bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of the electromagnetic and hadronic prototype segments of the ALICE Forward Calorimeter
Authors: Aehle M. , Alme J. , Arata C. , Arsene I. , Bearden I. , Bodova T. , Borshchov V. , Bourrion O. , Bregant M. , van den Brink A. , Buchakchiev V. , Buhl A. , Chujo T. , Dufke L. , Eikeland V. , Fasel M. , Gauger N. , Gautam A. , Ghimouz A. , Goto Y. , Guernane R. , Hachiya T. , Hassan H. , He L. , Helstrup H. , Huhta L. , Inaba M. , Inukai T. , Isidori T. , Jonas F. , Kawaguchi T. , Keidel R. , Kim M.H. , Kozhuharov V. , Kumaoka T. , Kusch L. , Loizides C. , Melikyan Y. , Miake Y. , Minafra N. , Nystrand J. , Novitzky N. , Økland T. , Oyama K. , Park H. , Park J. , Pascal I. , Peitzmann T. , Protsenko M. , Räsänen S.S. , Rarbi F. , Rauch M. , Rehman A. , Richter M. , Röhrich D. , Røed K. , Rusu A. , Rytkönen H. , Sakai S. , Sato K. , Schilling A. , Shimizu S. , Shimomura M. , Simeonov R. , Solheim E. , Sugitate T. , Tambave G. , Tapia Takaki D. , Tourres D. , Tymchuk I. , Yi J. , Yin Z. , Ullaland K. , Yang S. , Yokoo T. , Zhou D. , Zillien S.
Published: July 2024

We present the performance of a full-length prototype of the
ALICE Forward Calorimeter (FoCal). The detector is composed of a
silicon-tungsten electromagnetic sampling calorimeter with
longitudinal and transverse segmentation (FoCal-E) of about 20X
0 
and a hadronic copper-scintillating-fiber calorimeter (FoCal-H) of
about 5λ
int. The data were taken in various test
beam campaigns between 2021 and 2023 at the CERN PS and SPS beam
lines with hadron beams up to energies of 350 GeV, and electron
beams up to 300 GeV. Regarding FoCal-E, we report a
comprehensive analysis of its response to minimum ionizing particles
across all pad layers, employing various operational modes including
different pre-amplifier and bias voltage settings. The longitudinal
shower profile of electromagnetic showers is measured with a
layer-wise segmentation of 1X
0. As a projection to the
performance of the final detector in electromagnetic showers, we
demonstrate linearity in the full energy range, and show that the
energy resolution fulfills the requirements for the physics needs.
Additionally, the performance to separate two-showers events was
studied by quantifying the transverse shower width. Regarding
FoCal-H, we report a detailed analysis of the response to hadron
beams between 60 and 350 GeV. The results are compared to
simulations obtained with a Geant4 model of the test beam
setup, which in particular for FoCal-E are in good agreement with
the data. The energy resolution of FoCal-E was found to be lower
than 3% at energies larger than 100 GeV. The response of
FoCal-H to hadron beams was found to be linear, albeit with a
significant intercept that is about factor 2 larger than in
simulations. Its resolution, which is non-Gaussian and generally
larger than in simulations, was quantified using the FWHM, and
decreases from about 16% at 100 GeV to about 11% at 350 GeV.
The discrepancy to simulations, which is particularly evident at low
hadron energies, needs to be further investigated.
The Linac Extension Area at the Advanced Photon Source
Authors: Wootton K.P. , Berg W.J. , Borland M. , Brill A. , Byrd J.M. , Chitra S. , Collins J. , Dooling J.C. , Edwards J. , Erwin L. , Fystro G. , Grabinski T.L. , Henry M.J. , Heyeck E. , Keane R. , Lee S.-H. , Lenner J. , Lobach I. , Lumpkin A.H. , Puttkammer A. , Sajaev V. , Sereno N.S. , Sun Y. , Wang J. , Wang S.Y.G. , Zholents A.A.
Published: July 2024

The Linac Extension Area has been developed into a beamline
area for testing accelerator components and techniques. Beginning
commissioning activities in February 2023, we have delivered the
first electron beam to the Linac Extension Area at the Advanced
Photon Source at 425 MeV. In the present work, we summarise the
principal accelerator components and review safety controls of the
Linac Extension Area.
Markovian dynamics for a quantum/classical system and quantum trajectories
Authors: Barchielli Alberto
Published: July 2024

Quantum trajectory techniques have been used in the theory of open systems as a starting point for numerical computations and to describe the monitoring of a quantum system in continuous time. We extend this technique to develop a general approach to the dynamics of quantum/classical hybrid systems. By using two coupled stochastic differential equations, we can describe a classical component and a quantum one which have their own intrinsic dynamics and which interact with each other. A mathematically rigorous construction is given, under the restriction of having a Markovian joint dynamics and of involving only bounded operators on the Hilbert space of the quantum component. An important feature is that, if the interaction allows for a flow of information from the quantum component to the classical one, necessarily the dynamics is dissipative. We show also how this theory is connected to a suitable hybrid dynamical semigroup, which reduces to a quantum dynamical semigroup in the purely quantum case and includes Liouville and Kolmogorov–Fokker–Planck equations in the purely classical case. Moreover, this semigroup allows to compare the proposed stochastic dynamics with various other proposals based on hybrid master equations. Some simple examples are constructed in order to show the variety of physical behaviors which can be described; in particular, a model presenting hidden entanglement is introduced.
Design and Optimization of a High Frequency Miniature Pulse Tube Cryocooler
Authors: Li Geyang , Feng Tianshi , Gao Min , Liang Menglin , Tang Qingjun , Xun Yuqiang , Chen Houlei , Zheng Maowen
Published: July 2024

