bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance analysis of a new double stage compressor helium liquefaction cycle
Authors: Su H K , Li Z Y , Gong L H , Zhu W P , Zhang M M , Jia Q M 
Published: June 2020

Abstract
Large scale helium liquefaction/refrigeration plant plays a vital role in advanced large equipment such as fusion reactors and accelerators. A new helium liquefaction cycle with double stage compressor is proposed in this paper, which is different from the Collins cycle. The helium gas from the compressor is divided into two parts. The medium-pressure helium gas as one part flows through the heat exchangers and is liquefied by throttling in the valve. The other part, high-pressure helium gas flows into the turbine for adiabatic expansion with decrease of its temperature and pressure. Both high-temperature helium gas streams become low-temperature and low-pressure. In this paper, the new cycle is parametrically analysed to demonstrate the effect of each parameter on the performance of the cycle. The results of the liquefaction capacity are obtained in different working conditions. Exergy analysis, which is an effective way to analyse thermodynamic cycles, is performed on the liquefaction process and the result is significant for the appropriate design of helium liquefaction system.
Dynamic simulation of ITER cryogenic system under D-T operation
Authors: Maekawa R , Takami S , Iwamoto A , Chang H S , Grillot D 
Published: June 2020

Abstract
Co-simulation of Cryoplant and Tokamak superconducting magnet system (referred to as Magnet) has been performed to characterize operating condition associated with control strategies. Cryoplant model, developed by EcosimPro®, consists of three identical refrigerators connected with integrated Cryoplant Termination Cold Box (CTCB) which distributes the coolant to five Auxiliary Cold Boxes (ACB) for Magnet and CryoPump (CP) cooling. Meanwhile, Magnet model, developed by Visual Modeler®, consists of Toroidal Field (TF) coil, Central Solenoid (CS), TF STructure (ST) and Poloidal Field (PF)/Correction Coil (CC). Magnet model computes thermo-hydraulic behavior of a forced-flow Supercritical Helium (SHe), with specified thermal energy deposition along the conductor in the case of Deuterium-Tritium (DT) operation as well as plasma disruption followed by the fast energy discharge of CS and PF. Global simulation of ITER cryogenic system provides its operating characteristics for complex cryogenic processes. The paper discusses the coupling of Cryoplant and Magnet models and the control strategy for Cryoplant to manage substantial dynamic heat loads.
Commissioning of the Warm Compressor System for the ESS Accelerator Cryoplant
Authors: Wang X L , Wischhoefer R , Selva P , Nilsson P , Råström J , Goncalves R , Olsson M , Arnold P 
Published: June 2020

Abstract
The accelerator cryoplant (ACCP) providing the cooling for the cryomodules and the cryogenic distribution system for the cold part of the ESS proton linac is being built and commissioned at the European Spallation Source (ESS) in Lund, Sweden. The ACCP warm compressor system (WCS) consists of several compression stages. The sub-atmospheric pressure stage (SP) is used to compress helium coming from the cold compressors directly to middle pressure (MP) level. The low pressure stage (LP) compresses the helium from LP level to the same MP level, being merged with additional flow from the cold box and the flow from the SP stage. The total flow is compressed in a single compression stage (HP) from MP to HP. The oil-flooded screw compressors are chosen in a way that the flow in each stage SP, LP and MP is compressed by a single screw compressor. Both, SP and LP compressors are equipped with a variable frequency drive (VFD) to adapt the compressor capacities to the various load cases. The ACCP had been contracted to Linde Kryotechnik AG in 2015 and all compressors are made by the Aerzener Maschinenfabrik GmbH, Germany. Following successful installation and commissioning in 2018, the final 100 hours test run at maximum nominal design condition and the part load tests under various ACCP operation modes were carried out at the beginning of 2019. The key parameters, including mass flow, power consumption, isothermal and volumetric efficiencies, are well fulfilled with the design data. The paper describes the system features, project challenges, lessons learned and acceptance test results.
FRIB helium refrigeration system commissioning and performance test results
Authors: Knudsen P , Ganni V , Hasan N , Wright M , Casagrande F , Vargas G , Joseph N 
Published: June 2020

