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Large-scale electric aircraft is a disruptive technology to address the environmental impact of air travel. Fault current limitation is crucial to realise the safety and reliability of the electric aircraft, in particular for large-scale electric aircraft using DC distribution network. This paper investigates the behavior of the resistive SFCL under different cryogenic cooling systems including liquid nitrogen and helium gas circulation cooling systems for the electric aircraft DC distribution network. Electromagnetic and thermoelectric models were used to predict the characteristics of resistive SFCL. The simulation results demonstrate that it is promising to design resistive SFCL using liquid nitrogen cooling as well as helium gas circulation cooling systems, which offer flexibility for SFCL cryogenic cooling system for electric aircraft applications.

Current quantum systems based on spin qubits are controlled by classical electronics located outside the cryostat at room temperature. This approach creates a major wiring bottleneck, which is one of the main roadblocks toward truly scalable quantum computers. Thus, we propose a scalable memristor-based programmable DC source that could be used to perform biasing of quantum dots inside of the cryostat (i.e. in-situ). This novel cryogenic approach would enable to control the applied voltage on the electrostatic gates by programming the resistance of the memristors, thus storing in the latter the appropriate conditions to form the quantum dots. In this study, we first demonstrate multilevel resistance programming of a TiO2-based memristors at 4.2 K, an essential feature to achieve voltage tunability of the memristor-based DC source. We then report hardwarebased simulations of the electrical performance of the proposed DC source. A cryogenic TiO2-based memristor model fitted on our experimental data at 4.2 K was used to show a 1 V voltage range and 100 uV in-situ memristor-based DC source. Finally, we simulate the biasing of double quantum dots enabling sub-2 minutes in-situ charge stability diagrams. This demonstration is a first step towards more advanced cryogenic applications for resistive memories such as cryogenic control electronics for quantum computers.

This paper outlines the initial development of a novel magnetohydrodynamic (MHD) plasma control sys- tem which aims at mitigating shock-induced heating and the radio-frequency communication blackout typically encountered during (re-)entry into planetary atmospheres. An international consortium com- prising universities, SMEs, research institutions, and industry has been formed in order to develop this technology within the MEESST project. The latter is funded by the Future and Emerging Technologies (FET) program of the European Commission’s Horizon 2020 scheme (grant no. 899298). Atmospheric en- try imposes one of the harshest environments which a spacecraft can experience. The combination of hypersonic velocities and the rapid compression of atmospheric particles by the spacecraft leads to high- enthalpy, partially ionised gases forming around the vehicle. This inhibits radio communications and in- duces high thermal loads on the spacecraft surface. For the former problem, spacecraft can sometimes rely on satellite constellations for communicating through the plasma wake and therefore preventing the blackout. On the other hand, expensive, heavy, and non-reusable thermal protection systems (TPS) are needed to dissipate the severe thermal loads. Such TPS can represent up to 30% of an entry vehicles weight, and especially for manned missions they can reduce the cost- efficiency by sacrificing payload mass. Such systems are also prone to failure, putting the lives of astronauts at risk. The use of electro- magnetic fields to exploit MHD principles has long been considered as an attractive solution for tackling the problems described above. By pushing the boundary layer of the ionized gas layer away from the spacecraft, the thermal loads can be reduced, while also opening a magnetic window for radio com- munications and mitigating the blackout phenomenon. The application of this MHD-enabled system has previously not been demonstrated in realistic conditions due to the required large magnetic fields (on the order of Tesla or more), which for conventional technologies would demand exceptionally heavy and power-hungry electromagnets. High-temperature superconductors (HTS) have reached a level of industrial maturity sufficient for them to act as a key enabling technology for this application. Thanks to superior current densities, HTS coils can offer the necessary low weight and compactness required for space ap- plications, with the ability to generate the strong magnetic fields needed for entry purposes. This paper provides an overview of the MEESST project, including its goals, methodology and some preliminary de- sign considerations. ispartof: The Journal of Space Safety Engineering vol:10 issue:1 pages:27-34 status: published

International audience; For the HL-LHC project, a 90 mm NbTi cos(2θ) double aperture quadrupole magnet with an operating gradient of 120 T/m at 1.9 K has been designed as an option to replace the 70 mm aperture LHC quadrupole MQY. CEA in collaboration with CERN designed and manufactured a single aperture short model magnet with a magnetic length of 1.215 m at 1.9 K called MQYYM. The MQYYM cold test occurred at CEA at 4.2 K in a vertical cryogenic station. During the power test, the operating gradient at 1.9 K has been reached after two training quenches. All along the test, magnetic and mechanical measurements were done using respectively a rotating probe and strain gauges. This paper describes the performance of the MQYYM at 4.2 K and gives an analysis of the data acquired during the test, including training behavior, quench detection, protection and field quality measurements.

The Atmospheric Remote-sensing Infrared Exoplanets Large-survey (ARIEL) is the fourth medium (M4) mission selected in the context of the ESA Cosmic Vision 2015–2025 programme, with a launch planned in 2028. During 4 years of flight operations, ARIEL will probe the chemical and physical properties of approximately 1000 known exoplanets by observing their atmosphere, to study how planetary systems form and evolve [1, 2]. The mission is designed as a transit and eclipse spectroscopy survey, operated by a 1-m class telescope feeding two instruments, the Fine Guidance system (FGS) and the ARIEL InfraRed Spectrometer (AIRS), that accommodate photometric and spectroscopic channels covering the band from 0.5 to 7.8 μm in the visible to near-IR range [3, 4]. The mission high sensitivity requirements ask for an extremely stable thermo-mechanical platform. The payload thermal control is based on a passive and active cooling approach. Passive cooling is achieved by a V-Groove shields system that exploits the L2 orbit favourable thermal conditions to cool the telescope and the optical bench to stable temperatures

