bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preliminary Structural Design and Analysis of the Horizontal Cold Box for CFETR 25 kW@4.5 K Helium Refrigerator
Authors: Zhang C J , Zhang Q Y , Zhu Z G , Yao D M , Yang P C , Zong Y W , Chen S X 
Published: June 2022

Abstract
The China Fusion Engineering Test Reactor cryogenic system mainly provides necessary supercritical helium for cooling superconducting coils and structure to transfer the static thermal load and the dynamic thermal load generated during plasma operation mode. According to the conceptual design of CFETR cryogenic system, the cooling capacity at 4.5 K is about 125 kW, with five 25 kW@4.5 K helium refrigerators in parallel. As one of the main components, a horizontal cold box provides a vacuum and insulating working environment for plate-fin heat exchangers, turbines, adsorbers, control valves and pipes. This paper presents a preliminary structural design for the 25 kW@4.5 K helium refrigerator horizontal cold box. The structural strength and static heat leakage of the cold box including support seats are analyzed through the finite element simulation method. The simulation results further verify the rationality and feasibility of the cold box structure design, and provide a certain reference for the subsequent detailed engineering design.
Operational experience with the Proto-DUNE NP02 and NP04 large volume liquid argon cryostats and their cryogenic systems at CERN
Authors: Bremer J. , Chalifour M. , Creus-Prats J. , Fabre C. , Montanari D. , Pezzetti M. , Resnati F. , Nessi M. 
Published: June 2022

Abstract
The far Detector of the Deep Underground Neutrino Experiment (DUNE) will be housed in several large volume (about 12.500 m3) liquid argon cryostats. The design principle of these large cryostats, and of the cryogenic system belonging to them, are investigated through the design, construction and operation of a series of prototype installations.
The Neutrino Platform 02 (NP02) and 04 (NP04) cryostats, placed at CERN, contain DUNE proto-type detectors, each of them housed in an about 600 m3 liquid argon bath. These cryostats, based on the membrane cryostat principle, and their cryogenic systems have been designed according to the DUNE principle. Measurements performed in these test stands shall confirm the foreseen heat loads into the cryostat systems entering via its walls, via detector cabling and via the cold electronics, shall confirm the low temperature gradient over the active detector volume and shall certify the liquid argon purification principle.
This paper introduces the requirements for the NP02 and NP04 cryostats and their cryogenic systems, describes the design principle applied to these two systems and gives an overview of the different modes in which the two systems have been operating. The experimental results are presented and discussed, and “lessons learned” for future installations are dawn.
Assessment of the operation safety margin of the HL-LHC superconducting recombination Dipole D2 in case of helium filling failure
Authors: Rousset B , Bancel F , Besson N , Bon-Mardion M , Claudet S , Goy T , Millet F , Nivelon P , Perin A 
Published: June 2022

Abstract
After the successful completion of the cryogenic performance tests of the He II heat exchanger prototype for the D2 recombination dipole of the future HL-LHC project at CERN, specific measurements were performed to determine the operation safety margin in case of abnormal operating conditions. This is particularly relevant in case of the failure of liquid helium supply in the He II cold source. For nominal operation, the liquid level is regulated at a constant value and it is not necessary to know its value very accurately. However, in case of a partial drying of the heat exchanger due to discontinuation of the helium liquid supply, it is essential to monitor the absolute value of the liquid level to anticipate any cooling malfunction. This paper describes the procedure for an accurate in-situ He II level measurement as well as for the heat loss and mass flow rate estimates in a He II phase separator. The operation safety margins of the He II heat exchanger prototype for the D2 magnet are then analyzed for the different operating conditions considered during the HL-LHC runs in case of non-nominal liquid level in the He II cold source.
Heat loads measurements at the XFEL cold linac
Authors: Ramalingam R , Bozhko Y , Barbanotti S , Schnautz T 
Published: June 2022