A micro coaxial pulse tube cryocooler has been developed for infrared detection. This paper presents the experimental data of performance and describes the optimization process of a pulse tube cryocooler in detail. With a tiny size and high frequency, this cryocooler is driven by the linear compressor. The combination of inertance tube and buffer is adopted as phase shifter. The effect of the structure and operating parameters on cooling performance are investigated through experiments. As a result, the regenerator has a dimension of 40 mm length, and the optimal frequency is 175 Hz. It can provide a cooling power of 0.5 W at 80 K with a 30 W input electric power and 0.8 W at 150 K with a 10 W input electric power.
Transient Liquefaction on the Lunar or Martian Surface Operational Demonstration
Authors: Johnson W L , Balasubramaniam R , Grotenrath R J , Giddens P A , Smith J W
Published: July 2024

As developments of local production of cryogenic fluids on the Lunar or Martian surface progress, it is important to understand transient system responses to help with the balancing of process plant power and understanding system-level operations. During the Cryogenic Fluid In-situ Liquefaction for Landers (CryoFILL) testing, a series of transient oxygen liquefaction tests were completed. These tests included varying liquefaction flow rate, environmental temperature, tank fill level, and effective cryocooler lift while allowing the tank pressure to respond to the input controls. An additional transient test was run at the 90% fill level to determine the impact of injecting the gaseous oxygen at the bottom of the tank, allowing the vapor to bubble up through the liquid. Tests were run in a cyclical nature varying one variable at a time. The control variable was set in a manner to increase tank pressure for a period of time and then subsequently changed in a manner to decrease the tank pressure back to its original value with multiple cycles run for all tests. Tank pressure and system temperature responses were tracked as a function of time with an emphasis on repeatability. Results indicate that of the four variables tested, the environmental temperature is the least important. As expected, the bubbling of the liquefaction gas significantly decreased the pressurization and depressurization rates in the tank at the 90% full level.
Improvement of the two-stage Stirling cooler below 20K
Authors: Yasuda A , Otsuka K , Tsunematsu S , Hiratsuka Y , Kanao K
Published: July 2024

Sumitomo Heavy Industries, Ltd. (SHI) supplies 4K-class and 1K-class cooler for space use. The 4K-class and 1K-class cooler consists of Joule-Thomson (JT) cooler and two-stage Stirling cooler as a pre-cooler. To improve the cooling capacity of 4K-class and 1K-class coolers, we are developing the cooling capacity of two-stage Stirling cooler below 20K. The performance of the two-stage Stirling cooler essentially depends on the volumetric heat capacity of its regenerator. We investigated new materials which has higher volumetric heat capacity than stainless steel used in current model, and succeeded improve the cooling capacity of the two-stage Stirling cooler. This paper describes the numerical estimation and the results of cooling tests of the two-stage Stirling cooler using new materials.
Characterization testing of the Northrop Grumman MiniCoolerPlus (MCP)
Authors: Rich N , Amouzegar L , Petach M , Colbert R , Dair E , Russo J , Durand D , Hua J
Published: July 2024

Northrop Grumman Space Park (NGSP) introduced the Mini Cooler Plus (MCP) to their family of pulse tube cryocoolers in 2019 [1] and presented the details of its TRL6 qualification testing in 2022 [2]. The thermal mechanical unit (TMU) of the MCP is an extension of space-qualified pulse tube coolers, all of which are designed to provide a long life (ten-plus years) of delivering low-mass, high-cooling capacity for hyperspectral and infrared imaging payloads in tactical airborne and space applications. The cooler is of modular split configuration allowing flexibility in the compressor (wave generator) and cold head placements to meet the available envelope of packaging constraints. The cold head assembly can be oriented at any position relative to the compressor assembly, and the transfer line (length and shape) can be customized to individual applications. The TMU (thermo-mechanical unit) weighs less than 3kg and can lift 1.5 W at 45 K or 11 W at 110K with 150 W electrical input at 300 K reject. The thermal performance has been characterized as a function of input voltage and as a function of cold tip load and temperature at variety of heat sink temperatures of -20C, 0C, +20C and +40C. Functional testing of the MCP was performed to higher input powers and MCP performance data versus operating conditions were collected. An analytical expression for cold tip load (Qc), impedance (Z) and power factor (PF) as a function of reject temperature (Trej), cold tip temperature (Tc), frequency (f), and input power (Pac) were generated. These tests were repeated with third party control electronics. All results will be presented here.
Simulation and analysis on heat leakage structure of cold compressor in large-scale refrigeration system
Authors: Chen H Y , Shang J , Wang J Z , Liu S H , Lv C , Wu J H
Published: July 2024

