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Recent progress on CORC® cable, wire and magnet development Danko van der Laan, Advanced Conductor Technologies Advanced Conductor Technologies is developing HTS Conductor on Round Core (CORC®) cables and wires wound from REBCO coated conductors for use in high-field magnets. Conductor development is focused on compact fusion magnets that operate at currents between 50 and 100 kA at fields of 12 – 20 T and accelerator magnets operating at 10-20 kA and a Je of over 600 A/mm2 at 20 T. Here, we outline the latest results of CORC® cable and wire development tailored for each magnet application. We’ll discuss the introduction of CORC® wires containing tapes from SuperPower with substrate thickness reduced from 30 down to 25 micron. We will discuss the design of several CORC® Cable-in-Conduit-Conductors (CICC) for fusion magnets rated at 80 kA at 12 T and their test results in SULTAN. CORC® cables and wires are becoming mature magnet conductors and several magnet programs that incorporate CORC® conductors will be discussed. Characterisation of high current density REBCO tape of the H2020-ARIES program Lucio Rossi, CERN In the framework of the EC supported program H2020-ARIES, a task is dedicated to the development of high current density tape, for high field (10-20 T) and low temperature (4.2 K) for accelerator magnets for future post-LHC colliders. The tapes, developed by Bruker HTS, Alzenau (DE), have a stainless support of 50 µm and the best samples have a Jeng of about of 1000 A/mm2 at 20 T field (parallel to c-axis). However, a compensation of severe mechanical strain is needed for these tapes. Lacking this compensation, intrinsic deformations make these tapes very difficult to produce and to use. In this paper, we present the complete Ic characterization as a function of temperature and magnetic field, as well as a function of angle and discuss the future actions in the program to make this research line sustainable. Magnetic design of twin aperture cos-theta dipoles with a semi-analytic approach Alessandro Maria Ricci, Università di Genova, INFN sezione di Genova The magnetic design is a basic aspect of the superconducting magnets for particle accelerators. When dealing with single aperture cosθ type dipoles, at the first order, the design can be performed with an analytic approach based on a sector dipole approximation followed by a numerical optimization. For double aperture dipoles the magnetic cross-talk between apertures makes this approach unfeasible. We have developed a semi-analytic model, which starting from a sector dipole approximation, allows to consider the cross-talk between the two apertures. We also demonstrate that the iron yoke contribution to harmonics, although dominant, does not change the optimal configuration found in its absence. As examples, we show two possible electromagnetic designs for the D2 dipole of the High Luminosity upgrade of LHC and for the 16-T bending dipole of the Future Circular Collider. The semi-analytic model can be generalized to a larger class of magnets. Development of the superconducting dipole magnet for the CBM detector Aleksei Bragin, Budker Institute of Nuclear Physics The CBM detector will research compressed baryon matter on the FAIR facility, GSI, Darmstadt. The superconducting dipole magnet of this detector provides vertical magnetic field with field integral ~ 1 T*m along a beam length of 1 m. Maximal magnetic field on the coils is 4 T. The superconducting coils having 1.34 m of inner diameter will be made of NbTi wire having Cu/SC ratio as 7.4/1. The SC wire cross-section bare size is 2.02x3.25 mm2. This wire was manufactured by extrusion method and tested. The iron yoke having 150 t of mass is a part of the CBM magnet. This the SC coils are attracted to the iron yoke with 3MN of vertical force. The design of the SC coils is based on indirect cooling by 4.5 K helium with thermosyphone

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cooling method. The presentation will report on all design calculations, quench behavior and cryogenics of the CBM mgnet. Standalone Cold Testing of a High Performance HTS Insert-Magnet Jeroen van Nugteren, CERN TE-MSC-MDT High Temperature Superconductors (HTS) are necessary for pushing the magnetic field in accelerator magnets beyond 20 T. To study the use of HTS conductor in an actual accelerator magnet application the Feather-M2 was developed at CERN within the framework of the EuCARD2 collaboration. The first magnet, named Feather-M2.1-2, was constructed and tested successfully in summer 2017 [1]. This paper reports assembly and standalone cold-testing in helium gas of the next prototype magnet named Feather-M2.3-4, which is wound with a high-performance cable. This cable allows the magnet to well exceed the standalone design field of 5 T. During the test the temperature of the magnet is monitored using a set of distributed optical fibers. Additionally, the voltage over the coil is measured down to the micro-volt levels. These two measurements provide fundamental understanding on the current sharing and heat balance of multi-strand cables in HTS coils. Detector Magnets for the Future Circular Collider ee,eh,hh Experiments Herman Ten Kate, CERN The Future Circular Collider [1] comprises a 100 km tunnel and caverns for detectors probing electron-positron, electron-hadron and hadron-hadron collisions. Designs for the detector magnets were developed. Two for FCC-ee: a 7.6m bore and 7.9m long 2T/600MJ solenoid; and a 4m bore, 6m long, ultra-thin, radiation transparent 2T/170MJ solenoid. For FCC-eh, the solenoid is combined with a dipole magnet for guiding the electron beam and it comprises a 3.5T/230MJ, 2.6m free bore and 9.2m long solenoid. The FCC-hh detector features a 14GJ magnet system comprising a 4T main solenoid with 10m free bore, 20m long, in line with two 3.2T forward solenoids with 5.1m free bore, 4m long. This challenging family of detector magnets needs further engineering in the years to come. A survey of the magnets is presented and the engineering challenges highlighted. Assembly and Test of the HL-LHC Orbit Corrector based on Canted Cos-Theta design Glyn Kirby, CERN In the frame of the high-luminosity upgrade project (HL-LHC) at CERN, a double aperture, independently powered, family of beam orbit corrector magnets will be installed close to the two main LHC experiments Atlas and CMS. These 2.6 T magnets are built using a canted cosine theta design. This paper describes the development of the prototype, full size 2-m-long magnet. We first focus on design and assembly techniques: from coil winding using a CNC machined aluminium former to impregnation, layer-jump, quench protection, and yoke assembly. We then present the power test results at 1.9 K: training, field quality and protection.

Progress in the development of the HTS Power Cable Projects in Korea Chulhyu Lee, KEPCO In Korea, the first commercial project of the high temperature superconducting (HTS) power cable, ‘Shingal Project’ fully funded by KEPCO, had completed to connect two substations with a 23 kV HTS distribution line. Now, the real operation is started. The operation results will be introduced in this conference. In addition, KEPCO is establishing a gradual strategy for a HTS platform for the power switching of the distribution line by utilizing tri-axial HTS power cable. KEPRI had initiated the tri-axial project and the type test tri-axial HTS cable was installed in Gochang Test Center of KEPCO in Korea. The test results will be presented in this conference.In this paper, we introduce the recent progress and research results on the HTS power cable projects. And the business models of the HTS platform and Hybrid power system including economic evaluation are presented with a proper power transmission capacity.

