for vibration cancellation, high efficiency using GaN FET technology, and a combination of six thermistors and six precision RTD circuits for telemetry. Operational modes include constant power, constant temperature, or open loop. An engineering model of MACCE has been completed and is currently going through qualification. Performance data is presented from box level testing.
Design of 10 L/s liquid hydrogen pump with integrated inducer and centrifugal impeller
Authors: Li Ziwei , Lv Cui , Wang Jinzhen , He Ming , Wu Jihao , Gong Linghui
Published: July 2024

With the global focus on energy and environmental issues, hydrogen energy development has become more and more important. The liquid hydrogen centrifugal pump is an important equipment for hydrogen transportation. In this paper, we designed an integrated impeller and the space guide vane used in 10L/s hydrogen pump. The integrated impeller which is closed structure combined of an inducer and an centrifugal impeller shows better performance than traditional Semi-open impeller. We optimized the structure of the pump and finally obtained the performance curves. This results provide a guidance for the manufacture of the liquid hydrogen pump, and also provide a reference for the design and manufacture of other liquid hydrogen pumps.
Study of backflow volume due to check valve’s lag motion in liquid hydrogen piston pump
Authors: Wu W , Yang S Q , Xie X J , He M , Gong L H
Published: July 2024

The liquid hydrogen piston pump is the key equipment in the process of storage, transportation, and refueling of liquid hydrogen. The timely motions of suction and discharge valves are beneficial to the transport performance and volumetric efficiency of the pump. This study sets up an operation frame of the liquid hydrogen piston pump in which reciprocating pistons and check valves with a conical spool interact. Backflow occurs when there is a delay in the spool’s motion, which is more common in suction valves than in discharge valves. The influence of spring stiffness and spool-head angle of the valve cone on the suction valve’s backflow volume is analyzed and further optimized. The results indicate that there exists an optimal spool-head angle and spring stiffness for minimizing backflow volume during the closing phase of the suction valve. This research contributes to enhancing the volumetric efficiency of the liquid hydrogen piston pump.
Optimization investigation for heat transfer enhancement of fins for plate-fin heat exchangers in cryogenic helium systems
Authors: Zou Zhongyu , Zhu Zhigang , Zhang Qiyong , Yang Pengcheng
Published: July 2024

In order to further improve heat transfer performance and high compactness of plate-fin heat exchangers (PFHEs) in cryogenic helium systems, a new type of perforated-serrated fins is proposed by combining traditional serrated and perforated fins. In this paper, the flow and heat transfer characteristics of helium in perforated-serrated fins and serrated fins channels at low-temperature are investigated using numerical simulations. The numerical model invokes the properties of low-temperature helium by NIST-Real-Gas-Model. Meanwhile, Colburn factor j, friction factor f and JF factor are qualitatively evaluated for pressure drop, heat transfer performance and thermo-hydraulic performance, respectively. The results show that new perforated-serrated fins have better heat transfer performance. The j factor of the new fins increases by 32.58% to 15.63% compared with serrated fins. The flow performance of perforated-serrated fins is slightly worse than that of serrated fins, but the overall thermo-hydraulic performance is better, especially at low Reynolds number. Compared with serrated fins, the JF factor of perforated-serrated fins is significantly higher and increase by 25.95% to 10.86%. The optimizing method of fins structure can be used in the actual design of PFHEs in cryogenic helium systems.
Numerical study of heat transfer characteristics of intermittent flow cold storage surface heat exchanger
Authors: Cui W H , Gong L H , Jia Q M , Li Z Y , He M , Zhu W P , Zhang M M
Published: July 2024

