This study presents the design and analysis of a metal-insulated (MI) high-temperature superconducting (HTS) rotor for impact applications. The magnet comprises three double-pancake coils wound from REBCO tape, stacked to form a racetrack-shaped structure. To ensure mechanical integrity, the assembly is reinforced with stainless steel strips and a multi-stage compression scheme. A detailed finite element model of the magnet was developed using ANSYS Workbench to investigate its transient dynamic response under a half-sine shock load with a peak acceleration of 30 g and a pulse duration of 18ms. Simulation results demonstrate that the maximum deformation and stress of the magnet in the x-, y-, and z-directions are merely 0.144 mm and 70.2 MPa, respectively. These values are well below the material's allowable stress and the design specification of 0.5 mm for deformation, thereby verifying the structural safety and reliability of the magnet under harsh impact conditions. The analysis also identifies the welded base as a critical load-bearing component and reveals that the stiffness of the y-direction support is relatively weak, which should be the focus of subsequent structural optimization. This work provides a theoretical foundation and valuable insights for the design of impact-resistant superconducting magnets.

High-temperature superconducting (HTS) synchronous condensers improve grid stability and inertia through superconducting rotor magnets. This study investigates the dynamic AC loss behavior of racetrack-shaped HTS coils under strong excitation, with current ramping from the nominal value of 465 A up to 515 A (approximately 1.1 times the nominal current) within durations ranging from 0.5 to 2.5 s. A homogenized 2D cross-sectional Hformulation model is developed to compute cross-section-resolved loss density. Losses for straight and arc segments are obtained via a segment-wise equivalent approach, and then mapped as heat sources into a 3D transient thermal model that includes the detailed cryogenic structure. Simulation results reveal localized AC loss hotspots and temperature rise patterns, with all temperatures maintained within a safe operating range of 30 +/- 1.5 K. These insights offer guidance for rotor and cryogenic cooling system design. The modeling framework provides a basis for analyzing high-stress transient conditions in HTS rotors and supports the development of scalable, reliable synchronous condensers for future power grids.

High-temperature superconducting (HTS) synchronous condensers are regarded as promising reactive power compensation devices for renewable-energy-based power systems. Fast numerical analysis of the HTS excitation winding is of significant engineering importance. However, finite element methods are computationally expensive for large-scale HTS devices, which motivates the use of more efficient alternatives, such as the J-model. For HTS synchronous condensers without rotor iron cores, the operating characteristics of the HTS excitation winding can be evaluated using the J-model. Nevertheless, for configurations with rotor iron cores, the lack of an appropriate analytical magnetic-field model makes the direct application of the J-model difficult. In this article, an analytical magnetic-field model is derived based on the electromagnetic characteristics of a dual-iron-core structure using the mirror image method. By coupling this analytical model with the J-model, a J-A model is established for dual-iron-core HTS synchronous condensers. Furthermore, an iterative scheme for equivalent relative permeability is developed to incorporate iron-core saturation effects into the analytical model, enabling accurate calculation of nonlinear magnetic fields. The proposed J-A model is validated against the finite element method based on the H-A formulation. The results demonstrate that the proposed model achieves high accuracy in predicting losses, magnetic flux density, current density distribution, and critical current. Meanwhile, the computational efficiency of the J-A model is significantly higher than that of the finite element method, making it highly suitable for the design and optimization of HTS synchronous condensers.

In January 2026, the world record for a 35.6 T-35 mm all superconducting user magnet was achieved. The 35.6T user magnet consisted of the REBCO high temperature superconducting insert magnet and a low-temperature superconducting magnet. Furthermore, the REBCO high temperature superconducting insert magnet itself also reached 27.5T in liquid He, which also set a world record for the all high temperature superconducting user magnet. This magnet holds great significance for both cutting-edge scientific research and superconducting magnet technology.

