bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of the cool-down process for the ESS cryogenic moderator system
Authors: Tatsumoto H , Horvath A , Arnold P , Boros M
Published: July 2024

The ESS cryogenic Moderator System (CMS) has been designed to supply a subcooled liquid hydrogen (17.5 K and 1.0 MPa) to two hydrogen moderators where the nuclear heating is estimated to be 6.7 kW (to be increased to four in the future). The CMS is cooled by a helium refrigerator system with a cooling power of 30.3 kW at 15 K. In this study, a one-dimensional simulation code has been developed to understand temperature behaviors during the cool-down process. The operational methods and parameters have been optimized. The CMS cool-down process is divided into three phases (I: gaseous hydrogen above 36 K, II: condensation from 36 to 31 K, and III: liquid hydrogen below 31 K). It turns out from the simulation result that the CMS would be able to be cooled down to the nominal condition of 17 K within 27 hours.
Dynamic systems modeling of the spallation neutron source cryogenic moderator system to optimize transient control and prepare for power upgrades
Authors: Goth N , Liu F , Maldonado B , Ramuhalli P , Howell M , Maekawa R , Cousineau S
Published: July 2024

Through support of the US Department of Energy’s Office of Basic Energy Sciences, Oak Ridge National Laboratory has begun applying machine learning methods to improve accelerator and target performance of the Spallation Neutron Source (SNS). These methods are being applied to the control optimization and power upgrade of the SNS Cryogenic Moderator System (CMS). A numerical model of the CMS has been developed to study these optimizations and system modifications using EcosimPro. This paper compares steady-state and transient numerical results with experimental data. Control optimization studies focused on dampening mass flow, temperature, and pressure fluctuations during sudden losses of accelerator beam power. This analysis was conducted by adjusting five proportional-integral-derivative controllers connected to four flow control valves and one heater. Future efforts include power uprate studies focused on increasing the CMS cooling capacity. The current accelerator power is 1.4 MW; the first target station is being upgraded to 2.0 MW as part of the Proton Power Upgrade effort. The CMS cooling capacity is sufficient for 2.0 MW operation.
Conservation of Helium while Maintaining High System Purity
Authors: White M , Theilacker J , Barba M
Published: July 2024

Recent helium shortages and helium price increases have lead to an increased emphasis being placed on conserving helium. The need to conserve helium must be balanced with need to maintain the high levels of purity necessary to prevent operational problems caused by contamination. Helium losses and contamination control are especially important for test stands that have cryogenic distribution systems operating continuously with frequent changeover of cryogenic temperature components that are being tested. This paper describes a mathematical model to estimate the quantity of helium lost and the purity of the helium after the pump and backfill procedure is complete. The process to determine the optimal time during pump down to cut off pumping and start backfilling is described. There is a tradeoff between trying to achieve the lowest possible pressure during pumping and the quantity of air leaking into the volume while pumping is occurring. An additional benefit of careful selection of pump and backfill parameters in conjunction with real-time pressure monitoring can reduce the labor and time required to complete a successful pump and backfill procedure. This paper is intended to be a tool for engineers to review their pump and backfill procedures and measured data to optimize helium losses, system purity, and labor required.
Cryostat Design for an FEL SCU Demonstrator
Authors: Fuerst J , Bouchard G , Gassner G , Hasse Q , Ivanyushenkov Y , Kasa M , Kraft E , Krejcik P , Nguyen D , Permanyer X
Published: July 2024

A design for a 4.2 K cryostat to support superconducting undulator (SCU) magnets is being developed as part of an SCU free electron laser (FEL) technology demonstrator. An array of several cryostats will be installed as an afterburner at the end of the existing hard x-ray beam line of the LCLS-II facility at the SLAC National Accelerator Laboratory (SLAC). Cryostat requirements include high operational availability, precision positioning and measurement capability to support beam-based alignment, high undulator magnet packing fraction, operational transparency to the electron beam, and compatibility with the existing LCLS hardware and space constraints. A cryocooler-based refrigeration system is appropriate given the scale and operational profile of the demonstration. The design is being developed as part of a collaboration between SLAC and Argonne National Laboratory (ANL) and draws on ANL’s experience with SCUs at the Advanced Photon Source.
Cryogenic infrastructure upgrade for crab cavities validation at TRIUMF
Authors: Koveshnikov A , Matheson B , Lang D , Laxdal R , Pearce C , Kishi D , Keir J , Cheung J , Kolb P , Li R , Bjarnason R , Yao Z
Published: July 2024

The High Luminosity (HL-LHC) upgrade of the Large Hadron Collider at CERN is an example of large-scale international scientific cooperation which spans multiple international partners. Canada through TRIUMF is making an in-kind contribution to the project with the delivery of five crab cavity cryomodules. The cryomodules will be delivered to CERN by 2026 for installation in the LHC. TRIUMF will receive the RF dipole (RFD) crab cavities from a consortium of US labs. In preparation for the assembly of the cryomodules, TRIUMF has undergone a number of upgrades. Chief among these is the preparation and commissioning of a new cryogenic insert for the TRIUMF multi-purpose cryostat to allow testing of the jacketed cavities at 2 K. The insert consists of a heat exchanger and a JT expansion valve. The 2 K pumping power has been augmented from 20 W to > 40 W with the addition of a booster sub-atmospheric pump.
Cryogenic and safety design of the future high field cable test facility at Fermilab
Authors: Bruce R , Tope T , Koshelev S , Theilacker J , Nikolic V , Velev G
Published: July 2024