Rigid low-density polyurethane (PU) foams containing bio-based components are being increasingly considered as a sustainable substitute for petrochemical resources-based foams for thermal insulation in ambient conditions. However, for applications involving high temperature gradients, the thermal expansivity of foams also has to be characterised. With this aim, rigid low-density polyurethane foams have been manufactured using polyols derived from renewable resources (tall oil fatty acids) and their thermal expansion in the temperature range from 20 to −150 °C was studied. The mean coefficients of linear thermal expansion (CTE) in this range and the differential CTEs at 20 and -150 °C were determined. Increasing the cross-link density of the PU polymer matrix resulted in reduction of the CTEs of both monolithic polymer and closed-cell PU foams. Changing the molecular weight per branching unit of PU from 442 to 318 g/mol caused reduction of the differential CTE of the monolithic PU by about 30% at 20 °C and by 11% at −150 °C. The CTEs of anisotropic foams were expressed in terms of CTE of the polymer and mechanical characteristics of the foams. The predicted CTEs were found to be in good agreement with experimental ones within the temperature range considered.

Heat powered cycles are of great interest as they enable reduced electric power consumption. Therefore, they can lower the load on electric power plants and distribution infrastructure. Many systems incorporate compressors for driving thermodynamic cycles and processes, and these compressors are usually electrically driven. In the framework of research on a sorption Joule-Thomson cryogenic cooler, a three-stage sorption compressor is designed, manufactured, and tested. The experimental results are reported and analyzed in the current manuscript. Nine experiments are reported, with one, two, and three compression stages, in which the experiments differ in the number of sorption cells at every compression stage and the operating conditions. The results of the experimental apparatus validate a numerical model and show the ability to construct and operate sorption compressors. All nine experiments operate with nitrogen, which is the required refrigerant in the cryogenics cooling system of the current research. Nitrogen is a weakly adsorbed gas, and so the reported efficiencies are relatively low, around 0.5% of the Carnot efficiency. However, the current work proves the technology's maturity and suitability for many other applications, especially where the required working fluids are more intensively adsorbed gases.

The present work involves the development of helium based pulsating heat pipe (PHP), which containing 48 parallel tubing parts. The PHP is considered as one of the best alternatives for conducting metals and it is used for long distance heat transfer process. Their heat transfer capability and efficient thermal conductivity are the prominent properties which considered for applications. The region of the condenser was thermally sealed to the giffored mcmohanon cryo-cooler using a cooling cap of 1.49 W at 4.2 K while 1.1 W of heat are allowed to the evaporator section at a filling rate of 70%, through comparing the 48-turn PHP and 8-turn PHP, a most intense efficient thermal conductivity of 12329 W/ mK was achieved in the 48 turn PHP. The influence of no turns of warm movement execution was observed with the same operating parameters and topographical parameters. Observations revealed that the temperature variations of PHP 48-turn was significantly less than that of PHP 8-turn. It exhibited efficient thermal conductivity, high capacity heat transfer and a good dry-out temperature response. Thus PHP 48-turn of series and parallel configurations are defined as excellent system de-signs and are accessible to the PHP cryogenics framework architecture. This article has been retracted. Link to the retraction 10.2298/TSCI220630084E

We report on the development of scintillating bolometers based on lithium molybdate crystals containing molybdenum depleted in the double-$\beta$ active isotope $^{100}$Mo (Li$_2$$^{100\textrm{depl}}$MoO$_4$). We used two Li$_2$$^{100\textrm{depl}}$MoO$_4$ cubic samples, 45 mm side and 0.28 kg each, produced following purification and crystallization protocols developed for double-$\beta$ search experiments with $^{100}$Mo-enriched Li$_2$MoO$_4$ crystals. Bolometric Ge detectors were utilized to register scintillation photons emitted by the Li$_2$$^{100\textrm{depl}}$MoO$_4$ crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc underground laboratory (Spain). We observed that the Li$_2$$^{100\textrm{depl}}$MoO$_4$ scintillating bolometers are characterized by excellent spectrometric performance ($\sim$3--6 keV FWHM at 0.24--2.6 MeV $\gamma$'s), moderate scintillation signal ($\sim$0.3--0.6 keV/MeV depending on light collection conditions) and high radiopurity ($^{228}$Th and $^{226}$Ra activities are below a few $\mu$Bq/kg), comparable to the best reported results of low-temperature detectors based on Li$_2$MoO$_4$ with natural or $^{100}$Mo-enriched molybdenum content. Prospects of Li$_2$$^{100\textrm{depl}}$MoO$_4$ bolometers for use in rare-event search experiments are briefly discussed., Comment: Prepared for submission to MDPI Sensors; 16 pages, 7 figures, and 3 tables

We are developing a new instrument, the RF Josephson arbitrary waveform synthesizer (RF-JAWS), for communications metrology and quantum information applications. An important aspect of the RF-JAWS design is the accurate and traceable characterization of its superconducting devices. In this article, we present a procedure for characterizing microwave superconducting devices in a cryogenic RF probe station via a vector network analyzer (VNA) calibrated with a custom cryogenic calibration kit colocated with the superconducting device under test (DUT) in the cryogenic environment. By de-embedding lossy and dispersive RF interconnects linking the superconducting DUT to the measurement apparatus at room temperature, we characterize the DUT exactly at the cryogenic on-wafer reference plane. More importantly, we operate our VNA with an external modulated source and our procedure features metrology-grade multiline thru-reflect-line calibration and absolute power and phase corrections, as opposed to the more common relative scattering-parameter correction. In addition, we apply an X -parameter model to account for impedance mismatch in cryogenic Josephson microwave sources. Our techniques are also suitable for cryogenic characterization of microwave superconducting devices for solid-state quantum computers and could help to optimize the quantum-classical interfaces in these systems.