In the cooling system of high-temperature superconducting (HTS) synchronous condenser rotor magnets, cold helium gas serves as the primary cooling medium. The complex coupling relationships among its flow rate, temperature, and pressure require precise control to address the instability caused by localized hotspots in the superconducting magnets.This paper integrates the singular perturbation control theory of variable-domain Smith to construct a mathematical model of the cold helium gas circulating cooling system.The cold helium gas circulation cooling system is decomposed into fast and slow subsystems. By precisely controlling the flow rate and velocity of the cold helium gas, the goal of eliminating local hotspots and achieving uniform temperature distribution in the superconducting magnet is realized.Simultaneously, the system performance is optimized using fuzzy adaptive PID control.In addition, a simulation experiment was conducted on the cold helium gas circulation cooling system of the superconducting magnet using this method, which verified the effectiveness of the aforementioned approach in eliminating local hotspots and improving temperature uniformity.This study provides an engineering-feasible optimization scheme for the cryogenic thermal management of the rotor magnet in HTS synchronous condensers.

HTS synchronous condensers have attracted increasing attention as promising alternatives to conventional synchronous condensers due to their high power density, high efficiency, and large short-circuit capacity. However, existing designs typically rely on step-up transformers, which limit dynamic response and voltage support performance. To address this limitation, a 35 kV ring-type air-core armature stator is proposed for transformerless grid-connected HTS synchronous condensers. An oil-immersed structure is adopted to simultaneously meet the stringent insulation and cooling requirements under high-voltage conditions, enabling the armature current density to exceed 3.7 A/mm$^{2}$. Multiphysics coupled analyses, including electromagnetic, electric field, and thermal field simulations, are performed to systematically validate the proposed design. The results demonstrate that the stator achieves a favorable balance among electrical insulation strength, thermal performance, and electromagnetic characteristics, confirming its feasibility for practical implementation. Furthermore, to improve the electromagnetic performance of the HTS field winding, an analytical model capable of directly forming objective functions is developed and validated. Based on this model, a multi-parameter, multi-objective optimization framework is proposed. The results of Optimization Scheme 1 show that, with nearly unchanged superconducting material usage, the magnetic field utilization is improved, the critical current margin of the HTS field winding increases from 31.4% to 45.6%, and the total harmonic distortion of the back electromotive force is reduced from 6.4% to below 0.4%.

When researching and designing high-temperature superconducting (HTS) excitation motors, it is crucial to account for the impact of ferromagnetic structures on the critical current and losses in superconducting windings. The finite element methods based on the T-A formulation, H formulation, and other formulations are viable options. However, since the finite element method has to calculate the huge air domain, its computational efficiency is lower than the J-model, which only calculates the superconducting winding domain. Ferromagnetic structures in HTS excitation motors are circular, and the J-model has not been applied in such application. Therefore, to increase the efficiency of the research and design for superconducting windings in HTS motors, this article combines the J-model with the mirror image method and realizes the calculation of critical current density and losses in the superconducting winding of HTS motors. The accuracy of the improved J-model is increased by using current density instead of concentrated current. To further enhance the efficiency of the improved J-model, an adjustment method for calculation step-size is designed to ensure fast convergence and rapid calculations. A two-pole HTS excitation motor model is set up to verify the reliability of the improved J-model. The results demonstrate that the improved J-model achieves high accuracy in calculating critical current density and losses. Meanwhile, the improved J-model also has very high computational efficiency and strong convergence. Therefore, the improved J-model significantly increases the efficiency of research, design and optimization of HTS windings in HTS excitation motors. Moreover, it offers a valuable reference for calculating critical current density and losses based on the J-model in superconducting windings of other superconducting applications involving ferromagnetic structures.

Superconducting dynamic synchronous condensers (SDSCs) exhibit significant potential for replacing traditional dynamic synchronous condensers (DSCs) due to their powerful reactive power output capability and low thermal losses, which are attributed to their large short-circuit capacity, high air-gap magnetic density, and low synchronous reactance. This study comprehensively reviews the development trajectory and current research status of SDSC, both domestically and internationally, and conducts an in-depth analysis of their advantages. Based on this, this paper highlights three typical cases of SDSC and summarizes the key technologies of SDSC from the perspectives of the excitation winding, stator structure, rotor magnet, and cooling system. Finally, it proposes that cooling and insulation technology, quench issues of AC windings under magnetic fields, and torque tube transmission technology will be the key technical challenges for future research and resolution in SDSC.