Abstract
The European X-Ray Free Electron Laser (EuXFEL) at DESY is in operation since the beginning of 2017. The free electron laser is based on a superconducting linear accelerator that delivers electrons to the undulator section with beam energy up to 17.5 GeV. The linear accelerator consists of 96 cryomodules; each 12 m long module is an assembly of 8 superconducting cavities and one superconducting magnet. This paper focusses on the measurement of the static and dynamic heat loads of the cryomodules assembled in the linac. Heat loads are an important parameter to evaluate the efficiency of the refrigerator system, the quality of the cryomodule assembly and installation and the accelerating cavity performances, being the dynamic heat loads proportional to the cavity quality factor (Q0, the ratio of the stored energy to the dissipated energy). The paper describes at first the procedure to measure the static heat load without beam energy and the dynamic heat loads at different beam energy levels. The measurement results are then summarized and compared with the XFEL design values.
Development of a cryocooler conduction-cooled 650 MHz SRF cavity operating at ∼10 MV/m cw accelerating gradient
Authors: Dhuley R.C. , Posen S. , Geelhoed M.I. , Thangaraj J.C.T. 
Published: June 2022

Abstract
SRF cavities for particle acceleration are conventionally operated immersed in a bath of liquid helium at 4.2 K and below. Although this cooling configuration is practically and economically viable for large scientific accelerator installations, it may not be so for smaller accelerators intended for industrial applications such as the treatment of wastewater, sludge, flue gases, etc. In this paper, we describe a procedure to operate SRF cavities without liquid helium that can be used to construct electron-beam sources for industrial applications of electron irradiation (1-10 MeV electron energy). In this procedure, an elliptical single-cell 650 MHz niobium-tin coated niobium cavity is coupled to a closed-cycle 4.2 K cryocooler using high purity aluminum thermal links. The cryocooler conductively extracts heat (RF dissipation) from the cavity without requiring liquid helium around the cavity. We present construction details of this cryocooler conduction-cooling technique and systematic experiments that have demonstrated ∼10 MV/m cw gradient on the cavity. By straightforward scaling up the cavity length and number of cryocoolers, the technique will provide the complete range of 1-10 MeV electron energy for industrial applications.
Cryogenic testing of a 25 kV RIS bushing
Authors: Fink Stefan , Fuhrmann Uwe , Zwecker Volker 
Published: June 2022

Abstract
High voltage bushings for cryogenic current or voltage leads must master safely the special thermal stress in addition to the high voltage requirements. Resin impregnated synthetic (RIS) bushings have proven their usability for room temperature high voltage application since few years. Such paper free bushings are less hygroscopic than paper based bushings, which can be an advantage for components exposed to cryogenic temperatures on one side and to air conditions on the other. A conventional 25 kV, 2 kA room temperature RIS bushing was assembled to an open bath cryostat and subjected to five thermal cycles. High voltage tests were successfully performed under cryogenic conditions. No degradation of the bushing was found after the thermo-mechanical stress of the fast cool downs and one fast warm up. This paper focuses on the thermal tests.
Low level RF development for ESS high beta cavity test
Authors: Dumbell K , Lewis J , Wheelhouse A , Pattalwar S , Moss A , Corlett P , Goudket P , Hitchen S , Jenkins C , Ellis M , Pendleton M , Smith P , May A , Wilde S , Oates A , Middleman K , Wilson J , Lowe M , Mason D , Sollars P , Pattalwar N , Hornickel P , Mutch J 
Published: June 2022

Abstract
Testing of superconducting cavities requires the use of a Self-Excited Loop or Phase Locked Loop in order to track a cavity’s resonant frequency under the disturbances of micro-phonics. Many laboratories have successfully developed their own Low Level RF solutions and have implemented these using Field Programmable Gate Array at the heart of the digital system. This approach has also been adopted at Daresbury Laboratory. However, the dedicated system was identified as a single point of failure in the complex operational testing infrastructure and an alternative, back-up, system was sought. Rather than duplicate the existing system another approach has been adopted making use of Commercial Off The Shelf hardware with minimal requirement for interconnect to the existing high power system. The solution is based around the NI (National Instruments Corporation) FlexRIO transceiver adapter NI-5782 connected to the NI-7962R FPGA module inside a PXI chassis. This system is capable of working directly at an Intermediate frequency of 37.5 MHz and only requires a simple up-converter / down-converter stage. Testing the high Q (typically 2 × 1010) cavities up to accelerating gradients of 22.5 MV/m has been successful.
Experimental study on the pool boiling heat transfer of slush nitrogen under triple point to atmospheric pressure
Authors: Wang Q D , Jiang Q K , Jin T 
Published: June 2022

