bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical study of a consequence of a vacuum insulation degradation in a cryogenic system
Authors: Kopczynski A. , Baran B. , Malecha Z. 
Published: June 2020

Abstract
Vacuum is the primary method for a thermal insulation of cold elements in cryogenic systems, tanks and other cryogenic equipment. A dangerous situation arise in the case of vacuum envelope failure when a 300 K air enters the vacuum and the cold elements of cryogenics equipment are exposed to a potentially intense heat fluxes and air velocity. Depending on a mass flow of the air (equivalent to size of an insulation rapture), a different rate of the temperature and pressure growth in the vacuum chamber can promote various mechanisms of the heat transfer to the cold elements. Additionally, it can be limited by the air deposition, condensation and cryosorption. In the present work a simplified numerical model of a typical cryogenics system is developed and different scenarios of vacuum degradation are considered. The current studies aim to identify the development of the different thermal conditions in the cryogenics system in the function of the mass flow of the ventilating air. The present work presents numerical studies of vacuum degradation for various sizes of a rapture hole. Additionally, the work proposes a simplified zero-dimensional model, which includes a deposition of air and its influence on pressure buildup and heat transfer.
Ultimate Tensile Strengths of 3D Printed Carbon-fiber Reinforced Thermoplastics in Liquid Nitrogen
Authors: Hunt M , Salmon K , Haney J , Evans C , Gozen A , Leachman J 
Published: June 2020

Abstract
3D printed composites have potential to satisfy needs for lighter and more sophisticated materials for aerospace, medical, and other sectors. However, few mechanical property measurements of 3D printed parts at cryogenic temperatures are available. To address this need, this work performs ultimate tensile strength testing of 3D printed thermoplastics immersed in liquid nitrogen at approximately 77 K. Materials tested include carbon-fiber reinforced PETG and carbon-fiber reinforced Amphora AM1800 filament. The carbon-fiber reinforced PETG increased in ultimate tensile strength and modulus of elasticity by 49% and 43.2% from room temperature tests, respectively. The carbon-fiber reinforced Amphora AM1800 filament decreased in ultimate tensile strength by 29.9% from room-temperature.
Cryocooled cold trap system for the SuperCDMS dilution refrigerator
Authors: Tatkowski G , Hollister M , Dhuley R , Ruschman M , Bauer D , Lukens P 
Published: June 2020

Abstract
Operating 6,800 feet underground at the SNOLAB facility in Sudbury, Ontario, Canada, the dilution refrigerator-cooled SuperCDMS SNOLAB (Super Cryogenic Dark Matter Search at the Sudbury Neutrino Observatory Laboratory) experiment has been designed for maximum cryogenic up-time and remote operations. A key element in achieving these goals is a pair cold traps in the helium circulation stream of the dilution refrigerator; the first operating near liquid nitrogen temperatures and the second operating near liquid helium temperatures. Previous experience with the CDMS experiment, located underground at the Soudan Under-ground Laboratory, has given significant operational experience with dilution refrigerator cold traps and has solidified the demand of a system of dual cold traps. Unlike the CDMS-era system, the new SuperCDMS system will feature a cryocooler powered liquid nitrogen re-liquefying system (as opposed to regular under-ground re-filling of cold trap dewars using portable nitrogen dewars) and a cryogen-free 4 K cold trap, which eliminates the need for a bath of liquid helium.
The Effect of Shorted Secondary Circuit Material on Quench Protection of an HTS Tape Solenoid discharged across a Varistor
Authors: Green Michael A. 
Published: June 2020

Abstract
Studies suggest that an insulated ReBCO tape solenoid coil that is well-coupled inductively to shorted secondary can effectively be quench protected by discharging the coil across a constant voltage resistor. The discharge voltage across the constant voltage resistor is much lower than it would be for a constant resistance resistor that is used to achieve the same final quench temperature with or without a shorted secondary. How this quench protection works, depends on the constant voltage resistor characteristics, the properties of the shorted secondary circuit material and the amount of the material in the circuit. A previous paper suggests that the RRR shorted secondary circuit material is not important, which means that aluminum can be used in the secondary circuit and structural aluminum can support both the coil and the secondary circuit when that aluminum is on the outside of a solenoidal coil.
Cryogenic testing of fast ramping superconducting magnets for the SIS100 synchrotron
Authors: Bleile A , Datskov I , Fischer E , Khodzhibagiyan H , Marusov V , Roux C , Spiller P , Sugita K , Szwangruber A 
Published: June 2020