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Electrical and cryogenic tests of the 1200 m HTS DC cable system Victor Sytnikov, Federal Grid Company of Unified Energy System Comprehensive tests of all the components of the HTS DC line were carried out as a part of the project to create a superconducting cable line with a capacity of 50 MW for the power system of St.Petersburg. HTS DC cable line will connect two substations of different voltage in the center of the city.The experimental stand included several cable lengths with joints and current leads, a reverse cryostat, a two-circuit cryogenic system with a capacity of 12 kW at 77K, a converter station and a control and monitoring system. The total length of the cryogenic line exceeded 1200 meters.The report presents the results of vacuum, cryogenic and electrical tests carried out over several months. The electrical and hydraulic characteristics of the HTS cable line were determined. Some emergency modes of the cryogenic system were studied. The possible time of cable operation in various accidents in the cryogenic system was estimated. The 2nd in-grid operation of superconducting cable in Yokohama project Takato Masuda, Sumitomo Electric Industries, Ltd. The superconducting cable system was installed and operated in the real grid of Tokyo Electric Company Holdings from 2012 to 2013, successfully. At this operation, the system had no degradation of its electrical and mechanical performances. After then, its cooling system was replaced to new turbo-brayton refrigerator and the cable was re-connected to the grid in 2017. The cable system was successfully operated for another one year. In this operation, stable cooling system controlling, heat loads and vacuum rates of the cryostats etc. were observed continuously. After the operation, No Ic degradation of whole length was measured. In addition, the short sample cables cut from the system after the dismantlement, were applied with AC 90 kV and Imp 385 kV, successfully as the same condition of the shipping test in 2011. These results are one of the credibility confirmations for long time superconducting cable system operation. Feasibility of ultra-compact HTS CrossConductor based power transmission cables Dustin Kottonau, Karlsruhe Institute of Technology HTS CrossConductor is a compact stacked-tape REBCO conductor of high current density [1]. In this contribution, a non-concentric three-phase cable design based on HTS CroCos is presented, which offers the possibility to reduce the cable diameter significantly. One of the important aspects of a HTS-AC power cables are the AC-losses, which are investigated both theoretically and experimentally. For the measurement of the dissipated power loss in both single-phase and three-phase conductor arrangements, a calorimetric method is used. The results indicate that it is possible to reduce the outer cable diameter compared to concentric cables designs by a factor of two. When the losses of such a cable with HTS CroCo design shall not exceed 2 W/m for all three-phases, the maximum ampacity results in a current of 600 A (rms) per phase. Depending of the application there are many potential applications for such an ultra-compact HTS CroCo-based power transmission cable design. Development and test of a 35 kA - HTS CroCo cable demonstrator Klaus-Peter Weiss, Karlsruhe Institute of Technology The answer to energy-efficient electric power transfer of high currents in the range of several tens of kA can be given by high temperature superconducting (HTS) cables. BSCCO and MgB2 have been used widely for such cables, reaching maximum currents of about 20 kA. REBCO coated conductors are promising for future HTS cables beyond 20 kA and allow the operation based on subcooled liquid nitrogen. Several cabling concepts based on REBCO tapes were developed world-wide to realize such cables. Using the stacked-tape concept, a scalable semi-industrial process was developed by KIT, called HTS CrossConductor (HTS CroCo). Key aspects of the conceptual design of high-current HTS cables are discussed and the design of a 35 kA DC cable demonstrator made from HTS CroCo strands is presented. Aspects regarding joints, current redistribution between individual strands and electrical stabilization are highlighted. The performance of this demonstrator cable was tested, reaching the envisaged current.

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Compact 2G HTS power cable: new cold tests results Vitaly Vysotsky, Russian Scientific R&D Cable Institute In Russian Cable Institute we continue R&D to develop as compact as possible 2G HTS power cables for electric power systems. Compact cables should have minimized diameter compared to other co-axial HTS cables developed before. We developed the cable prototype with four HTS layers in the core and two layers in the shield [1]. The first cold test of the compact cable demonstrated that we can control the homogeneous current distributionsamong layers in a compact cable with the inner diameter of the core ~10 mm and the outer diameter of the shield ~20 mm [1]. In this work we are presenting more test results of this cable, including AC loss analysis, mechanical test and high voltage tests. New test results demonstrated very high parameters of the compact cable developed. The compact cables perspectives for electric systems are discussed Superconducting Gas-insulated DC Coaxial Dipole Sastry Pamidi, FAMU-FSU College of Engineering High temperature superconducting (HTS) cables are being developed to provide a high power dense solution for various applications. Coaxial dipole superconducting gas-insulated line (S-GIL) is a HTS cable design with great potential. This design builds upon our previous research on a monopole S-GIL where the helium gas (GHe) functions both as cryogen and the dielectric medium. This design was demonstrated to operate at significantly higher voltages than what is possible with solid insulated GHe cooled HTS cables. GHe cooled HTS cables are of interest because of their ability to support larger operating currents and can utilize MgB2 as the superconducting material. A coaxial dipole S-GIL reduces the number of cryostats required while also reducing the self-field effect on critical current and reduces/eliminates the magnetic field leaking out of the cable system. This paper discusses the conceptual design of a gas cooled coaxial superconducting dipole and characterization of prototype designs.

The Route to the Use of Nb3Sn in ITER: Overcoming Failures and Successes Neil Mitchell, ITER Organisation Development of Nb3Sn strands for fusion applications started in the 1980s and the selection of the material for the Toroidal and Central Solenoid Coils in the first phase of ITER 1988-1991 was a key driver of the overall tokamak parameters. The development, qualification and procurement, both before and after the decision to use it, gives us an unusual opportunity to look the implementation of a novel technology in its entirety, with the unexpected and expected problems we encountered and how they were solved. The final performance tests on compound conductors were completed last year. Although successful for ITER, they showed that even in its final stages, novel technologies can produce surprises and that there are still aspects of Nb3Sn behaviour that we do not understand and which could be the subject of future research. There are many lessons which can be learned for future applications of new superconductors. The European DEMO Kamil Sedlak, École Polytechnique Fédérale de Lausanne (EPFL) The European DEMO, i.e. the demonstration fusion power plant designed in the framework of the Roadmap to Fusion Electricity by the EUROfusion Consortium, is approaching the end of the pre-conceptual design phase, to be accomplished with a Gate Review process in 2020, in which all DEMO subsystems will be reviewed by panels of independent experts. The latest 2018 DEMO baseline has major and minor radius of 9.1 m and 2.9 m, plasma current 17.9 MA, toroidal field on the plasma axis 5.2 T, and the peak field in the toroidal-field (TF) conductor 11.5 T. The 900-ton heavy TF coil is prepared in four low-temperature-superconductor (LTS) variants, some of them differing slightly, other significantly, from the ITER TF coil design. Two variants of the CS coils are investigated – a purely LTS one resembling the ITER CS, and a hybrid coil, in which the innermost layers made of HTS allow the designers either to increase the magnetic flux, and thus the duration of the fusion pulse, or to reduce the outer radius of the CS coil. An issue, presently

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investigated in detail by mechanical analyses, is the fatigue load. Two variants of the poloidal field coils are being investigated. The magnet and conductor design studies are accompanied by the experimental tests on both LTS and HTS prototype samples, covering a broad range of DC and AC tests. Testing of quench behaviour of the 15 kA HTS cables, with size and layout relevant for the fusion magnets and cooled by forced flow helium, is in preparation. The “Divertor Tokamak Test” (DTT) Facility Antonio della Corte, ENEA The “Divertor Tokamak Test” (DTT) Facility is an experimental tokamak currently under construction in Italy, at the Frascati research center of ENEA. The main goal of this nuclear fusion project is to explore various divertor solutions for defining the best way to manage power and particles exhaust, in view of the realization of the EU-DEMO machine. The DTT magnet system is fully superconducting and it is based on NbTi and Nb3Sn Cable-in-Conduit Conductors. It consists of 18 Toroidal Field (TF) coils, 6 Poloidal Field (PF) and 6 Central Solenoid (CS) stacked module coils, all independently fed. In this work the main design drivers and up-to-date solutions for the magnet system are presented, from the superconducting strand up to the main structural components, and the outcome of their main analyses discussed in detail. An overview of the technical needs leading to the present design is provided, having particular care of discussing the aspects that mainly impact on the procurement and construction phases, which are already on-going. Development of Toroidal Field Superconducting Prototype Magnet for CFETR Jinxing Zheng, Institute of Plasma Physics, Chinese Academy of Sciences With the pushing forward of CFETR (China Fusion Engineering Test Reactor) project, a comprehensive research facility center is financially aided by China government (~$60 Million) from 2019. One of the key targets is to design and manufacture a toroidal field superconducting prototype magnet for CFETR. Due to the fact that high magnetic field (6.5 T at R= 7.2m) provided by TF coils is required to get high performance plasma with current of 14 MA, the peak field will reach to 14.3 T. Enough stability and temperature margin of the high-Jc NB3Sn conductor, and high enough electromagnetic-cooling-structure safety margin (conductor jacket, coil case, support structure) will be key design points. The peak stress and overturning moment is 750MPa, 710 MN.m (ITER is only 205 MN.m ),respectively. It hopes that the new design of TF prototype coil can be good reference for fusion and DEMO research work. Quench detection of fast plasma events for the EAST PF coils Yanlan Hu, Institute of Plasma Physics, Chinese Academy of Sciences Very large current variations induce a significant voltage signal in the EAST PF Quench Detection circuit in fast plasma events.Though co-wound coil has been employed as primary compensation, its residual noise would still be much larger than the target resistance detection value (of around 0.5 V), which calls for secondary noise cancellation for one to get the desired SNR (signal to noise ratio).Even though the uncompensated disturbances are responsible for the false triggers of the EAST PF coils fast discharge following a Major Disruption or VDE.Specific solutions have been proposed for the optimizing voltage compensation to effectively reduce the large inductive components to a certain level ,meanwhile for the using the quench behaviour to distinguish the real quench.Several scenarios have been provided by EAST , for studies purposes .The lessons learned can be conveniently extrapolated to other QDS. An ANSYS-Based Model for Arcs in Large Superconducting Magnets Sam Tippetts, UKAEA, ITER Electric arcs can occur in large superconducting magnets during the failure following an unmitigated quench. The resistive heating from the quench can cause insulation breakdown, melting and vaporisation of the conductors and potentially lead to the formation of inline and bypass arcs. Arcs are sustained by stored energy in the magnets and may cause enormous damage to coils and other components. A coupled-field finite element model using ANSYS software is presented to model arc initiation and propagation. The model predicts melt damage, both to conductors and other components using temperature-dependent material properties derived from experiments. The ANSYS finite element model is coupled to PSpice electric

