Compact fusion energy based on the spherical tokamak

In a High Temperature Superconducting (HTS) magnet consisting of pancake windings, HTS tape with the same width has been used for all pancake windings. If a wider HTS tape is used for the outer pancake windings, the critical current of the HTS magnet can be increased. This paper shows the properties of BSCCO magnets in which the outer pancake windings are wound with a wider HTS tape. In order to examine the effects of a wider HTS tape, a HTS magnet with an inner radius of 20 mm and a height of 202.4 mm was used. The number of turns of each pancake winding was 150, and the number of pancake windings was 46. The critical current of the pancake winding was determined by using E-J relation. Results of calculation show that the critical current was higher in the HTS magnet with a wider HTS tape at the outer pancake windings than in the HTS magnet with the same width of HTS tape for all pancake windings.

Maglevs are typically accelerated using electromagnetic propulsion and levitation. High-temperature superconducting (HTS) magnets along with electrodynamic suspension (EDS) and linear synchronous motors are one of the best options for Hyperloop. However, the strong magnetic fields generated by HTS magnets on the pods inevitably interact with the magnetic and conductive structures in the vacuum tubes, along with the tube itself, while the pods move through the tubes. This interaction is observed as a drag force on the pods, significantly reducing the propulsion efficiency. This study comprehensively analyzes the electromagnetic drag force (EDF) generated by HTS magnets on pods, which accounts for most of the drag forces faced by Hyperloop. Theoretical analysis and 3D FEA simulations are performed to analyze the propulsion forces with HTS magnets and all the drag forces on the pods. The EDF generated by AISI 1010 steel rebars in concrete guideways is even greater than the designed propulsion forces of 40 kN. Consequently, high-manganese (Hi-Mn) steel and insulated steel rebars are adopted and analyzed using 3D FEA simulations. The EDFs generated by the AISI 1010 steel and Hi-Mn steel vacuum tubes are determined by varying the distance between the HTS magnets and tubes at 50 and 1200 km/h, respectively; a minimum distance of 0.75 m is determined by a drag force below 8 kN within their operating velocities. Lastly, the total EDFs of the AISI 1010 steel and Hi-Mn steel tubes with EDS rails are obtained through the optimal design of rebars and tubes. The simulation results show that the total EDFs can be significantly reduced to below 10 kN (approximately 25% of the designed propulsion force after the levitation of pods).

Fabrication and test results of 2 T conduction cooled HTS magnet

Seoul National University and Hanmi Techwin Inc. have launched a program for the development of a large bore, low field, and low-cost high temperature superconductor (HTS) magnet for industrial applications. HTS coils exhibit defect-irrelevant behaviors when wound using no-insulation (NI) technique, i.e., wound without turn-to-turn insulation. Incorporation of defect-irrelevant winding (DIW) technique would be favorable to constructions of HTS magnets as it may drive the cost of production down and curtail construction time if used appropriately. An HTS magnet having a center magnetic field of 2 T and cold bore size of 230 mm has been designed, and charging simulation was performed using a turn distributed circuit model. Defect-irrelevant behaviors are examined stochastically, considering random occurrences of defective turns. Using the turn distributed circuit model indicates that the magnitudes of defects have limited effects on resistive heatings in both steady state and transient operations. The upper bounds of excess heat contributed by defective turns are numerically formulated using characteristic resistances and operating currents.

Preheating for nonferrous metals in industry is realized through induction furnaces with a large capacity at commercial frequency. The energy efficiency of this process is about 50%-60% due to enormous energy loss through the copper coils. An ac induction furnace applying 2G high-temperature superconducting (HTS) magnets has been suggested in order to achieve higher efficiency. The most important factor in this technology is the ability to predict and minimize the ac loss, which is generated in HTS magnets during operation. In this paper, we demonstrate the simulation and experimental results of a large-scale HTS ac induction furnace for practical design. The HTS ac induction furnace was designed and simulated through a finite-element method (FEM) tool and an equivalent circuit model. The inductors were designed by using 2G HTS magnets, with consideration given to the ac loss generated in the magnet. To predict the ac loss of the magnet, the FEM was used, and the results were compared with those of the fabricated HTS magnets. The simulation and experimental results will be applied to fabricate a full-scale HTS ac induction furnace.