Large-scale helium cryogenic refrigeration facilities are indispensable equipment for many cutting-edge researches, and the cold compressor is the most advantageous pressurization scheme in superfluid helium systems with capacity of more than 200 watts. Due to the extremely low operating temperature zone of the cold compressor, the efficiency of the compression process decreases as the external heat leakage increases, especially when building systems with greater cooling capacity, this phenomenon becomes more significant. In order to reduce the influence of heat leakage, a conjugate heat transfer analysis is carried out on the cold compressor using commercial CFD software, and the internal structures, including thermal anchor, thermal insulation materials, are analysed and optimized base on the simulations.
High-speed tilting-pad gas journal bearing flow field analysis
Authors: Shi N Y , Li K R , Ke C L , Qiu S , Dong B , He M , Liu L Q , Zhang X H , Peng N
Published: July 2024

Tilting-pad gas journal bearing are widely used in the field of high-speed turbine machinery, especially in the special environment of low temperature. However, the performance is limited by structure, so a clear understanding of the field is particularly important. In this paper, finite volume method is used to simulate the three-dimensional flow field of high-speed tilting-pad gas bearing, then the effects of shaft speed, eccentricity and gas film thickness on the bearing capacity are studied. The simulation results show that the two factors of shaft speed and gas film clearance play a decisive role in producing sufficient bearing capacity of tilting tile radial gas bearings compared with other factors.
Cryogenic Modules for Synergistic O2 Generation and CO2 Retention in Closed-Circuit Escape Respirators
Authors: Swanger A.M. , Fernando R. , Mahony C. , Carro R. , Harrison A.
Published: July 2024

Since 2018, NASA and the National Institute for Occupational Safety and Health (NIOSH) have been developing a liquid oxygen storage module (LOXSM) based on the NASA patent-pending Cryogenic Flux Capacitor (CFC) technology. LOXSM’s could potentially replace the gaseous or chemical-based oxygen supply in current closed-circuit escape respirators (CCER), with reducing CCER size being a primary goal. By virtue of the CFC functionality, cryogenic oxygen stored within the LOXSM is released in response to heat input, ideally from the breathing loop. Prior efforts focused on the oxygen storage potential of silica aerogel materials that the CFC utilizes, and were previously reported. Current work explored the LOXSM’s potential to remove and retain CO2 produced by the CCER user, in conjunction with oxygen generation, creating a synergy that may be exploited to reduce or eliminate the chemical CO2 absorber used in current CCERs. A test program for determining CO2 retention is presented, as well as the evolution of LOXSM prototypes. Testing showed that it is possible to completely remove CO2 out of an effluent stream at the flowrate required for the capacity of the CCER for an appreciable time, and that the LOXSM prototype design progression had a positive effect on that duration.
Results of a nitrogen-based pulsating heat pipe with varied configurations
Authors: Jiang Zhiyi , Pfotenhauer John , Miller Franklin
Published: July 2024

In this paper, the results of a nitrogen-based pulsating heat pipe (PHP) with the ability to change the number of turns are presented. The experiment assembly consists of two identical PHP subsections with their own fill lines. The length of the condenser, the adiabatic section, and the evaporator section of each PHP are 90mm, 1000mm, and 60mm respectively. Because of the unique design of the condenser section of the PHP, it can change the configuration into 1-turn, 3-turn, 5-turn, and 7-turn PHP. The PHP was tested at the condenser temperatures 77.4K, and 84.5K, which are at, and above the boiling point of the liquid nitrogen at ambient pressure. At each condenser temperature, the PHP was tested at three different initial fill ratios (50%, 63%, and 75%). The experimental results and analysis for the 1-turn setup of this nitrogen-based PHP assembly are presented in this paper.
The design and development of the cryogenic compressed gas refueling system
Authors: Lv Cui , He Ming , Wang Jinzhen , Zhou Gang , Wu Jihao , Gong Linghui
Published: July 2024

As a new economical, efficient and feasible high density hydrogen storage method, cryogenic compressed hydrogen has been widely explored by scholars in recent years. In this paper, a new cryogenic compressed hydrogen refueling system based on liquid nitrogen cooling is proposed on the basis of the existing high pressure hydrogenation station at normal temperature. The main operating modes of the system include precooling, refueling and standby mode. During the refueling process, it can generate cryogenic compressed hydrogen at 80K temperature and 35MPa pressure, with a mass flow rate of 1kg/min. Additionally, when the cryogenic compressed hydrogen tank requires refueling at high temperatures, the system can provide precooling to reduce hydrogen loss and increase the refueling speed. To validate the feasibility of key equipment and the proposed system, helium gas is used as the working medium for testing. The construction of the cold box, compressor, and cryogenic tank have been completed, and the system is expected to undergo commissioning in the near future.
Small-scale industrial hydrogen liquefaction and refrigeration
Authors: Higgins P , Fesmire J , Baik J , Williams M , Earls A
Published: July 2024