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circuit models using the STEAM framework developed at CERN. The model is used to predict potential arc damage in the ITER feeders after being benchmarked against the LHC arcing incident in 2008 and arc experiments available in the literature. Estimation of Performance of Nb3Sn CICC with Thermal Strain Distribution Rainer Wesche, École Polytechnique Fédérale de Lausanne (EPFL) In the last few years, the critical temperature (Tc) of several ITER cable-in-conduit conductors (CICC) was determined by magnetization measurements at zero current. The distribution of Tc values, caused by variation of strain in the Nb3Sn strands, was found to vary with the number of load cycles. A comparison with mechanical modelling requires the strain distribution, while the Tc distribution is sufficient to determine the CICC performance. The current sharing temperature (Tcs) is calculated supposing that the measured distribution of Tc is representative of its variation along a single strand and that the current is uniformly distributed among the strands. The Tcs values, found for background and peak magnetic field, are compared with the results of the test in SULTAN. The differences of the estimated and measured Tcs values are discussed including the effect of different current-voltage characteristics of single strands and CIC conductors.

Tests of a 10 kV 10 kA DC Resistive Type Superconducting Fault Current Limiter Bin Xiang, Xi'an Jiaotong University Resistive-type superconducting fault current limiter (R-SFCL) is the best choice for HVDC systems [1-3]. This paper developed a 10 kV 10 kA R-SFCL and tested current limiting properties of the R-SFCL. The R-SFCL includes a 216 meter long YBCO-coated superconducting tape with critical current of 225 A at 77 K under self-field. The R-SFCL was tested in a 10 kV DC circuit in Suzhou Electrical Apparatus Science Research Institete Co., Ltd. The rising rate and amplitude of testing fault current was 7.4 kA/ms and 10 kA, respectively. Experimental results showed that the response time of the R-SFCL was around 0.1 ms. The R-SFCL limited the 10 kA fault current to peak value of 1.57 kA. Fault current was limited to 1.0 kA at 1 ms and 0.8 kA at 5 ms. The rising rate of current was limited to 1.5 kA/ms. The fault current decreased 85% by the R-SFCL. Design and Testing a 160 kV/ 1 kA DC Superconducting Fault Current Limiter Shaotao Dai, Beijing Jiaotong University One resistive type superconducting fault current limiter (SFCL) module for the ±160kV power grid application has been designed and manufactured. The active part of the SFCL module consists of 24 bifilar coils made of 12 mm wide steel-stabilized YBCO conductor supplied by Shanghai Superconductor, and is housed in a cryostat operated at normal state liquid nitrogen. In total the SFCL passed 20 power switching tests at various fault currents between 5 and 12 kArms for a fault duration of 10 ms and 60 ms. The maximum limited resistance is 3.0 Ω, and the fault response time is less than 1.0 ms. The dc withstand voltage test at 252 kV for 1 min, the lightning impulse withstand voltage test at 550 kV(1.2 μs/50 μs) and the switching impulse withstand voltage 450 kV(250μs /2500 μs) were carried out according to the Chinese national standard GB 1094.3. Development of 150 V/m HTS conductor for fault current limitation Guillaume Escamez, Supergrid Institute In HVDC grids, Superconducting Fault Current Limiters (SFCL) are considered as a promising solution to limit fault currents. To reduce the length of tape, the production of a conductor able to withstand a high electric field of 150 V/m is under study within the European project FASTGRID.In this contribution, we present the work carried out to transform a bare ReBCO tape into a robust and suitable conductor for HV SFCL. In operation, two situations can be encountered. The first one is a short-circuit current that quenches the entire tape at once. In this case, the conductor must remain below a given temperature threshold. The

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second one is an operating current reaching a value close to the critical current, which is likely to trigger a local hot spot that could destroy the conductor. The two scenarios have been experimentally tested on different conductors to select the most robust designs. Development of SFCL for a Four-terminal ±160kV MMC-HVDC Network Chao Yang, School of Electrical and Information Engineering, Tianjin University Abstract: The Modular Multilevel Converter (MMC) High Voltage Direct Current (HVDC) transmission technology has begun to play a great role in power transmission industry since last decade. The development of protection technology for an MMC-HVDC system becomes immediately critical to large scale applications of MMC-HVDC power transmission. One of the task is to find an effective way to deal with the short circuit fault in an MMC-HVDC network, which may cause severer damage as compared with an AC transmission system. In this paper, we introduce our project to develop a resistive superconducting fault current limiter for a four-terminal ±160kV MMC-HVDC network. Computer simulations were firstly carried out. Then, a laboratory prototype was designed, built, and tested. The details of the development of this project will be reported in this presentation.Keywords: Superconductivity; SFCL; MMC-HVDC network; Power transmission Current flow diverted coated conductors for advanced fault current limiters Pedro Barusco, Materials Science Institut of Barcelona (ICMAB-CSIC) The Superconducting Fault Current limiter comes as a promising candidate for enabling direct fault isolation in multi-terminal HVDC systems thanks to its fast intrinsic resistive switching operation. However, for fault current levels close to its average critical current, state-of-the-art architecture 2G HTS tapes are prone to develop destructive hot spots due to variations in their local critical current. The Current Flow Diverter (CFD) is a relatively new architecture concept that aims to increase the so-called normal zone propagation velocity (NZPV) with the insertion of a high resistive layer that partially covers the interface between the metallic shunt and the superconducting (Re)BCO. In this work, we used bare THEVA GdBCO tapes as a template for testing different oxides for the resistive layer. The experimental CFD tapes were analyzed using Scanning Hall Probe Microscopy, and their critical current and NZPV were compared with that of tapes with classical architecture, without CFD. Recovery Performance of Partially-Joined Porous-Stabilized REBCO Tape for RFCL Kohei Yuki, Tohoku University To improve current-limiting and recovery performances of resistive type superconducting fault current limiters using REBCO tapes, an earlier study has proposed a new type of REBCO tape with a metal porous medium as a stabilizer (porous-stabilized REBCO tape [1]). The porous medium has high resistance compared to a bulk material and prevents film boiling [2] even in a high heat flux region. In this tape, a porous medium is joined to the REBCO tape using indium inserted in-between and indium has the large effect on the recovery performance [1]. This study evaluates the effect of layout of indium on the recovery performance by the over-current simulation. The result showed that the heat load in the REBCO tape was reduced by joining indium partially on the REBCO tape and its recovery time was shortened by 20% compared to that for a stabilizer-free REBCO tape. Fault Current Limitation Coordination of Multiple SFCLs in IEEE 14-Bus System Naoki Hayakawa, Nagoya University We have proposed the concept of “fault current limitation coordination” of multiple superconducting fault current limiters (SFCL) to be introduced in a future electric power grid. Using a simplified test system, the transients on fault current and internal phase angle of generators were analyzed by PSCAD/EMTDC and the modeling of resistive SFCL with a variable resistance as a function of both current and temperature at the recovery under load. In this paper, we extended the analyses to the fault current limitation coordination of multiple SFCLs in IEEE 14-bus test system. The effective coordination strategy on the introduction and operation of multiple SFCLs, e.g. introduction lines of SFCLs, operation parameters such as operating

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current, critical current and prospective fault current of each SFCL, was discussed and optimized for an arbitrary fault location in the test system.