Abstract
At its maximum capacity condition, the 4.5 K refrigerator system for the Facility for Rare Isotope Beams (FRIB) accelerator supports a 180 g/s 30 K 1.16 bar cold compressor return flow, a 14 g/s 4.5 K liquefaction load, a 4 kW 4.5 K refrigeration load, and a 20 kW 35-55 K shield load. Five additional design conditions, ranging from liquefaction to refrigeration and a stand-by/reduced load state, were specified for the sizing and selection of its components. The cold box system is comprised of a 300-60 K vertical cold box that incorporates a liquid nitrogen pre-cooler and a 60-4.5 K horizontal cold box housing seven turbines that are configured in four expansion stages including one Joule-Thompson expander. This cold box system, operates using the Ganni-Floating pressure process, automatically adjusting to the linear accelerator (Linac) load with the cold box supply (and compressor discharge) pressure varying from 6 to 21 bar, without introducing additional (artificial) loads or throttling turbine inlet valves (or other exergy loss mechanisms), and with minimal liquid nitrogen usage. This paper will briefly review the salient 4.5 K system design features and discuss the recent commissioning results.
Design, fabrication, commissioning and testing of FRIB 2 K cold compressor system
Authors: Knudsen P , Ganni V , Casagrande F , Fila A , Hasan N , Wright M , Vargas G , Joseph N 
Published: June 2020

Abstract
The FRIB cryogenic engineering group designed and built the sub-atmospheric cold box which supports the 2 K (31 mbar) operation of the FRIB accelerator cryo-modules. The centrifugal cryogenic (cold) compressors, designed with room temperature motors and active magnetic bearings, were supplied by Air Liquide to FRIB specifications and were integrated into the cold box which was built on site. The preliminary commissioning tests demonstrated that the system has achieved all the specification goals of operating from 110-180 g/s with a suction pressure of 0.028 mbar, discharge pressure of 1.15 bar and a discharge temperature less than 30 K. This paper will briefly review the sub-atmospheric 2 K system design features and discuss the recent commissioning results.
FRIB helium compression system commissioning and performance test results
Authors: Knudsen P , Ganni V , Wright M , Casagrande F , Vargas G , Joseph N 
Published: June 2020

Abstract
The design for the FRIB helium compressor system, used for the cryogenic refrigeration, was mainly based on the advancements developed for NASA James Webb project, improving the efficiency, reliability and maintainability from previous helium compression systems. The skid designs were further improved, first for the JLab 12 GeV project, and now with additional improvements for the FRIB project. The FRIB helium compression system has five operating compressors at maximum refrigeration capacity with an additional spare compressor. This spare can be configured to align its suction to any one of the three pressure levels of the five, discharging to the high pressure (4.5 K cold box supply) stream. This compressor system can support the 4.5 K cold box operation with a supply pressure varying from 6 to 21 bar, and without complex-sophisticated control of the gas management valves. This paper will briefly review several of the skid improvements and discuss some of the recent commissioning and test results.
Thermodynamic and cost-effectiveness analyses of chosen cooling loops for local production of saturated superfluid helium in large cryogenic systems
Authors: Fydrych J , Pietrowicz S 
Published: June 2020

Abstract
Large scientific facilities applying HeII technologies usually use the Joule-Thomson expansion for the final production of saturated superfluid helium at their cryogenic users. The users are usually supplied with subcooled liquid helium at 4.5 K and 3 to 4 bar(a). Then, to produce HeII, the 4.5 K helium is precooled in a local heat exchanger and throttled to a subatmospheric pressure below 50 mbar(a). This final throttling goes along an isenthalpic line which leads to the zone of wet vapour at the quality of 15.9%. The efficiency of this process can be strongly affected by additional heat loads, which may result in a significantly higher quality of the throttled helium. This imperfection can be partly decreased by using a local subcooler or by splitting the expansion process into two phases with an intermediate point around 1.2 bar(a). However, these solutions require additional components, such as phase separators with some instrumentation and another throttling valve. The paper presents the comparative thermodynamic analysis of the three identified cooling loops. Potential savings due to thermodynamic efficiency improvements are verified against the capital costs for different operation times.
Stable operation of cryogenic system at 2K during the RF or magnet power variations
Authors: Putselyk S 
Published: June 2020