Abstract
Slush nitrogen is a solid-liquid two-phase cryogenic fluid, with temperature of about 63.15 K under pressure between the triple point of nitrogen and atmospheric pressure. High-temperature-superconductor (HTS) cables generally require the cryogenic coolant such as subcooled liquid nitrogen. Compared with the subcooled liquid nitrogen, slush nitrogen has lower temperature, higher density and higher heat capacity, and is considered a promising coolant for HTS cables. In order to intuitively understand the boiling heat transfer characteristics of slush nitrogen, a pool of slush nitrogen of 0-30% solid volume fraction was prepared as coolant and was filled into a dewar, and helium was charged to change pressure from triple point to atmospheric pressure. Experiments under different pressure conditions were carried out to obtain the variation of boiling curves. The critical heat flux (CHF) of slush nitrogen was found to be reduced by increasing solid volume fraction, because of denser solid nitrogen with lower heat transfer capacity within the main boiling field. By fitting the result to Kutateladze Correlation which predicts CHF, while considering the influence of subcooling, the improved coefficients applicable for slush nitrogen are obtained with an accuracy of ±10%.
Epoxy Electret: A Remedy for Partial Discharge at Cryogenic Temperature
Authors: Haque Farhina , Park Chanyeop 
Published: June 2022

Abstract
Epoxy-based composites exhibit mechanical compatibility at cryogenic temperatures. Owing to these properties, composites based on epoxy are used as electrical insulators in high temperature superconducting (HTS) power applications. However, the inevitable presence of voids in solid insulators, triple points, and airgaps at high-voltage conductor-insulator interfaces increase electric fields locally. The intensified electric field around these defects and interfaces is the main cause of partial discharge (PD), which is a dielectric challenge for numerous power applications including HTS cables. Recently, electret has been introduced as a promising solution to mitigate PD activities caused by voids and triple points. In this work, we intend to report the PD mitigation performance of electrets fabricated from epoxy resin, which is suitable for cryogenic power applications.
Experimental Evaluation of Dielectric Losses of PPLP for Single Phase HTS Cable at Subcooled LN2
Temperatures
Authors: Sarkar Maalika , de Souza I , Sarkar A , Gour A S , Rao V V 
Published: June 2022

Abstract
For the operation of high-temperature superconducting (HTS) power cables in liquid nitrogen (LN2
) at high voltage levels, there is a need for reliable and cost-effective insulating materials. This article investigates the dielectric losses in poly-propylene laminated paper (PPLP- Sumitomo) which is used as a cold dielectric for HTS cables. To calculate the dielectric losses, an experimental setup was developed to measure the relative permittivity of PPLP at different temperatures from 65 to 300 K at various frequencies. Using an in-house developed experimental setup, the dielectric loss for different layers of PPLP, at various temperatures and operating frequencies was estimated to evaluate one of the criteria of cold dielectric material and the same was compared with the data at room temperature. The temperature was reduced to 65 K using a vacuum pump-assisted sub-cooling system. The effective relative permittivity increases marginally for subcooled LN2
impregnated PPLP, however there is reduction in tan delta loss which in turn reduces the dielectric loss and is useful for high voltage HTS based AC cables. This paper provides a comparative study on PPLP performance variation with respect to operating temperature and frequency.
Thermal conductivity of niobium and thermally sprayed copper at cryogenic temperature
Authors: Fouaidy M. 
Published: June 2022

