Prototype High Temperature Superconducting Research Articles

The spherical tokamak path to fusion power: Opportunities and challenges for development via public–private partnerships

In this article, we aim to show that the spherical tokamak (ST) device with high temperature superconducting (HTS) magnets could offer the quickest and lowest risk path to develop commercial fusion energy, which may be significantly advanced by the use of private–public partnerships. Our starting point is based on what we have learned and will continue to learn from publicly funded research on STs. Keeping prototype ST devices and HTS magnets small has enabled rapid innovation toward a commercial goal. Our ST40 compact, high field ST has proven exceptional performance, with plasma ion temperatures over 100 × 106 °C (above 8 keV) and a record triple product for any private company (n T τE ∼ 1019 keV s/m3). Meanwhile, our robust, compact, quench-safe, HTS magnets can routinely achieve over 24 T. We now have results of great interest to fusion scientists, so as well as pursuing our commercial goals, we are contributing to scientific progress in fusion. Opportunities to participate in public–private partnerships are emerging with Tokamak Energy already selected for the U.S. Department of Energy milestone program and well-positioned to participate in the U.K. Government Spherical Tokamak for Energy Production program. Other countries are likely to adopt similar approaches as the need for rapid development of fusion energy becomes ever more apparent.

A Review on Insulation and Dielectrics for High- Temperature Superconducting Cables for Power Distribution: Progress, Challenges, and Prospects

The high temperature superconducting (HTS) AC and DC cables are gradually finding their way towards commercialization due to their ability to transfer bulk electric power with negligible dielectric loss. In this context, this paper critically reviews the different aspects of HTS cables used in various applications and related accessories. The operational, lab-scale, and prototype HTS cable projects are discussed in detail. Different dielectrics, electrical insulations, superconductors, cooling systems, cryogens, and upcoming projects of HTS cables are reviewed. The underlying challenges and future directions in AC and DC cables, electric aircraft and ships, associated costs, cryogenic insulation materials, cooling technologies, superconductors, and electrical insulations of HTS cables are discussed in detail. The space charge performance of presently-used polypropylene laminated paper (PPLP) insulation and future insulation, i.e., Kapton material, is experimentally analyzed, to show the future challenges in the insulation design. The technology readiness level, market trends, and relevant test standards are explored. The research and market trends suggest that HTS cables can replace conventional transmission methods. However, their consistent growth and adaptation of HTS cables will depend on design of cryocoolers, raw material cost of superconductors, and large-scale production.

Fabrication and Test of a 1:4 Scaled HTS Coil for the Defocusing Magnet of 2 GeV FFAG Accelerator

The basic design of a 2 GeV fixed field alternating gradient (FFAG) accelerator was proposed by China Institute of Atomic Energy (CIAE) in 2019. A preliminary study of high temperature superconducting (HTS) magnet for the 2 GeV FFAG accelerator lattice scheme was carried out, considering the beam loss of high energy proton beams and energy efficiency of the main machine. In order to demonstrate the feasibility of manufacturing a spiral-shaped HTS magnet with concave edges based on ReBCO tapes, a 1:4 scaled HTS model magnet is being developed in CIAE. First, the design and fabrication of the 1:4 scaled prototype HTS magnet with concave edges will be described in detail. Then, each double pancake (DP) was tested by liquid nitrogen (LN) immersion. The terminal voltage and magnetic field variation were measured and simulated. Finally, the whole assembled HTS magnet was cooled down to 23 K using helium gas pipeline contact cooling and operated on 300 A for over 24 hours. The central magnetic field reached 719.5 mT, without iron. More detailed electromagnetic characteristics of the magnet during the excitation will be illustrated, which is much helpful for the fabrication of the final full-size HTS magnets.