Abstract
In the last 40 years several large laboratories, e.g. CERN, DESY, TJNAF, constructed the accelerators with large number of superconducting (sc) cavities or sc magnets operating at 2 or 4 K temperature levels. The sc cavity operation requires more stringent ranges of pressure variation than ones of sc magnets. In comparison to small testing benches or single cavities modules, for large accelerators a complicated controlling of refrigerator and cryogenic system is required. In the present paper, a review of controlling principles and loops, typically applied for the controlling of liquid helium (LHe) level and pressure for large accelerators is presented. Other possible control loops, e.g. cascade control or multivariable feed-back (or with feed-forward option), are discussed. Activities related to the commissioning of control loops and some supporting measurements are mentioned. Experimental data on investigation of gas/liquid thermal equilibrium are also presented.
Hydrogen contamination in liquid helium
Authors: Will J , Haberstroh C 
Published: June 2020

Abstract
For some years now, massive problems are often occurring when operating standard flow cryostats with pumped liquid helium. There are a large number of reports from various parts of the world, describing blockage problems arising typically within a few hours. Standard equipment for measuring material properties at temperatures below 4.2 K is massively affected. Hydrogen contamination within the used liquid helium could be identified as direct cause. With helium evaporating in the narrow throttling passages, hydrogen in solid state accumulates and is forming blockages. Usually internal capillaries or inlet valves are concerned. In consequence, the helium flow is reduced or ceasing completely, the operating temperature of the cryostat can’t be upheld, and the measurement run must be interrupted. Extremely low concentrations in the sub-ppm range are sufficient to block the helium flow within a few hours of operation. This contribution contains first quantifications regarding these contamination. A semi-quantitative analysis method using a narrow flow resistor, as well as gas chromatographic investigations led to new findings. Effects within the liquid helium supply that give rise to the problem were scrutinized. The collected results should lead to an understanding and to feasible solutions of the problem.
A New Superconducting Undulator Cryostat for the APS Upgrade
Authors: Anliker E , Fuerst J , Hasse Q , Ivanyushenkov Y , Kasa M , Shiroyanagi Y 
Published: June 2020

Abstract
The Advanced Photon Source (APS) is in the midst of a major facility upgrade including both a new electron storage ring (SR) and many new insertion devices (IDs) providing x-ray photon beams to a new suite of experimental end stations. Included among the new IDs are four 4.8-meter superconducting undulator (SCU) cryostats, each containing two 1.8-meter planar undulator magnets operating at 4.2 K in either a phase shifted or canted configuration. We describe a new, compact cryocooler-based cryostat design which supports the magnets and associated subsystems and also fits the space constraints of the SR ID straight sections. The design is an evolution of earlier single-magnet 2-meter cryostats, retaining some subsystem commonality while incorporating lessons learned and several features unique to the challenge of supporting two independently operable undulator magnets in a single device.
Supercritical helium expansivity effects on magnet protection systems
Authors: Vanderlaan M H , Brumm T J 
Published: June 2020

Abstract
The recent commissioning of the 36 T Series-Connected Hybrid Magnet at the National High Magnetic Field Laboratory has uncovered an undesirable consequence of using super critical helium for cooling of superconductors. This recent dry magnet cooling technology greatly reduces the LHe requirements of the magnet and may be utilized more frequently in the future. Because the supercritical helium does not complete a phase transition with the addition of heat, the fluid can quickly expand. The increased expansivity of supercritical helium over liquid helium for a given heat load is capable of creating larger pressure waves. The impact pressure for compressible helium gas flow is combined with the speed of sound for ideal gases to determine if a high-speed pressure wave is sufficient to explain the premature failure of the burst discs in the over-pressurization protection system. The addition of an impact pressure can explain, under the right conditions, a reduction of up to 40% in the burst disc pressure rating. The Grüneisen parameter is shown to relate to the expansivity and values for the parameter are given in the supercritical range. A proposal to reroute the pipe near the burst disc is made to mitigate the effects of the impact pressure.
Design and Commissioning of a 700 W@3 K Sub-cooled Helium Test Facility
Authors: Lu X F , Zhang Q Y , Chen A Y , Zhu P , Zhou Z W , Fu B , Li S S 
Published: June 2020