Superfluid helium has been used for cooling superconducting magnets in nuclear fusion and high energy physics. This paper presents a simplified final stage process of 1.8 K superfluid helium cryogenic system and its key component sub-atmospheric heat exchanger. Influence of variable thermal parameters of sub-atmospheric heat exchanger on the system performance is studied. The application of sub-atmospheric heat exchanger can increase refrigerating capacity by 61.34% under given conditions. The helically finned-tube heat exchanger (HFHE) is selected, and three-dimensional steady-state numerical simulations of flow and heat transfer performance have been carried out. Nu and f of tube side are 4.5-6 times higher and 95-97% lower than those of shell side, respectively. It is found that HFHE with low fin height and HFHE with filler (nylon rope) have better comprehensive heat transfer and flow performance, and PEC can reach 1.65 and 1.41 respectively under given conditions.

At scaled nodes, Back End of Line (BEOL) interconnect resistance increases super-linearly and creates performance and energy bottlenecks. While it is known that metal resistance deceases with temperature, understanding and quantifying the behavior of interconnects from a foundry process design kit (PDK) at low temperature is critical for designing circuits and systems operating at cryogenic temperatures including Quantum and Superconducting Computers and other High-Performance Systems. In this letter we use parametric path based ring oscillators along with reference ring oscillators and Metal-on-Metal Capacitors for 22nm Fully Depleted Silicon on Insulator to measure RC delays of BEOL elements from room temperature to 4.2K. The extracted resistance of the elements show reduction of up to 30% for M1/M2, 33% for M3-M6 and 19% for Via1. With simple assumptions for interconnect structure, we perform least-squares fit of Fuchs-Sondheimer-Mayadas-Shatzkes (FS-MS) models with line-Edge roughness incorporated in the model using the Namba Model. The empirically fitted parameters track well with literature. The fitted model is within 3.7% error of all experimental results.

In order to fully understand switching transients of SiC power MOSFET, an easy-to-implement transient model is built to evaluate the switching characteristics regarding to the influences of parasitic elements and circuit parameters. Under two testing conditions of room temperature and cryogenic temperature, it is shown that all the simulations generally fit the measurements well with different operating currents and voltages. For the switching energy loss during the turn-on and turn-off transients, further analysis shows that the relative error is less than 20% between the experiments and simulations. By considering the zero-loss superconductor and its equipped cryogenic environment, it can be well expected to explore a new concept of superconducting power electronics involved with superconducting and semiconducting devices in one system.

In superconducting system, current lead connecting cryogenic device and normal temperature copper cable is the main leakage heat source of entire system. Its performance directly affects cooling cost of cryogenic system. Multi-current leads have advantages of eliminating Joule heat and reducing heat conduction leakage. As a commonly superconducting material, MgB2(magnesium diboride) has broad application prospects. In this paper, the current lead of 200 A MgB2 cable and normal temperature copper cable are designed and calculated. The heat transfer power of superconducting section and the conventional current lead section are 17.90 W and 18 W, respectively. The numerical simulation method is used to verify and analyze calculation results. The temperature at interface between normal temperature copper wire and current lead is lower than 70 K.

Memory devices for low-temperature electronics have great application potential in emerging fields like quantum computing, deep-space exploration etc. However, the practical non-volatile memory device for cryogenic use still remains as a challenge today. We propose a delicately designed resistive memory device with bi-layer structure. The resistive switching layer is covered by a thermal enhancement capping layer which confines the Joule heat for better switching performance and also serves as an oxygen vacancy reservoir. This structure gives the device the multilevel resistive switching capability within a large temperature range from 8 K to 300 K. The endurance more than $10^{{6}}$ cycles at 8 K is demonstrated. Combined with kinetic Monte-Carlo simulation, the role of the thermal enhancement capping layer is analyzed.

Frost frequently forms on cryogenic equipment and is the main reason for the decline in the heat transfer of cryogenic ambient air vaporizers. In this paper, the characteristics of frosting on the surface of a finned tube in the regasification process of liquid nitrogen were investigated by a series of experiments. The experiments were conducted in an air temperature range of 2–12°C and a humidity range of 1.4–4.0 g·kg–1. The results show that frosting of the finned tube is complex, and a new “wisteria-type” frost crystal is observed at the inlet of the finned tube. The “wisteria-type” frost crystal is formed in the area of the fins with an initial temperature drop rate of higher than 2.32°C·min–1. The data on the frost layer thickness show that along the tube, the frost layer thickness first decreases and then increases, which results from the wall temperature and the concentration of water vapor. A comparison of the measured data with the frosting models in the literature is also presented. Moreover, the wall temperature is identified to modify the frosting model. The modified frosting model can predict 62.4% of the present database within a ±25% error band. This work highlights the vital role of the wall temperature in the frost porosity.

We present compact models that capture published cryogenic temperature effects on silicon carrier mobility and velocity saturation, as well as fully depleted silicon on insulator (FDSOI) and fin field effect transistor (FinFET) devices characteristics within the industry-standard Berkeley short-channel IGFET model (BSIM) framework for cryogenic IC applications such as quantum computing. For the core model charge density/surface potential calculation, we introduce an effective temperature formulation to capture the effects of the band tail states. We also present a compact model that corrects the low-temperature threshold voltage for the band-tail states, Fermi–Dirac statistics, and interface traps. New temperature-dependent mobility and velocity saturation models are accurate down to cryogenic temperature. In addition, we propose that experimentally observed ${I}_{D}$ dependence of subthreshold swing (SS) at cryogenic temperatures is a consequence of the expectedly higher rate of Coulomb scattering of free carriers.