The intermittent flow cold storage surface heat exchanger is a key component of the new pulse tube expansion cryogenic refrigerator, which is responsible for the periodic heat transfer of cold and hot helium, and its heat exchange efficiency directly affects the thermodynamic efficiency of the whole machine. In this study, a three-dimensional model of the heat exchanger unit is established, and numerical simulation is employed to investigate its heat exchange characteristics. The analysis focuses on understanding the internal temperature distribution patterns within the heat exchanger and explores the influence of wall materials on its heat transfer characteristics. Results show that the existence of the temperature lag loop minimizes the effective heat transfer temperature difference, consequently decreasing the heat exchanger’s efficiency. Moreover, the choice of wall material significantly affects the performance of the heat exchanger, with optimal thermal conductivity and volumetric specific heat enhancing its efficiency. This research provides valuable insights for future design and improvement of similar heat exchangers.
Design, configuration, and thermal optimization of advanced cryostats
Authors: Shu Quan-Sheng , Demko Jonathan , Fesmire James , Duckworth Robert
Published: July 2024

To address new challenges in the design of current and future advanced cryostats, guidelines can be developed by leveraging successful technical experience with existing cryostat assemblies. A brief review of eleven representative advanced cryostat designs is presented, based on six typical cooling methods, including cryogen baths, dry cryostats, mixed-cooling method, continuous cryogen flow, dilution refrigeration, and demagnetization. Also provided are engineering figures, tables-plots, and equations that can be used to design, configure, and optimize the thermal performance of cryostats. The following technical data are introduced: optimal Carnot power versus temperature for various two heat intercept stations in cryostat support, ten representative performances of different MLI blankets at various (Th-Tc), and a graphical summary of the ‘MLI patch-cover-crack’ experiments, among others. The cold mass thermally isolated in cryostats could be a quantum apparatus, test specimen, instruments in-space, or superconducting (SC) devices. The cryostat must provide all functional interfaces for obtaining the required data. The design methodologies for crucial components of a cryostat are discussed in-depth, including: 1) creating a lightweight support structure and placing thermal anchors in optimal locations, 2) designing MLI systems with cost-effective thermal shields, and 3) constructing sophisticated structures to accommodate heavy RF couplers or current leads.
Research on matching supply of power and cold energy of liquid hydrogen cold chain logistics vehicles
Authors: Wang J Z , Chao B H , Lv C , Gong L H , He M , Zhang M M , Wu J H
Published: July 2024

Liquid hydrogen cold-chain logistics vehicle (LHCCLV) is a special vehicle using liquid hydrogen (LH2) as the source of both power and cold energy. A significant weakness of LH2 is its high energy consumption during the hydrogen liquefaction process, thus the utilization of cold energy in LHCCLV can improve the economic performance and competitiveness of LH2. Because of the high energy storage density of LH2 and the relatively high efficiency of fuel cells, we find that cold energy can not meet the demand of LHCCLV. Therefore, we consider enlarging the cold energy by efforts including the para-ortho hydrogen conversion (POC), whose reverse reaction consumes an energy level exceeding 20% during the hydrogen liquefaction process. In this paper, numerical models of discharging hydrogen from the LH2 and subcooling hydrogen tank are established, and the influence of POC and other efforts on the supply of cold energy is analyzed. The changes in instantaneous and total cold energy supply under different working conditions are analyzed, and the important influence of POC and other efforts is confirmed. The beneficial effect of POC is quantified in the paper, especially for the cold energy supply. This paper provides an essential reference for the research and development of LHCCLV. Also, it guides the comprehensive utilization of cold energy in other situations to promote the improvement of the economy of hydrogen energy utilization routes in the form of LH2.
Simulation test platform for the controlled storage and transfer of liquid hydrogen
Authors: Fesmire J , Guerrero M , Williams M , Glenn M , Coleman B
Published: July 2024