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Holistic system approach for electric aircraft using superconducting components Martin Boll, Siemens Aktiengesellschaft- Corporate Technology- eAircraft Currently hybrid-electric aircraft are under investigation as one possible solution to reduce the emissions of the aviation industry according to the Flightpath 2050 of the European Union. To meet the drive train’s requirements on smallest mass while aiming for highest efficiency, superconducting technologies are regarded as a key enabling technology for drive train powers of several tens of megawatts.Within the German nationally funded project TELOS an exemplary mission profile of a 200-passenger aircraft is used to derive the requirements for a cryogenic cooled hybrid-electric propulsion system (CEPS). To optimize the total system performance, we subsequently evaluated the superconducting and cryogenic cooled components by using computationally fast, analytical models. This approach allows to quantify the system performance by using component technologies being available today and formulating required developments for the future. fully superconductive propulsion motor with 1MW for airborne application Thomas Reis, Oswald Elektromotoren GmbH To increase the efficiency and reduce emissions of airplanes according to ACARE's flightpath goals for 2050 the electrification of the drivetrain is the most promising approach. For mid- and longrange airplanes the power/weight ratio of standard components is insufficient, superconducting devices are seen as enabling technology. The presentation gives an overview on specific needs for a fully superconductive propulsion motor suitable to drive a fan or propeller, followed by a description of the 1MW demonstrator developed and tested within the EU funded ASuMED Project. This motor uses a superconductive AC winding system in the stator combined with in service magnetized superconductive stacks in the rotor. The whole motor is operated with liquid hydrogen to improve effiency and power/weight ratio at its best. Redundancy and safety issues particularly for the used HTS tapes are considerd, as well as the cryogenic and power supply will be addressed. Design consideration of fully HTS machines for future electric aircraft Min Zhang, University of Strathclyde Fully HTS machines need to achieve a power density of 25 kw/kg in order to drive large electric aircraft. Currently the AC losses of HTS stator winding increase the weight and size of machine cooling system. This paper presents design considerations for fully HTS machines using state-of-art 2G HTS materials. We use a rotational machine model to demonstrate how 2G HTS helps to achieve the power density for electric propulsion. To validate our model, a HTS machine platform has been estabilished to measure the AC losses of 2G HTS machine windings in a rotational magneti field. The model results with be compared to measurements for validation. Recommendations on future improvements in HTS materials will be provided to help maximise machine power density for futher electric aircraft. High Power Density 10 MW HTS-Generator for eAircraft Lars Kuehn, SIEMENS AG Currently hybrid-electric aircraft are under investigation as one solution to reduce the emissions of the aviation industry according to the Flightpath 2050 of the European Union. To meet the drive trains requirement on smallest mass while aiming for highest efficiency, superconducting technologies are regarded as a key enabling technology for drive train powers of several megawatts. High temperature superconducting (HTS) rotating electric machines offer a significant advantage in gravimetric and volumetric power density over conventional machines. Based on our previous experience in superconducting electric machines we analyzed the potential of the technology to build very light

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generators for future application in short range aircraft. In this talk we outline a concept of a high power density generator that could be coupled directly to a gas turbine. Our detail design studies that cover electromagnetic, thermal, structural, cryogenics and insulation design suggest that gravimetric power densities beyond 10kW/kg can be achieved. Construction and Test of a Flux Modulation Superconducting Machine for Aircraft Alexandre COLLE, Safran Tech / GREEN, University of Lorraine The increasing of drives towards More Electric Aircraft (MEA) or the development of electric propulsion aircraft calls for MW-class electrical machines with more compact and power dense designs. One way is to explore the use of superconducting materials to create a high magnetic field in order to reduce the mass of ferromagnetic components. This paper presents the construction and the test of a brushless axial flux superconducting machine. The brushless topology satisfies the aeronautics industry requirements in terms of maintenance, while the axial configuration ensures an optimal use of the anisotropic HTS tapes. The machine is classed as partially superconducting, only the inductor is made with superconducting materials. A special design concerning the use of a stationary cryostat is presented. This improvement reduces significantly the electromagnetic air-gap length. A 50kW prototype is manufactured with a minimal mass objective. The prototype constitutes a first step to a scale-up MW-class machine design. AC loss in the distributed stator winding of a 1 MW motor for aviation Enric Pardo, Institute of Electrical Engineering, Slovak Academy of Sciences Superconducting motors and generators are very promising for air-borne applications, thanks to their high power-over-weight ratio. Stators made of 2G HTS containing multi-tape conductors cause high AC loss, which needs to be reduced. We present several strategies to reduce the AC loss, supported by modeling and experiments. For the model, we use a design of a 1 MW motor with distributed winding for airplane propulsion [1]. Modeling combines commercial FEM with a self-programmed method [2] for the non-linear eddy currents in the superconductor [3]. As input, we use measured Jc(B,theta,T) between 20 and 40 K. In the experiments, a single coil is submitted to its self-field or under anti-symmetric applied magnetic field, having opposite directions at each straight part of the coil. For distributed windings, we found that using parallel-tape conductors with tapes isolated along their length reduces the AC loss to the theoretical limit of ideally transposed cables. Developing HTS electric propulsion machines using no-insulation (NI) coils Yawei Wang, University of Strathclyde A Marie Curie project under Horizon 2020 has been funded to develop thermally robust HTS machines for electrical aircraft using NI coils. NI coils can improve the thermal stability of HTS coils, thereby improving the robustness of HTS machines. This is essential for electric propulsion applications where safety is the primary concern. A 2MW HTS synchronous motor was designed based on NI technique. We will demonstrate in this paper how NI coils help to improve machine thermal stability by both experimental and numerical methods. We will also discuss technical challenges associated with the use of NI coils in machines: heat dissipation in a ripple magnetic field and the ramping delay.

Development of FAIR conductor and HTS coil for fusion experimental device Toshiyuki Mito, National Institute for Fusion Science (NIFS) We have begun research towards the development of high-temperature superconducting magnets for the application to a fusion experimental device next to the LHD (Large Helical Device) in NIFS. By applying the features of HTS, it can balance high current density with the high stability. As a candidate conductor, REBCO tapes and pure aluminum sheets are laminated and placed in a groove of an aluminum alloy jacket with a circular cross-section, after covering the jacket by friction stir welding, and twisting the conductor to homogenize its electrical and mechanical properties. The FAIR conductor derives its name from the

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processes and materials used in its development: Friction stir welding, an Aluminum alloy jacket, Indirect cooling, and REBCO tapes. The development of the FAIR conductor, design concept of the FAIR coil cooling structure using liquid hydrogen, and coil protection utilizing the secondary windings as a quench heater are reported herein. Development of 20 T conduction cooled non-insulated REBCO magnet technology Robert Slade, Tokamak Energy Tokamak Energy are developing REBCO magnets for fusion applications. We have tested several small non-insulated coils with high thermal conductivity. All coils were wound with one or more pairs of HTS tape and solder encapsulated. The magnets were conduction cooled in the range 12-50 K and energized up to 3000 A. Six double pancake coils, each using ~100 m of tape from a different supplier were initially tested, followed by two larger magnets, made from six individual pancake coils with more turns. All magnets displayed remarkable and counter-intuitive behaviour, including significant defect tolerance and fully stable operation when operating in excess of nominal short sample critical current. One of the larger magnets, using Development of HTS CORC® Cables and Joints for use in Magnets for Fusion Jeremy Weiss, University of Colorado Advanced Conductor Technologies is developing High-Temperature-Superconducting (HTS) Conductor-on-Round-Core (CORC®) cables and wires wound from ReBa2Cu3O7-x (ReBCO) coated tapes for use in fusion magnets. Several cable-in-conduit CORC® based conductors have now been tested in the Sultan test facility in a background field of 11 T, with more tests planned in the near future, to demonstrate operating currents of 50-100 kA at temperatures of 4-50 K. In addition, low resistance terminations and joints are being developed to enable demountable fusion magnets that would allow easier access to the fusion experiment for maintenance and parts replacement. Several joints between individual cables were constructed and tested in liquid nitrogen and liquid helium as a step to develop stable 100 kA-class CICC joints with contact resistances of less than 1 nΩ. Current progress of CORC cable and joint development is presented with an emphasis on the most recent results. Quench Study of REBCO Cable-In-Conduit Conductors Rui Kang, University of Science and Technology of China Quench behavior of REBCO Cable-In-Conduit Conductor (CICC) is studied by experiment in SULTAN facility and simulation with THEA code. Due to the limitation of SULTAN, one 15 kA conductor is scaled down from the 50 kA REBCO conductor developed by SPC. The scaled down conductor contains three strands, which are composed of a twisted soldered stack of REBCO tapes encased with copper profile. Apart from this, conductors with different layouts are designed and tested to study the influence of thermal contact resistance between cable and conduit. Hot spot temperature and normal zone propagation velocity are measured for different conductors and used to evaluate their quench behavior. The results are also compared with simulation on sub-scale conductors to verify and improve the model. Then the verified model is further applied for full-size conductors to study their quench behavior. Recent progress in development of HTS CICC for CFETR magnet Jinggang Qin, Institute of Plasma Physics, CAS The CFETR, “China Fusion Engineering Test Reactor”, is a new tokamak device. The main goal of this project is to build a fusion engineering tokamak reactor with fusion power of 50-200 MW. The maximum field of CS and TF will get around 15 T, which is much higher than that of other reactors. Tremendous investigations have been made in the development of high performance CICCs in the last two years. High temperature superconductors used for CICCs were considered. In this paper, the recent progress in development of HTS CICCs for CFETR magnet are introduced and described in details. Firstly, the performance of superconducting material (Bi2212 and YBCO) from China was introduced, including mechanical properties, critical current with strain and so on. Secondly, the conductor design was proposed. Three different designs