Persistent current mode (PCM) is an ideal operation mode for high temperature superconducting (HTS) magnets with static magnetic fields. However, it's impracticable for HTS magnets fabricated by winding due to the joint resistance. Recently, several concepts of HTS magnets based on PCM have been proposed, which are stacked by HTS plates and energized by the flux pump or the field cooling (FC) method. This paper focuses on the thermal stability performance of HTS magnets stacked by gourd-shape HTS plates and proposes two improved structures using copper plates for heat dissipation based on the simple stacked structure. One structure is alternately stacked by HTS plate and copper plate. The other one is alternately stacked by HTS plate, HTS plate and copper plate, in which the HTS films of two adjacent HTS plates are back-to-back arrangement. The thermal models of the two improved structures and simple stacked structure are established and the thermal stability under bath-cooling is compared by finite element method. The influence of peripheral edge extension length and thickness of copper plates on thermal stability and magnetic flux density of HTS magnets is also investigated. The results show that, compared with the simple stacked structure, both the two improved structures have better thermal stability. The alternating stacked structure has the best heat dissipation, and the back-to-back structure uses fewer copper plates and has higher excitation efficiency. The two improved structures are potential choices for stable operation of the compact HTS stacked magnets with PCM.

The high-temperature superconducting (HTS) magnet used in particle accelerators for cancer treatment exhibits a large current change for a short period of time due to its fast ramp-up characteristics, which results in high voltage and instant vulnerability to electrical insulation. This research introduces the saddle-coil, which, due to its complex shape and small bending radius, allows for the local concentration of electric field intensity. Reports from the European particle physics laboratory, CERN have revealed dielectric breakdown due to 1000V between layers during low-temperature superconducting (LTS) magnet experiments for accelerators, yet no research has been conducted to solve this problem. HTS magnets operating in vacuum may be susceptible to electrical breakdown due to high induced voltage and local quench due to rapid-ramp characteristics. Therefore, this paper deals with the dielectric characteristics of vacuum to develop an electrically stable HTS magnet. Specifically, dielectric experiments on penetration and creepage discharge were conducted under various vacuum conditions, and empirical formulae for calculating the electric field intensity at sparkover for the insulation design of HTS magnets was derived.

High speed transportations gradually become promising and important in economic development of a country. Maglev, as one of the novel high speed transportations, has been operated commercially like Shanghai Maglev Trains. To enable even faster speed, superconducting Maglev is proposed with the slider in its linear synchronous motor (LSM) is made of high-temperature superconducting (HTS) magnets. The HTS magnets can provide rather strong magnetic field intensity to not only ensure large thrust during operation but also reduce copper consumed in the LSM stator. This paper presents a conceptual design of a HTS magnet used as the slider in a small-scale LSM which is tested for future high-speed superconducting Maglev application. Purpose of the design is to find optimal dimensions of the magnet to reduce HTS tape consuming while meeting the spatial constraints and generating a required magnetic field intensity. Results of the design parameters are plausible. Furthermore, the weakest points corresponding to the lowest critical current in the winding pack are also investigated according the designed parameters, for the sake of operation safety of the HTS magnet.

A magnetic spectrometer determines the signed rigidity of charged particles by measuring their trajectories in the presence of a magnetic field. High Temperature Superconducting (HTS) magnets can operate in space without the use of a cryogenic liquid. While HTS magnets have many potential applications in space, including active magnetic radiation shielding, we present the design of an HTS magnetic spectrometer with a toroidal magnet providing a bending strength of 3 T m. The toroidal magnet is about 2 m in outer diameter, 2 m in height, and requires about 60 km of 12 mm wide ReBCO HTS tape. The magnet operates with an engineering current density of 855 A/mm² at a temperature of 20 K and a peak magnetic flux density of about 12 T. In the context of the HTS Demonstrator Magnet for Space (HDMS) project, we have designed and are building a small-scale coil pack of the toroidal magnet. The demonstrator magnet consists of two racetrack-like coils enclosed with copper bands that function as current leads and layer jumps. The no-insulation winding method facilitates self-protection against quenches. A lightweight mechanical structure made from aluminum alloy supports the coils.

We have built a magnetic separator based on the conduction-cooled high temperature superconducting (HTS) magnet. In the paper, the high temperature superconducting magnet is made of Bi-2223 pancakes, and has inner and outer coil diameters of 120 mm and 212 mm and coil height of 111.8 mm. The magnet is conduction-cooled to generate a magnetic field of 3.22 T at a temperature of 10 K. The cooling time from room temperature to 10 K is about 24 h. The maximum operating current of magnet is 120 A with the ramping rate of 5.06 A/s. We recently tested a Bi-2223 pancake coil confirmed that the magnetic separator is a reasonable option to use. The separating efficiency for waste water in the iron-steel factory is about 84.1%. The fabrication technology of the HTS magnetic separator and separating results for industrial waste water are reported.

The Navy has had a long standing interest in power applications of superconductivity. Recent advances in high temperature superconducting (HTS) materials have caused the Navy science and technology community to assess the potential of HTS magnets for Naval applications. A program has begun to test HTS conductors and magnets in order to determine realistic performance expectations from which to determine proper systems integration. This paper presents some early results of industrially produced HTS magnets and discusses possible Naval applications. Speculative application toward magneto-hydrodynamic (MHD) propulsion is also discussed-specifically with respect to HTS materials.

