The Superconducting Conductor Experimental Test Facility (Super-X) is a core component of the Comprehensive Research Facility for Fusion Technology (CRAFT), designed to conduct full-scale performance evaluations of superconducting conductors required for fusion reactors. Successfully cooling the background field superconducting magnet to its target temperature is the critical first step in the experimental process. However, in actual engineering tests, the limited number of temperature measurement points cannot fully capture the global temperature distribution of the magnet, making it even more challenging to accurately predict its evolution over time. To achieve real-time monitoring and prediction of the magnet’s temperature distribution and to effectively prevent cooling anomalies, this study proposes a novel deep learning model named ThermoNet. This model not only reconstructs the complete temperature distribution of the superconducting magnet from sparse temperature point data in real time but also predicts its evolution over a future time horizon. The model integrates the thermodynamic equations of the superconducting magnet, incorporates residual structures, and embeds a Convolutional Block Attention Module (CBAM) regulated by key physical scalars. This design not only significantly improves prediction accuracy but also enhances the model’s generalization capability and interpretability through deep physical guidance. In the Super-X cooldown simulation tests, ThermoNet achieved an average prediction error of 0.24 K with an inference time of 0.34 s. When validated in the experimental cooldown of the Central Solenoid Model Coil (CSMC), ThermoNet continued to perform reliably. Its temperature prediction error complied with engineering requirements, while maintaining an efficient average processing time of 0.30 s.

In a magnetic resonance system, the magnetic field homogeneity of the imaging area plays a crucial role in imaging quality. However, due to design tolerances and environmental magnetization, shimming is usually necessary to achieve highly uniform magnetic field. And passive shimming, one of the shimming methods, is a widely used technique that utilizes ferromagnetic materials to reduce B0 deviation. Some papers present field contribution of the shims only in the z-direction for the central DSV region, often ignoring the magnetic field in x- and y-directions. This will generate a problem: whether the addition of ferromagnetic shims would cause indelible field deviations for the background magnetic field (BG) in x and y directions, that prone to cause failure to the entire shimming operations. For this reason, this article applied a case study exploring the homogeneity of the BG fields in all the directions and using the ferromagnetic shims for shimming in these three scenarios. First, only the background field is considered. Second, the shims to only optimize the BG fields in the z direction as most literature suggests. And third, the shims optimize the entire three directions adopting our method. Based on this, a practical passive shimming design scheme is provided. Through the optimization, it is found that the new method not only significantly improves BG fields in all the directions, greatly reducing the deviation of tilt angle of the total magnetic field B0 relative to the z-axis, but also no more increases in design difficulty nor consumption of ferromagnetic materials which greatly improve efficiency for the entire shimming procedures. The design theory of this article is a practical method for magnetic resonance imaging (MRI) shimming, which has certain guiding significance for various MRI applications.

The Comprehensive Research Facility for Fusion Technology (CRAFT) is a big platform dedicated to advancing key technologies and conducting performance tests on critical components of fusion energy reactors. It comprises 20 specialized test facilities and 4 auxiliary systems. Among these, the NDE (Non-Destructive Examination) laboratory is a sub-system of the SC (Superconducting) test facility, which is one of the 20 core facilities. The laboratory integrates phased array ultrasonic testing (PAUT, 0.5 MHz similar to 15 MHz), high-frequency acoustic microscopy (up to 100 MHz), digital radiography, and multi-scale X-ray computed tomography (micro-XCT up to 300 kV and high-penetration XCT up to 9 MeV). In addition, a dedicated cryogenic ultrasonic testing system has been developed, enabling defect inspection under temperatures ranging from -196 degrees C to 150 degrees C. Specialized NDE methodologies have been established for cable-in-conduit conductors (CICC), brazed joints in in-vessel components, and superconducting structural assemblies. Furthermore, an intelligent defect recognition algorithm based on a multi-round cross-modal attention mechanism has been implemented, achieving an accuracy of 99.25% in weld defect classification. The developed platform has been successfully applied in ITER, BEST, and CRAFT engineering projects, demonstrating its effectiveness in ensuring structural integrity and reliability of superconducting fusion components.