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were proposed for conductor sample evaluation. Finally, the testing results of sub-size conductor samples with 10kA@4.2K, 7T were given. Transposition in superconducting cables: which differences between LTS and HTS? Davide Uglietti, Ecole Polytechnique Fédérale de Lausanne (EPFL) The microstructure of LTS strands and the transposed cable designs were developed in the 60’ and 70’; the choices were justified by low stability and small temperature margin of LTS materials. In the last 10-15 years, the most common strategy in the development of HTS cable for magnets has often been to imitate the LTS cable designs without verifying if the requirements for LTS were still valid in the case of HTS materials, which are extremely stabile. In contrast with LTS wires, non transposed multifilamentary Bi-2223 tapes can be used in magnets. Analysis of the inductances and considerations on coupling losses in non-transposed stacks suggest that high transposition may not be needed. The benefits of a drastic reduction in transposition could be simpler, more efficient and more cost effective cable designs, especially for highly anisotropic materials (coated conductors). D shaped REBCO model coil for fusion by in-suit winding technology Xinsheng Yang, Southwest Jiaotong University High-temperature superconducting (HTS) material is considered to be used in the next generation of fusion reactors due to extremely high critical current density as well as high critical field at low temperature. REBCO conductor has been considered for EU DEMO. In the design of Chinese Fusion Engineering Test Reactor (CFETR), Bi2212 and REBCO will be used. Here, we report the fabrication of D shaped HTS model coil (TF coil) for fusion magnet using REBCO tapes by in-suit winding technology. This model coil is 1/20 to ITER TF coil and the central field is 1T. More importantly, the stress, deformation and defect caused by ordinary conductor to coil winding procedure, due to the coated conductor (CC) structure, will be significantly decreased by in-suit winding technology.

Applied Superconductivity for Medical Accelerators Arno Godeke, Varian Medical Systems Particle Therapy GmbH At present, there are 76 proton therapy sites in operation globally, but less than 3% of the cancer patients that could benefit from this form of treatment have access. The root causes for the limited availability are the large installation- and operating costs, which are driven by the overall system size, weight, and complexity. Substantial reductions in size and weight can be achieved by replacing copper magnets with superconducting versions. The use of superconductors therefore has the potential to provide substantial cost reductions if the higher conductor cost, and added complexity due to the cryogenic cooling requirements, can be mitigated. In this presentation, I will provide a brief introduction into the treatment of cancer with charged particles, explain where in the systems the use of superconductors could be beneficial, and highlight specific complications that emerge. Flux Pumping into Large Inductances Archie Campbell, University of Cambridge A simple circuit model of a flux pump is presented, in which a magnet crosses superconducting wires.The main parameters are the flux of the magnet f, the load inductance LL and the critical current density Ic. If the results are expressed in terms of cycles they are independent of frequency.The results are :-1) If the critical current is constant and only two wires are crossed there is no significant flux pumping.2) If the critical current under the magnet is a factor k times Ic a saturated load current Is of about (1-k)Ic can be obtained.3) If the magnet has to cross three wires instead of two the load current can be pumped to Ic..4) For cases two and three the initial pumping rate is f per cycle and saturation is achieved in about 2*LLIs/f.5) The loss in reaching saturation is 4*LLIc2 Joule

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Small cryo-cooled no-insulation 2G HTS coils for space propulsion applications Stuart Wimbush, The Robinson Research Institute of Victoria University of Wellington Small satellites provide an affordable route to space qualifying new technologies such as those based on high temperature superconductors. We have constructed and ground tested HTS coil assemblies fitting within the envelope of the smallest (“1U”) CubeSat while generating a magnetic flux density over 1 T, aiming at the development of a compact, energy-efficient self-propulsion system. We demonstrate the dry winding of 2G double-pancake coils to a tight (1 cm) inner diameter to achieve the desired number of turns (~500). A no-insulation coil configuration provides robustness under fault conditions, launch and operational stresses. We demonstrate how different winding tensions affect the turn-to-turn resistance and consequently the no-insulation characteristics. The electrical and thermal design, utilising a space-qualified electrical cryocooler, operates on a power budget of just 20 W. The coil design is supported by finite element modelling, providing a pathway towards the development of further designs optimised for this niche application. Manufacture of 7.5 M Long Cryogen-Free Magnet System for Neutron Decay Studies Zakiya Omar, Cryogenic Ltd The design of a large purpose built cryogen-free magnet is reviewed. The system has been manufactured for the Fundamental Neutron Physics Beamline (FNPBL) at the Spallation Neutron Source (SNS), Oak Ridge, Tennessee.The magnet system will house a custom spectrometer and be used to measure a, the electron-neutrino correlation parameter, and b, the Fierz interference term in neutron beta decay.The cryostat is 7.5m along its axis and 1.43 m in diameter. It houses a complex set of niobium-titanium superconducting windings which provide a varying magnetic field profile along a 320mm diameter gold-plated UHV bore. A vacuum of -10 mbar is achieved.The stray field generated by the magnet windings surrounding the UHV bore is compensated by a series of negatively wound co-axial windings. The magnet can be operated in both horizontal and vertical orientations. Experimental Study on the Quench Characteristics of a Roebel Cable Coil at 77K Yifeng Yang, Institute of Cryogenics, University of Southampton Experimental studies on the quench characteristics of a pancake coil wound with Roebel cable of 15 ReBCO strands were carried out at 77K in liquid nitrogen. Point-like disturbances by a miniature heater were used to initiate quench at transport different current up to 500A at 50%-95% of the critical current. The minimum quench energy (MQE) were ascertained systematically by bracketing the heater energy between recovery and quench. It was found that the MQE tends to a constant with increasing heater power thus confirmed an adiabatic quench behaviour for the epoxy impregnated pancake coil in liquid nitrogen. Global stability was also obtained below a critical heater power when the normal zone was stabilised by the cooling from the current terminals. The MQE as well as the associated quench temperature and current sharing voltage of the hop spot were analysed using computer modelling and the classical quench theory of effective medium. Magnetic shielding above 0.7 T at 77K with a stack of 2G coated conductor annuli Philippe Vanderbemden, University of Liege We report the magnetic shielding performance of a stack of YBCO tape annuli cut from a 46 mm wide coated conductor. The height and inner bore of the stacked tape magnetic shield are 24.4 mm and 26 mm respectively. Experiments are carried out at 77 K. Under an axial field, magnetic shielding is found to be effective up to Blim = 700mT. Finite element modelling shows that Blim is primarily determined by the finite height of the stack and not by material properties. Remarkably, the stack is found to able to shield transverse inductions up to 20mT in spite of its layered structure. This is partially due to the contribution of the ferromagnetic substrate, as evidenced by shielding measurements at room temperature. Finally, the results are used to predict the magnetic shielding properties of higher stacks, demonstrating their significant potential to shield axial fields above 1 tesla at 77 K. Quench dynamics in different configurations of MgB2 Rutherford cables

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Elena Martínez, Instituto de Ciencia de Materiales de Aragón (CSIC – University of Zaragoza) The operating temperature and superconducting characteristics of recently proposed Rutherford cables based on MgB2 create particular challenges compared to LTS-based ones. At the present state of knowledge, it is important to understand their behaviour to further optimize their superconducting properties and thermal stability.In this communication we analyse the generation and propagation of quench of two different Rutherford cables under local heat disturbances. The analysed cables share a similar geometry (12 strands of monocore MgB2 wires with transposition length of about 30 mm), but have different strand sheath material (Al+Al2O3 vs Cu10Ni), metal barrier (Ti or Ta vs Nb) and wire processing (IMD vs in-situ reaction).Measurements of voltages intra- and inter-strands have been performed to analyse the superconducting-to-normal transition, current-sharing behaviour and homogeneity of these cables during a quench. It is observed that the time-dynamic regime for quench development is strongly influenced by the characteristics of the metal sheath.