The EDELWEISS collaboration reports on the search for dark matter particle interactions via Migdal effect with masses between 32MeV⋅c−2 to 2 GeV⋅c−2 using a 200 g cryogenic Ge detector sensitive to simultaneously heat and ionization signals and operated underground at the Laboratoire Souterrain de Modane in France. The phonon signal was read out using a transition edge sensor made of a NbSi thin film. The detector was biased at 66 V in order to benefit from the Neganov-Trofimov-Luke amplification and resulting in a resolution on the energy of electron recoils of 4.46eVee (102.58 eV at 66 V) and an analysis threshold of 30eVee. The sensitivity is limited by a dominant background not associated to charge creation in the detector. The search constrains a new region of parameter space for cross sections down to 10−29cm2 and masses between 32 and 100MeV⋅c−2. The achieved low threshold with the NbSi sensor shows the relevance of its use for out-of-equilibrium phonon sensitive devices for low-mass dark matter searches., The EDELWEISS project is supported in part by the French Agence Nationale pour la Recherche (ANR) and the LabEx Lyon Institute of Origins (ANR-10-LABX0066) of the Universite de Lyon within the program “Investissements d’Avenir” (ANR-11-IDEX-00007), by the P2IO LabEx(ANR-10-LABX-0038)inthe framework “Investissements d’Avenir” (ANR-11-IDEX-0003-01) managed by the ANR (France), and the Russian Foundation for Basic Research (Grant No. 18-0200159). This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 838537. B.J.K. thanks the Spanish Agencia Estatal de Investigación (AEI, MICIU) for the support to the Unidad de Excelencia María de Maeztu Instituto de Física de Cantabria, Ref. MDM-2017-0765.

From simple physical systems to full production lines, numerical models could be used to minimize downtime and to optimize performances. In this article, the system of interest is the SPIRAL2 (Syst\`eme de Production d'Ions RAdioactifs en Ligne de 2e g\'en\'eration) particles accelerator cryogenic system. This paper illustrates three totally different applications based on a SPIRAL2 cryostat model: optimal controller synthesis, virtual sensor synthesis and anomaly detection. The tow firsts applications have been deployed on the system. Experimental results are used to illustrate the benefits of such applications., Comment: 11 pages, 8 figures

Plate-fin heat exchangers provide a broad range of applications in many cryogenic industries for liquefaction and separation of gasses because of their excellent technical advantages such as high effectiveness, compact size, etc. Correlations are available for the design of a plate-fin heat exchanger, but experimental investigations are few at cryogenic temperature. In the present study, a cryogenic heat exchanger test setup has been designed and fabricated to investigate the performance of plate-fin heat exchanger at cryogenic temperature. Major parameters (Colburn factor, Friction factor, etc.) that affect the performance of plate-fin heat exchangers are provided concisely. The effect of mass flow rate and inlet temperature on the effectiveness and pressure drop of the heat exchanger are investigated. It is observed that with an increase in mass flow rate effectiveness and pressure drop increases. The present setup emphasis the systematic procedure to perform the experiment based on cryogenic operating conditions and represent its uncertainties level.

The construction of magnets with ever higher magnetic fields requires ever stronger and tougher reinforcement materials. Nitronic stainless steels are sometimes used for this purpose. Avoiding the sensitization temperature of these steels during fabrication is of critical importance because excessive exposure to this temperature may make them sensitive to corrosion. Even though these steels have exceptionally high mechanical strength and satisfactory toughness for use at room temperatures, low cryogenic temperatures may reduce their toughness to the degree that they are rendered unsatisfactory as reinforcement materials. This low toughness at cryogenic temperature in Nitronic steels often stems from the microstructure established during fabrication, even when the heat treatment profile follows the required protocol. Even materials that have not previously been exposed to sensitization temperatures during fabrication may later be exposed during the construction of magnets. Consequently, quality control of reinforcement materials must include both toughness tests and microstructure analyses. This paper reports recent studies of the effect of component volume and microstructure on cryogenic temperature toughness in Nitronic-type stainless steels. By comparing four different shells, we established that the presence of grain boundary particles caused lower impact fracture energy but had no significant impact on mechanical strength.

As a high-efficiency cooling technology for high-temperature superconducting coils, we have begun research and development to examine the feasibility of a cooling assist technology that maintains a cryogenic state by combining the magnetic force generated by the superconducting coil with magnetic refrigeration technology. Magnetic refrigeration requires the magneto caloric material to change the magnetic field. In many cases, the magnetic field change is obtained by moving the magnetic source, but moving the superconducting coil is not a good idea. Although it is possible to generate a change in the magnetic field by turning on and off the power supply of the high-temperature superconducting coil, it is unlikely to be established as a system that assists cooling of the superconducting coil because the coil generates heat due to AC loss. Therefore, it was considered that the magnetic field change can be obtained if the magnetic force generated from the superconducting coil can be controlled by the magnetic shield. As a verification of the principle, it was clarified experimentally that a magnetic field change can be obtained by repeatedly inserting and removing the magnetic shield into and from the gap between the magnetic field generation source and the magneto caloric material, and the temperature change can be extracted by the magneto caloric effect. In the experiment, the temperature change obtained when a magnetic shield was inserted into the air gap was measured by a simple test device using an iron-based magneto caloric material having high magneto caloric effect performance at room temperature and a permanent magnet. The principle verification confirmation test was performed using several types of magnetic shielding materials such as Permalloy bulks and the electrical steel sheets. In addition, numerical analysis is performed on the magnetic shielding effect, and the shielding effect is improved by increasing the thickness of the shielding material and the possibility of using high temperature superconductors as magnetic shielding materials were also analyzed. In this study, we report the possibility of cooling the high-temperature superconducting coil with high efficiency by combining the magnetic field created by the superconducting coil and magnetic refrigeration.