As the hydrogen economy expands, the need for point of use production with smaller liquid hydrogen (LH2) production capacities will increase. Examples of this are transportation hubs in remote locations and numerous other applications where the required LH2 production is less than 5 MT/day. In response to this need, a small-scale industrial 1,000 kg/day hydrogen liquefaction plant is being developed and is planned for operation in 2024. The plant will achieve localized, efficient production, on-demand, in remote locations or any location advantageous for use in transportation, where complicated logistics, with associated transportation costs and tanker evaporative losses are eliminated or minimized. The chief advantages of the design are small size/footprint, safety, reliability, low cost, lack of restrictions on site location, and ability to make practical use of renewable energy. The liquefaction plant utilizes a closed-loop helium reverse-Brayton cycle refrigerator where refrigerant temperatures significantly less than the hydrogen liquefaction temperature cause the hydrogen gas stream to be liquefied. The liquefied hydrogen is maintained in the liquid state via a helium side stream taken from the refrigeration loop routed through the LH2 storage tank. This optional system can maintain LH2 temperatures in the storage tank lower than 18 K to eliminate boiloff and facilitate zero loss transload from tanker trucks and eliminate losses in transfer/dispensing. The hydrogen liquefaction plant does not require liquid nitrogen (LN2) pre-cooling and so can be located in remote areas wherever there is 480 V electricity and hydrogen production capacity available. A slightly modified reverse-Brayton cycle is also used in the refrigeration/storage plants. These plants can facilitate zero loss tanker transload and zero boiloff for LH2 storage plants of virtually any capacity. The smallest of these reverse-Brayton cycle refrigerators, currently in detailed design, refrigeration system RS1500 (1000 W heat lift @ 20K) will be capable of eliminating boiloff losses of the largest storage tanks currently in operation with very low electrical energy consumption.
Hydrogen permeability testing of fibre reinforced thermoplastics under cryogenic conditions – validation of a test rig concept
Authors: Just T , Will J , Haberstroh C
Published: July 2024

The need to decrease the gross weight of cryogenic hydrogen fuel systems in future zero emission mobility leads to increasing activities in the field of cryogenic lightweight engineering. Fibre reinforced thermoplastic composite materials (FRT) are considered for cryogenic applications despite their bias towards permeation. However, permeation through plastic materials is of major concern in cryogenic applications. Even tiny fluxes can very much compromise the insulating power of high vacuum spaces required for insulation of cryogenic systems such as tank structures or transfer lines. Hence, it is essential to qualify those FRT in terms of their hydrogen permeability for future usage in mobile cryogenic applications. The conventional concepts for measuring permeability in plastic materials are not sufficient for cryogenic measurements of FRT as shown in a previous paper. For that, a novel laboratory test rig concept was proposed. In this paper, we validate this concept and show its eligibility for measuring permeation of hydrogen through thermoplastic materials. Therefore, we report results of helium permeation through polytetrafluoroethylene (PTFE) at room temperature and compare those results to literature permeability data.
Preparing the cryogenic moderator system for higher beam power
Authors: Howell M , Armstrong R , DeGraff B , Denison J , Fabre Y , Maekawa R
Published: July 2024

The Spallation Neutron Source (SNS) incorporates a 20 K helium refrigeration system to cool three circuits supplying cold hydrogen to neutron moderators. The helium refrigeration system consists of a warm compressor, oil removal, purifier, 20 K cold box, and three helium-hydrogen heat exchangers. The hydrogen loops consist of a circulator, moderator, accumulator with expandable bellows, and the heat exchangers. Historically, the cryogenic system has had periods of instability and has operated with a reduced capacity. While performing the Proton Power Upgrade, the proton beam power on the first target station will increase from 1.4 MW to 2 MW. This will result in a 43% increase in dynamic load to the cryogenic system. The first directive in preparing the system for higher beam power was to achieve consistent operational stability at 1.4 MW beam power. After this was achieved, the next task was to increase the system capacity. This paper will describe the initiatives taken to produce consistent high-capacity performance.
Development status of the in-situ measurement system for ortho-to-parahydrogen fractions for the ESS cryogenic moderator system
Authors: Tatsumoto H , Sakamoto Y , Hasegawa T , Kobayashi H , Shiro Y , Horikawa Y , Horvath A , Sina H , Hartl M , Arnold P , Kickulies M , Beßler Y , Teshigawara
Published: July 2024

The Cryogenic Moderator System (CMS) is equipped with a catalyst to convert hydrogen from the ortho state to the para state in order to keep desirably high parahydrogen fractions of 99.5%. An in-situ measurement system for the ortho and para fractions of liquid hydrogen (OPMS) by means of a Raman spectroscopy with an accuracy of 0.1% is being developed to detect any undesirable shift towards a high orthohydrogen fraction caused by neutron scattering driven para-to-ortho back conversion. We have demonstrated that our developed sapphire window, through which the laser and backscattered photon travel, has endured the required pressure and thermal cycles in a liquid hydrogen environment. Meanwhile, a Raman optics system has been developed using normal hydrogen. Eventually, we have succeeded in detecting the parahydrogen peak at J = 4, which is our primary goal, because the peak ratio of parahydrogen at 1245 cm−1 to ortho hydrogen at 587 cm−1 corresponds to 0.5%. It can be expected that it would achieve our requirement for liquid hydrogen with higher density.
Current status of main distribution box for Korean heavy ion accelerator, RAON
Authors: Yoo J , Yoon S , Park I , Lee D , Ki T
Published: July 2024