Results and lessons learned from the 3 MW EcoSwing wind power generator Markus Bauer, THEVA Dünnschichttechnik In the EU funded EcoSwing project the world’s first large-size superconducting multi megawatt wind turbine generator was successfully realized, tested and operated in a real operational environment. THEVA’s first task was the development and manufacturing of 40 large superconducting coils for the rotor. We were also in charge of controlling the operational parameters of the superconducting rotor during ground testing and commissioning of the generator on a wind turbine in northern Denmark. Several hundred hours of operational experience were achieved while power in the MW range was delivered to the grid.An overview on the results and lessons learned from the small series manufacturing of the superconducting coils as well as from operating them in the real wind turbine will be given. HTS synchronous machine dynamic simulation modelling and comparison with tests Peter O'Brien, Queensland University of Technology High temperature superconducting machines offer advantages of improved efficiency, higher power density and high electrical stiffness in power systems. Advancing HTS technology in maritime generator and propulsion motor applications requires a very high standard for performance and resilience.In operation the HTS rotor coils of a synchronous machine may be exposed to alternating current fields from sources including the field excitation supply current ramping, field current control and machine dynamic load and speed changes.A machine model has been developed to estimate HTS field current and rate-of-change limits, predict HTS winding zones exposed to quench and estimate cooling power during machine operation. The model uses finite element methods and adopts the H-formulation for the HTS rotor winding area and the A-formulation in the copper stator winding region.Results from model simulations are compared with tests using the Siemens 400 kW HTS1 demonstrator at the Queensland University of Technology test facility. The general design of a 300-kvar class HTS synchronous condenser prototype Timing Qu, Tsinghua University China Southern Power Grid, Ltd. has established a project to study the feasibility of installing large-scale HTS dynamic synchronous condensers in Ultra High Voltage Direct Current (UHVDC) transmission grid. As the pre-research a small–scale one, such as 300-kvar class HTS synchronous condenser prototype is designed. The rotor excitation winding, composed of totally 8 double-pancake racetrack coils, are wound by ReBCO coated conductors. It is cooled by forced-flow helium gas and the working temperature is expected below 30 K. The water-cooled stator winding is embedded in non-ferromagnetic stator teeth. Made by fibre glass epoxy, the torque tubes are optimized to balance the thermal leak and mechanical requirement. The pair of copper (OHFC) current leads are designed to transport current from room temperature to cold

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terminals. All the rotor structures are enclosed in a vacuum chamber. Before assembling, the critical current of the rotor magnets are tested in liquid nitrogen. HTS rotor coils and joints for high power density rotating machines Marijn Oomen, Siemens AG, Corporate Technology Very compact electrical synchronous machines with high power density can be achieved with High-Temperature Superconducting (HTS) field coils in the rotor. If such coils are series-connected with good soldered or other low-resistance joints, and shorted via an HTS switch, they can be operated in “quasi-persistent mode”. The rotor current decay is then slow enough to operate for hours or days before the rotor must be recharged, which can save the weight of a rotor current supply. We have designed and produced many impregnated race-track coils with >100 turns of coated-conductor HTS tape. Multiple coils were assembled into geometries relevant for an HTS rotor, surrounded with a cold structure capable of holding the large electromagnetic and centrifugal forces in high-rpm machines, and then tested at temperatures of 77K…20K. Special winding and impregnation techniques enable current densities and magnet fields clearly larger than those achieved earlier with coated-HTS racetrack coils. A Cryo-cooled HTS Dynamo which outputs >1kA Chris Bumby, Robinson Research Institute, Victoria University of Wellington HTS dynamos are a class of flux pump which can inject a DC current into a closed superconducting circuit. These small devices eliminate metal conducting current leads and heavy power supplies from the circuit, opening the door to entirely new designs of high-current cryo-cooled magnets. Here we report a cryo-cooled dynamo based on a barrel-type stator topology, and connected in series with a solenoid coil wound from 3 parallel coated conductor tapes. The output of this device has been characterised across a range of temperatures from 90 K to 35 K, with output currents >1 kA obtained at temperatures ≤ 60 K. Interestingly, maximum output voltages occur at higher temperatures (> 80 K), where flux penetration is maximized. As a result the choice of optimal operating conditions for this type of device is determined by the operating requirements and impedance of the load coil circuit. Effect of HTS stack sectioning on pulse magnetization efficiency in a motor Anis Smara, University of Cambridge Stacks of HTS superconductors can be magnetized and used as a surface mounted magnet for electrical machines [1]–[4]. Pulse field magnetization is considered as a practical method, however the amplitude of the pulse can be limited in an electrical motor which results in an under-saturated stack with the superconducting currents penetrating only a part of it making the magnetization less efficient [4]. A solution to this problem could be sectioning the stack along its width enabling effective penetration of the superconducting currents.In this paper we investigate the effect of sectioning of HTS surface mounted stacks on the efficiency of pulse magnetization method in trapping the flux using low pulsing field. It is shown that the sectioning of wide stacks into several narrower parts results in a higher trapped flux. Experimental measurements are performed on a lab-scale motor to validate the theoretical analysis. Development and testing of 10 kW fully HTS generator Nickolay IVANOV, MOSCOW AVIATION INSTITUTE Electrical machines based on modern superconductors could possess extremely high specific power. It gives opportunities to develop new systems like electric aircraft.The most promising concept of electrical machine with high specific parameters is fully superconducting synchronous electric machine with a nonmagnetic core. At the output power of more than 1 MW, the specific power is anticipated to exceed 10 kW/kg at 77 K.This work presents the small scale prototype of fully HTS electrical machine with output power 10 kW operating with 77K. To develop such machine analytical technique for calculating of magnetic field distribution in the active zone of fully HTS machine was created. Besides finite element modeling was produced. Machine was designed and manufactured in Moscow aviation institute, Russia. Finally 10 kW prototype was tested.Results of this project could be used for developing of new large-scale machines with high specific power.

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Overview - Materials Requirements For Superconducting RF Cavities Anne-Marie Valente-Feliciano, Thomas Jefferson National Accelerator Facility While bulk niobium (Nb) has been, thus far, the material of choice for superconducting accelerator applications, superconducting RF (SRF) cavity performance is approaching the material theoretical limit. Some margin is gained with novel processes such as N surface doping or infusion. For further SRF performance improvement, research interest is renewed towards alternatives such as Nb films and higher-Tc superconductors. Another interesting approach is to delay vortex penetration in Nb surfaces with superconductor–insulator– superconductor multilayer structures, benefiting from the higher critical field Hc of higher-Tc superconductors without being limited with their lower Hc1. Candidate SRF materials need not to be only good superconductors (high Tc), but have good normal state metallic behavior at low temperature to minimize RF losses. The crystallographic quality has also a strong influence on trapped flux pinning, impurity segregation, efficiency of engineering processes (N doping ...). This paper gives an overview of the requirements for SRF cavity materials. Applying material science of pinning in high Jc materials to SRF materials Lance Cooley, Florida State University / National High Magnetic Field Laboratory Superconducting radio frequency (SRF) cavity materials are now branching out from a decades-long basis on niobium metal and Nb thin films on Cu toward Nb3Sn, (Nb,Ti)N, MgB2 and other intermetallic compounds. Yet, connections between near-surface structure and composition, properties under surface RF fields, and cavity performance are not completely understood even for Nb-based technology. SRF performance is generally improved by reducing flux pinning, in contrast to the goals for processing the same materials above as magnet conductors. The presence of nano-hydride precipitates, oxy-carbo-nitride surface layers, residual cold work, artifacts of electrochemistry, and other consequences of processing have been correlated with quality factor loss and higher surface resistance. Since many processing techniques are similar to those used to engineer high current density in magnet conductors, it worthwhile to compare metal forming, deposition, and heat treatment techniques intended to improve flux pinning from a different point of view relevant for SRF cavities. Theoretical understanding of pinning in SRF cavities Alex Gurevich, Old Dominion University In this talk I will give an overview of basic mechanisms of pinning which can result in trapped vortices causing significant RF losses in superconducting resonant cavities. Different contributions of trapped flexible vortex lines oscillating under the surface RF currents to the residual surface resistance and its dependencies on the RF frequency, temperature and the impurity mean free path will be discussed. Materials fabrication in SRF cavities: beyond niobium Sergio Calatroni, CERN Niobium has been for decades the material of choice for accelerating SRF cavities for particle accelerators. Requirements of new accelerators, such as the Future Circular Collider at CERN, in terms of increased efficiency and global energy savings, call for the development of novel materials beyond niobium that might operate at a higher temperature. We will discuss the potential material choices and their most promising fabrication technologies for future SRF applications, with an accent on those which have already lead to successful prototypes, and might pave the way to the next-generation accelerator cavities. First Protons Beam Tests of Crab Cavities in the SPS Rama Calaga, CERN