We describe our initial approach and progress towards a reliable and useful technique to connect multiple flexible superconducting cables using a cable-to-cable connector. The test structure comprises multiple components, including flexible thin-film superconducting cables, a bridging connector, a silicon well chip, and a polyimide membranes with Cu pillars. The thin-film superconducting cables used in this work contain 12 parallel Nb lines. A bridging connector which was used to connect two superconducting cables had a stripline structure with 12 parallel superconducting Nb transmission lines with 300 $\mu$ m pitch among them. A silicon well chip and a polyimide membrane with Cu pillars have been used in the assembly for high-precision micro-mechanical alignment and to apply uniform pressure on the contact points of cables and the bridging connector. DC resistances of signal traces of connected flexible cables were measured at temperature ranging from 293 K to 4.2 K in an evacuated cryogenic environment. We present the details of the design, fabrication, assembly, and test results, which show that this is a promising cable-to-cable connection approach.

BabyIAXO, a 20 m-long telescope aiming at the search for solar axions, is planned since late 2017 as a smaller scale but fully functional demonstrator of the International Axion Observatory (IAXO). It essentially comprises a superconducting magnet, optics and X-ray detectors, installed on a Sun-tracking drive system providing rotation and tilting of the detector. The preliminary design of the BabyIAXO magnet has been developed with time and the most recent modifications are reported. The magnet concept is based on using Al-stabilized NbTi conductor in a common-coil winding layout, fully resembling the baseline IAXO design and providing two free bores of 700 mm diameter and 10 m length with a magnetic field of about 2 T. The key challenges for construction and operation of the conduction cooled 40 MJ BabyIAXO magnet are addressed, such as procurement of the conductor, quench protection of the magnet components and magnetic shielding of vacuum and cryogenic equipment. Following the lab-scale experiments carried out to verify the magnet concept, their relevance and main results are further discussed before taking up the construction of the full project anticipated in 2020.

China Southern Power Grid Corporation started a project to develop a 10-Mvar high-temperature superconducting (HTS) dynamic synchronous condenser (DSC). As the first stage of the project, a 300-kvar HTS DSC prototype was developed to verify some key technologies, such as HTS rotor magnets, helium gas circulating cooling and rotating signal acquisition. In this prototype, conduction-cooled REBCO coils were installed in the rotor and air-core copper windings were used in the stator. Cold helium gas at around 20 K was used as the coolant circulating between the rotor and the external cryogenic unit through a cryogenic rotary coupling. The REBCO coils were conduction cooled by distributed helium-gas tubes embedded in the cover plates of the coils. The rotor magnet was successfully charged up to 200 A under both static and rotating conditions. For the requirement of an HTS DSC, rapid excitation tests from 170 A to 200 A were carried out at both 500 rpm and 1500 rpm.

This paper presents a 1-2 K cryogenic system for cooling the superconducting nanowire single-photon detector (SNSPD). The system is based on the Stirling-type pulse tube cryocooler (SPTC) and the Joule-Thompson (JT) cryocooler technologies and thus named as the hybrid cryogenic system. It eliminates any moving component at the cold end which endows it with evident advantages over the Gifford-McMahon (GM) cryocooler in terms of low vibration, low electromagnetic interference (EMI) and long life. It can operate at 1-2 K and has an expected mean-time-to-failure of 10 years. The overall weight is below 30 kg, which makes it an attractive cryocooler candidate for the space applications. Furthermore, the operating temperature can be adjusted conveniently for the SNSPD other than being at a fixed temperature as the superfluid helium does. The design approaches and system integration are described in detail, and the performance characteristics presented and discussed. The cooling system has an experimental cooling temperature of 1.52 K. It is also expected to reach 1 K and below provided that the further performance improvement is conducted.

By rapid development of high temperature superconductors (HTS), the HTS magnet has become an enabling technology for compact, high magnetic field tokamaks requiring larger current densities and higher magnetic fields where low temperature superconductors (LTS) have limitations. Thus, a preliminary conceptual design study on HTS magnet for toroidal field (TF) coil, a major component of compact and high field tokamak, is presented to investigate the possibility of the use of an HTS. General features relevant to a large-scale superconducting magnet are discussed such as electromagnetics, mechanical stress, protection, and cryogenics. Two types of HTS tapes are used to design TF coils for a tokamak that targets 9.2 T at its major radius 3.3 m: 1) Design A , using an HTS tape used in previous high field HTS magnets; and 2) Design B , using the same HTS tape with twice the performance. The results convey the possibility of HTS TF coil with currently available technology, but with the expense of a large amount of HTS tapes inferring that a reduction in the HTS tape cost is required. Improvement on the HTS TF coil design is needed using the unique characteristics of HTS. Hence, some of the challenges for HTS fusion magnet are addressed including performance degradation of conductors, quench detection and protection method, and joint for demountable TF coil.

The recent trends in High Temperature Superconductor (HTS) development and HTS based applications have led to the exploration of various methods for achieving cryogenic temperature suitable for the superconducting cables and magnet characterization. An existing test facility at ITER-India has been augmented to deliver 80 K helium for testing, particularly for thermo-hydraulic characterization of superconducting cables. Such characterization is very important for the prediction of performance during operation to ensure adequate mass flow rate through the cable for heat load removal and to maintain the cable stability. The facility is capable of supporting the test on a superconducting short sample at 80 K with a mass flow rate up to 35 g/s and pressure up to 7 bar(a) using helium as a fluid. The functional acceptance of the developed test facility has been performed with the first experiment conducted on a short coiled shaped mock sample cable-in-conduit conductor (CICC). The longitudinal friction factor obtained from the measurement has been compared with the existing correlations for Reynolds number ranging between 50-400. The wound CICC short sample has been analyzed using Computational Fluid Dynamics (CFD) approach, considering the bundled region as a porous media to cover a wide range of various thermo-hydraulic and geometrical parameters involved in the test sample. A comparison of the experimental and the CFD simulation results is presented.