A main distribution box is a large cryogenic valve box which connects two cryoplants with two superconducting linear accelerators (LINACs) of Korean heavy ion accelerator. A major role of the main distribution box is transferring cryogenic helium from the cryoplants to LINACs and controlling flow rate of the helium. It can take other several roles when it encounters special situations. It has total 44 cryogenic valves to manage the helium. DN10 to DN250 valves are applied according to sizes of the cryogenic lines in the main distribution box. Designed heat loads of the main distribution box are 440 W for thermal shield, 24 W for 4.5 K lines and 43 W for 2 K line. At present, the main distribution box keeps its cold status and is operated well although it needs some improvements. The improvements will be gradually carried out when our cryogenic system will be warmed up. Some occurred issues, our solutions and current status of the main distribution box are shared in this paper.
Design of GRETA Cooling Systems
Authors: Wang L , Buice E , Crawford H , Doyle J , Fallon P , Hodgkinson A , Loew T , Regis M , Zimmermann S
Published: July 2024

The Gamma-Ray Energy Tracking Array (GRETA) is a full 4π gamma-ray tracking detector capable of reconstructing the energy and three-dimensional position of gamma-ray interactions within a compact sphere of high-purity germanium crystals. The GRETA Detector Array Sphere will have the capacity to accommodate a total of 30 Germanium Quad Detector Modules (QDM). The 30 QDMs are to be cooled and maintained below 100 K using liquid nitrogen (LN) at all times while the array is in normal operation, and will require regular filling of a LN Dewar on each module. The Dewar is designed to allow the Quad Module to be operated in any orientation with a LN holding time of no less than 12 hours when the detector module is fully powered. An automated LN cooling and refilling system is required to supply LN to the 30 QDMs and ensure them maintained below 100 K. Each of the GRETA QDMs houses a total of 148 pre-amplifier units within the module, and with the high power consumption of each pre-amplifier, active cooling of the pre-amplifier compartment is required. Additionally, each Quad Module will have 4 digitizer modules attached to it, which generate heat and require cooling as well. A closed-loop liquid (Glycol) cooling system will provide the required temperature stability and dissipate power generated heat for electronics. This paper presents design of the GRETA LN cooling system for detectors and the closed-loop liquid cooling system for electronics including technical requirements, design schemes, key components, operation modes, and so on.
Co-simulation of cool down process from 300 to 80 K for ITER Tokamak
Authors: Takami S , Iwamoto A , Maekawa R , Qiu L , Grillot D
Published: July 2024

Dynamic simulation of Tokamak superconducting magnet system has been conducted to investigate the cool-down process from 300 to 80 K. The simulation focuses on the cool-down speed variations with respect to the global temperature gradients in the different coils; Toroidal Field (TF) coil, TF STructure (TF-ST), Central Solenoid (CS) and Poloidal Field (PF)/Correction Coil (CC) systems. As imposing the maximum temperature gradients dT
max ≤ 50K, the speed should be adjusted, ensuring the limited mechanical stresses due to thermal contractions. So far, the process simulation of Tokamak cryogenic system has been concentrated on the Deuterium Tritium (DT) operation phase; therefore, it is necessary to revise the model to extend its capability for the cool-down; for example, the thermo-hydraulic properties of Cable-in-Conduit Conductor (CICC) for each coil, mechanical properties of materials for the magnet system. The cool-down process is implemented at the helium refrigerator by utilizing LN2 heat exchanger up to 80 K. Its speed is set at -0.8 K/hr as a baseline, which can be controlled by the global temperature gradients in the magnet system. The process will be on hold as dT
max ≥ 50K, and resumed once dT
max < 50K. The paper discusses the cool-down processes of the Tokamak and identifies the impact on the speed, dT
i/dt, of each component.
Overview and status of the PIP-II cryogenic system
Authors: Martinez A , Creus Prats J , Soyars W , Dhuley R , Hansen B , Jia Y , Chakravarty A , Goyal M , Banaszkiewicz T , Duda P , Stanclik M
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. The PIP-II Linac consists of 23 SRF cryomodules operating at 2 K, 5 K, and 40 K temperature levels supplied by a single helium cryoplant providing 2.5 kW of cooling capacity at 2.0 K. The PIP-II cryogenic system consists of two major systems: a helium cryogenic plant and a cryogenic distribution system. The cryogenic plant includes a refrigerator cold box, a warm compressor system, and helium storage, recovery, and purification systems. The cryogenic distribution system includes a distribution box, intermediate transfer line, and a tunnel transfer line consisting of modular bayonet cans which supply and return cryogens to the cryomodules. A turnaround can is located at the end of the Linac to turnaround cryogenic flows. This paper describes the layout, design, and current status of the PIP-II cryogenic system.
First results of the cryogenics operation from the LHC physics Run 3 at the increased energy to 6.8 TeV
Authors: Delprat L , Bradu B , Brodzinski K , Ferlin G , Ferrand F , Gahier V , Herblin L , Wagner U
Published: July 2024