The superconducting coil with high current carrying capacity and DC resistance-free characteristics is used to replace the copper coil on the traditional motor rotor, which can greatly improve the air gap flux density and power density of the motor. This paper introduces the cryogenic system of a high-temperature superconducting (HTS) Synchronous Condenser rotor. The HTS magnet in the rotor is cooled centrally by embedding Gas-Helium pipes in each coil, and cold rings are set at both ends of the magnet for temperature partitioning to reduce the temperature influence of other components on the magnet. According to the theoretical formula of heat transfer, the total thermal power of the cryogenic system in the rotor was calculated, and the Gas-Helium input parameters required by the rotor are deduced. Subsequently, the temperature distribution of the HTS coils inside the rotor was simulated by the fluid thermodynamic method. The simulation results show that the HTS coils and cold rings are separately cooled to 27.05 K and 36.35 K by the externally introduced 25 K Gas-Helium, and the temperature difference of the coils is only 0.2 K, which shows the reliability of the cryogenic system in the HTS synchronous condenser rotor.

Klystron as a typical vacuum electronic device has been widely used in the field of microwave devices. During the development of the klystron, leaks were generated due to factors such as process and material properties, resulting in losses due to the scrapping of the klystron. Au-Ge12 has been widely used as an excellent soldering material for material welding and metal encapsulation. In this paper, the ability of Au-Ge12 to repair leaks after klystron leakage is investigated with respect to its dispersion on oxygen-free copper and nickel-plated metal surfaces and the weldability of the two substrate materials. The experimental results show that Au-Ge12 has better dispersion on the nickel-plated surface; The dispersion is flatter on the oxygen-free copper surface with an average thickness of 78um; However, the welding properties of Au-Ge12 are worse, which can reduce the leakage rate to some extent.

This article focuses on the design and implementation of superconducting shim coils for the 9.4 T whole-body magnetic resonance imaging (MRI) superconducting magnet developed at the Institute of Electrical Engineering, Chinese Academy of Sciences. Through conducting a comparative analysis of the harmonic components of the magnetic field, we observed that the long solenoid structure of the ultrahigh field magnet often has a better homogeneity and smaller high-order harmonics compared with lower field split-design magnets. Thus, the third-order shim coils were able to be eliminated, leading to cost reduction and a simplified magnet structure. The implementation of this active shimming strategy resulted in significant improvements in field homogeneity in an efficient manner. Compared with the bare magnetic field over a 30 cm diameter spherical volume, the peak-to-peak and root-mean-square homogeneity of the shimmed field was 15.82 ppm and 4.11 ppm, which achieved 78.9% and 83.2% improvement, respectively. These enhancements will effectively facilitate subsequent passive shimming procedures. The research findings presented in this work provide valuable insights into the practical implementation of shimming methods for the ultrahigh field whole-body MRI superconducting magnet.

Background: Increase in volume in the bearingless permanent magnet slice motor (BPMSM) control system for artificial hearts is the major problem in the existing works.Objective: A sensorless control method of the BPMSM for the artificial heart is proposed in the study based on an improved sliding mode observer (SMO) and improved high-frequency injection method. Also, a full-speed rotor position detection method combining the high-frequency injection (FHI) method and sliding mode observer is designed.Methodology: In this method, an improved high-frequency injection method was designed in the low-speed domain, and an improved sliding-mode observer was designed in the medium-high-speed domain. Besides, the speed domain switching method based on the genetic particle swarm optimization (GAPSO) algorithm was adopted at the critical point of the low-speed domain and the medium and high-speed domain to realize the smooth switching between different estimation methods, and then realize the sensorless control of the rotor in the full speed domain. Secondly, the simulation study by Simulink was used to compare the detection effects of the BPMSM rotor position and speed of the artificial heart pump under different methods are compared in this work.Result: The results show that the speed estimation value and rotor position estimation value of the new method in this paper were closer to the actual value, the position estimation error is 3%, and the speed estimation error was within 1.5%. Further, the experimental study was carried out on the principal prototype of the sensorless control part of the artificial heart to verify the effectiveness of the proposed method.Conclusion: The method proposed in this paper has certain generality in the field of motor sensorless control technology, and has important reference value for researchers in this field.