We systematically investigate the improvement of superconducting (SC) properties in Ta films through controlled annealing processes. We focus on the Ta films deposited at room temperature using Nb as the seed layer, which exhibits excellent performance in SC quantum circuits. It is found that, prolonged annealing under limited vacuum conditions leads to degradation of SC performance due to the incorporation of oxygen elements. By reducing the annealing time to maintain improved vacuum conditions, combined with an cleaning process on the film surface using ion beam etching, we successfully increased the residual resistivity ratio (RRR) of the film from 3.65 to 4.57. Furthermore, by optimizing the annealing temperature at a fixed duration, the value of RRR was further improved to 4.84. Characterization of structure and surface morphology confirms the enhanced crystallinity and reduced surface roughness in the annealed samples. Our results indicate that surface cleaning and the vacuum quality of the annealing environment are key factors determining the quality of annealed Ta films.

Fusion reactors represent one of the ultimate solutions to humanity's energy challenge. China is accelerating the construction of the China Fusion Engineering Test Reactor (CFETR). In preparation, the Comprehensive Research Facility for Fusion Technology (CRAFT) project was initiated to tackle key engineering and technological challenges anticipated for CFETR. The fabrication of the CRAFT Toroidal Field (TF) magnet represents a critical milestone in the development of the CFETR superconducting magnet system. The CRAFT TF coil measures approximately 19.5 m in length, 11.5 m in width, and 1.1 m in height. This design introduces, for the first time, a unique graded winding and nesting structure that integrates superconducting coils of NbTi, ITER-grade Nb3Sn, and high-performance Nb3Sn. However, Nb3Sn must undergo a specific heat treatment (HT) process to form the superconducting A15 phase, and the reacted Nb3Sn wire is highly sensitive to stress and strain. Consequently, the TF coil fabrication follows the "wind-and-react" (W&R) manufacturing sequence. This paper details the design, simulation, and experimental validation of a full-argon protective atmosphere furnace system for the HT of the CRAFT TF Nb3Sn coil. With temperature uniformity maintained within +/- 5 degrees C across all holding stages, this result confirms the suitability of controlled atmosphere HT for meeting the stringent requirements of TFC in nextgeneration fusion reactors.

The development of high-field superconducting magnets for next-generation fusion devices requires robust, high-current cable-in-conduit conductors (CICCs) that withstand combined electromagnetic, thermal, and mechanical loads. In this work, a 2.8 m-long full-size prototype of a twisted stacked-tape rare-earth barium copper oxide (REBCO) CICC with a lateral support structure was designed, fabricated, and tested at the SULTAN facility. The prototype comprises three twisted stacked slotted-core sub-cables (336 REBCO tapes total), vacuum-solder consolidated onto a slotted copper former, wrapped with copper and 316 l tape and compacted into a CHSN01 stainless-steel jacket. Baseline tests at 77 K and self-field obtained a critical current (Ic) of 16.6 +/- 0.3 kA and an n-value of approximately 27. At a magnetic field of 10.85 T and operating currents of 60 kA and 70 kA, the measured current sharing temperature (Tcs) values were approximately 23.5 K and 19.6 K, respectively, deviating within 1.0 K of the predicted average for REBCO tapes. Under electromagnetic cycling conditions with currents reaching 75-80 kA and a background field of 10.85 T, the prototype exhibited only a 1.3% reduction in Tcs after the 53rd cycle, and remained stable throughout subsequent cycles, demonstrating excellent capability to withstand high-field electromagnetic loads. This represents the successful operation of a twisted stacked-tape conductor-type high-temperature superconducting (HTS) CICC under an electromagnetic load of similar to 830 kN & centerdot;m-1. The results confirm that vacuum soldering combined with a lateral support structure can effectively enhance the capability of HTS CICC to prevent the degradation under high transverse electromagnetic loads, providing crucial engineering experience for the future development of high-field HTS conductors for fusion magnet applications.

The Super-X facility for testing large size superconducting conductors is making significant progress. However, the magnetic force between two coils arises when the centers of their respective magnetic fields do not coincide. Coil misalignment is nearly unavoidable during the installation of magnets which will lead to this eccentric force. In particular, for suspended background magnet in Super-X facility, the eccentric force amplifies the stress on structural components, thereby potentially compromising the magnet's safe operation. Therefore, it is imperative to evaluate its impact on the structural components of the magnet. The pull rope structure of the background magnet is elaborated upon in this article, followed by the analysis of the electromagnetic force generated under different eccentricities of the magnet. Subsequently, the stresses on the structural components of the magnet with and without the pull rope structure are analyzed separately. The results demonstrate that the presence of a pull rope structure is crucial for withstanding magnet eccentricity. Thus far, it can be concluded that the mechanical performance of the magnet still meets the design requirements, taking into account coil misalignment.