The HFVMTF (High Field Vertical Magnet Test Facility) is a new experimental facility under development at Fermi National Accelerator Laboratory (FNAL) to test large superconducting magnets (up to 20 tons weight and 1.3 m diameter) in a double bath superfluid helium cryostat (1.9 K and 1.2 bar). Coupled with a superconducting dipole magnet fabricated by Lawrence Berkeley National Laboratory (LBNL), this facility will be able to test future high-temperature superconductor (HTS) cables under a background magnetic field of 15 T for fusion magnets. This paper describes the design of the cryostat and its 1.4-meter diameter lambda plate, as well as the different components for a safe operation of the facility, even during critical events such a magnet quench or a vacuum breaking situation. The project is funded by US DOE Offices of Science, High Energy Physics (HEP), and Fusion Energy Sciences (FES).
Mechanical and process design of the interface to a 20,000 liter liquid helium dewar
Authors: Wright M , Hasan N , Ganni V , Knudsen P , Jones S , Nguyen C
Published: July 2024

A new 20,000-liter (20 kL) liquid helium dewar is being integrated in to the existing cryogenic system at the Facility for Rare Isotope Beams at Michigan State University (MSU-FRIB). This dewar will mainly be used for the helium inventory management at FRIB (preserving helium inventory during unplanned / planned maintenance of the cryogenic system) and also in sharing the capacity to support the various cryogenic refrigeration systems to increase the operational efficiency and availability. It is also designed to interface to future cryogenic system upgrades (i.e., new 4.5 K refrigerators). This dewar has a single large penetration, or ‘neck’, that all the process lines and instrumentation pass through. On top of the ‘neck’ is a vacuum insulated interface box, or ‘neck can’, which houses all the connections between the dewar and the connecting distribution system. Though not generally common, this design approach has been successfully implemented on 5 to 10 kL liquid helium dewars at the Spallation Neutron Source (SNS), Jefferson Lab (JLab), and also at FRIB. It has been found that this approach greatly simplifies the mechanical design, while allowing for multiple process and instrumentation interfaces and still permitting a low heat in-leak. This paper presents an overview of the mechanical and process design of this neck can.
Pressure safety approach for PIP-II cryogenic distribution system and cryomodules
Authors: Soyars William , Banaszkiewicz Tomasz , Dhuley Ram
Published: July 2024

The Proton Improvement Plan-II (PIP-II) is a superconducting linear accelerator being built at Fermilab that will provide 800 MeV proton beam for neutrino production. The linac consists of a total of twenty-three (23) cryomodules of five (5) different types. Cooling is required at 2K, 5K and 40K. The Cryogenic Distribution System (CDS) consists of a Distribution Valve Box, ~285 m of cryogenic transfer line, modular Bayonet Cans to interface with cryomodules, and a Turnaround Can. The cryogenic system must provide protection from over-pressure by sizing pressure relief devices for all volumes and process line circuits. The cryomodule cavity circuits have dual pressure ratings, 4.1 bara when cold and 2.05 bara when warm (T>80K). Worst case relieving cases will be identified. The methods for determining heat flux will be presented. For the relieving occurring in the linac tunnel, flow must vent to outside to avoid an oxygen deficiency hazard. Also, we will present vacuum vessel relief sizing to protect the cryogenic distribution system vacuum shells from over pressure during an internal line rupture. The project is funded by US DOE Offices of Science, High Energy Physics.
Six years’ experience of the XFEL 2K operation
Authors: Barbanotti S , Bozhko Y , Jensch K , Schnautz T , Sellmann D
Published: July 2024

The European X-Ray Free Electron laser (XFEL) has successfully been operated for more than 5 years. The superconducting cavities and magnets being key components of the cryomodules constituting the XFEL linac and injector are operated at 2 K in a liquid helium bath. A four stages cold compressor system is used to return the vapor to the XFEL helium refrigerator with the capability of pumping up to 110 g/s for compensating static and dynamic heat losses at 2 K.

In this paper technical challenges with regard to the cold compressor system such as availability, 2K pressure stability and contamination of the 2K circuit are summarized. Influence of hydrostatic head on operation of all cooling circuits is analyzed. Issues related to the use of some kinds of instrumentation as pressure transmitters, flow meters and level sensors are discussed. The experiment regarding the future XFEL project as doubling of safety valves is described.
Spallation Neutron Source Hydrogen Relief Analysis for the Cryogenic Moderator System
Authors: DeGraff Brian , Howell Matthew , Dominguez-Ontiveros Elvis , Goth Nolan , Williams Wesley , Winder Drew
Published: July 2024

The Spallation Neutron Source at Oak Ridge National Laboratory operates the Cryogenic Moderator System (CMS) which provides hydrogen cooling at 20K to three neutron moderators. Each hydrogen loop is protected by multiple burst discs and reclosing relief valves. As a result of the Proton Power Upgrade project, the CMS moderator loops will hold more hydrogen and thus require piping modifications. Operational experience has demonstrated that transient pressure increases in these hydrogen loops occasionally result in the rupture of the burst discs. The causes for pressure transients in the system that might lead to hydrogen venting are varied and complex, for example loss of vacuum or cooling. Dynamic simulation and analysis of the parameters considered as the worst-case relief venting scenario were performed and will be presented.
Dynamic simulation of CHL at SNS
Authors: Maekawa R , Howell M , Kim S H
Published: July 2024