Cold Performance Tests of the ITER 68 kA HTS Current Lead Prototypes

• The cold performance test under 4 K is crucial and essential for the most challenged TF prototype HTS current leads. Detailed test process and method are presented. • Many overcurrent and over cooling case were performed to study the TF current leads, and the 1-hand test results and some analysis were presented • The test process and result is important for all the series TF current leads and for the operation in the future. The Toroidal Field (TF) current leads which supply 68 kA DC current for the TF coils are the largest capacity High Temperature Superconducting (HTS) current leads among the three types of HTS current leads for ITER. Two TF HTS current leads prototypes have been successfully built and cold tested at the Institute of Plasma Physics of the Chinese Academy of Sciences (ASIPP). The cold performance test is a crucial step to verify the design parameters and manufacturing process before starting the series production. The cold performance test includes rated current steady state operation and Loss Of Flow Accident (LOFA) test, different Heat eXchanger (HX) boundary operation, over-current, joint resistance, and heat conduction tests. This paper will present the major results of those tests.

Electromagnetic analysis of 0.2 MW High Temperature Superconducting (HTS) synchronous machine for HTS pole coils development

High Temperature Superconducting (HTS) synchronous machine consisting of six HTS poles in the rotor and air gap copper windings in the stator will help in manufacturing compact, lightweight, high power density, high over load capacity and low noise machines for ship propulsion applications. In this paper electromagnetic simulation of pole coils for 0.2 MW HTS synchronous machine is discussed. This involves FEM based electromagnetic simulation of 0.2 MW synchronous machine with air gap configuration of copper stator winding and HTS rotor. The primary focus of the paper is to calculate magnetic field along parallel and perpendicular directions to HTS tapes in six pole rotor configuration. These results are required for selection of HTS to develop superconducting pole coils for manufacturing prototype HTS synchronous machine. In this process, air gap flux density and voltage generated in the machine are also calculated.

Prototype HTS Quadrupole Magnet for the In-Flight Fragment Separator of RISP

The Rare Isotope Science Project (RISP) for constructing a heavy ion accelerator complex was launched in 2011 in Korea. As one of the rare isotope production systems, an in-flight fragment (IF) separator system will be installed for the RISP. We plan to use high-temperature superconducting (HTS) quadrupole magnets in the forepart of the IF separator to cool efficiently the magnets from large radiation heat load at around 40 K. The HTS quadrupole magnet should withstand a high radiation dose (~10 MGy/year). A prototype HTS quadrupole magnet was designed and fabricated taking into account the radiation damage and heating. The magnet employs two kinds of HTS wires, and the HTS wire is cowound with a stainless steel tape for electrical insulation. The magnet is cooled by circulation of cold helium gas through the cooling channels. Various tests were performed under normal and abnormal operating conditions. The test results show that the HTS quadrupole magnet can operate in the required field gradient stably. The magnet can also be self-protected by metal insulation under the abnormal operating conditions.

Predictive 1-D thermal-hydraulic analysis of the prototype HTS current leads for the ITER correction coils

We present an analysis of the prototype high-temperature superconducting (HTS) current leads (CLs) for the ITER correction coils, which will operate at 10kA. A copper heat exchanger (HX) of the meander-flow type is included in the CL design and covers the temperature range between room temperature and 65K, whereas the HTS module, where Bi-2223 stacked tapes are positioned on the outer surface of a stainless steel hollow cylindrical support, covers the temperature range between 65K and 4.5K. The HX is cooled by gaseous helium entering at 50K, whereas the HTS module is cooled by conduction from the cold end of the CL. We use the CURLEAD code, developed some years ago and now supplemented by a new set of correlations for the helium friction factor and heat transfer coefficient in the HX, recently derived using Computational Fluid Dynamics. Our analysis is aimed first of all at a “blind” design-like prediction of the CL performance, for both steady state and pulsed operation. In particular, the helium mass flow rate needed to guarantee the target temperature at the HX–HTS interface, the temperature profile, and the pressure drop across the HX will be computed. The predictive capabilities of the CURLEAD model are then assessed by comparison of the simulation results with experimental data obtained in the test of the prototype correction coil CLs at ASIPP, whose results were considered only after the simulations were performed.