Abstract
In order to increase the magnetic field and temperature margin of superconducting magnets, a test facility for a 700 W@3 K sub-cooled helium refrigerator was proposed to decrease the operation temperature from 4.5 K down to 3 K. The process flow of the 3 K sub-cooled helium test facility has been designed with two cold compressors arranged in series to pump the vapour pressure from 120 kPa to 24 kPa. This 3 K sub-cooled unit has been constructed and operated successfully to decompress the 4.5 K saturated helium to 3 K sub-cooled helium. The preliminary commissioning results indicated that this 3K sub-cooled helium unit could achieve more than 700 W capacity at 3 K sub-cooled helium. Thermodynamic parameters and performances of this 3 K sub-cooled helium unit were introduced and compared with the designed values in good agreement. The rotation speeds, pressures and temperatures of cold compressors during the transient state and the steady state were also analysed.
Neutron irradiation effect on critical current of Nb3Sn wire under 8 T to 15.5 T
Authors: Nishimura A 
Published: June 2020

Abstract
Superconducting magnets for fusion application will be irradiated by fast neutrons produced by fusion reaction, and it has been reported that the superconducting properties of the superconducting wires vary drastically by the irradiation. A bronze route Nb3Sn wire and an internal tin process wire were irradiated in a fission reactor up to 1.7 × 1023 n/m2 (> 0.1 MeV neutron), and the change in the critical current was measured by 15.5 T superconducting magnet and a variable temperature insert. The 4.9 × 1022 n/m2 irradiation for the bronze route wire increased the critical current by 1.75 times, but the 7.9 × 1022 n/m2 irradiation showed 1.03 times increase for the bronze route wire and 0.72 times decrease for the internal tin process wire. The 1.7 x 1023 n/m2 irradiation for the internal tin process wire decreased the critical current severely and the critical magnetic field down to around 16 T. This was the first result that the high fluence neutron irradiation caused the degradation of both the critical current and the critical magnetic field in this type of a Nb3Sn wire. Some irradiation defects will become the magnetic flux pining sites and strengthen the pining force. But the strong irradiation will damage the superconducting phase and degrade the properties.
Increased flux pinning force and critical current density in MgB2 by nano-La2O3 doping
Authors: Zhang Danlu , Wan Fang , Sumption Michael D. , Collings Edward W. , Thong CJ , Rindfleisch Matt , Tomsic Mike 
Published: June 2020

Abstract
MgB2 superconducting wires and bulks with nano-La2O3 addition have been studied. A series of MgB2 superconducting bulk samples with nano-La2O3 addition levels of 0, 5, 7, 18wt% were prepared. AC resistivity data showed slight increases of Bc2
and unchanged Birr
for the bulk samples with doping levels lower than 7 wt% and decreased critical fields for the heavily doped (18 wt%) bulk. X-ray diffraction (XRD) showed the presence of LaB6 in the nano-La2O3 doped MgB2 bulk samples and decreased MgB2 grain size in nano-La2O3 doped bulks. Monocore powder-in-tube (PIT) MgB2 wires without and with 5 wt% nano-La2O3 addition (P-05) were prepared for transport property measurement. 2mol%C-doped Specialty Materials Inc. (SMI) boron powder was used for wire P-05 and previously prepared control wires (control wires were made without the addition of nano-La2O3 powder, W-00 and P2). Low field magnetic properties were obtained from magnetization loop (M–H), transport critical current density (Jc) was measured at 4.2 K for the nano-La2O3 doped PIT wire (P-05) and the control samples (P2 and W-00). The transport critical current density Jc (B) of P-05 at 4.2 K and 8 T (6.0 ×104 A/cm2) was twice that of the control wire. The critical magnetic fields (Bc2
and Birr
) of P-05 and the control sample P2 were compared. The critical fields of P-05 were slightly less than those of P2. Kramer-Dew-Hughes plots indicated a change from surface pinning to a mixture of volume pinning and surface pinning. It is shown that enhancement of P-05’s transport properties is due to additional flux pinning by the fine-size rare-earth borides rather than enhanced Bc2
or Birr.
Flux Pinning Enhancements of YBa2Cu3O7-x with Nanosize Magnetic Additions
Authors: Sebastian M A , Pierce N A , Maartense I , Kozlowski G. , Haugan T J 
Published: June 2020