A dynamic simulation model of Central Helium Liquefier (CHL) has been developed by the process simulation software; EcosimPro™. CHL consists of 4 K and 2 K cold boxes to sustain the operation of LINear ACcelerator (LINAC) which is composed of Superconducting Radio Frequency (SRF) cavities installed in the Cryomodules. 4 K cold box is a modified Claude cycle refrigerator, having LN2 precooler with two Brayton Cycle turbines, followed by the series connected Turbines (Tu3 and Tu4), and a Supercritical Helium (SHe) turbine (Tu5) for high thermodynamic efficiency. The product of 125 g/s of SHe is subcooled at the LHe immersed Heat eXchanger (HX) before supplying to Cryomodules, which has its own precooled HX for He II vapor vs. SHe, to have high liquid yield for He II at 2.1 K. Four series connected Cold Compressors (CCs) keep the LINAC pressure at 0.04 bar for the proton beam acceleration. The paper discusses the modeling of CHL, including four CCs. The benchmark of the model against a design specification of CHL and the validation of CC model is also described in detail.
Characterization of centrifugal compressors operating in FRIB’s sub-atmospheric compression system
Authors: Howard J , Engeda A , Knudsen P , Hasan N , Ganni V
Published: July 2024

Helium cryogenic systems operating below the normal boiling point (of 4.22 K) are required for many modern high-energy particle accelerators to achieve the necessary performance criteria. Temperatures below the normal boiling point are established by lowering saturation pressure below atmospheric conditions using vacuum equipment. FRIB operates a multi-stage string of cryogenic compressors (or ‘cold-compressors’) to achieve the sub-atmospheric pressures required (30 mbar) for the accelerator operating conditions of approximately 2 K. Housed within a vacuum insulated vessel (i.e., the sub-atmospheric cold box), the cold-compressor system re-pressurizes the helium from approximately 30 mbar to above atmospheric pressure condition before injecting the flow back into the helium refrigerator. Despite the implementation of cold-compressors in several existing large-scale cryogenic systems, openly available literature is insufficient to provide the information necessary for a general characterization of the performance and stability for these cold compressors. A one dimensional steady-state model to predict the performance of cryogenic centrifugal compressors has been developed. This model enables performance prediction by using optimally selected enthalpy loss correlations and basic impeller and diffuser geometrical data. The present work provides an initial comparison of the estimated performance of the individual and string of cryogenic centrifugal compressors to the operational / test data. With appropriate validation, the model is anticipated to allow assessment and prediction of optimal operational envelops that ensure stable and efficient operation at different operating conditions.
The SPARC cryogenic system
Authors: Dalesandro A , Weiner A , Kelley J P , Hall K , Trainor J , Herrmann J , Wilder D , Yung R , Quack H
Published: July 2024

The SPARC project at Commonwealth Fusion Systems (CFS) is a tokamak system designed to demonstrate commercially relevant fusion energy and achieve net fusion power output during the first operating campaign, with eventual fusion pulse energies exceeding 1 GJ. The SPARC tokamak includes eight magnet systems, three that use high-temperature superconducting (HTS) tapes. The SPARC cryogenic system (CRYO) consists of three supercritical helium cryogenic loops at nominal temperatures of 8 K, 15 K, and 80 K. CRYO 8 K and 15 K loops cool the HTS magnets to maintain thermal stability and prevent quench, while magnets cooled to 80 K are normally conductive. CRYO provides cold helium using a hybrid system that includes a Brayton-cycle-based cryoplant supporting all CRYO temperature loops, and a fixed volume 8 K blowdown system to remove heat and maintain temperature stability of the toroidal field (TF) magnets during and immediately following fusion pulses. CRYO 4.5 K equivalent peak cooling power is 17 kW for the cryoplant and 2.9 MW for the blowdown system during a 10-second fusion pulse. Primary cryoplant mechanical equipment includes screw compressors, turbo-expanders, heat exchangers, and circulation pumps, while the blowdown system consists of a series of warm and cold helium storage tanks operating at independent temperatures and pressures, with make-up compressors to reset the blowdown system between pulses. CRYO also includes a distribution valve box and multiple vacuum-jacketed (VJ) process lines ranging in nominal diameter from 20 to 600 mm. This paper investigates the various sub-elements which in combination represent SPARC CRYO, and attempts to address some of the technical challenges identified by the team.
Operation of the cryogenic plant at NSLS-II. Problems and Solutions.
Authors: Bozeat B. , Gash W. , Oliva J. , Rose J. , Sikora R. , Sitnikov A.
Published: July 2024

The cryogenic plant operating 10+ years at the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory (BNL) and supplying the liquid Helium for three superconducting Radio Frequency cavities. The objective is the continuous liquid Helium supply without interrupting operation. This paper outlines our experience in troubleshooting of various failures of the cryogenic plant and main considerations regarding the selection of the equipment and components.
LCLS-II Linear Accelerator Cool-Down And Pump-Down
Authors: Ravindranath V , Apte A , Fauve E. , Pflueckhahn D. , Rama B. , Shrishrimal S. , Vyawahare S. , Bhattacharya R , Creel J , Norton R , Mieral A
Published: July 2024