Abstract
The international Facility for Antiproton and Ion Research FAIR is currently under construction at GSI, in Darmstadt, Germany. The core component of FAIR, the superconducting SIS100 synchrotron will operate with a high repetition rate of up to 1 Hz. The SIS100 ring with a circumference of 1083 m contains 108 main dipole magnets with a maximal field of 1.9 T. The ion-optical lattice of SIS100 contains also 166 main quadrupoles and 137 corrector magnets. The quadrupole and corrector magnets are assembled in the quadrupole units that are pair-wise integrated in quadrupole doublet modules. All superconducting magnets will be tested at liquid helium temperature to assure their compliancy with the specification. The main dipole modules are being tested at the magnet test facility at GSI. Cold testing of the quadrupole doublet modules is split in the testing of the quadrupole units at JINR, Russia and in testing of fully assembled quadrupole doublet modules at INFN, Italy. The cold testing program includes dynamic AC loss measurements and hydraulic adjustment of the parallel cooling channels of SIS100 next to the training, magnetic field measurements and other tests. We present the scope of cold testing of different types of magnet modules as well as the test results.
Analysis of the thermal recovery of HTS cables after an overcurrent fault
Authors: Demko J A , Duckworth R C , Churu G , Hasssenzahl W 
Published: June 2020

Abstract
High temperature superconducting (HTS) power transmission cables are cooled to operating temperatures typically below 80 K. A valuable feature of some HTS cables is that they can limit short-circuit fault currents, which can be more than ten times the maximum operating current of a cable. When a fault occurs the HTS wire is no longer superconducting and the heating which occurs will raise the temperature above the allowable operating point. To recover from the fault, the conductor must be cooled down before returning to service. The recovery is affected by the refrigeration system’s performance which varies with load and temperature. A transient numerical model of an HTS cable is applied to investigate the thermal recovery after a fault for some HTS cable system configurations and operating conditions.
Thermal Optimization of Functional Insertion Components (FIC) for Cryogenic Applications
Authors: Shu Q S , Demko J A , Fesmire J E 
Published: June 2020

Abstract
Various functional insertion components (FIC), directly connecting a cold mass and the ambient environment, are irreplaceable and play crucial technical roles in many superconducting cryogenic applications. However, such components also bring a huge heat leak to the cold mass. The heat leak is usually much greater than that through entire evacuated MLI insulation system and solid support structures combined. Therefore, this situation brings unimaginable challenges not only to the refrigeration loads to be met but also critical aspects of the FIC design in satisfaction of highly restrictive, even contradicting technical functions. The FIC must simultaneously minimize the heat leak provide a large amounts of DC current and RF power to/from the cold mass, as well as provide a reliable ultrahigh vacuum thermal isolation break with strong mechanical stability. Reviewed are the following commonly used FICs: 1) various RF input couplers for transmitting MW-RF power; 2) high DC power current leads for energizing various SC magnets; 3) various high order mode (HOM) couplers for damping unwanted RF energy; 4) instrumentation cable/wire to cold mass. Approaches to efficiently minimize the DC current heating, RF surface heating, heat leak through the solid body of FIC, efficient cooling approaches, while reliably providing the technical functions, are briefly summarized and compared for select applications from around the world.
Adiabatic Two-Phase Flow Patterns for Zeotropic Mixtures of Tetrafluoromethane/Ethane in a Horizontal Smooth Tube
Authors: Song Q L , Chen G F , Wang H C , Deng Z , Shen J , Gong M Q 
Published: June 2020