A Novel AC Loss Measurement Technology for High Temperature Superconducting Cable With Large Current Capacity Using a Compensation Coil

High temperature superconducting (HTS) cable is a new development of applying superconducting technology in power system. AC loss measurement technology is a key factor in designing HTS cable as it decides the stability and operating cost of the cable. In this paper, a novel AC loss measurement technology for HTS cable is proposed based on LabVIEW. A compensation coil with large current carrying capacity and a stepping motor are used to test the variation of AC losses of HTS cable. A closed loop system is developed to obtain AC losses measured using modules of high-precision Data Acquisition (DAQ) and motion controller of National Instruments (NI). Finally, AC losses of a 0.2 m, 110 kV/1.5 kA prototype HTS cable are measured at 49.9 Hz and 60 Hz frequency considering compensation coil and lock-in amplifier. Obtained results show that AC losses linearly increase with the transport current in logarithmic coordinates. The comparison results applying with compensation coil and lock-in amplifier prove that the proposed measurement system is effective in measuring AC loss of HTS cable with large current capacity in different frequency.

Improvement of Flux Deflection With Light-Weight Magnetic Material

Intensified magnetic flux generated by high-temperature superconducting (HTS) field-pole magnet has been studied for the key to improve the machine efficiency of industrial application. An increase of the critical current density allows a further improvement of the operating current in HTS ship propulsion motors. In our previous work, an effect of flux deflection to the critical current of HTS magnet was evaluated. Magnetic flux deflection is a technique to control perpendicular flux to the a-b plane of the HTS tape by magnetic material. Thanks to the magnetic properties of the material, heat loss reduction was confirmed. In this paper, the outcome of the verification experiment with a lightweight magnetic material FINEMET adopted as magnetic flux deflector will be described. In response to the results which increase of the total weight of HTS winding by mounting a magnetic material, weight reduction of the magnetic flux deflector is necessary for practical employment. Compared with the carbon steel, FINEMET has higher saturation magnetic flux density and higher permeability. I-V curve was measured while a pair of the magnetic flux deflectors were installed on the prototype HTS coil connected to the DC current source. In the case of adopting light-weight magnetic material, the reduction of heat generation was confirmed to be 27% which is equivalent to the previous material. At the same time, a weight reduction of 73% was achieved. Results show that FINEMET is effective to improve flux deflection. It is one of feasible material which can be adapted to the field-pole magnet of practical HTS propulsion motor.

Performance Analysis of a Linear Motor with HTS Bulk Magnets for Driving a Prototype HTS Maglev Vehicle

This paper presents the performance analysis of a linear synchronous motor which employs high-temperature superconducting (HTS) bulk magnets on the mover and normal copper windings on the stator. The linear motor is designed to drive a prototype HTS maglev vehicle in which the mover is suspended by the levitation force between HTS bulks on the mover and permanent magnets on the ground. Finite element magnetic field analysis is conducted to calculate the major parameters of the linear motor and an equation is derived to calculate the electromagnetic thrust force. Theoretical calculations are verified by the measured results on the prototype.

First Electrical Characterization of Prototype 600 A HTS Twisted-pair Cables at Different Temperatures

Following the development of twisted-pair cables prepared with High Temperature Superconducting (HTS) tapes and their initial tests at 4.2 K in liquid helium at CERN, the cable samples of 2 m lengths were subsequently tested in flowing helium gas at temperatures between 10 K and 77 K at University of Southampton. A cryostat with optimized hybrid HTS current leads was purposely built for the tests up to 2.5 kA. The cryostat has two separate helium flow conduits, each accommodating a twisted pair and allowing independent temperature control. With the completion of the tests on the twisted-pair cables, a 5 m long semi-flexible Nexans cryostat was also set up for the testing of prototype HTS links assembled at CERN. The link, which is optimized for application to the remote powering of LHC 600 A electrical circuits, consists of a compact multi-cable assembly with up to 25 twisted-pair 600 A HTS tapes. The cables are cooled by a forced-flow of helium gas the inlet temperature of which can be changed in order to compare the electrical performance over a range of temperatures. The paper reports on the results of powering tests performed on the individual cables and the integration process for the forthcoming tests of the prototype links.