Abstract
Different methods of flux pinning are being tested world-wide to enhance critical currents (Ics) of high temperature superconductor YBa2Cu3O7-x (YBCO) coated conductors exposed to high magnetic fields. Magnetic materials are interesting to consider as flux pinning additions because of their potential for very strong pinning strength. To our knowledge, there have been limited demonstrations of magnetic pinning additions to YBCO conductors. This paper describes the study of different M magnetic phase additions to YBCO including M = BaFe12O19, La0.67Ca0.33MnO3, and other oxide phases. Nanosize additions were incorporated by depositing multilayer (M/YBCO)N films to minimize degradation of Tc, and testing volume % additions of M phase from 0.5 % to 5%. Results indicate that Tc onsets are depressed with magnetic additions, however in some cases interestingly without degrading the transition width. With optimization of magnetic additions a 50% increase of critical current density has been obtained, for low magnetic fields of < 10,000 Oe at 65K to 77K. Microstructural and superconducting properties are summarized, including SEM analysis.
A fully superconducting air-core machine for aircraft propulsion
Authors: Balachandran T , Lee D , Salk N , Haran K S 
Published: June 2020

Abstract
Partial and fully superconducting (SC) machines promise high power density capabilities required for electric propulsion. These machines need to achieve high power densities while reducing electrical heat losses to minimize the required cryogenic power and subsequent additional weight. Hydrogen powered all-electric planes provide a design space where ac losses are manageable. However, the high electrical frequencies in high-speed fully superconducting machines pose a significant challenge to reducing armature ac losses. In high-speed applications, coupling loss in the SC armature coils dominates and becomes a barrier for practical application of these machines. In this paper a fully superconducting machine is proposed for a hydrogen powered regional all-electric plane. An air core design is considered utilizing low ac loss MgB2 wires. The design is targeted to achieve 50 kW/kg specific power while requiring ac losses to be less than 3 kW. This study explores the possibility of replacing a passive iron shield with active shielding coils to contain the magnetic flux inside the machine while reducing weight and increasing power density. The study focuses on minimizing weight as well as ac losses in the armature coils. An optimization algorithm is used to determine the trade-offs between iron shield and active shield coil designs. Results show that optimal designs for electric propulsion eliminate the passive shield in favor of active shielding coils - increasing the power density of the machine while maintaining the outside flux density below standard safety limits.
Offshore oil exploitation in the Caribbean Sea: Challenges for Colombia
Authors: Grimaldo-Guerrero J.W. , Contreras-Rueda Y.F. 
Published: June 2020

Abstract
Colombia began an expansion plan for oil exploration in the Caribbean Sea, this industry is recognized for the high impact it can generate, being necessary to identify mechanisms to improve management. This research presents a review of the experiences in the offshore oil industry, describes the case of oil exploration in the Arctic, a fragile ecosystem; methodologies and indicators used to strengthen the industry in order to achieve sustainability are identified. The results allow to conclude that it is necessary to strengthen the development plan from the institutional and political frameworks using a Strategic Environmental Assessment, also they indicate how this can improve the instruments and achieve improvement in the social, economic and environmental dimensions.
Influence of thermal-varying material properties on stress calculation for creep life assessment of seamless medium-carbon steel boiler tubes
Authors: Castellanos-González L M , Hernández Herrera H , Goytisolo Espinosa R , Castellanos Molina L M , Vergara Verbel E E , Alcalá Ballestero J A 
Published: June 2020

Abstract
Seamless medium-carbon steel boiler tubes from a thermoelectric plant are studied to predict their remanent life. An alternative for stresses calculation in creep life-assessment method is presented. The proposed stress calculation incorporates not only material dimensions and working pressure but also thermal-varying properties of the material and the radial temperature gradient in the tube wall. The methodology for creep life prediction established by ISO / TR 7468-1981 is used. It is compared with the API std 530 to show that the predicted creep rupture times can result longer when thermal-varying properties and the radial temperature gradient in the tube wall are considered. This enhanced creep failure prediction method may favour a cost reduction avoiding premature maintenance and unnecessary plant shutdowns.