Abstract
We have developed a test facility dedicated to thermal conductivity k(T) measurements at low temperature. These experimental devices allow the test of four samples simultaneously during each run. The measurements are performed using steady-state axial heat flow method with a careful control of heat leaks to the surrounding. The apparatus was successfully used for measuring k(T) (Temperature T in the range: 1.5 K - 10 K) of niobium and other materials used for the fabrication of Superconducting Radio Frequency (SRF) cavities. We have tested the following samples: 1) niobium samples from different supplier (as received or/and after various high temperature Heat Treatments (HT)), 2) thermally sprayed copper coatings. The resulting experimental data are presented and compared to the experimental results previously reported by other groups and theoretical values. As expected heat treatment have a strong impact on k(T) and in particular on the phonons peak at T∼2K. More precisely, HT @ 1200°C with Ti gettering improves the Nb Residual Resistance Ratio (RRR) by a factor of 3 and consequently k(T). Finally, the correlation between the niobium RRR and the thermal conductivity. at T=4.2 K is confirmed in good agreement with the Wiedemann-Franz law
Fatigue life characterization of hand folded and vacuum formed Kresling origami bellows at 77K
Authors: Dunne Francis , Westra Kjell , Mattox Caleb , Leachman Jacob 
Published: June 2022

Abstract
Propellant migration in microgravity is a critical challenge for in-space fuel storage and transfer. Origami fuel bladders are a new design solution to prevent cracking in polymeric materials within the cryogenic regime. This paper explores manufacturing techniques for producing origami bladders as well as the limits of possible thicknesses for origami bladders. Origami bladders are manufactured from polyvinylidene fluoride (PVDF) and polyethylene terephthalate glycol (PETG). Hand folded bladders follow a Kresling bellows origami pattern while the thermoformed samples are prepared using a mold of the Kresling bellows and an EZFORM LV 1827 thermoformer is used to shape the polymeric film. Compressive fatigue testing is carried out within liquid nitrogen to confirm the sample can survive deformation at cryogenic temperatures. Hand folded origami bellows specimens survived 3300+ cycles with minimal signs of degradation, while similar PVDF specimens cracked in fewer than 10 cycles.
Current sharing and stability in an extremely low AC-loss MgB2 conductor
Authors: Kovacs C J , Haugan T J , Sumption M D , Tomsic M , Rindfleisch M 
Published: June 2022

Abstract
In the push to develop high power electric aircraft, superconducting technology promises to significantly reduce mass and volume of motors and generators. However, challenges related to AC-loss and thermal management are a significant factor in preventing the proliferation of aerospace superconducting technologies. Increasing the resistance of the metal matrix stabilization has only gone so far in reducing coupling currents for higher frequency applications. In this research, Multiphysics simulations of a single composite filament were used to investigate stability decreases when using very high thermal conductivity electrical insulator (CsI) or metal-to-insulator transitioning material (V2O3) to replace the slightly resistive metal matrix typically used for a low AC loss MgB2 composite wire. The insulators separate the MgB2 filaments entirely, only allowing transient current sharing to occur with the high purity Nb diffusion barrier or with the metallic state V2O3. These simulations show that for these very low AC-loss composites at 20 K, instability will become a major issue due to reductions in current sharing. With higher electrical conductivity metal-to-insulator materials, higher thermal conductivity impregnation materials, and thicker metallic diffusion barriers it may be possible to find a reasonable balance between AC-loss and stability.
Mechanical stability of SIS100 Bypass Line busbars clamping system under AC current load
Authors: Iluk A , Chorowski M , Poliński J , Eisel T , Streicher B , Trockel R , Grzegory P 
Published: June 2022

Abstract
This paper presents the lessons learned from tests of first module of superconducting cryogenic bypass line (BPL), a part of the international Facility for Antiproton and Ion Research (FAIR) SIS100 cryogenic system, currently under construction in Darmstadt, Germany. Design, manufacturing, and installation of the superconducting cryogenic bypass line is a part of a Polish in-kind contribution to the FAIR project, realized by the Wroclaw University of Science and Technology. The main goal of the tests was to check the superconducting, Nuclotron type busbar system containing four pairs of busbars, transferring 13.2 kA pulsing current with the ramp rate of 28 kA/s. The mechanical stability of the busbars, especially at the connection region, was investigated with the use of vibration sensors and cameras located inside the vacuum space. The tests revealed insufficient mechanical stability of the busbars in the connection area due to pulsing Lorentz forces, and necessity of additional supports and clamps. Results of the tests were presented and discussed. The conclusions can be significant not only for the bypass line design, but also for design of the busbar connections in the superconducting magnets.
Development of Arduino Based Power Conditioning Unit for Superconducting Magnetic Energy Storage (SMES) System used as UPS for Load Leveling during Charging of Electric Vehicles
Authors: Sarkar A , Anand A , Datta T S , Gour A S , Rao V V 
Published: June 2022