SLAC National Accelerator Laboratory has upgraded to LCLS-II, featuring a 4 GeV superconducting linear accelerator composed of 37 cryomodules and two large helium refrigeration systems with a cooling capacity of 4 kW at 2.0 K. LCLS-II linear accelerator was successfully cooled from ambient temperature to 4.5 K and then to its final operating temperature of 2.0 K (31 mbar). In this paper, we describe the cool-down strategy, provide details of the 2.0 K pump-down results, and discuss the challenges faced during commissioning.
Influences of distributed J-T effect on the performance of mixed-refrigerant Joule-Thomson refrigeration cycle
Authors: Sun Y W , Wang H C , Gong M Q , Dong X Q
Published: July 2024

In a mixed-refrigerant Joule-Thomson (MRJT) cycle, the working fluid usually produces a throttling effect in the expansion element. However, the high-pressure flow in the recuperator could also generate a throttling effect due to the narrow channels, i.e., the distributed Joule-Thomson effect (DJTE). Previously published studies indicated that the cooling performance of cryocoolers would be improved by DJTE accompanying the heat recovery process. However, most of the current research on this phenomenon is focused on the heat transfer characteristics of the cryocooler itself, with a lack of research on the effect of DJTE on the cycle performance in much detail.

Therefore, a detailed investigation of the influence pattern of DJTE on the cycle performance is carried out by combining with the exergy analysis. The simulation is conducted under three quintessential conditions of the recuperator. The results indicate that it is possible to manipulate the DJTE to maintain satisfactory cycle performance under specific conditions. In addition, at a constant minimum temperature difference in the recuperator, the maximum achievable DJTE is closely related to the isothermal throttling effect of the mixed refrigerant. The conclusions of this paper clarify the effect and the application value of DJTE on the cycle efficiency, which provide a reference for determining reasonable operating conditions and ensuring the cycle efficiency in practical applications.
Thermodynamic and exergetic evaluation of CO2 liquefaction for ship transport
Authors: Zheng Pingyang , Zhang Zhentao , Yue Yunkai , Yang Junling , Li Xiaoqiong , Hao Jiahao , Zheng Maowen
Published: July 2024

CO2 liquefaction is significant to ensure CO2 transport safety and improve efficiency. Aiming at the temperature and pressure required for ship transport, this paper examines four liquefaction schemes including the compression refrigeration system, the Linde Hampson system, the precooled Linde Hampson system and the Claude system. The thermodynamic and exergetic ananlysis models are established primarily and total power consumption, liquefaction efficiency as well as exergy efficiency of the four systems are calculated and compared. The precooled Linde Hampson system shows the best performance with the three indicators of 391.74 kJ/kg, 97.97 % and 55.86 %, respectively. Additionally, exergy destruction among the system components are analyzed for Linde Hampson system and precooled Linde Hampson system. The maximum exergy destruction stem is from compressors. Another thing to note is that the proportion of the total exergy destruction with Joule-Thomson (J-T) valves are 19.38 % and 2.63 %, respectively. Furthermore, the replacement of the J-T valve by a liquid expander allowed for 9.35 % and 0.94 % electric power saving for the two systems, respectively. The pressure drop before and after the J-T valve directly determines the effect of this change. The research results could provide some vital reference for choosing proper CO2 liquefaction methods and reducing energy consumption during the process.
Spallation neutron source purifier replacement project for the central helium liquefier
Authors: DeGraff B , Harrell P , Howell M , Maurisak M , Wilson C
Published: July 2024

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) operates the Central Helium Liquefier (CHL) to provide 2K helium refrigeration to the superconducting radio frequency (SCRF) cavities in the linear accelerator (LINAC). To maintain the purity of the helium, the CHL operates a LN2 cooled, dual-bed purifier. This purifier was purchased as a refurbished unit during the construction of SNS about 20 years ago. The current operational issues with the existing purifier will be discussed. The procurement, fabrication status and commissioning plans for this new purifier will also be discussed.
Design of Muon Campus full flow purifier for varying operational conditions and horizontal shipping
Authors: Subedi J. , Tope T. , Hansen B. , Jia Y. , Makara J. , Tillman J. , Tang Z.
Published: July 2024

Constant ingress of impurities in Muon Campus g-2 experiment at Fermilab has resulted in reduction of efficiency of cryogenic expanders and occasional undesired downtime to flush the impurities. Due to insufficiency of current 0.06 kg/s mobile purifier, a full flow purifier is designed to be used in Muon Campus which purifies 0.24 kg/s of Helium throughput of 4 compressors through charcoal bed at 80 K and returns ambient Helium back to the system. The purifier is designed to be operated near liquid Nitrogen temperature during cold operations and up to 400 K during regeneration. Both warm and cold operational range of the purifier has required use of appropriate clearances in design due to expansion and contraction. The vessel of around 5.5 m height which is designed to be operated vertically is to be shipped horizontally. The asymmetrical position of heavy stainless steel heat exchanger in the purifier support frame and 5g vertical load design consideration for shipping has required use of shipping supports and heat exchanger rotational stops to comply with design requirements. FEA of purifier system is performed in cold, warm and shipping cases to verify that the purifier satisfies the design requirements.
The Study and Improvement of Pressure Degradation of Helium Cryogenic System at NSRRC
Authors: Tsai H. H. , Hsiao F. Z. , Chuang P. S. , Li H. C. , Liao W. R. , Chiou W. S. , Chang S. H.
Published: July 2024