Test of a Liquid Argon TPC in a magnetic field and investigation of high temperature superconductors in liquid argon and nitrogen

Tests with cosmic ray muons of a small liquid argon time projection chamber (LAr TPC) in a magnetic field of 0.55 T are described. No effect of the magnetic field on the imaging properties were observed. In view of a future large, magnetized LAr TPC, we investigated the possibility to operate a high temperature superconducting (HTS) solenoid directly in the LAr of the detector. The critical current Ic of HTS cables in an external magnetic field was measured at liquid nitrogen and liquid argon temperatures and a small prototype HTS solenoid was built and tested.

Conceptual Design of an HTS large power transformer with continuously transposed coated conductors

This paper shows results of a design work of a program that is to develop a large power single phase high temperature superconducting (HTS) transformer. The program forms a part of a national project in Korea. A target of the design work is an HTS power transformer with rated voltages of 154 kV/22.9 kV and material for windings is supposed to be coated conductor. The design results presents in this paper will include: 1)HTS winding structures for high voltage in liquid nitrogen, 2)design result of continuously transposed coated conductor (CTCC), 3)conceptual design of high voltage bushings, 4)cooling system. A feasibility study will succeed to this design work for construction of a prototype HTS power transformer with capacity/voltage of 33 MVA/154 kV.

Design and evaluation of 66 kV class RE-123 superconducting cable

In the new national project, as wire and cable development, Sumitomo Electric Industries, Ltd. (SEI) is trying to develop a 66kV/5kArms high temperature superconducting (HTS) cable with its own REBa2Ca3Ox (RE-123, RE=rare earth element) coated conductors. In an actual power grid, an inflow of current higher than the normal rated power (fault-current) can occur. The maximum fault-current condition is set at 31.5kArms for 2s for 66kV-class transmission system in this project. Therefore, one of the technical targets in this project is to design the wires and cables to survive at this fault-current condition. As the first step, the prototype HTS cable was designed against the fault-current condition of 31.5kArms for 2s. The wires have copper plating as a stabilizer layer not to be damaged by over-currents. The designed HTS cable has a copper former and copper shield layers in parallel with the HTS conducting layers and HTS shield layers, respectively, to control the temperature rises in the cable core at fault-current conditions. As the second step, a sample HTS cable core was fabricated and fault-current tests were conducted to check its soundness. The temperature rises in the cable core were measured under various fault-current conditions. The critical current of the cable core was measured before and after the fault-current tests, and no deterioration in the critical current characteristics was observed. However, there was slight degradation of the n value. The investigation will be conducted, and the results will be fed back to designs of the RE-123 wires and cables.

Development of a 13.2 kV/630 A (8.3 MVA) High Temperature Superconducting Fault Current Limiter

This paper deals with fabrication and development of a high temperature superconducting (HTS) fault current limiter (FCL) based on YBCO coated conductor (CC) wire for distribution systems. The capacity of the developed HTS FCL is 8.3 MVA and its rated voltage is 13.2 kV which corresponds to a three-phase power equipment voltage class of 22.9 kV. Tests of the developed prototype HTS FCL were conducted at Korea Electrotechnology Research Institute (KERI) accredited as a testing laboratory by the Korea Laboratory Accreditation Scheme (KOLAS). A short-circuit test and an AC dielectric withstand voltage test for the HTS FCL were conducted under sub-cooled liquid nitrogen (LN2 ) conditions of 3 bar and 65 K. The magnitude of an asymmetric short- circuit current without FCL reached 30 kApeak in a short-circuit test. The superconducting coil quenched instantaneously after the fault, and the magnitude of the fault current was limited to 3.6 kApeak within quarter cycle by the developed resistance of the superconducting coil. An AC dielectric withstand voltage test was performed, and the HTS FCL successfully withstood 143 kV for 1 minute. Also, it was found that there was no electrical or mechanical damage on the superconducting coil after the tests.