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The high luminosity LHC (HL-LHC) will employ transverse deflecting cavities (aka crab cavities) to collide the bunches head-on at the high luminosity interaction points (IP1 and IP5). Crab cavities will recover the geometric luminosity loss due to a finite crossing angle at the IP without which the peak luminosity loss for HL-LHC can be up to 70 %. The paper will discuss the development of the superconducting crab cavitieis for the first beam tests in the Super Proton Synchrotron (SPS) with protons. The main highlights from the beams tests in the SPS are outlined.

Progress on No-Insulation HTS Magnet Technology Seungyong Hahn, Seoul National University, National High Magnetic Field Laboratory It was a milestone that 45.5 T was achieved by use of a 14.4 T no-insulation (NI) high temperature superconductor (HTS) insert coil in a background field of 31.1 T at the National High Magnetic Field Laboratory. Wound with the latest 30-um substrate REBCO tapes made by SuperPower Inc., the NI insert coil was operated at an overall engineering current density of 1200 A/mm2 at 45.5 T. Although this demonstrates a strong potential of the REBCO conductor for the next-generation ultra high field (>40 T) user magnets, recent reports on mechanical failures of multiple high field NI REBCO magnets are a clearly wakeup call on the operation reliability of NI REBCO magnets. This paper presents a summary of design, construction, and operation of selected NI HTS magnets, identifies key technical challenges that we have learned to date, and discusses some potential solutions. A 10 T HTS Insert made of MI Pancakes Tested in a Magnetic Field up to 20 T Xavier CHAUD, LNCMI-EMFL-CNRS, UGA, INSA, UPS In the frame of a project called NOUGAT, we focused our effort on the characterization of HTS inserts in a 170 mm RT 20 T resistive magnet available at LNCMI. We used REBCO coated conductors because of their high electrical and mechanical performance under very high field and their commercial availability in length enabling a first design as a stack of pancake coils. Building HTS inserts remains challenging specially about quench protection. We chose the Metal-as-Insulation concept (MI) which relies on the co-winding of a bare HTS tape with a metallic ribbon such as Hastelloy, a stainless steel, for mechanical reinforcement as well as for electrical protection purpose. We have designed and fabricated a 10 T HTS insert that consists in an assembly of 9 MI HTS double pancake coils. We will report on the performance and behaviour of this insert up to 20 T. Design and performance evaluation of a 25 T all superconducting magnet Huajun Liu, Institute of Plasma Physics, Chinese Academy of Sciences A 25 T all superconducting magnet composed of a 11 T YBCO insert coil and a 14 T low temperature superconductor (LTS) background magnet has been designed and tested. In this paper, the axial tensile strain/stress dependence of critical current of YBCO coated conductors at 4.2 K in different magnetic field have been investigated to obtain the irreversible strain/stress limits. In addition, the stress distributions in the insert coil during the winding process, the cooling down process and the excitation process were analyzed by using the Finite Element Method (FEM). The performance of the insert coil was evaluated at 4.2 K in 14 T background field, and the results show that the maximum central magnetic field can reach 25.2 T at a transport current of 330 A. It proves that there is no mechanical damage to the YBCO insert coil and the experimental and analytical results are believable. High Field Flux Pumped Magnets Tim Coombs, University of Cambridge For many years now we have had MRI machines, typically made from LTS, they perform a vital function in the Healthcare market. MRI machines are a subset of NMR machines, which enable us to push back the boundaries of physics examining states of matter inaccessible by any other means. NMR machines are typically classed by the frequency at which they work. The higher the frequency the better the resolution of

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the machine. Typically NMR machines are available up to 900 MHz which requires a flux density of 21.2 T, although Bruker market the 1GHz Aeon which uses a flux density of 23.5 T. We are working with Maglab towards enabling higher field HTS magnets by using flux pumping to induce currents in 1000's of Amps. Bi-2212 Coil R&D for High Field Magnets Ulf Trociewitz, Applied Superconductivity Center/NHMFL The properties of Bi-2212 have been improved significantly, making it a feasible candidate in high field magnets. Magnets for the high energy physics and solenoids for nuclear magnetic resonance are the two major technology pushes. One focus at the NHMFL is high field NMR magnets beyond 1 GHz. In our high pressure furnace Bi-2212 coils can be processed to achieve reliable transport properties. Controlled high pressure processing has enabled systematic R&D work on Bi-2212 wire and coils. Bare Bi-2212 wire has low mechanical strength by itself and has to be reinforced. To understand how Bi-2212 can be used in high field magnets we are making a series of coils focusing on various types of reinforcement. FEA models predict the coils’ mechanical behavior under various load conditions. These coils are tested in our 14 T magnet to explore their operational limits. This presentation will provide an overview of our work. Electrical and thermal behaviours of INS and NI HTS-wound pancake coils at 77 K Roland Gyuráki, Karlsruhe Institute of Technology HTS-wound coils are being developed for use in motors, generators as well as magnet applications. Determining the stability and safe operating margins of such coils still poses challenges. While the recently introduced no-insulation winding method provides a remedy for many problems, it comes with its own limitations.For comparison, we have wound two pancake coils from HTS coated conductors with the insulated and non-insulated winding techniques. Both coils were coated with a fluorescent, temperature-sensitive coating, which allowed monitoring the surface temperatures during operation [1] . The coils were cooled to 77 K via a combination of conduction and gas cooling, where their electrical and thermal behaviour was observed while applying different current ramping rates, sudden discharge and overcurrent tests. This approach allowed us to gain more insight into the thermal and electrical stability of the coils. The measurements have also highlighted potential weak spots in the coils and their design. A REBCO superconducting switch for reducing temporal fluctuations in driven-mode Sadanori Iwai, Toshiba Energy Systems & Solutions Corporation High-temperature superconducting magnets are generally driven by the power supply (driven-mode), where the temporal instability of the power supply such as ripple noise directly affects the magnetic field stability. A method of suppressing such the temporal fluctuations by short-circuiting both ends of a coil with finite low-resistance joints somewhat similar to persistent current switch has been proposed to form a closed loop which has the large time constant L/R. In this research we developed a REBCO superconducting switch. To obtain the high resistance with short wire length during excitation, the switch was mainly constructed by non-inductive winding of non-copper coated REBCO tapes. However, at the end of winding the copper coated REBCO tapes were jointed to prevent the degradation by exposure to the moisture. The design, and test results of the switch attached to the test REBCO magnet under conduction cooling configuration will be presented.