Abstract
Mixed-refrigerant Joule-Thomson refrigeration (MJTR) systems have distinct advantages in the temperature range from 80 to 230 K. Tetrafluoromethane (R14) and ethane (R170) are essential components of mixed-refrigerants. Heat transfer and pressure drop for twophase flow are closely related to corresponding flow patterns. In this paper, an experimental investigation on adiabatic twophase flow patterns for R14/R170 mixtures in a horizontal smooth tube with inner diameter of 4 mm was presented. Experiments were carried out at mass fluxes from 100 to 350 kg m−2 s−1 and saturation pressures from 1.5 to 2.5 MPa over the entire range of vapor quality. The effects of concentration, mass flux, saturation pressure and vapor quality were analyzed and discussed. Furthermore, the observed flow patterns were compared with six existing flow pattern maps. Our previous model developed for pure R14 shows the best predictive ability with 80.16% of the data points can be accurately predicted.
RRR measurements and tensile tests of high purity large grain ingot niobium
Authors: Zhao Z , Owen C , Abdo G G R , Ribas R M , Myneni G R , Chiesa L 
Published: June 2020

Abstract
Residual resistivity ratio (RRR) measurements and tensile tests were performed on samples taken from seven high purity large grain niobium ingots produced by CBMM. Test specimens were taken from the top, middle and bottom regions of each ingot. The RRR measurements were performed with a GM cryocooler system and more than 60% of the samples exceeded RRR values of 250. Room temperature tensile tests were performed on samples from the same regions. 17 samples were machined according to ASTM standard test methods for tension testing of metallic material. Tests were performed with an Instron tensile/compression testing machine, and various mechanical properties such as Young’s modulus, 0.2% proof stress, ultimate tensile strength and strain at fracture were measured. For all the samples, the fracture strain exceeds 35% while the ultimate tensile stress is close to 100 MPa. Contents of impurity (N, O, C, H, Ta) of each region of the seven ingots were also measured. These data provide insights for a possible correlation among RRR values, mechanical properties and impurity contents of niobium ingots.
Resins for Superconducting Magnet Construction – An Overview of Requirements, Processing and Properties
Authors: Evans David 
Published: June 2020

Abstract
The resin used for bonding and insulating superconducting magnets can be a major factor in ensuring reliable and stable operation of the completed assembly. There are many resin systems and available to magnet designers and engineers. The selection of the correct material depends on the application technique selected, the processing requirements and the end properties required of the cured resin. Available techniques for magnet construction and bonding include vacuum impregnation (VPI), so called ‘wet winding’ and the use of pre-impregnated fabrics. The advantages and disadvantages of these techniques are considered and the processing requirements for each are discussed. Materials selection requires an understanding of the processing characteristics such as viscosity and ‘useable lifetime’ but these must be married with the properties required of the cured resin. A low viscosity and long useable life is a frequent requirement for VPI processing of large magnet systems and this may be difficult to match with high thermal shock resistance that may be required to minimize cracking possibilities in resin rich regions. Examples are presented of resin systems resistant to cracking and structural features that enhance this parameter. For many magnets that may operate in an ionising radiation environment, radiation stability is an important requirement. Radiation stable systems are described and structural features that promote such stability are considered, along with the difficulty of matching all competing requirements.
Cryogenic Power Electronics: Press-Pack IGBT Modules
Authors: Park C , Mauger M J , Damle T , Huh J , Steinhoff S , Graber L 
Published: June 2020

Abstract
With the goal of enabling high-power-density cryogenic power converter technology and superconducting power applications for future aircraft and shipboard power systems, the dynamic and static performances of a press-pack IGBT module (T0160NB45A) at ambient and cryogenic conditions are reported. Compared to the wire-bond IGBT’s, press-pack IGBT’s are more suitable for cryogenic conditions as they do not have bonded connections and use fewer materials types, which reduces the risk of coefficient of thermal expansion (CTE) mismatch. The study has been conducted with a cryogenic testbed that provides a condensation-free condition during and after tests, which is essential for the preservation of the physical properties of IGBT’s being tested. The dynamic performance characterization results show that the switching speeds of both turn-on and turn-off are improved with substantially reduced tail current and increased dv/dt at cryogenic conditions. Moreover, the static performance characterization results show a reduction in collector-emitter voltage drop, indicating higher conductivity of the IGBT at cryogenic conditions. Furthermore, the impact of clamping force and gate lead length on the press-pack IGBT’s dynamic characteristics is reported. The findings of this study suggest that press-pack IGBT modules are suitable for cryogenic operation.
Cryogenic Power Electronics: Capacitors and Inductors
Authors: Park C , Obadolagbonyi O , Graber L 
Published: June 2020