This paper is aimed at studying and improving the phenomenon of pressure degradation in a helium cryogenic system. There are two 450W helium cryogenic systems for the Taiwan light source (TLS) and one 890W helium cryogenic system for the Taiwan photon source (TPS) housed at the National Synchrotron Radiation Research Center (NSRRC). The TLS helium cryogenic system is used for one superconducting radio frequency (SRF) cavity and five superconducting magnets. The TPS helium cryogenic system is used for two SRF cavities at the present stage. These three helium cryogenic systems have experienced pressure degradation, which reduced their performance and increased liquid nitrogen consumption for precooling over the past few years. A cryogenic adsorber was set up in an effort to capture the impurities, but this made no difference for pressure degradation in the system. The impurities were comprised of not only gas but also moisture. It was found that the cryogenic adsorber was not efficient enough to remove the moisture. This paper presents the study for the phenomena of pressure degradation. A moisture removal system was designed which is also discussed.
PIP-II cryoplant non thermal cycling updates
Authors: Creus-Prats J , Soyars W , Dhuley R , Martinez A , Hansen B , Jia Y , Wielgos R , Chakravarty A , Goyal M
Published: July 2024

The Proton Improvement Plan-II (PIP-II) is a crucial upgrade to the Fermilab accelerator complex, featuring a new 800-MeV Superconducting Radio-Frequency (SRF) linear accelerator (LINAC) with 23 cryomodules operating at 2 K. The LINAC thermohydraulic conditions are satisfied by the cryogenic subsystems: Cryogenic Distribution System (CDS), a helium refrigerator cold box (CB), a warm compression station (WCS) and a helium recovery system (RSYS). The accelerator has a strict requirement of non-thermal cycling of the LINAC cryomodules during planned and unplanned subsystem outages. This paper presents an integrated reliability analysis of the PIPII cryoplant. The study evaluates both normal and abnormal operating modes, with a focus on identifying integrated scenarios that put subsystems components under stress. The conclusions of this study will help build redundancy to mitigate LINAC thermal cycling risks during planned and unplanned subsystem outages.
Process design for FRIB’s experimental refrigeration system
Authors: Hasan N , Ganni V , Knudsen P , Casagrande F , Howard J
Published: July 2024

The experimental system (ES) for the Facility for Rare Isotope Beams (FRIB) at Michigan State University (MSU) has several segments. Following the acceleration through the three superconducting LINAC segments, the heavy ion beam is guided through the target, a fragment pre-separator and (the A1900) separator segments. There are many beam lines and then it can be split and sent to various experimental vaults and instrumentation, e.g. S800 spectrograph, and the newly proposed High Rigidity Spectrometer (HRS). Presently, superconducting magnets at the target and fragment pre-separator segments, along with the LINAC superconducting cryo-modules, are supported by FRIB’s main central helium liquefier/refrigerator (CHL). The remainder of the cryogenic loads are supported by the legacy NSCL Cryogenic Refrigerator (a re-commissioned Bureau of Mines helium liquefier from the mid 1970’s) and has many obsolete components for reliable operation. Considering the operational reliability of the accelerator, maintainability of the entire cryogenic system at FRIB and ever-growing experimental beam lines – it is logical to segregate the experimental system loads from the accelerator system loads. A new 4.5 K refrigerator along with a thermal shield (55 K) refrigerator are planned to support the operation of these experimental system (ES) loads and make plans for the CHL maintenance. These refrigerators will be able to support a combination of 4.5 K isothermal refrigeration, 4.5 K liquefaction (for magnet lead cooling and transients) and thermal radiation shield loads. The design loads, modes of operation and the planned operation of the FRIB cryogenic system with these refrigeration systems are discussed. This paper outlines the key selection parameters and design modes for the major components, such as the warm compressors, turbo-expanders and heat exchangers.
Modelling and optimization of cryogenic mixed-refrigerant cycles for the cooling of superconducting power cables
Authors: Boehm F , Grohmann S
Published: July 2024

For the green energy transition, the transport of large amounts of electrical energy is needed both in densely populated areas and over long distances. Superconducting power cables represent one possible solution, requiring energy-efficient liquid nitrogen re-cooling stations for an economical operation at cable lengths longer than about 1 km to 2 km.

In this contribution, a model for simulating cryogenic mixed-refrigerant cycles (CMRC) based on the Joule-Thomson effect and an associated optimization algorithm are presented. The distinctive feature of CMRC is the combination of good scalability of the cooling capacity, adaptability of the mixture to the specific application and an inexpensive process design. While the process is relatively simple, the identification of ideal operating conditions and mixture compositions requires complex modelling. In order to optimize these characteristics for CMRC processes, the Differential Evolution algorithm is adapted to a model built in Mathematica. Thermodynamic property data is calculated with the Peng-Robinson Equation of State as part of CoolProp, an open-source thermophysical property library. First simulation results are presented and further improvements are being discussed.
Development of Brayton circulating cooling system
Authors: Gandla S K , Longsworth R C , Sloan R B
Published: July 2024