As air traffic has been increasing in recent years, the environmental impact of aviation is more obvious, forcing governments to impose stringent regulations on emissions. In order to meet these regulations, and reduce the carbon footprint, research has been directed towards the all-electric and hybrid aircraft, where the use of cryogenic HTS machines and cables has been proposed to reduce the overall size of the aircraft. With the cryogenic system already in place, research has been exploring the use of power electronics at lower temperatures in order to obtain systems with higher power densities and lower losses. In this paper several power semiconductor devices are tested at room and cryogenic temperature in order to evaluate their performance at lower temperature. One of the tested devices, a 'CoolMOS' superjunction MOSFET, is used in a single voltage source phase-leg which is experimented with at room and cryogenic temperature to evaluate its efficiency as a primary indication of its usefulness in the All-Electric Aircraft.

We present a design overview of the MIT 1.3-GHz LTS/HTS NMR magnet (1.3G) with a newly designed 835-MHz REBCO insert (H835) as a replacement for the 800-MHz REBCO insert (H800) that was damaged when it quenched during operation in 2018. The new H835 is designed to contribute 19.6 T in a background field of 10.93 T by an LTS NMR magnet that normally rated at 11.74 T (500 MHz): combined, 1.3G generates a total field of 30.53 T corresponding to a proton resonance frequency of 1.3 GHz. H835 is designed to operate stably while meeting 1.3G design constraints. We have also designed H835 to protect it from permanent damage in an improbable event like a quench. Key design features are: 1) a single-coil formation, composed of 38 stacked metal-co-wound no-insulation and 2 stacked no-insulation double-pancake coils, all with mechanically improved cross-over sections; 2) enhanced thermal stability; and 3) reduced current margin with a detect-and-heat method. This paper includes: 1) electromagnetic and mechanical design of H835; 2) cryogenics overview; 3) quench protection strategy; and 3) discussion on the next steps to successfully complete 1.3G.

Glass Fiber Reinforced Plastic (GFRP) is usually employed as the insulator material of superconducting cable terminal, owing to its excellent mechanical properties and insulation strength at cryogenic temperature. However, in the presence of a void defect, both the insulation life span and mechanical strength of GFRP decrease significantly at superconducting temperature conditions. In this paper, efforts have been made to investigate the degradation process of GFRP at cryogenic temperature and give insight into its degradation mechanism. By comparing PD activities at 278.7 K, 223 K and 153 K in initial phase of aging, it is found that PDs are inclined to be inhibited at lower temperature. Experiments indicate that the deposited charge accumulation and mechanical properties degradation, instead of chemical aging and PD energy, play a crucial part in dielectric degradation. At cryogenic temperatures, the local heat accumulation brought by PDs increases the material internal mechanical stress, and the accumulation of deposited charges causes instantaneous energy release. On the basis of the decrease of the mechanical properties of the material, the crack expands rapidly, which leads to the dielectric failure of the material. In conclusion, the degradation of GFRP at cryogenic temperature is the result of the combined effects of deposited charge accumulation and mechanical properties decline.

The superconducting nanowire single photon detectors (SNSPD) are now widely used in space quantum communication, satellite laser ranging, and quantum key distribution, etc. However, a very low temperature around 2 K is required for its operation and performance improvement. We are developing a 1.6 K hybrid cryocooler to meet this demand, which is composed of a three-stage Stirling-type pulse tube cryocooler (SPTC) and a Joule-Thomson cryocooler (JTC). The hybrid cryocooler has no moving component at the cold end and is driven by the long life linear compressor, thus realizing high reliability, low vibration and long operation life time. The cryogenic system, including the coupling structure with the SNSPD, is descripted in detail. The thermodynamic enthalpy analysis of the last-stage of the hybrid cryocooler is carried out, by which the upstream pressure and precooling temperature are optimized to meet the required base temperature and cooling capacity with less input power. The model is described and the experiments coupling with a SNSPD simulated load are carried out. The results show that the hybrid cryocooler can achieve 16.3 mW at 1.6 K, 20 mW at 1.8 K and 25 mW at 2.1 K, respectively, and thus suggests a promising space cryocooler for cooling the SNSPDs.

A Chinese group is collaborating with CERN in producing the HL-LHC MCBRD magnets (D2 corrector). Before delivery to CERN, the MCBRD magnets should be trained and cold tested at 4.5 K to check that the magnets are up to standard. To meet the requirements of cold testing, the IMP team made an upgrade plan for the existing cryogenic test facility and designed 4 m long anti-cryostats for the rotating coil. To control the temperature difference and avoid nitrogen contamination during the pre-cooling, the IMP team developed an indirect cooling method which can pre-cool the magnet with LN2 by radiation and convection through gaseous helium. With this method, the LN2 does not touch the magnet and even not need a circulation of the cold helium gas. The first Chinese produced magnet which is called MCBRDP2 has been tested on this stand. The details of the cryogenic test facility, the indirect cooling method, and their performances during MCBRDP2 cold testing are discussed in this paper.