Abstract
Capacitors and inductors that are suitable for cryogenic use are presented in this study. With the long-term goal of developing power electronic converters for cryogenic use, we studied various off-the-shelf metalized polypropylene film capacitors at cryogenic and ambient conditions. Capacitance and breakdown voltage of the film capacitors were the main parameters measured at room temperature and in liquid nitrogen. The results show that the material of dielectric film and the method of packaging play a role in the characteristics of breakdown voltage and capacitance in cryogenic conditions. In general, both capacitance and voltage rating of the capacitors were comparable if not better at cryogenic conditions. Moreover, with the long-term goal of developing inductors for cryogenic applications, we built and tested inductors with and without a magnetic core. The resistance, inductance, maximum current, and energy density were measured and compared. According to the results, the energy density of the cryogenic inductor without a magnetic core can be designed to be much higher than its room temperature counterpart mainly due to the superior cooling power of liquid nitrogen and the reduced resistivity of the windings at cryogenic temperatures.
Pressure-induced critical current reduction in impregnated Nb3Sn Rutherford cables for use in future accelerator magnets
Authors: Gao P. , Dhallé M. , ten Kate H. H. J. 
Published: June 2020

Abstract
The measured critical current reduction in Nb3Sn Rutherford cables under magnet-relevant transverse pressure levels is analyzed in terms of the strain state of the filaments inside their strands. Several straightforward mechanical 2D FE models of the cables’ cross-section are used to translate the stress that is applied to the surface of the impregnated cables into a strain distribution on its strands. The resulting critical current reduction of the cable is then estimated from the average deviatoric strain in the strands’ filamentary zone, using the well-established strain scaling relations obtained for isolated strands. This allows to identify the main factors that influence the pressure response of impregnated Nb3Sn accelerator cables. The analysis is presented for state-of-the-art cable samples that were measured at the University of Twente and shows how especially stiff and incompressible resins reduces the deviatoric strain in the filamentary zone of the cable strands, but also how relatively small alignment errors can lead to stress concentrations that reduce the critical current density significantly.
The Role of CHPD and AIMI processing on enhancing JC
and transverse connectivity of in-situ MgB2 strand
Authors: Wan F , Sumption M D , Rindfleisch M A , Collings E W 
Published: June 2020

Abstract
Research into in-situ MgB2 strand has been focused on improvements in JC
through reduction of porosity. Both of cold-high-pressure-densification (CHPD) and advanced-internal-magnesium-infiltration (AIMI) techniques can effectively remove the voids in in-situ MgB2 strands. This study shows the nature of the reduced porosity for in-situ MgB2 strands lies on increases in transverse grain connectivity as well as longitudinal connectivity. The CHPD method bi-axially applying 1.0 GPa and 1.5 GPa yielded 4.2 K J
CM║s
of 9.6 × 104 A/cm2 and 8.5 × 104 A/cm2 at 5 T, respectively, with compared with 6.0 × 104 A/cm2 for typical powder-in-tube (PIT) in-situ strand. Moreover, AIMI-processed monofilamentary MgB2 strand obtained even higher J
Cs and transverse grain connectivity than the CHPD strands.
Development of an in-situ analysis instrument for microstructure of materials with low temperature
Authors: Liubiao Chen , Yuanheng Zhao , Xuming Liu , Xiaotong Xi , Jue Wang , Yuan Zhou , Junjie Wang 
Published: June 2020

Abstract
The development of instruments capable of dynamically observing the microstructure at different temperatures is of great significance for the study of materials. The liquid nitrogen and a self-developed high-frequency pulse tube cryocooler were used as the cold source to develop the cryogenic system of scanning electron microscope (SEM) in this paper. The vibration and temperature control problems and solutions involved in using these two cold sources as SEM cryogenic systems were described and discussed in detail. It was found that it is necessary to fully achieve the heat balance at a certain temperature and adjust the image displacement to overcome the adverse effects caused by the thermal expansion and contraction of the low temperature components, and the cryocooler needs to use an intermittent operation mode to avoid distortion of the material microstructure image caused by vibrations of the cryocooler. Whether it is for liquid nitrogen or cryocooler, a thermal switch between the cold source and the thermal bridge is helpful for temperature control of the sample and reduced heat leakage of the system.
The Effect of Reinforcement Substrate Alloy Selection on Mechanical Properties of REBCO Coated Conductors
Authors: Radcliff K. J. , Walsh R.P. , Larbalestier D.C. , Hahn Seungyong 
Published: June 2020