High Magnetic Field NMR Superconducting Magnet Technology Qiuliang Wang, Institute of Electrical Engineering, Chinese Academy of Sciences The Nuclear magnetic resonance (NMR) system is a powerful tool in the material composition analysis, chemical functional group identification, molecular steric configuration inspection, etc. The augmentation of the magnetic field intensity of NMR magnet will elevate NMR spectrum resolution significantly, resulting in more accurate explanation of material microscopic structure.Development of high magnetic field superconducting magnet of NMR system is a challenging work. Various technical problems will emerge in

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magnet design and engineering implementation compared with conventional low-field situations. High-field NMR superconducting magnet technique research should take careful consideration of superconducting wire critical performance, mechanical structure, shimming strategy, cryogenic system, quench protection, etc.For extremely-high magnetic field, the commonly-used low-temperature superconducting material will be incapable of meeting magnetic field requirement and high-temperature superconducting material with superior critical current performance is adopted.In the presented work, the high-field superconducting magnet technology applied in NMR instrument will be elaborated. Superconductivity and High Magnetic Field Facilities charles simon, LNCMI CNRS Following the discovery of the High Temperature Superconductors, more superconducting materials have been discovered. These regular successive discoveries have continued to renew the interest of scientists into these fascinating quantum phenomena. Access to high magnetic fields is a key capability for probing the mechanisms of superconductivity. The high field world-wide facilities hosts and welcomes researchers working on superconductivity in high magnetic fields combined with low temperature or/and high pressure with different experimental tools: NMR, optical spectroscopy, ultrasonic, etc.. A personal prospective of these facilities will be reviewed.Among them, LNCMI provides in Grenoble access to steady fields up to 37 T and is developing superconducting magnets for the production of larger fields. A hybrid magnet will provide a field of 43 T in the coming years and HTS inserts have been tested in 20 T environment, leading the way to an all superconducting magnet with fields larger than 30 T. Development of High Field, Wide Bore Superconducting Magnets beyond 18 Tesla Wenbin Ma, Oxford Instruments Oxford Instruments has successfully developed a series of large bore, high field magnet systems, using conventional NbTi and Nb3Sn low temperature superconductors (LTS). The most recent of these systems achieving a central field of 18 T with 150 mm cold bore is described. This system was designed for a scanning tunneling microscopy application and the challenges included achieving high mechanical and temporal stability with minimized liquid helium boil off.In this paper, we will also introduce the development of a new high field and large bore magnet system, with a central field of 20 T and a cold bore of 100 mm. This magnet will be integrated with a special low-loss cryostat, utilizing conductive radiation shields designed to withstand induced forces in the event of a magnet quench. The key technical challenges which have to be met to provide such magnet systems will be discussed in this paper. Development of a 27.2 T superconducting magnet at IEE Jianhua Liu, Institute of Electrical Engineering, CAS Institute of Electrical Engineering (IEE, CAS), has developed high field magnet for many years, and have successfully finished a 27 T superconducting magnet on Nov. 28, 2017. This magnet consists of a 15 T LTS magnet and a 12 T REBCO insert, which are powered separately. Design and fabrication techniques like current grading, winding pretention, overbanding, splice joint soldering, axial pretention and so on are mainly focused on to achieve a high-performance high field superconducting magnet. The designed highest engineering current density in this REBCO coil is 382.7 A/mm2, the operation margin for the REBCO coil is 42.6%, and the maximum hoop stress was 438 MPa after employing winding pretention. Details of these design and fabrication aspects and how they affect the performance of the high field REBCO insert will be introduced in details in this paper.

Modular HTS bulk system for magnetic train transportation Frank Werfel, Adelwitz Technologiezentrum GmbH (ATZ) Based on high-quality YBCO bulks we provide and analyze large-scale system techniques and progress of portable compact cryostats. We measure trapped flux efficiency, magnetic forces, and cryogenic

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parameters in detail. In a modular updated solution, the vacuum cryostat consists of 30 rectangular YBCO bulks in a plane area of totally 900 cm². As a technical highlight a constant magnet distance of 3 mm is obtained. The stainless steel cryostat type 500 itself has a rectangular size of 45 cm x 30 cm, a weight of 30 kg, whereby half of the weight is being the active cold part. The device is portable with an independent LN2 cryogenics. With 5 l LN2 on board a perfect insulation of less than 4 Watt thermal loss allows a two-day operation without refilling. We report about the adaptation to a maglev train experiment where 12 cryostats are combined to levitate and transport passengers. Dynamic Characteristics of the HTS Maglev Vehicle System Zigang Deng, Southwest Jiaotong University High-temperature superconducting (HTS) maglev, with simple structure and self-stable characteristics, has been considered as a potential means of high-speed transportation. Before commercial applications, simulation and experiments are necessary to predict its dynamic characteristics. We firstly proposed new numerical models of levitation force and guidance force respectively and then introduced them into the HTS maglev system to investigate the nonlinear vibration behaviors and the motion stability. On this foundation, an HTS maglev vehicle / bridge coupled system was built to analyze the vertical dynamic response. The influences of velocity, air spring parameters, bridge types and guideway irregularity on the ride quality of vehicle were studied. Besides that, the curve negotiation performance was systematically investigated. The transverse suspension parameters of the maglev vehicle were suggested and the recommended values of curve radius were also proposed as a proposal. These works provide reference for the further design of the HTS maglev vehicle and its test line. Comparative Study between Electromagnet and Permanent Magnet for HTS Maglev Yuyan Wen, Tianjin University Abstract In this paper, we investigated the magnetic levitation characteristics of the high temperature superconductor (HTS) YBCO bulk with both permanent magnet guideway (PMG) and electromagnet guideway. The structure of the magnetic field, the levitation force and guidance force were compared and discussed. Specifically, we carried out experiments at different magnetic field conditions by changing the excited current of electromagnet guideway, including varying the current direction, and the current strength, etc. Or by changing the arrangement of the PMG, etc. The measurements were conducted with a high precision force-measuring platform. The experimental results show that the electromagnet guideway has several advantages as compared with PMG. And the levitation performance is related to the peak value of the magnetic field, the structure of the magnetic field, etc. The results encourage further studies on improving the levitation performance of electromagnetic guideway for HTS maglev.keywords YBCO bulk, levitation force, guidance force, electromagnet, permanent magnet A new HTS multi-filament cable to improve the efficiency of electric aircraft Min Zhang, University of Strathclyde Minimizing AC losses is crucial for developing highly efficient fully HTS machines for future electric aircraft. A new HTS multi-filament cable is proposed in this paper to minimizing AC losses [1]. The cable involves slitting, soldering and stacking HTS filaments Progress Towards the Realization of a DC Superconducting Power Filter Loic Queval, Group of electrical engineering - Paris (GeePs) Various HTS devices, such as power cables and fault current limiters, are being developed to operate in DC electrical grids. Here, a new device referred to as “superconducting power filter” (ScPF) is introduced. It aims at increasing the stability of DC grids by adding a current-dependent resistance to a RLC filter. In comparison with other stabilization techniques, it achieves fully passive stabilization without losses in nominal operation. To clarify its operation, a DC voltage source feeding a power electronics load through a ScPF is considered. Using an electrical-thermal model of the device, the stability of the DC grid is assessed depending on the design parameters of the device. To back up the numerical results, we built a ScPF with a non-inductive coil wound with ReBCO and cooled down at 77 K in liquid nitrogen.The corresponding

As at 20 May 2019

experimental setup has been assembled and the preliminary results confirm that a ScPF can provide the expected functionality. HTS Power Switch for Flux Pumps James Gawith, University of Cambridge This report is on the design and results from a fast-acting, high power density HTS switch. The switch uses thin films of YBCO on sapphire switched into the off-state through application of an AC magnetic field to the superconductor, which causes any transport current to experience a dynamic resistance. The switch can reliably and repeatably transistion between an on state with Ic of 100A and an off-state of 10mΩ with ms trasition times. These results are promising for further development of a high power, fast-acting HTS power switching device for use in applications such as flux pumps or superconducting power converters. AC Loss calculation in Electrical Machines with HTS Coils using T-A Formulation Tara Benkel, Karlsruhe Institute of Technology Second-generation high-temperature superconductor (HTS) tapes are the promise of numerous technological breakthroughs in many fields including rotating machines, for which the AC loss calculation is necessary, particularly to dimension the cooling system. However, modelling HTS machines remains challenging mostly because of the presence of materials with non-linear electrical and magnetic properties and the high aspect ratio of the superconductors. The recently developed T-A formulation [1] overcomes these challenges: in particular, it allows simulating the whole superconducting machine and calculating the AC losses within the same model. The method is applied on a synchronous motor and the results are first compared to those obtained with the MEMEP method [2], with different coupling scenarios for the stator windings. Then, in an attempt to gain computational speed, the method is compared to the homogenization technique [3]. Finally, the influence of the anisotropic Jc(B) dependence on the AC losses is investigated.