A superconducting magnet with a warm-bore size of 800 mm and a center magnetic field of 9.4 T for the whole-body magnetic resonance imaging (MRI) system was developed in IEECAS, China. To achieve a highly homogeneous magnetic field over the 400 mm diameter of spherical volume (DSV), both active shimming and passive shimming techniques were employed. This paper mainly focuses on the implementation of passive shimming for the 9.4 T MRI magnet system. After four iterations, we were able to achieve peak-to-peak and root mean square field homogeneities over the DSV at 3.05 and 0.94 ppm, respectively. In addition, this paper analyzes the electromagnetic forces and system errors of passive shimming for ultra-high fields, providing valuable insights into MRI magnet engineering.

This paper describes the design and analysis of the cryogenic system of a 15 Mvar high-temperature superconducting (HTS) dynamic synchronous condenser rotor. The excitation winding of the condenser rotor is wound with HTS strip, and the HTS windings are cooled by 20 K cold helium gas flowing inside. To maintain the stability of the low-temperature environment inside the rotor and reduce system heat loss, special materials such as epoxy fiberglass and insulation film will be used for insulation treatment. Calculate the overall heat loss of the rotor, and then simulate the cooling effect of helium gas in the rotor. The simulation results show that the maximum temperature of the coil is 25.8 K, which meets the low temperature requirements of HTS materials.

Purpose Artificial heart pumps are widely used for medical auxiliary blood supply, but the existing technology has some defects. To solve the problems of traditional artificial heart pumps, such as weak pulsation, easy suction and reflux, this paper proposes a new control method. Methods First, we designed a sliding mode controller for aortic pressure and formulated the feedback adjustment mechanism: two mutually converted reference values of aortic pressure were introduced to make the aortic pressure jump between the two extreme values, thereby improving blood pulsatility. Second, the target value of the average aortic pressure was set according to the actual situation of patients with heart failure. Based on the target value, a sliding mode controller (SMC) was designed to stabilize the average aortic pressure near the target value. For the second and third steps, a genetic algorithm particle swarm optimization (GAPSO) was introduced to optimize the parameters of the sliding mode controller. Finally, a prevention mechanism for regurgitation and suction was proposed to avoid possible regurgitation and suction phenomena. Results When the artificial heart pumps is assisted by the new control, the aortic pressure difference can reach 31 mmHg. Additionally, suction and reflux do not appear in new control method. Conclusion The results show that this method can improve blood pulsatility in addition to satisfying the blood perfusion required by the human body. It can also prevent reflux and suction, which promotes the functional recovery of a damaged heart.

BACKGROUND:Magnetic field shimming of the magnet is a routine practice in a magnetic resonance imaging (MRI) system. For clinically-used 1.5 T or 3 T MRI superconducting magnets, it is generally straightforward to achieve desired magnetic field uniformity with the passive shim technique. In comparison, superconducting shims with higher shimming efficiency are usually introduced in combination with passive shimming to satisfy the higher magnetic field uniformity requirement for ultrahigh field magnets (≥7 Tesla). However, superconducting shim usually involves a complex winding structure and low-temperature environment, bringing considerable engineering challenges and extra costs in practice.PURPOSE:In this study, we aimed to improve the passive shimming method that can incorporate the unique electromagnetic properties of ultrahigh-field MRI magnets and is thus more effective for field corrections at 7T and above.METHODS:In this work, we propose a dedicated passive shimming strategy for a 7 T whole-body MRI superconducting magnet. In this method, the iron usage and magnetic force due to the iron-field interaction are strictly managed to ensure a shim tray insert is operable by manpower (without specially designed tools).RESULTS:To validate the proposed shimming strategy, a shimming experiment was implemented on a 7 T/800 mm superconducting magnet. Alternating with the odd and even shim trays in our two-round operation, the magnetic field inhomogeneity was successfully corrected from 85.36 to 7.91 ppm, achieving the magnetic field quality elevation of more than one order of magnitude.CONCLUSION:The experimental results indicated that the proposed electromagnetic technology is expected to be effective for developing ultrahigh-field MRI instruments.