The Brayton Circulating Cooling System is a unique refrigeration system designed to demonstrate the basic technology needed to provide cold helium gas refrigeration at high pressures to an external superconducting magnet or any remote load for cool down purposes. The system is designed to provide cool down refrigeration from room temperature to target minimum temperatures of approximately 40 K. The system consists of an F-70H helium compressor with gas control manifold, interconnecting gas lines, cables, the Brayton refrigeration unit mounted in a Dewar assembly and control system. The helium compressor uses high purity helium gas for its refrigerant. Electricity, cooling water for the compressor and a source of pure helium (99.995%) for make-up gas are the only required utilities. The scope of the project, system design, target specifications and summary of test results will be discussed in this paper.
Design and performance of the J-T component of dry dilution refrigerator
Authors: Zheng Maowen , Pan Zijie , Wei Lingjiao , Quan Jia , Wang Guopeng , Liang Jingtao , Li Ruixin , Hong Guotong
Published: July 2024

An effective J-T component is crucial for the operation of dilution refrigerator due to its function as a 3He liquefier in a refrigeration cycle. This paper briefly introduces the principle of the J-T component in dry dilution refrigerator, studies the influence of J-T component on the still and its design method. An effective J-T component is designed to cool over 3 K of 3He gas to almost 1 K of 3He liquid. The basic still temperature is below 0.5 K in a dilution refrigerator prototype. In this prototype, a two-stage step heat exchanger was adopted to obtain the lowest temperature below 26 mK.
Development of a 5 W/4.2 K two-stage pulse tube cryocooler
Authors: Hao X , Zerkle B , Cosco J , Dausman R
Published: July 2024

The 2.7 W/4.2 K two-stage pulse tube cryocooler (Model PT425) was developed and introduced by Cryomech, Inc. in 2021, which, at the time, was the largest, commercially available, 4 K pulse tube cryocooler. Our newest model, the PT450, has been successfully developed, providing a minimum of 5.0 W at 4.2 K on the 2nd stage with 65 W at 45 K on the 1st stage simultaneously, operating on either 60 or 50 Hz power. The PT450 answers the market’s need for the continuing development of large cryogen-free dilution refrigerators, superconducting magnets, helium liquefiers and other applications requiring large cooling capacities at 4 K.

In addition, a new helium compressor (Cryomech CPA3027) has also been developed to provide sufficient helium flow for the PT450 and other large cooling power cryocoolers. This new model also allows multiple cryocoolers to operate on one compressor. The CPA3027 is the largest commercially available helium compressor for the Gifford-McMahon and pulse tube cryocooler market.

The system configuration and main cooling performance of the PT450 cold head will be presented in this paper.
Cooling power analysis of a small scale 4 K pulse tube cryocooler driven by an oil-free low input power Helium compressor
Authors: Schmidt J-A , Schmidt B , Falter J , Höhne J , Dal Savio C , Schaile S , Schirmeisen A
Published: July 2024

Here we report the performance of a small scale 4 K pulse tube cryocooler operating with a low input power reaching a minimum temperature of 2.2 K, as well as a cooling capacity of over 240 mW at 4.2 K. The compressor is air cooled and can be supplied by single phase power sockets. With an input power of about 1.3 kW the coefficient of performance reaches values of up to 185 mW/kW, which is among the highest currently reported values for small to medium power pulse tubes. The combination of an oil-free Helium compressor and low maintenance pulse tube cryocooler provides a unique miniaturized, energy efficient and mobile cooling tool for applications at 4 K and below.
Study on a 20 K two-stage thermally-coupled pulse tube cooler with independent ambient displacers
Authors: Ding X.P. , Li Z.K. , Wang X.T. , Zhang Y.B. , Dai W. , Li H.B.
Published: July 2024

Pulse tube cooler has the advantages of higher reliability and longer MTTF compared to Stirling cooler due to the elimination of moving components at the cold end. Pulse tube cooler working at liquid hydrogen temperatures has already become a strong candidate in sensor cooling, high-temperature superconductivity, etc. However, the efficiency of the pulse tube cooler at liquid hydrogen temperatures remains relatively low. In this paper, a two-stage thermally-coupled Stirling-type pulse tube cooler working at liquid hydrogen temperatures is designed and simulated. The first and second stage use independent ambient displacers as phase shifters. The simulation results show that the pulse tube cooler can reach a higher relative Carnot efficiency due to the improvement of the phase distribution of the whole system by using independent displacers. Meanwhile, the influence of factors such as average pressure and operating frequency on the system performance is also discussed.
Accelerator magnet development based on COMB technology with STAR® wires
Authors: Kashikhin V V , Cohan S , Lombardo V , Turrioni D , Mai N , Chavda A K , Sambangi U , Korupolu S , Peram J , Anil A , Goel C , Sai Sandra J , Yerraguravagari V , Schmidt R , Selvamanickam V , Majkic G , Galstyan E , Selvamanickam K
Published: July 2024

This paper reports progress in the development of COMB magnet technology with STAR® wires. A two-layer dipole magnet with 60 mm clear bore has been recently fabricated and tested in liquid nitrogen. The purpose of the test was to determine what kind of critical current degradation occurs in the process of winding the STAR® wire into the COMB structure.
Reengineering the RHIC helium cooled current leads for EIC
Authors: Micolon F , Bruno D , Mi C , Holmes D , Lambiase B , Than R , Tuozzolo J
Published: July 2024

The electron ion collider (EIC) Hadron Storage Ring (HSR) will reuse most of the existing superconducting magnets (SC) from the RHIC storage ring. However, for some sectors of the machine, a modification of the accelerators optics will be required. To do this, the existing RHIC magnet electrical circuits will have to be modified and some superconducting current leads will need to be used at higher current. A work has been conducted to understand the current leads design parameters and their operational flexibility around these parameters, in particular for use at higher current.