Clean-energy propulsion machines, including trucks, tractors, ships, and aircraft, for heavy-duty and long-range mobility have moved, by necessity, to onboard liquid hydrogen (LH2). However, the established method of storage and transfer is problematic due to losses and for any duty-cycle of a sporadic or on/off nature. Integral servicing system methodology is needed for both safety and cost effectiveness in the key drivers of time savings, product savings, and venting exposures. Modern controlled storage technology enables quick and effective vehicle servicing at the point of use. Simulations of controlled storage/transfer (CS/T) methodologies are performed using a multi-purpose LH2 simulation test platform comprised of two primary systems: Cryostat CS900 tank and transfer system and the LS20 liquefaction/refrigeration and storage system. Testing includes both steady-state and transient modes of operation to demonstrate both zero boiloff (ZBO) and zero-loss transfer (ZLT) modes. Technical areas of use include product development for tanks, refrigeration, transfer systems (lines, dispensers, pumps, valves); experimental validation of analytical models and thermofluidic properties; thermal insulation performance test data under relevant conditions; thermophysical characterization of materials and structures; instrumentation and sensors development; tank boiloff and heat flux engineering design data. Descriptions and preliminary test results are given along with thermal performance analyses from real-world testing and experimentation.
Assessment of insulation systems for aircraft liquid hydrogen tanks
Authors: Johnson W L , Baltman E , Koci F D
Published: July 2024

Liquid hydrogen (LH2) has ~2.8 times more energy per pound of fuel than Jet-A, however, it requires ~4 times the volume for the same energy. As a result, LH2 aircraft developments are highly dependent on the hydrogen tankage as well as the insulation system requirements. To better understand the sensitivities that hydrogen puts onto the aircraft as a system, Georgia Tech investigators, as part of a NASA preliminary evaluation activity, have developed a single-aisle LH2 passenger jet. As a part of the activity, NASA and Georgia Tech developed the ability to integrate a tank set into the aircraft including insulation systems. Assessments are made on several insulation system options to assess the amount of venting as well as the impacts to aircraft fuel consumption. Based on the results, it is observed that even though polyurethane foam is lightweight, the associated boil-off losses drove the system level mass higher than vacuum jacketed insulations. Composite tanks are observed to decrease fuel system dry mass by several hundred kg over AL5083 tanks.
Liquid hydrogen tank chill and no-vent fill prediction using computational fluid dynamics
Authors: Pesich J M , Hauser D M , Yamashita K G , Baker M C , Sakowski B A
Published: July 2024

Cryogenic tank chill and fill is an important cryogenic fluid management technology that supports and enables many of NASA’s long-duration space missions. For no-vent fill, the receiver tank pressure remains below the supply tank pressure during the entire duration of the fill so that the tank does not require venting. This is especially advantageous for tank fill operations in low gravity where the position of the liquid is not always known and venting the tank may cause loss of propellant by venting liquid. In lieu of expensive tests conducted on-orbit, accurate computational models capable of predicting receiver tank pressure during cryogenic propellant tank fill may be used to reduce system and propellant mass as well as mission risk. However, these numerical models must be validated or anchored to test data. This study presents computational fluid dynamics (CFD) models with conjugate heat transfer that are used to predict a liquid hydrogen tank chill and no-vent fill ground test conducted at Lewis Research Center (now Glenn Research Center) in 1991. The specific test case chosen for model validation implemented an upward-facing jet near the bottom of a cylindrical 34 liter tank. CFD predictions are compared to experimental measurements of tank pressure, fill level, and wall temperature. The CFD results show reasonable agreement to the test data but overpredict the pressure collapse near the end of the fill despite the liquid jet penetrating the liquid-vapor interface.
Development of a measurement system to measure in-situ the ortho/para concentration of liquid hydrogen
Authors: Hannot M. , Beßler Y. , Rosenthal E. , Natour G.
Published: July 2024