The China Fusion Engineering Test Reactor (CFETR) will be a superconducting tokamak featuring sixteen toroidal field (TF) coils; a full-size TF coil, based on a national scientific research project, has been designed and is currently being built. The first cool-down test of the TF coil is foreseen to take place in 2025. During the entire cool-down process, it is necessary to ensure that the temperature difference between any two positions of the TF coil is <50 K to avoid irreversible damage to the coil caused by excessive thermal stress. However, the maximum temperature (Tmax) within the TF coil cannot be directly and accurately obtained through experimental measurements; therefore, the thermal hydraulic analysis is crucial to prepare the cool-down strategy of the coil. In this paper, the first cool-down analysis of one CFETR TF coil is completed using the 4C code. The code is based on a 1D model of the helium flow inside the cable-in-conduit conductors coupled to a set of 2D cross sections of the steel structures, where the heat conduction is modeled. The thermal coupling between the turns and the pancakes, as well as the coupling between winding and casing, is also considered. The maximum temperature evolution within the magnet is computed and the optimized cool-down strategy (inlet temperature, inlet and outlet pressure evolution) is proposed.

The fabrication of a prototype toroidal field (TF) coil for the Comprehensive Research Facility for Fusion Technology (CRAFT) represents a critical component of the China Fusion Engineering Test Reactor project. The CRAFT TF coil, characterized by its distinctive "D" shape, measures approximately 19.5 m in length, 11.5 m in width, and 1.1 m in height. The coil incorporates Nb3Sn cable-in-conduit conductors in both its high-field and medium-field windings. Owing to the intense sensitivity of Nb3Sn superconductors to stress and strain, the manufacturing process will adhere to the established "wind and react" methodology. Among the various manufacturing stages, heat treatment emerges as a pivotal step in the production of TF Nb3Sn coil. We have engineered China's largest superconducting coil heat treatment facility, incorporating a fully argon-purged oven environment. This investigation primarily addresses the computational modeling and experimental validation of thermal gradients and fluid dynamics within the system. The design specifications, structural configuration, and processing parameters of the CRAFT TF heat treatment system have been experimentally validated. System performance evaluation demonstrates compliance with technical specifications, particularly in maintaining temperature uniformity within +/- 5 degrees C during the critical 650 degrees C stabilization phase.

To provide candidate materials for the high-field winding-package (WP) of the toroidal field coil (TF) in next-generation Chinese compact burning plasma tokamak, Western Superconductor Technology Co., Ltd (WST) has newly developed a type of high Jc Nb3Sn wire with restacked-rod process (RRP) of the distributed barrier layout. To avoid the conductor degradation during electromagnetic and thermal cycling, the high-field WP is designed as a short-twist-pitch (STP) cable. After cabling and compaction of conductor, the STP design can cause severe indentation damage to the strands. The indentation not only impact the transport performance of the strand, in the meantime impact the thermo-magnetic stability. To investigate the effect of indentation on the performance for the WST high Jc Nb3Sn strand, series measurements were carried out. In this paper, the critical current (Ic) measurement, residual resistance ratio (RRR) measurement, magnetization measurements, and V-I tests were performed on indented samples, and the results were compared with other two types of high Jc Nb3Sn strands used in high-field WP. It was shown that the critical performance of the samples decreased significantly at an indentation depth of 0.4 mm, and the RRR value decreases with increasing indentation depth.

The next generation tokamak aiming to carry out D–T experiments and to demonstrate power generation, is under development at the Institution of Plasma Physics, Chinese Academy of China (ASIPP). A hybrid magnet configuration is proposed for the central solenoid (CS) coil of this tokamak, a high-temperature superconducting coil is inserted into an outer Nb 3 Sn coil for increasing the flux. Minimization of the coupling losses is investigated in the Nb 3 Sn cable-in-conduit conductor (CICC) with rectangular cross-section for the outer CS coils using numerical modeling and experimental verification. The AC loss was measured on several candidate conductors with a superconducting AC Dipole at ASIPP and the numerical modeling was performed with the JackPot-AC/DC © model, which was developed by University of Twente (UT). The data from the experiments tested in UT were used for calibrating and validating the model computations. With the model, further optimization on cable parameters was then carried out. The results show that the twist pitch (TP) of the first stage and the TPs ratio have an important impact on the rectangular CICC coupling loss, and the influences of these two factors are related. In addition, the use of a rectangular cross-section CICC can have significant advantages when used in CS magnets.