Abstract
Rare earth Barium Copper Oxide (REBCO) coated conductors are promising candidates for high field (>25 T) user magnets. However, as the demand for higher fields increase, so does the potential to overstrain the conductors being used. Coated conductor substrates, such as 310s stainless steel and the super-alloy Hastelloy C276, serve as the backbone for mechanical strength in these conductors. Both substrate alloys share similar properties when optimally processed into strips prior to manufacturing of the REBCO coated conductor. We find that with subsequent REBCO manufacturing processes the strength of the substrate changes, the magnitude of which depends on whether Hastelloy C276 or 310s stainless steel is used. In this study, we investigate the stress-strain variability found in coated conductors and how the manufacturing process affects the mechanical properties. The manufacturing step of concern is the short time that the substrate is exposed to high temperature (700 to 800 C) during the REBCO deposition process. To better relate manufacturing processes and mechanical properties, we subjected bare substrates to different heat treatments at 700, 750, and 800 C for 15 minutes each. With post heat-treatment room-temperature tensile tests, we found that the 310s stainless steel substrate was sensitive to the variations of time and temperature, exhibiting yield strength reductions of 20 to 50 % depending on the heat treatment. By contrast, Hastelloy C276 did not weaken and initially showed strengthening effects with exposure to the lower temperature heat treatments. Coated conductor manufactures may prefer 310s stainless steel as their substrate due to cost and availability, however, moving to Hastelloy C276 will offer better mechanical robustness and reproducibility of mechanical properties within their coated conductor.
Improvement of in-field performance for EuBCO with heavily doped BHO coated conductors by PLD method with high temperature deposition and low temperature annealing
Authors: Ibi A , Machi T , Nakaoka K , Sato M , Izumi T , Nishimura J , Miura M , Yokoe D , Kato T , Hirayama T 
Published: June 2020

Abstract
Recently, we have found that BaHfO3 (BHO)-doped EuBa2Cu3O7-X (EuBCO) coated conductors by the combination of the IBAD and PLD methods show high critical current (Ic
) even in an applied magnetic field. However, for the wide application of BaMO3 (BMO, M: metal)-doped REBa2Cu3O7-X (REBCO) coated conductors to industrial and commercial applications, much higher in-field performance is required. It is known that the critical temperature (Tc
) of BMO-doped REBCO layers, especially by the PLD method, decreases with the increase in the amount of doped BMO apparently due to the strain of the REBCO induced by BMO doping. Therefore, it is difficult to improve the critical current density (Jc
) in the applied magnetic field of BMO doped REBCO coated conductors only by increasing the quantity of BMO especially at high temperatures such as 77 K. To solve this problem, we tried to optimize the deposition conditions, especially the deposition temperature and O2 annealing processes for heavily BHO doped-EuBCO layers fabricated by the PLD method. As a result, the combination of high temperature deposition and low temperature O2 annealing was effective in obtaining high Tc
and high in-field performance of heavily BMO-doped REBCO coated conductors. The Tc
of 10 mol% BHO-doped EuBCO coated conductors was 93.9 K (setting a deposition temperature of 1150 ° C and O2 annealing temperature of 280 ° C) which is nearly the same as that for non-doped EuBCO coated conductors. On the other hand, overdoping is preferred for high in-field Jc. Therefore, a high Jc
under a magnetic field was obtained in the BMO-doped REBCO layer annealed at a low temperature. The Jc

(min.) of 5 mol% BHO-doped EuBCo coated conductors was 0.62 MA/cm2 at 77 K and 3 T (setting deposition temperature of 1150 ° C and O2 annealing temperature of 250 ° C). Using these results, we confirm the successful fabrication of heavily BHO-doped EuBCO coated conductors showing high in-field performance by the PLD method.