Back in 2018, LHC completed its Run 2 physics period. Consolidation, maintenance, and upgrade activities performed during the subsequent Long Shutdown 2 period (LS2), based on a data-driven approach, allowed for full potential availability of the LHC cryogenics infrastructure before tackling the 2021 magnet quench training campaign, preparing the whole machine for operation at the increased energy of 6.8 TeV. This paper will first give a summary of the main upgrades, consolidations and maintenance performed during the LS2. Magnet training of the machine to the increased energy of 6.8 TeV will be addressed. Results of the first year (2022) of Run 3 physics will be presented, achieving high cryogenic availability in a heavily sustained operational context of the accelerator (beams energy increase, induced heat load, peak & integrated luminosity). Helium inventory management aspects will be discussed, with a particular highlight on the necessary operational adjustments taken to cope with the present supply market evolution. Implementation of several operational modes for cryogenic plants will be presented, towards significant electrical power savings while maintaining nominal physics production at the highest availability rate.
Design of nonflammable mixed refrigerants based on the partial molar enthalpy difference in mixed-refrigerant Joule-Thomson refrigerators with/no pre-cooling stage
Authors: Wang Yunxiao , Zhao Yanxing , Sun Yuwei , Wang Haocheng , Gong Maoqiong
Published: July 2024

Mixed-refrigerant Joule-Thomson refrigeration (MJTR) is an important cooling method at temperatures from 80 to 230 K. It can be used in cryosurgery, high-temperature superconductivity and sensor cooling etc. However, most of the studies are on nitrogen-hydrocarbon refrigerants, which are not allowed in applications where there is a special need to avoid flammability risks. Therefore, non-flammable mixed refrigerants were investigated in this study.

The composition of the mixed refrigerant is a key factor in the system performance (refrigeration temperature, refrigeration capacity, etc). However, the purely mathematical optimization methods lack system knowledge in the optimization of the process, and may have the disadvantages of being a time-consuming process. In this study, the isothermal throttling effect of mixed refrigerants is optimized, and the optimization process is based on the partial molar enthalpy difference of each component. The method is based on thermodynamic properties and is time-saving relative to purely mathematical optimization techniques.

Non-flammable mixed refrigerants (NFMR) with refrigeration temperatures from 100 K to 140 K were designed in this study. The results show that the designed mixed refrigerant has a higher COP compared to the reference. Argon has an advantage at refrigeration temperatures from 120 K to 140 K, while nitrogen has an advantage from 100 K to 120 K. In addition, mixed refrigerants for systems with pre-cooling stage were optimized and the results showed that the highest exergy efficiency is achieved at a pre-cooling temperature of 250 K. The exergy efficiencies with pre-cooling stage are nearly twice as high as those without that. Therefore, a pre-cooling stage for nonflammable mixed refrigerants is necessary where there is no requirement for system size.
LCLS-II Helium Refrigeration System : A comprehensive overview of the project
Authors: Fauve E. , Pflueckhahn D. , Sevilla J. , Ravindranath V. , Chung C. , Hogan J. , Bevins M. , Bhattacharya R.
Published: July 2024

SLAC National Accelerator Laboratory has upgraded to LCLS-II, featuring a 4 GeV superconducting accelerator composed of 37 cryomodules and two large helium refrigeration systems with a total cooling capacity of 8 kW at 2.0 K. The cryogenic system at SLAC is the successful outcome of a nine-year partnership between SLAC, Fermilab, and Jefferson Lab. This paper highlights the joint efforts between Jefferson Lab and SLAC in the development and implementation of the LCLS-II Cryogenic Plants. It details the project organization, schedule, budget, staffing profile and procurement strategy.
Two new helium refrigerators for the LHC accelerator upgrade (HL-LHC) at CERN; From concept and tender to contract
Authors: Monneret E , Claudet S , Ferlin G , Gahier V , Wagner U
Published: July 2024

The High Luminosity LHC (HL-LHC) project is aiming to upgrade the Large Hadron Collider (LHC) at CERN by increasing its peak luminosity by a factor of five with respect to its nominal value. This upgrade will include the replacement of the final focusing superconducting magnets and additional superconducting radiofrequency crab cavities in the long straight sections of the interaction points 1 and 5 of LHC. The cryogenic heat loads in points 1 and 5 of the LHC accelerator will significantly increase, mainly because of the higher luminosity. Therefore, two new Refrigerators will be required in points 1 and 5, with each an equivalent capacity of 14 kW@4.5 K, including 3.25 kW@1.9 K. This paper presents the functional requirements and conceptual design, the key choices and specific challenges including the civil engineering constraints and the major technical requirements detailed in the Technical Specification documents for the supply from the European industry of two new helium Refrigerators for HL-LHC. A procurement contract based on this specification, was placed in 2022.
Commissioning of the ESS large-scale 20 K helium refrigeration system for the cryogenic moderator system
Authors: Tatsumoto H , Arnold P , Boros M , Horvath A , Segerup M , Tereszkowski P , Arriagada J , Huber R
Published: July 2024