This paper details the study of the existing RHIC current leads, their potential for use at higher current and where required the modifications to extend their operational range.
Exergy analysis and improvement of helium internal purifier
Authors: Du J J , Li Z Y , Liu L Q , Gong L H , He M
Published: July 2024

Exergy analysis was applied to the evaluation of helium internal purifier in this paper. The important operating parameters has been given to determine the exergy destructions in components as well as in the entire cycle of internal purifier. The analysis results show that the recovery of liquefied air energy can improve the performance of purifier and the exergy destruction of different heat exchanger is different. Results from the analysis helped evolving guidelines for designing appropriate technological process for practical helium internal purifier. An internal purifier with an optimized structure was designed to remove air impurities up to 10 mol%, beyond previous maximum impurity content. The impact on liquefaction capacity is minimized because of the small consumption of cold flow. The achievable performance was also provided in this paper. The purifier could remove air impurities up to 8 mol%.
Experimental study of two-phase cryogenic cooling of aluminum stator conductors using a single slot test configuration
Authors: Guo Y , Majoros M , Cantemir C G , Kwon J , Kovacs C , Rindfleisch M , Tomsic M , Doll D , Sumption M , Collings E W
Published: July 2024

An important goal to enable widespread adoption of electric aircraft propulsion is to develop higher power density motors and generators which are at the same time highly efficient. One way to do this is to use conductors that can carry higher currents and/or generate lower losses. One approach to this is the use of superconducting windings. However, here we focus on very low resistance normal state conductors operating at cryogenic temperatures. The resistivity of both aluminum and copper drops quickly with decreasing temperature, such that the resistivity of Cu drops by about a factor of 7, and that of aluminum by 10, by the time we reach 77 K (LN2). OSU and Hyper Tech have teamed to develop a motor with liquid cryogen cooled aluminum windings (LN2 or LNG cooled). It includes a multi-slot stator with direct cryogen cooling. Here we present the results of a simple “single slot” test which explores the temperature rise of a pair of conductors in a slot directly cooled by LN2. These two aluminum bars are made of 1100 commercial purity Al alloy were placed in parallel with a 1.6 mm gap, which behaved as 120 mm long cryogenic flow channel. Current densities up to 75 A/mm2 were explored, with LN2 flow rates ranging from 1.9 g/s to 6.4 g/s. Thermocouples and voltage taps were used to capture temperature and voltage data during the experiment. As a result, we found stable cooling and operation at these flow rates and current densities, and we characterized the temperature gradient which developed along the conductor bars.
Validation of Universal Cryogenic Flow Boiling Correlations in Thermal Desktop for Liquid Helium
Authors: Tesny Erin , Hartwig Jason , Ganesan Vishwanath , Mudawar Issam , Mercado Mariano , Johnson Brian
Published: July 2024

Understanding two-phase cryogenic propellant behavior is key to enabling technologies for future spaceflight missions. Developing accurate models of two-phase flow phenomena, particularly in the current work, flow boiling in the heating configuration, is relevant to the propellant transfer process both in 1-g and microgravity. Currently there is a need for more accurate, direct cryogenic data anchored models for various boiling phenomena. Recently, universal correlations for cryogens flowing in heated tubes have been developed for a wide variety of fluids, thermodynamic conditions, and various regimes across the boiling curve, and have been patched to provide a smooth, continuous predictive curve. This paper describes implementation and validation of these correlations into Thermal Desktop to improve predictive performance, with a focus on liquid helium. Results from Thermal Desktop using both the built-in and new correlations are validated against a historical dataset of flow boiling experiments in the heating configuration using liquid helium. Based on results, the new correlations show a substantial improvement over the original built-in flow boiling correlations in Thermal Desktop in predicting the wall temperature as a function of preponderant parameters for this quantum fluid at temperatures greater than the lambda temperature, T
λ = 2.17K.
Critical heat flux of liquid hydrogen, liquid methane, and liquid oxygen: a review of available data and predictive tools
Authors: Baldwin Michael , Ghavami Ali , Mostafa Ghiaasiaan S. , Majumdar Alok
Published: July 2024

Available experimental data dealing with critical heat flux (CHF) of liquid hydrogen (LH2), liquid methane (LCH4), and liquid oxygen (LO2) in pool and flow boiling are compiled. The compiled data are compared with widely used correlations. Experimental pool boiling CHF data for the aforementioned cryogens are scarce. Based on only 25 data points found in five independent sources, the correlation of Sun and Lienhard (1970) is recommended for predicting the pool CHF of LH2. Only two experiments with useful CHF data for the pool boiling of LCH4 could be found. Four different correlations including the correlation of Lurie and Noyes (1964) can predict the pool boiling CHF of LCH4 within a factor of two for more than 70% of the data. Furthermore, based on the 19 data points taken from only two available sources, the correlation of Sun and Lienhard (1970) is recommended for the prediction of pool CHF of LO2. Flow boiling CHF data for LH2 could be found in seven experimental studies, five of them from the same source. Based on the 91 data points, it is suggested that the correlation of Katto and Ohno (1984) be used to predict the flow CHF of LH2. No useful data could be found for flow boiling CHF of LCH4 or LO2. The available databases for flow boiling of LCH4 and LO2 are generally deficient in all boiling regimes. This deficiency is particularly serious with respect to flow boiling.
Optimization of thermoelectric generator power density for cryogen cold exergy recovery
Authors: Sierpowski K J , Gizicki W , Malecha Z M , Chorowski M
Published: July 2024