Testing of an HTS Power Cable Made From YBCO Tapes

Oak Ridge National Laboratory (ORNL) has designed, built, and tested a 1.25-m-long, prototype high temperature superconducting (HTS) power cable made from second-generation YBa2Cu3Ox (YBCO)-coated conductor tapes. Electrical tests of this cable were performed in liquid nitrogen at 77 K. DC testing of the HTS cable included determination of the V-I curve with a critical current of about 2100 A, which was consistent with the critical currents of the two layers of 4.4-mm wide YBCO tapes. AC testing of the cable was conducted at currents up to about 1500 Arms. The ac losses were determined electrically by use of a Rogowski coil with a lock-in amplifier. Over-current testing was conducted at peak current values up to 4.9 kA for pulse lengths of 0.3-0.5 s. Test results are compared to earlier data from a 1.25-m-long power cable made from 1-cm-wide YBCO tapes and also comparable BSCCO cables. This commercial-grade HTS cable demonstrated the feasibility of second-generation YBCO tapes in an ac cable application.

Excitation Tests of Prototype HTS Coil With Bi2212 Cables for Development of High Energy Density SMES

Development of the SMES using high temperature superconducting (HTS) coil has progressed as a Japanese national project since FY 2004. The objective of the project is to obtain around twice the normal energy density via an HTS-LTS coil system compared to an LTS coil system. The HTS coil is composed of sixteen double-pancake coils and the double-pancake coil is wound with a Bi2212 Rutherford-type cable. The HTS coil is operated at 4.2 K in liquid helium bath with the LTS coil, and operated at maximum field of 8.9 T. Before we made a hybrid coil system, we verified the design issues using HTS experimental coils. In this paper mechanical compression tests, DC operation tests and thermal runaway tests using the experimental coils are discussed.

Flywheel Challenge: HTS Magnetic Bearing

A 200 mm cylindrical engineering prototype high temperature superconducting (HTS) was designed and fabricated. Measurements show that the 17 kg PM rotor can suspend safely 1000 kg in axial direction and 470 kg radially. The rationale for the bearing performance is to stabilize a 400 kg rotor of a new compact 5 kWh/280 kW flywheel energy storage system (COM - FESS). Measurements of the magnetic bearing force, stiffness and drag-torque are presented indicated the successful targeting a milestone in the HTS bearing technology. The influence of the PM configuration and the YBCO temperature on the bearing performance was experimentally studied, providing high-force or high-stiffness behaviour. The axial stiffness 5 kN/mm at 0.5 mm displacement is the highest value of a HTS bearing we know.

Design and Preliminary Results of a Prototype HTS SMES Device

The University of Wollongong (UOW) has developed the design for a 20 kJ high transition temperature Superconducting Magnetic Energy Storage (SMES) device, and constructed a nominally 2.5 kJ prototype. The coil for the prototype was wound using High Temperature Superconducting (HTS) BSCCO-2223 tape. It was refrigerated to 20 K using a gaseous helium cold head cryocooler. The SMES device has been constructed as a prototype for a larger commercially realizable system, and hence is capable of supplying a 3-phase load during voltage sags or short (<1 s) power interruptions. This paper discusses the modeling and design of the electromagnetic and thermal aspects of the coil, the Power Control Circuit (PCC), current leads and cryogenic system. Also presented are preliminary results of the SMES coil, cryogenics, and system energy storage and delivery capabilities.

Superconducting filters based on mixed resonators

In high-temperature superconducting (HTS) microwave filters, the requirements for miniaturization and high power handling are difficult to match simultaneously. In this paper, we report on the design and realization of HTS filters realized by combining dual-mode cross-slotted and stepped resonators in order to obtain a compact size and a relatively high power handling. Prototype HTS four-pole filters operating in C-band and L-band, with quasi-elliptical responses, on both MgO and LaALO3 substrates, have been designed and tested at T = 77 K. The filters present a high degree of miniaturization as they save more than 50% of the area compared with those realized with dual-mode and/or hairpin resonators. The measured responses agree well with the simulation even if the in-band ripple should be optimized. As far as the power handling is concerned, the C-band filter grown on LaAlO3 presents a power handling of Pin = 20 dBm limited by the power handling of the dual-mode cross-slotted resonator, while we have observed no power degradation in the L-band filter grown on MgO up to Pin = 33 dBm limited by power supply.