This article presents the design and evaluation of the first cryogenic switched capacitor array (SCA)-based waveform digitizer (CryoSCA) for HPGe detectors for low-background physics experiments. The chip has integrated 16 channels and was fabricated using a 0.18- $\mu \text{m}$ CMOS process with modified BSIM3v3 model parameters at 77 K. Each channel employs two 32-cell sample blocks working in the ping–pong mode, a 256-cell storage array, 32 parallel Wilkinson-type ADCs with 12-bits dynamic range, and registers. The chip was fully evaluated and showed promising performance at 300 K and 77 K. The measured power consumption of each channel increased from 3.3 mW at 300 K to 3.6 mW at 77 K. The averaging integral nonlinearity (INL) over 1–V dynamic range was measured to be 0.3% and 0.2% at 300 K and 77 K, respectively. The static noise decreased from 0.8 mV at 300 K to 0.6 mV at 77 K. The leakage current decreased from 18.2 fA at 300 K to 2.2 fA at 77 K.

A cikkben a szerzők ismertetik a kriogén rendszerekkel kapcsolatos kutatási tevékenységüket. A bevezetést, valamint a kriogenika rövid történetét követően bemutatjuk a repülésben alkalmazott kriogén gázokat, elemezve a folyékony hidrogén használatát. Egy példán keresztül olyan számítógépes szoftver használatát mutatjuk be, amely a valósághoz hűen képes a közegek áramlásának fizikai-matematikai modellezésére. Célunk egy átfogó, könnyen megérthető összefoglaló elkészítése a modernkori repülés alternatívájáról.

The main issue in machining glass fiber reinforced polymers is a rapid wearing of the cutting tool caused by the superior properties of the fiber reinforcement within the matrix. Cooling in machining processes reduces tool wear and extends tool life. Cryogenic cooling is an alternative method for effective, environmentally friendly, clean and safe cooling. This paper studied the tool wear characteristics of carbide inserts coated with TiCN and Al2O3in turning glass fiber reinforced epoxy resin pipe. The cutting parameters were various, with cutting speed, feed rate, depth of cut and cutting conditions (without cooling and with cryogenic cooling). Not all cutting speeds that were cooled under cryogenics showed good outcomes. However, the experimental results suggest that using high cutting speed at 1800 rpm and high feed rate at 0.13 mm/rev, together with cryogenic cooling, can reduce the flank wear of the tool compared with no cooling.

Operating circuits under cryogenic conditions is effective for a large spectrum of applications. However, the refrigeration requirement for the cooling of cryogenic systems introduces serious issues in terms of power dissipation. Gain-cell embedded dynamic random access memory (GC-eDRAM) is a low-area, logic-compatible embedded memory alternative to static random access memory (SRAM), which has the potential to provide ultralow-power operation under cryogenic conditions due to the lower leakages at these temperatures. In this article, we present the first comparative design exploration of GC-eDRAM under cryogenic conditions performed with transistor models characterized based on actual silicon measurements under temperatures as low as 77 K. Our study shows that the two-transistor (2T)-based GC-eDRAM configurations turn out to be the best solutions for very low-temperature operation. In particular, the 2T mixed GC-eDRAM configurations allow read sensing margin improvements (up to 99%) within the 2T-based configurations while at the same time excel in terms of data retention time (+44%) and power consumption (−27%) when compared to more complex GC-eDRAM topologies. Moreover, even better improvements in terms of area (−73%), leakage power (−97%), retention power (−76%), and energy (−66%) are observed when compared to conventional 6T-SRAM.

There are axial and radial electromagnetic forces between the stator and rotor of axial flux disk motor besides the useful torque. The electromagnetic forces act on the rotor and are crucial to the stable operation in magnetic levitation applications driven by disk motor. This article concerns the behaviors of axial and radial electromagnetic forces of disk motor using for cryogenic submersible pump. It is measured experimentally that the electromagnetic properties of motor materials, including the electrical conductor and magnetic conductor materials, in room temperature (RT) and liquid nitrogen (LN2) environment. Then, the 3D finite element model (FEM) of the three-phase asynchronous disk motor in RT environment is built which is also validated by the RT experimental tests. Finally, the behaviors of axial and radial electromagnetic forces in LN2 environment are investigated using the modified FEM taking account of the effect of cryogenic environment on the motor material. It is concluded that the axial electromagnetic force decreases monotonously with the increasing air-gap thickness or the decreasing rotating speed. When the rotor exhibits radial eccentricity, there is a restoring radial electromagnetic force, trying to pull the rotor back to the central position. The radial electromagnetic force increases with the increasing rotational speed and radial eccentric displacement.

In this report, a pulsed electro-acoustic (PEA) device is modified to test the charge profile in epoxy resin at 77 K (-196°C) and successfully obtains the charge signal. A piezoelectric material suitable for cryogenic application is chosen for the measurement. In the experiment, the polarization and depolarization tests are operated with different voltage supply procedures. After initial wave recovery, the waveforms are discernable enough to identify the charge information. It is found that the charges are much less active at the low temperature with both slow dissipating rate and low injection quantity, comparing to the case at 293 K.

The avalanche ruggedness of power devices becomes a crucial issue to ensure the safe operation of the power conversion systems, particularly under the extreme temperature conditions. In this article, the avalanche capability of SiC planar/trench MOSFETs is systematically evaluated and analyzed over the temperature range of 90 to 340 K. Importantly, the essential mechanisms and temperature dependence of avalanche failure under cryogenic conditions are further explored by combining many analysis methods such as TCAD simulations, the unclamped inductive switching characterizations, and the transient junction temperature prediction. The highest avalanche energy density of 171.24 mJ/mm2 at 90K indicates the great application potential of SiC planner mosfet in cryogenic electronics. Moreover, the safe avalanche operation boundary (AOB) model is established over the cryogenic temperature range. The relevant analysis method and AOB model can be used to accurately evaluate and quantitatively predict the avalanche capability of SiC planar/trench mosfet s for the cryogenic converter design.

Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada., et al., The QUIJOTE (Q-U-I joint Tenerife) experiment combines the operation of two radio-telescopes and three instruments working in the microwave bands 10–20 GHz, 26–36 GHz and 35–47 GHz at the Teide Observatory, Tenerife, and has already been presented in previous SPIE meetings (Hoyland, R. J. et al, 2012; Rubi˜no-Mart´ın et al., 2012). The Cosmology group at the IAC have designed a new upgrade to the MFI instrument in the band 10–20 GHz. The aim of the QUIJOTE telescopes is to characterise the polarised emission of the cosmic microwave background (CMB), as well as galactic and extra-galactic sources, at medium and large angular scales. This MFI2 will continue the survey at even higher sensitivity levels. The MFI2 project led by the Instituto de Astrof´ısica de Canarias (IAC) consists of five polarimeters, three of them operating in the sub-band 10–15 GHz, and two in the sub-band 15–20 GHz. The MFI2 instrument is expected to be a full two–three times more sensitive than the former MFI. The microwave complex correlator design has been replaced by a simple correlator design with a digital back-end based on the latest Xilinx FPGAs (ZCU111). During the first half of 2019 the manufacture of the new cryostat was completed and since then the opto-mechanical components have been designed and manufactured. It is expected that the cryogenic front-end will be completed by the end of 2022 along with the FPGA acquisition and observing system. This digital system has been employed to be more robust against stray ground-based and satellite interference, having a frequency resolution of 1 MHz., Partial financial support is provided by the Spanish Ministry of Science and Innovation (MICINN), under the projects AYA2017-84185-P, IACA15-BE-3707, EQC2018-004918-P and the FEDER Agreement INSIDE-OOCC (ICTS-2019-03-IAC-12). We also acknowledge financial support of the Severo Ochoa Programs SEV-2015-0548 and CEX2019-000920-S.

In this work, we report the characterization and modeling of a 14 nm bulk FinFET technology from room-temperature down to 4.6 K. A cryogenic device model is used which shows excellent fit to measured data and can accurately predict the performance of the devices at low temperatures. The nMOS device showed subthreshold swing of 20 mV/decade, V T shift of 80 mV and gm enhancement of 30%, all at 4.6 K. These results show that a tailored cryogenic FinFET technology, i.e. one accounting for the change in V T and SS, could achieve a sharp reduction of dissipated power by reducing the drive bias. Such technology has potential for strong impact e.g. in quantum computing, by enabling integration of dense advanced cryogenic ICs inside the cryostat.

This article provides for the first time a very extensive experimental characterization coupled with a fully analytical modeling in order to investigate, in a systematic and comprehensive way, the sensing performance of a two-port surface acoustic wave (SAW) resonator from room down to cryogenic temperatures. The motivation behind this work is twofold: to quantitatively assess the temperature sensitivity of the SAW technology for cryogenic applications and to gain a better understanding of the underlying physics in terms of the equivalent-circuit elements. Although the measurement-based analysis is developed by focusing on a SAW from Murata as a case study, the developed investigation methodology is independent of the considered technology and extensible to other SAW types. A cryogenic system based on a closed-loop helium refrigerator is used to cool the tested SAW from 300 K down to 20 K with a step of 10 K. At each studied temperature, the scattering parameters are measured using a vector network analyzer over a narrow frequency band around the nominal resonant frequency of 423.2 MHz, spanning from 420 MHz to 425 MHz with a small step of 3.125 kHz. The measured scattering parameters are then transformed into the admittance ones, as they are more useful for sensing performance assessment and for equivalent-circuit model extraction. The extracted model is successfully validated through the achieved good agreement between measurements and simulations of the temperature- and frequency-dependent behavior of the studied resonator.

Cryogenic computing can achieve high performance and power efficiency by dramatically reducing the device’s leakage power and wire resistance at low temperatures. Recent advances in cryogenic computing focus on developing cryogenic-optimal cache and memory devices to overcome memory capacity, latency, and power walls. However, little research has been conducted to develop a cryogenic-optimal core architecture even with its high potentials in performance, power, and area efficiency. In this article, we first develop CryoCore-Model, a cryogenic processor modeling framework that can accurately estimate the maximum clock frequency of processor models running at 77 K. Next, driven by the modeling tool, we design CryoCore, a 77 K-optimal core microarchitecture to maximize the core’s performance and area efficiency while minimizing the cooling cost. The proposed cryogenic processor architecture, in this article, achieves the large performance improvement and power reduction and, thus, contributes to the future of high-performance and power-efficient computer systems.

Advantages such as high energy density, minimal environmental impact, use of established system components and the absence of geographical limitations drive further research and development in cryogenics-based energy storage technology. This paper evaluates an adiabatic cryogenics-based energy storage system (large capacity of 100 MW/400 MWh) using advanced exergy-based methods in order to identify the potential for improvement (avoidable/unavoidable parts of thermodynamic inefficiencies, investment costs and environmental impacts) of the system components and the interdependencies among these components (endogenous and exogenous parts of thermodynamic inefficiencies). The simulation of the system was conducted in Aspen Plus®. The results show that the interactions among the components are strong. From the cost viewpoint, the two main heat exchangers are the most important components. The cost minimization of these components indicates that the minimum temperature difference in both heat exchangers should be increased. From the thermodynamic viewpoint, the expander and the main heat exchanger 2 dominate the avoidable inefficiencies. After application of the recommendations made here, cryogenics-based energy storage technology is expected to become thermodynamically and economically viable.

Inconel 625 is a nickel-based super alloy especially used in aeronautical industries, due to its high mechanical strength, exceptional weldability and good corrosion resistance properties. However,...