The article presents the optimization of the power density of a thermoelectric generator (TEG) operating in cryogenic temperature conditions. Optimization of TEG power density was performed as a function of TEG leg length and its effect on TEG performance. The figure of merit (ZT) of the TEG was experimentally verified for the temperature range of a cold sink from 160 to 250 K, which corresponds to the temperature of the wall subjected to the boiling film of LNG. The numerical model proposed in the article was verified by comparison with experimental data, and then used to simulate the operation of the TEG at a cold sink temperature of 80 K corresponding to the wall temperature in the process of LH2 regasification. The obtained results showed that the optimal length of TEG legs is less than 10 mm and depends on the boiling and heat transfer regime. The results of the presented research can be used to improve the effectivity of cold exergy recovery from cryogenic systems.
Thermal conductivity measurements for additively manufactured AlSi10Mg and Al6061-RAM2 Aluminum composites at cryogenic temperatures
Authors: Shenton M , Reising L , Leachman J
Published: July 2024

Advances in 3D printing are disruptive opportunities for material selection and component design in cryogenics. However, thermophysical property measurements for these novel materials are generally unavailable at cryogenic temperatures. This experiment explores the variation in thermal conductivities due to print direction of two aluminium composites (AlSi10Mg and Al6061-RAM). The direct linear heat flow method was utilized to calculate thermal conductivities using a measured wattage input, temperature differential, and Fourier’s Law of Conduction. A multi-measurement linear regression was applied to determine thermal conductivities at fixed average temperatures over the range of 20-100K. The AlSi10Mg composite had a greater thermal conductivity than Al6061-T6 for both printing planes by approximately 230%. The XY-plane print direction resulted in a reduction in thermal conductivity compared with the Z-plane by approximately 30%. The AL6061-RAM composite had effective thermal conductivities smaller than the machined Al6061-T6 by approximately 70% for both print directions. The thermal conductivity in the Z-plane print direction was consistently greater than the thermal conductivity in the XY print direction. Validation studies were conducted utilizing Al6061-T6 and SS-304/304L. The calculated deviation for the validation samples depicted a 20% difference from the National Institute of Standards and Technologies (NIST) recommended reference values. The calculated uncertainty of the experimental system was 5-10%, increasing as temperature decreased. These preliminary measurements depict the need for further analysis on 3D printed composite materials and reverification of common materials due to improvements in current manufacturing methods since the classic experimental measurements were carried out for SS-304/304L and Al6061-T6.
Cryogenic thermo-physical properties of additive manufactured materials
Authors: Weiss Klaus-Peter , Bagrets Nadezda , Schulz Camelia
Published: July 2024

Environmentally friendly aviation is one of the great challenges of this century. One promising approach is electric flight, in which an energy carrier (e.g. liquid Hydrogen LH2) and an electric powertrain work together. Within the scope of the joint project AdHyBau, the overarching goal is the development of new additive processes and fibre composite-metal hybrid designs for use in the cryogenic environment of such an electric propulsion system. Additive manufacturing of complex components for use in the cryogenic temperature range down to 20K (LH2) is one essential component in the production. For the design and optimization of the different components it is necessary to know the thermo-physical behaviour of such materials like high purity copper, Ti6Al4V alloy, Al-Mg-Sc alloy, and Inconell 718. The thermo-physical parameters investigated are thermal expansion, thermal & electrical conductivity and heat capacity. Further production-related influences coming from the method used (SLM, DED or Cold-Spray) and orientational dependences are discussed.

Supported by the Federal Ministry for Economic Affairs and Climate Action of the Federal Republic of Germany. Grant-No.: 20M1904D.
Ultimate Tensile Strengths and Elastic Moduli at 20 K of Additively Manufactured PA840-GSL, A6061-RAM2, and AlSi10Mg
Authors: Adams R , Rinauro G , Leachman J
Published: July 2024

The additive manufacturing (AM) of polymer matrix composites (PMCs) and metal matrix composites (MMC) systems presents novel opportunities for reducing the mass of aerospace vehicles. These solutions also have the potential to reduce the cost of terrestrial applications where cryogenic temperatures are present. To address this need, this paper explores the mechanical characterization of three AM materials at 20 K: a nylon-based PMC PA840-GSL, and two aluminum-based MMCs A6061-RAM2 and AlSi10Mg. A Cryogenic Accelerated Fatigue Tester (CRAFT) used for the mechanical testing is first detailed. Next, ultimate tensile strengths and elastic moduli of the additively manufactured AlSi10Mg alloy and A6061-RAM2 are obtained. Third, the mechanical performance of an additively manufactured PMC liquid hydrogen tank constituent is collected in addition to an analysis on the effect the processing parameters, such as scan spacing, have on the mechanical behavior. A6061-RAM2 exhibited superior mechanical performance and is recommended for structural applications. Variation of PA840-GSL scan spacing resulted in decreased mechanical performance.