Molecular hydrogen occurs in two forms, the so-called ortho-hydrogen and para-hydrogen. At a temperature of 293 K and above, hydrogen has 75% of ortho- and 25% para-content. The content of para-hydrogen increases with falling temperature. At a temperature of 20 K almost 100% para-hydrogen is present. While hydrogen is cooled down and liquefied the exothermic natural conversion starts, but much slower than the liquefaction itself. However, the conversion can be accelerated by using a catalyst. To avoid an unintentionally evaporation due to the exothermic ortho to para conversion it is important to verify that the conversion is completed before the liquid hydrogen is stored, transported or used. To accelerate and to ensure a complete conversion an oversized ortho/para-catalyst is normally used. However, the activity of the catalyst decreases over time. Therefore, a continuous in-situ measurement of the ortho/para-ratio can contribute to effective use of the catalyst and can help to reduce hydrogen losses due to unintentional evaporation. A measurement system based on Raman-spectroscopy is currently being developed at the ZEA-1. First tests with the measuring system show promising results on a laboratory scale. The aim of these investigations is to develop a compact measuring system that measures the ortho/para concentration of liquid hydrogen in-situ.
Multi-scale systematization of damage and failure modes of composite cryogenic hydrogen vessels according to the Fault Tree method
Authors: Schlegel David , Hurtado Antonio , Gude Maik
Published: July 2024

Achieving a safe and lightweight design of composite liquid hydrogen (LH2) vessels without much empirical data requires advanced reliability assessment. An approach based on the Fault Tree method is proposed, to allow the systematization and modelling of functional and structural failure modes and their interactions. A hierarchical system model spanning across the length scales of the LH2 vessel down to the composite material is established. Subsequently, the failure probability of the composite material is estimated in dependence on temperature and load case using Weibull analysis. Using the accident data of US Air Carriers operating under 14 CFR 121 between 2012 and 2019, the probabilities of the load cases are derived, allowing a quantitative reliability analysis of the selected failure modes. Requirements for material and system design are derived in dependence of the maximum allowable failure probability.
Liquid deuterium cold source concept for the NIST neutron source
Authors: Jurns J , Cook J C , Celikten O , Arnold P
Published: July 2024

The National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR) houses an aging reactor that serves more than 40 % of all cold neutron research needs in the U.S. First critical in 1967, the National Bureau of Standards Reactor (NBSR) is now more than 50 years old. NCNR engineers have initiated a design effort for a replacement reactor, namely the NIST Neutron Source or NNS. The NNS is conceived as a 20-MWth light-water cooled and moderated, and heavy-water reflected compact core design. The NNS will include two liquid deuterium cold sources to moderate neutrons to effective temperatures well below that of thermal neutrons. These cold neutron sources will require new cryogenic infrastructure to operate. This report describes a preliminary proposed design concept for the NNS cold sources and associated ancillary infrastructure.
Dynamic simulation of DALS test facility cryoplant
Authors: Sun Z , Wang X L , Hu L B , Xu L , Shi X
Published: July 2024

Dalian Advanced Light Source (DALS) test facility program requires a 370 W cryoplant to meet the cooling requirements of four testbenches. The utilization of dynamic simulation holds significant potential for diverse applications such as process design, control logic optimization, and virtual commissioning. These applications are helpful in facilitating the subsequent stages of commissioning and operation. This paper describes the establishment of a model for the DALS test facility cryoplant based on the Ecosimpro software. The model includes the main components of the cryoplant, incorporating most control loops and sequential control strategies. The simulation encompasses three operation modes, namely liquefaction mode, refrigeration mode and fast cooldown mode. The simulation results match the Temperature-Entropy (T-S) diagram from the manufacturer well. This model will be used in the upcoming commissioning of the cryoplant for resolving challenges that may arise in future operation.
Installation, commissioning, and testing of the HB650 CM at PIP2IT
Authors: White M , Makara J , Ranpariya S , Pei L , Barba M , Subedi J , Dong J , Hansen B , Akintola A E T , Holzbauer J , Ozelis J , Chandrasekaran S , Roger V
Published: July 2024

The Proton Improvement Plan-II (PIP-II) is a major upgrade to the Fermilab accelerator complex, featuring a new 800-MeV Superconducting Radio-Frequency (SRF) linear accelerator (LINAC) powering the accelerator complex to provide the world’s most intense high-energy neutrino beam. This paper describes the conversion of the PIP-II Injector Test Facility (PIP2IT) cryogenic system into a test stand for PIP-II High-Beta 650 MHz (HB650) cryomodules at Fermilab’s Cryomodule Test Facility (CMTF). A description of the associated mechanical, electrical, and controls modifications necessary for testing HB650 cryomodules are provided. The cooldown and warmup requirements, procedures and associated controls logic is described.
The first cooldown of SCL3 cryogenic system
Authors: Yoon S. , Ki T. , Yoo J. , Lee M. , Meyer T. A. , Bodin E. J. A. , Daoudi K.
Published: July 2024