Linear programming is usually adopted in passive shimming design for MRI. Its main method is to optimize the thickness of the shims, whereas for high field MRI, the thickness of the shims arranged on the internal rail track is larger due to higher field deviation. In addition, the design error resulting from it cannot be ignored. To address these challenges, a hybrid technique is proposed to achieve more accurate passive shimming. First, linear programming is adopted to determine the preliminary layout of the shims in the pre-arranged space lattice and then integrate the three dimensions of the shims including the thickness by non-linear programming to determine the more accurate configuration of passive shims. Due to the slow speed of integration and iterative optimization, this paper adopts a spherical uniform sampling method with stronger representation to selectively optimize the local integral of the initial shims of linear programming. In addition, we propose an efficient multi-dimensional matrix integration method to achieve the purpose of optimization more quickly and accurately. It is found that the homogeneity designed by the proposed hybrid method is tens of ppm better than that of the previous linear programming method. The proposed hybrid passive shimming technique can efficiently achieve more accurate and better homogeneity results, which promote the development of high-end MRI systems.

A promising way to realize controlled nuclear fusion involves the use of magnetic fields to control and confine the hot plasma configuration. This approach requires superconductor magnets operating above 15 T for the next generation of fusion devices. Due to their high in-field transport current capacity, rare-Earth barium copper oxide (REBCO) coated conductors are promising materials for manufacturing of cable-in-conduit conductors (CICCs) for fusion. However, the high-aspect-ratio geometry makes it difficult to find a multi-tape CICC configuration that fulfills the high engineering current density requirements while retaining enough flexibility for winding large-scale magnets. Moreover, the multilayer structure and inherent brittleness make the REBCO tapes susceptible to degradation during CICC manufacturing and operation. For more than a decade, the development of a reliable REBCO-based CICC that can sustain the huge combined mechanical, thermal, and Lorentz loads without degradation has been ongoing, albeit with limited progress. In this paper, we report on a prototype REBCO CICC that can withstand an applied cyclic Lorentz load of at least 830 kN m-1, corresponding to a transport current of 80 kA at 10.85 T and 4.5 K. To our knowledge, this is the highest load achieved to date. The CICC uses 288 tapes wound into six strengthened sub-cables, making it capable of having a current sharing temperature, Tcs, of around 39 and 20 K when operated under 10.85 T with a current of 40 and 80 kA, respectively. Scaled to a 20-T peak field and 46.5-kA transport current, this provides a temperature margin of over 10 K with respect to an operating temperature of 4.5 K. In addition, no perceptible transport current performance degradation was observed after cyclic Lorentz loading, cyclic warm-up/cool-down (WUCD), and quench campaigns. The proposed REBCO CICC is a milestone in the development of high-temperature superconductors for large-scale and high-field magnet applications. (c) 2025 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

We present the development of a planarized fabrication process for large-scale Single Flux Quantum (RSFQ) circuits, termed "SIMIT Nb03b." This process utilizes chemical-mechanical polishing (CMP) to planarize the SiO2 interlayer dielectric, enabling reduced feature sizes and improved scalability. Dummy fill has proven to be an effective technique for reducing process variation and to improve planarization for chemical mechanical polishing, however, few studies have been reported on how to determine the appropriate fill pattern for superconducting integrated process. In this work, dummy fill structures were strategically placed outside the circuit region to minimize their impact on the circuit's logical functionality. Then we determine the pattern density of dummy fill based on the standard cell library of the process and a fill pattern density of 45 %, length of 7 mu m, and spacing of 3.5 mu m between each other is chosen. Experimental results show that, at this dummy fill setup, the non-uniformity of the SiO2 film thickness after CMP is <5 %. We also developed an indirect method for assessing the residual SiO2 thickness in circuit regions after CMP, which overcomes the limitations of direct measurement on small, narrow circuit patterns. This method enhanced the accuracy of measuring the residual SiO2 film thickness in circuit regions by over 50 % compared to direct measurement techniques. The SIMIT Nb03b process has achieved a critical current of 6 kA/cm(2) and supported junction sizes down to 0.4 mu m, small-scale superconducting integrated circuits fabricated by this process demonstrated a sufficiently wide operating margin, validating the efficacy of the developed fabrication technology.

The Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) has been engaged the conceptual design and prototype coil development for the main coil of the whole-body 14 T magnetic resonance imaging (MRI) superconducting magnet since 2017. In order to improve the thermal and mechanical stability of the coil, a type of conductor called Rutherford cable-in-channel (RIC) will be used in the main coil of the 14 T MRI magnet system. The Rutherford cable is the core component of the RIC conductor. Assessing the electromagnetic performance of the Rutherford cable under operating conditions allows prediction and evaluation of the performance of RIC conductors and 14 T MRI magnets. In order to verify the critical performance of the Rutherford cable, a 2-layer, 2-turn (2 x 2) insert coil was manufactured and tested under a WM3 (maximum magnetic field of 20 T) resistive magnet at the High Magnetic Field Laboratory of the Chinese Academy of Science (CHMFL). The insert coil reaches a critical current of 3489.2 A with n-value of 24.39 after 12 times of quench training under a 14 T background field. The joint resistance is around 20 n Omega. The design, fabrication, testing and analysis of 2 x 2 insert coil will be presented in this paper.

The design and development of quench detection for the China Fusion Engineering Test Reactor (CFETR) toroidal field (TF) prototype coil is in progress, which is expected to be completed in the fourth quarter of 2025. According to the quench simulation analysis, voltage detection with a threshold of 200 mV and a delay of 2 s satisfies the quench detection design criteria, that is, the hot spot temperature is less than 150 K. The foundation of a successful quench detection system, of course, is the reliable measurement of the original high-voltage signals, high-precision suppression of inductive voltage noises, and accurate execution of quench discrimination. Key technologies include many different things such as optimal design of installation schemes for co-wound tape (CWT) and co-wound wire, automatic wrapping of CWT, welding and extraction of high-voltage taps, transfer of high-voltage wires and cables, high-resolution data acquisition, and sensitive quench discrimination mechanism. The installation process for the primary compensation circuit and the key processes for high-voltage measurement have been developed successfully to manufacture the subcoils of the CFETR TF prototype coil, and the test results meet the design requirements. These technologies can not only further improve the reliability of CFETR TF prototype coil quench detection but also provide robust assurance for the secure and stable operation of international thermonuclear experimental reactor (ITER) and future full superconducting fusion reactors.

China achieved a major milestone in its nuclear fusion program with the successful first test campaign of the Central Solenoid Model Coil (CSMC), a critical subsystem of the Comprehensive Research Facility for Fusion Technology (CRAFT), completed in late 2024. The CSMC surpassed its design target by achieving a steady-state current of 48 kA (vs. 47 kA design) at a peak magnetic field of 12 T. This validates essential large-scale superconducting magnet technologies for fusion reactors. The coil, constructed using Nb3Sn and NbTi conductors, features a 1.5 m inner diameter, weighs 140 t, and stores 407.6 MJ of energy. Key challenges overcome include magnet design methodologies, complex manufacturing processes (winding, insulation, heat treatment, VPI, assembly, joints), and advanced testing/diagnostics (quench protection, cryogenic safety). Following cooldown to ∼4.5 K and subsystem checks, the coil demonstrated stable excitation to 48 kA. This success provides crucial technical support for the construction of the China Fusion Engineering Test Reactor (CFETR) and advances China's pursuit of practical fusion energy.

The Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) has announced a project to design a 14 T MRI magnet with a 900 mm warm bore and comprised of Nb 3 Sn Rutherford cables, the homogeneity of the magnetic field is better than 0.5 ppm in a 22 cm diameter spherical volume. The diameter of main coil is about 4 m and the total weight is about to 130 tons. This article describes structural design of 14 T MRI suspension system. A global finite element model is created based on the design geometry data to investigate the mechanical property of the suspension system under the seismic load.

The 15 T DC magnet is one of the key components of Super-X testing facility. The magnetic field configuration and uniformity depend on the shape accuracy of the background coil. There are 31 radial turns of the coil. Tension-free bending analysis for the coil turns with specific radii was carried out. The pressing distance of the pressing wheel for turns bending has been obtained. The reliability of the finite element model is verified by comparing calculated tension-free specific radii with the experimental results of a tension free bending test. It provides the technical parameters support for the tension-free bending of background coil.

The Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) has announced a project to design a 14 T MRI magnet with a 900 mm warm bore and comprised of Nb3Sn Rutherford cables, the homogeneity of the magnetic field is better than 0.5 ppm in a 22 cm diameter spherical volume. This paper presents three design schemes for 14 T MRI magnets based on manufacturing technology perspective, which are layered solenoid design, multi-coil design and multi-coil layered design, and compares them from the aspects of mechanical design, inductance and total conductor usage to obtain the optimal scheme.