Abstract
With the advancements in Electric Vehicle (EV) technology, more and more EVs are entering into service and simultaneously the number of charging stations are also increasing. These charging stations are connected to the EVs for a small duration of time. Hence, as the number of EVs increases, the simultaneous charging of multiple EVs generates a peak active power demand for this duration. The available peak load compensation technologies such as fywheel storage, pumped hydro storage or Battery Energy Storage System (BESS) take a long time to respond and are not very efcient. With an operational efciency exceeding 90 % and quick reaction time (< 1 second), a Superconducting Magnetic Energy Storage (SMES) system can be a viable solution for this scenario. A SMES system generally consists of a superconducting coil system being charged during the low load/no load period and discharged during the peak demand, with the help of a power conditioning unit (PCU). This paper describes the development of various sub-systems of the SMES-PCU, such as a three-phase rectifer, bidirectional chopper unit, three-phase inverter and the controllers with a description of various modes of operation and sizing of components. The paper also includes the simulation of overall SMES-PCU with suitable assumptions, to present the operational characteristics of the integrated system.
Comparative evaluation of different DC-AC converter topologies for cryogenic applications utilizing superconducting materials
Authors: Ul Hassan M , Emon A I , Azadeh Y , Luo F 
Published: June 2022

Abstract
Modern transportation applications including electric vehicles (EVs), more electric aircraft (MEA) and electric comprise of different power conversion systems. Reduced weight and improved semiconductor efficiency are the major challenges towards their improved overall performance. To overcome them, cryogenic operation of power electronics converters (CPEC), electric motors, cables, and energy storage components has been under research and evaluation. CPEC are being investigated to drive superconducting machines (SCM) because of their lightweight structure and improved efficiency. CPEC can offer improved switching performance, reduced conduction losses and therefore increased efficiency; because of reduced on-resistance and increased carrier mobility of active devices. This article will discuss how can the benefits of lower operating temperature (< 93 K) be utilized in determining the most suitable DC-AC converter configuration. The paper compares three basic converter topologies: (a) two level voltage source inverter (2L-VSI), (b) three level t-type neutral point clamped inverter (3L-TNPC) and (c) two-level current source inverter (2L-CSI). Analysis is provided based on volume of passive components, electromagnetic interference (EMI) spectra and number of active devices, where all components considered are compatible with low temperatures. It can be observed that utilization of cryogenic temperature affects the volume of passive components, and therefore the overall selection of converter.
Influence of magnetron sputtering process parameters on low-temperature electrical transport characteristics of zirconium oxynitride thin films
Authors: Sun X M , Bai X B , Chen F C , Huang R J , Yuan J , Jin K , Su H J , Li L F 
Published: June 2022

Abstract
In order to determine the influence of process parameters including nitrogen and oxygen flow rate on the structure and electrical transport characteristics of zirconium oxynitride(ZrOxNy) thin films, the ZrOxNy films were prepared on sapphire substrates by RF reactive magnetron sputtering deposition technology. The crystal orientation and morphology of ZrOxNy films prepared at different nitrogen and oxygen flow rate were characterized by XRD and SEM, respectively. The electric transport behavior of ZrOxNy films at 300K to 3K was measured by PPMS. The results show that the insulativity of ZrN films is enhanced with the increase of nitrogen flow rate in sputtering atmosphere. With the increase of oxygen flow rate in sputtering atmosphere, the insulativity of ZrOxNy film is enhanced.