In order to solve the problem that the traditional artificial heart pump has poor dynamic bionic performance and cannot respond to blood perfusion in real time according to the patient’s state, this paper proposes a new physiological control method based on adaptive adjustment of heart rate. Firstly, a coupled model of the cardiovascular circulatory system and artificial heart pump was established, and the correctness of the model is verified by hemodynamic simulation. Secondly, according to the model-free adaptive control theory, the artificial heart pump physiological control strategy for adaptive regulation of heart rate is designed, including pseudo partial derivative estimation algorithm and adaptive control law. Then, the parameters of the adaptive controller are optimized by the improved beetle antennae search algorithm. Finally, the auxiliary effect and dynamic performance of the adaptive control strategy are studied by numerical methods. The results show that the physiological control method based on adaptive regulation of heart rate realizes the adaptive modulation of heart rate and blood flow, which can meet the needs of blood perfusion in different states and help to promote the recovery of damaged heart.

For the superconducting magnetic resonance imaging (MRI) magnet, passive shimming technique in low field is more complicated than that in high field, due to the unsaturated magnetization of the used shim pieces and other issues, such as the oversized minimum shim piece and insufficient accuracy. For common problems of the MRI magnets and the special problems caused by low field, an experimental study was carried out on the 0.5 T superconducting magnets by adopting some improved strategies for passive shimming of low field in this article. Three magnets of the same type were used as experimental objects, and the proven measures were proposed to improve the problems of the unsaturated magnetization, shim piece specification, and position difference. The experimental results showed that the passive shimming reliably enables the static magnetic field of the 0.5 T MRI magnet to achieve the required homogeneity, which have practicality and reference value for the fabrication and shimming of the low-field MRI magnet.

The death rate of heart failure is extremely high, and the number of patients continues to rise. Artificial heart pump is the most effective way, even the last hope, for the heart failure patients to prolong their survival. Most of the third-generation magnetic levitation magnetic levitation artificial heart pumps are driven by bearingless permanent magnet slice motor, whose performance directly affects the curative effect of an artificial heart pump. In order to improve the rotor levitation performance of artificial heart pump, a novel configuration of bearingless permanent magnet slice motor is proposed in this paper. Firstly, the working principle of BPMSM, the current common rotor structure and its defects was described. Then a novel Halbach arrays permanent magnet rotor that can levitates steadily in the pump chamber was designed to optimize the structure of the artificial heart pumps bearingless permanent magnet slice motor. Secondly, the finite element analysis and comparison were carried out for the surface-mounted permanent magnet rotor, the conventional Halbach array permanent magnet rotor and the novel Halbach array permanent magnet rotor. Finally, the magnetic field distribution, the induced electromotive force, the cogging torque and the radial levitation force of the mentioned-aboverotors were obtained, which can reflect the electromagnetic characteristics of the motor. The analysis results demonstrated that the novel Halbach array designed in this paper can significantly improve the dynamic torque performance the levitation performance of the bearingless permanent magnet slice motor. By using the new design, permanent magnets with the same material and thickness can generate greater air-gap flux density and thus greater levitation force and electromagnetic torque, which are the crucial criterion for evaluating the performance of an artificial heart pump. Therefore, the novel Halbach array BPMSM has a good application prospect in the field of artificial heart pumps.