At the ESS, a large-scale 20 K helium refrigeration system with a cooling capacity of 30.3 kW at 15 K, which is called Target Moderator CryoPlant (TMCP), has been designed to cool the cryogenic moderator system (CMS) where subcooled liquid hydrogen will be circulated at 1.0 kg/s through four hydrogen moderators where the total nuclear heating is estimated to be 17.2 kW for the proton beam power of 5 MW. The first phase of the TMCP installation and commissioning for the TMCP compressor skids and cold box was completed in 2019. The phase 2 installation of 300 m-long cryogenic helium transfer lines (CTLs) and a valve box located at one end of it in the Target building has been completed in the summer of 2022. Subsequently, the commissioning has been conducted until December 2022. This paper will describe the performance evaluation test results of the CTL heat load and pressure drop, the TMCP cooling capacity, and a test result of a failure action caused by instrument air failure.
Thermal analysis of 4 K J-T cryocooler equipped with an ejector
Authors: Hu Yayi , Wang Yanan , Wang Xiaotao , Dai Wei , Yang Zhaohui , Sun Yiwei , Li Haibing , Luo Ercang
Published: July 2024

This paper introduces a 4 K Helium Joule-Thomson (J-T) refrigeration system equipped with ejector technology to enhance thermodynamic efficiency, reduce the lowest cold head temperature, and avoid higher compressor suction pressure. The J-T cryocooler, pre-cooled by a Stirling cryocooler, typically requires a high compression ratio when operating at 4 K or below. The ejector serves as a device that converts pressure energy into kinetic energy, enabling it to draw in secondary fluid and then reconvert kinetic energy into pressure energy, thus increasing the pressure of the low-pressure fluid. To investigate the impact of the ejector on J-T refrigerator performance, this study employs a one-dimensional theoretical calculation. The results are used to establish a performance chart of the J-T refrigeration system with an ejector, which is compared to the system without an ejector. The analysis reveals a promising 10-20% improvement in performance with the ejector technology implemented.
Numerical modelling of thermoacoustic Stirling engines & refrigerators
Authors: Butson H , Gschwendtner M , Caughley A , Badcock R , Weijers H , Lumsden G
Published: July 2024

This paper investigates how numerical modelling can be used to explore thermoacoustic machines and compares the accuracy of the performance predictions for different simulation software. The software used includes one designed for modelling Stirling machines called ‘Sage’ and for modelling thermoacoustic machines called ‘DeltaEC.’ To compare their results, a model of both a thermoacoustic Stirling engine and refrigerator were developed from existing models in published papers, which contained experimental data to validate the numerical models. Overall, it was found that although both can accurately model thermoacoustic machines, they present different optimal conditions, and Sage’s solving method makes it more complex to model the standing wave.
A Retrospective on how Cryostats have changed with Cryostat Use and the Cooling Methods used to keep Superconducting Magnets Cold
Authors: Green Michael A
Published: July 2024

Prior to the invention of the vacuum flask by James Dewar in 1895, cryogenic temperatures below 100 K could not be sustained very long. The Development of the modern cryostat was an extension of the basic Dewar vacuum flask. The design of the cryostat, its insulation, and the cold mass support system is a function of the cryostat’s intended use. The type of refrigeration available also influenced the development insulation systems, support systems, transfer lines and electrical leads that are part of the cryostat. In recent years the availability and the cost of helium has been a significant factor in cryostat design and the methods used to cool and cool-down cryostats. This paper explores the historical development of today’s cryostats and how that can be tied to the source of cryogenic cooling. This paper is focused on earth bound cryostats. Some of the same principles can be applied cryostats used in space.
Investigation and perspectives of using Graph Neural Networks to model complex systems: the simulation of the helium II bayonet heat exchanger in the LHC
Authors: Stoklasa R , Calabrese N , Serio L
Published: July 2024

Large cryogenic systems, like those installed at CERN, are complex systems relying on many diverse physical processes and phenomena that are difficult to simulate and monitor in detail. With only a limited number of properties measured and made available for monitoring and control purposes, several processes contributing to the dynamics of the systems are ignored. This lack of information can reduce the accuracy and the capability of a model to track, predict, and anticipate the behavior of the system. Accurate analytical or numerical computer modeling can be developed to simulate the non-linear dynamics of the processes but they are complex, computationally intensive, and cumbersome to test, validate, and implement with different configurations and limited measurements of the hidden properties. In this work, we present our investigation of using Graph Neural Networks (GNN) to build a model of the helium II bayonet heat exchanger operating in the LHC at CERN. We are proposing to use a hybrid machine learning approach, where the parameters of the GNN model are estimated by a combination of supervised learning algorithms trained on experimental data and bounding physics equations and parameters. The GNN model was initially trained on data from the experiments performed on the LHC prototype magnet strings and validated on data extracted during the operation of the LHC machine. We demonstrate the model’s accuracy, repeatability, and robustness in various configurations. The model is also well inspectable and explainable, providing the time evolution of all variables. We report on the results and expected applications, which include predictive control, diagnostic, and operator training.
Modeling of cryogenic heated-tube flow boiling experiments of nitrogen and methane with Generalized Fluid System Simulation Program
Authors: Baldwin Michael , LeClair Andre , Majumdar Alok , Hartwig Jason , Ganesan Vishwanath , Mudawar Issam
Published: July 2024