RAON, Rare isotope Accelerator complex for ON-line experiments, is the first superconducting linear accelerators in S. Korea. It will have three linear accelerators (Linac), SCL1, SCL2, and SCL3. Now, construction of the SCL3, the third superconducting Linac was finished in the middle of 2022 and the commissioning of its cryogenic system was done July, 2022. The first cooldown of the Linac with the cryogenic system was started from September, 2022 and their temperature was reached at 2.05 K in January, 2023. The first cooldown was successfully completed and the static and dynamic heat loads of the Linac were measured. This paper shows the results of the first cooldown and the heat load tests.
Effect of a thermal fluctuation caused by a proton beam injection on the ESS large-scale 20 K helium refrigeration system
Authors: Tatsumoto H , Arnold P , Boros M , Horvath A
Published: July 2024

In the European Spallation Source (ESS), a large-scale 20 K helium refrigeration system with a cooling capacity of 30.2 kW at 15 K, which is called Target Moderator CryoPlant (TMCP), has a function to cool the cryogenic moderator system (CMS) that provides subcooled liquid hydrogen with a temperature of 17.5 K to two hydrogen moderators (to be increased to four in the future) and remove nuclear heating generated of 6.7 kW and 17.2 kW for two and four moderators at the proton beam power of 5 MW. The commissioning has been completed by December 2022. We studied the stability of the TMCP operation when the heat load of 5.92 kW and 17.5 kW was rapidly applied and how to mitigate the propagation of the temperature fluctuation in order not to affect the CMS supply temperature.
Cryogenic Testing of Molecular Sieve Materials for use in Hydrogen Liquefaction
Authors: Richardson I. , Saelid G. , Shokrian M.
Published: July 2024

As hydrogen continues to gain momentum as a clean fuel and energy carrier in industrial sectors, hydrogen liquefaction has emerged as an essential part of the supply chain to reduce transportation and storage costs. Hydrogen is typically produced from either electrolysis, steam-methane-reforming, or as a biproduct from chemical processing, which leads to a broad range of potential impurities in the hydrogen feed gas. Molecular sieve materials have traditionally been used to remove impurities in the hydrogen feed to prevent impurities from freezing out during liquefaction, creating blockages which disrupt operations. This work presents a new experimental system that has been developed to study cryogenic purification materials over a broad range of cryogenic temperatures and impurity levels. Results of common molecular sieve materials are presented.
2 K J-T cooler for quantum detection: emphasis on the Stirling-type pulse tube pre-cooler
Authors: Latella T , Prouvé T , Duval J M
Published: July 2024

Quantum detection of single photon achieves its highest sensitivity for temperature below 2 K. The cooling requirements for such application are very low, a few milliwatts for current harness heat intercept and radiation shielding. For that purpose, we are developing a compact cryocooler based on a 4He JT cooler. A high frequency pulse tube will provide the pre-cooling of two intermediate stages on the JT. The pulse tube is the key component for miniaturization and energy consumption. With low cooling power goals, a miniaturization work has been done on the pulse tube with the aim of reducing the size and power of compressor units. The pulse tube configuration is using two cold fingers, connected together by a heat intercept providing precooling for the lowest temperature stage. Cooling power at the cold tip as well as intercept heat flow have been measured. Numerical simulations have been conducted in parallel to study the impact of the size of the pulsation tube and of the regenerator on the pulse tube performances. Three cold units pulse tubes have been tested in similar conditions. Net cooling power, power at the intercept and impact of the tube and regenerator size on performances will be discussed.
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

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

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

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

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

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

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

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

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

An 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

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

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

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

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

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

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.