Bulk high temperature superconductor magnet (HTSCM) has been considered to get the better stable levitation in applied magnetic field which is not the original field-cooling magnetization (FCM) field in this paper. The vibration disturbance experiments firstly showed that a permanent magnet (PM) can suspend stably under a bulk Yttrium Barium Copper Oxide (YBCO) HTSCM. This implies that the stable levitation of one single bulk HTSCM is able to realize in the other magnetic field even from one single small PM due to the re-magnetization effect. Secondly, it is found that the HTSCM with more trapped flux produced larger guidance forces and smaller repulsion levitation forces compared with the well-recognized FCM condition of the30mm field-cooling height by the permanent magnet guideway (PMG). Especially, the HTSCM with the 0.349T trapped field achieved a maximum 9.8N guidance force, which is over impressive 7 times than the conventional FCM condition. So, it is feasible to introduce the bulk HTSCM into the HTS Maglev transportation system because this pre-magnetization method of the onboard superconductor bulks is not only helpful to improve the levitation capability and stability, but also enhance the dynamic property above the practical PMG.

The screening current–induced magnetic field (SCIF) brings bad effects on the field quality of REBCO high-temperature superconducting (HTS) magnet, which is mainly due to its specific large aspect ratio structure. In this paper, numerical simulation and experiments were conducted to investigate SCIF in a non-insulated HTS DP coil firstly. Then, a heating flux method was proposed to help eliminate the effect of screening current in a GdBCO HTS double pancake (DP) coil. A heating plate was mounted under the DP coil and used to generate a heating flux, which could increase the temperature and decrease critical current of the HTS coil in a short time. The decreasing of critical current could reduce the margin left for the screening current and eliminate the effect of SCIF further more. Heating flux experiments were performed to verify its effects on eliminating SCIF in the DP coil at the end. The results show that the SCIF could be reduced obviously by the method of heating flux. The research provides an important reference to eliminate SCIF in the HTS magnet.

High-temperature superconducting (HTS) magnets are widely used in high field applications due to their exceptional current-carrying capabilities. Traditionally, these magnets are powered by high current power supplies via current leads, which complicates insulation between cryogenic and room temperature environments and introduces significant heat leaks. Recent advancements in flux pumps for HTS magnets now allow charging currents in the kA range without the need for traditional power supplies. However, while some research has realized conduction-cooled traveling wave HTS flux pumps, much of the focus for transformer rectifier flux pumps remains on operating them to charge magnets at liquid cryogen temperatures, with limited attention given to the heat load and cooling capabilities of modern dry cryocoolers. This study presents a compact, modular flux pump designed for operation in conduction-cooled environments. It examines the impact of cooling power on the flux pump’s performance in such settings. A lumped element model implemented in PLECS is validated through experiments conducted at 70 K and 30 K, demonstrating consistent results. Based on this validation, we demonstrate the capability to charge an HTS magnet to 300 mT ( ≈ 800 A) in a conduction-cooled environment using a compact, self-regulating HTS flux pump.

Nuclear magnetic resonance (NMR) is a powerful technique for the structure elucidation of organic molecules and significantly important in the pharmaceutical industry supporting the discovery and development of drug substances or active pharmaceutical ingredients (APIs). Following an initial study and assessment of a prototype NMR instrument with a high-temperature superconducting (HTS) power-driven magnet of 9.4 T (400 MHz for 1H observation) operating with standard commercial electronics and probes, we tested the instrument with three compounds representing typical pharmaceutical drugs. We compared results from two probes and shimstacks with different geometries (broadband fluorine observe (BBFO) with Bruker orthogonal shim system-3 (BOSS3) and Bruker quattro nucleus probe (QNP) with BOSS1 shims) testing standard one-dimensional (1D) NMR experiments including selective excitation experiments, and two-dimensional (2D) homonuclear and heteronuclear experiments for the purposes of evaluating the equipment for structure elucidation capabilities. In our initial study on cinacalcet HCl, only the 1D 1H experiment showed a loss of resolution when using the longer coiled BBFO probe with the BOSS3 shims compared to the shorter coiled QNP probe with BOSS1 shims. The selective excitation experiments using the cinacalcet HCl were successful. Our characterization of 1D (1H, 13C, 19F) and 2D (1H-1H and 1H-13C) NMR experiments for compounds I and II with the two probes and shimstacks indicated no significance differences. Overall, these results are satisfactory with the HTS magnet at the field of 9.4 T for the structural elucidation work of standard pharmaceutical compounds. This new technology has the advantage of being able to locate the HTS NMR magnet system in any chemistry or analytical laboratory where the samples are produced, facilitating rapid analysis with minor needs from the facilities and without cryogenic liquids.