Accurate modeling of cryogenic boiling heat transfer is vital for the development of extended-duration space missions. Such missions may require the transfer of cryogenic propellants from in-space storage depots or the cooling of nuclear reactors. Purdue University in collaboration with NASA has assembled a database of cryogenic flow boiling data points from heated-tube experiments dating back to 1959, which has been used to develop new flow boiling correlations specifically for cryogens. Computational models of several of these experiments have been constructed in the Generalized Fluid System Simulation Program (GFSSP), a network flow code developed at NASA’s Marshall Space Flight Center. The new Purdue-developed correlations cover the full boiling curve: onset of nucleate boiling, nucleate boiling, critical heat flux, and post-critical heat flux boiling. These correlations have been coded into GFSSP user subroutines. The fluids modeled are nitrogen and methane. Predictions of wall temperature are presented and compared to the test data.
Advanced ice lithography system using a micro-machined Joule-Thomson cooler
Authors: Qi Limin , Zheng Rui , Liu Dongli , Pei Haiyue , Zhao Ding , Qiu Min
Published: July 2024

This study introduces a novel ice lithography system integrated with a low-vibration micro-machined Joule-Thomson cooler. Ice lithography is an eco-friendly method for high-resolution nanofabrication on delicate substrates and requires to operate below 130 K in the vacuum of a microscope chamber. Previously, liquid nitrogen rather than cryocoolers was used to cool the system due to its low vibration, but it is both bulky and costly. To overcome these challenges, this study employs a low-vibration micro-machined cooler in a scanning electron microscope (SEM) for ice lithography. The design and methodology of the system are described in detail. The results show that the substrate can reach a temperature of 105 K within 30 minutes with a measured mechanical vibration of less than 10 nm, enabling high-resolution nanofabrication. As proof of concept, the system successfully fabricates nanoscale patterns on a silicon wafer. This low-vibration cooling system has great potential for use in cryogenic electron microscopes (cryo-EMs) in the future.
High Accuracy Resisitivity and Temperature Coefficient Measurements of Invar Wire from 5K to 300K
Authors: Hamilton B , Adams J L , Brisson J G
Published: July 2024

The temperature coefficient of resistivity is a critical element of many AC-based hot-wire measurements of thermal properties. At cryogenic temperatures, most metallic materials suitable for wire and film-based forms have either a temperature coefficient or absolute resistivity that is too small to enable practical, accurate measurements. Invar (36Ni 64Fe) controlled thermal expansion alloy has a significant temperature coefficient of resistance while also maintaining significant absolute resistivity at cryogenic temperatures, and so has seen some use in low temperature 3-omega measurements. Prior data on the temperature coefficient of resistivity of Invar is limited and the uncertainty is high. In this work, we present high-accuracy resistance and temperature coefficient data for this material from 5-300 K.
Study on irradiation effect of insulating materials for fusion superconducting magnets: temperature dependence of mechanical strength
Authors: Akiyama Y , Ohta A , Manabe Y , Sato F , Iwamoto A , Imagawa S , Utoh H , Nishijima S
Published: July 2024

Insulating materials used in the superconducting magnets of fusion reactors are exposed to cryogenic temperatures, intense radiations, and strong electromagnetic forces. In the experimental fusion reactor ITER, resin mixed with epoxy resin (EP) and cyanate ester (CE) (CE content: 40 wt.%) is used as a matrix of glass reinforced plastics (GFRP) as an insulating material to maintains mechanical strength and insulating performance in such environments. This composition ratio is basically determined by strength tests at room temperature or liquid nitrogen temperature, so the study at liquid helium temperature is required. In this study, the effects of the resin composition of GFRP on interlaminar shear stress (ILSS) at room temperature, liquid nitrogen temperature, and liquid helium temperature before and after γ-ray irradiation were evaluated. The ILSS after γ-ray irradiation of EP showed a maximum value at liquid helium temperature, while the addition of CE caused the ILSS after irradiation to show a maximum value at liquid nitrogen temperature. It was also shown that the temperature dependence of the ILSS decreased with increasing CE content. The results showed that the addition of CE to EP contributes to the improvement of radiation resistance, but excessive addition of CE promotes embrittlement at LHeT.
Mechanical properties and damage development in glass-fiber epoxy laminates subjected to tensile loading at sub-zero temperatures
Authors: Krzak A. , Al-Maqdasi Z. , Matula G. , Nowak A. J. , Joffe R.
Published: July 2024

In various structural applications polymer composites are exposed to sub-zero and even cryogenic temperatures which may initiate of microstructural damage. To anticipate these events, one needs to understand the behavior of composites in a sub-zero environment. This study focuses on damage initiation and accumulation, and its influence on the properties of cross-ply glass fibers epoxy composites at sub-zero temperatures. The effect of bromine modification of epoxy, and the dissolution in an organic solvent on the mechanical performance of the produced composite is also investigated. To evaluate the influence of a sub-zero environment on the mechanical performance of glass fiber epoxy laminates, tensile tests in a sub-zero environment of unconditioned specimens were carried out. The quasi-static tensile tests were performed to measure the elastic modulus of the composites while loading-unloading experiments were performed to monitor the initiation (and accumulation) of microstructural damage and its influence on the stiffness of glass fiber epoxy laminates. The results of cryogenic damage and fracture in the laminates are discussed with a focus on the degradation of properties of glass fiber crucial for their use in structural applications: strength and stiffness.