Search

Background: In proton therapy, robotic couch was used for patient positioning to achieve high precision in cancer treatment. However, no studies have focused on the real-time motion management system (MMS) for the robotic couch. This study was to develop the MMS and verify its feasibility. Methods: A real-time MMS was set up with a robotic couch, an NDI Vega optical tracking system, a Special Measurement Tool (SMT) and the developed software. A Leica laser tracker was adopted to verify the accuracy of the tests in this study. The stability and accuracy of the SMT in NDI Vega system were verified to guarantee the reliability of the results. The coordinate transformation was used to unify the measurement. 83 points inside the treatment volume were applied to verify the accuracy of the MMS, with the comparison of results measured by the laser tracker. The synchronism of the SMT in the MMS and Patient Positioning System (PPS) based on the reciprocating motion along axis z was tested to obtain the maximum time delay. Trajectory tracking was performed with different payloads on the couch top. Results: The Means and Standard Deviation (SD) of the stability of the SMT in NDI tracking system on the axis x, y, z, and Rx, Ry, Rz were 0.005 ± 0.004 mm, 0.013 ± 0.005 mm, 0.014 ± 0.005 mm, 0.010 ± 0.003º, 0.013 ± 0.005º, 0.008 ± 0.007º, respectively. For the MMS, the means ± SD along axis x, y, z were 0.24 ± 0.09 mm (0.12 ± 0.03 mm With Laser Tracker (WLT)), 0.31 ± 0.12 mm (0.10 ± 0.03 mm WLT), 0.18 ± 0.06 mm (0.14 ± 0.05 mm WLT), respectively. The max time delay was about 110 ms, with a 60 s of motion tracking. Trajectories tracking showed the real-time graphical traces of the SMT in NDI Vega and Room Coordinate system, and the combined curves by using the coordinate transformation. Conclusions: A real-time MMS was developed and verified with the accuracy of submillimeter in this study. The results demonstrated the feasibility of potential applications based on real-time motion capturing and monitoring.

In this study, firstly, an artificial intelligence algorithm based on particle swarm optimization was adopted to create the electromagnetic and structural mechanics coupling design program of the main magnet system and its active shield. Using this computer program, the main magnet was optimally designed to be a split structure composed of HTS multi-stacked pancake coils, and its operating temperature was under 20 K. Then, we confirmed that the magnet accuracy in 200 mm DSV, the magnetic error of spherical harmonic expansion, the magnetic field distribution in the room-temperature bore, the distance to 5-Guass line and the electromagnetic stress characteristic of an optimally designed magnet are all sufficed requirement of the design. Finally, we reported the system integration of the main HTS split magnet and active shield, verified the effectiveness of the structural stability during the operation of the compact 3-T MRI.

High temperature superconductors have zero resistance under critical temperature and the HTS tapes have low thermal conductivity. The China Fusion Engineering Test Reactor(CFETR) project requires current leads with current carrying capacity up to 100 kA, making high temperature superconducting current leads the ideal choice. The main work of this paper is the theoretical analysis and optimization design of the 100 kA HTS current lead. Current leads are designed to minimize heat leakage to the cryogenic system and to reduce the mass flow of cooling gas. In this paper, some important design parameters are introduced firstly, and then one dimensional thermal analysis is carried out for the heat exchanger and high temperature superconductor parts. The LOFA time and overheating time of the current lead were calculated through simulation, and it was verified that the design meets the requirements of the project. Finally, the factors that have great influence on the performance of current leads are analyzed. In view of the four influencing factors, which are joint resistance, GHe inlet temperature, hPw and RRR, we respectively produced an optimized design.

SC200 cyclotron is a compact superconducting cyclotron for proton therapy developed by the ASIPP (Hefei, China)-JINR (Dubna, Russia) collaboration. In this paper, some beam dynamics simulations are done to evaluate the magnetic field of SC200 measured by mapping system. Magnetic field is optimized by shimming bars and coils to make sure beam can be accelerated to the entrance of extraction system. The optimization of isochronism of magnetic field, beam radial oscillation caused by imperfect first harmonic of magnetic field, magnetic vertical focusing force and radial magnetic field at median plane are presented. The tolerance of imperfect average magnetic field bump and radial magnetic field are studied by beam dynamics simulation.

The Tri-axial high temperature superconducting (HTS) cable usually subjects to the impact of the fault currents in the power system. During the fault, a large amount of the Joule heat is generated, which may be damage cable. In this paper, an analysis model of electromagnetic thermal transient characteristics of the 10 kV/1 kA cable is built. The transient characteristics of the HTS cable are analyzed under a fault current of 15 kA rms lasting 0.14 s, and the current, resistance and temperature of the HTS cable are obtained. The maximum temperature of the HTS cable is 153.1 K under fault current. Meanwhile, the safe operating range of the HTS cable under the fault current of 15 kA to 25 kA is obtained. the analysis results will provide the theoretical basis for the quench protection and relay protection strategy of the tri-axial HTS cable in the Grid.

Flash radiotherapy technology could significantly improve the way radiotherapy is delivered by producing much higher dose rate in much shorter irradiation time. But all existing cyclotrons could hardly meet clinical or experimental requirements. Besides, the future requirements for ultra-high dose rate is not clearly revealed nowadays. Therefore, our task is to increase the cyclotron beam intensity as much as possible by utilizing external injection system. Physical design of injection line and simulations are performed with the code DONS. Simulation results show more than twenty times increase of dose rate can be achieved.

In this paper, an approach for minimizing stress concentration by optimizing the cross section of a toroidal magnet to D-type is presented. To attempt, the magnetic field distributions of both toroidal and D-shaped toroidal magnets were evaluated and compared using the finite element method (FEM), and a convergence curve of maximal magnetic field effect on the winding part was established. We also reproduced an optimal scheme of the ‘D-type' toroidal HTS magnet for a 400 MJ grade SMES based on this convergence curve, and evaluated the distribution of electromagnetic stress in the winding of the magnet, including von-mise stress and hoop stress. We next constructed a reinforcement structure for the ‘D-type' toroidal HTS magnet and investigated the effect of the reinforcement structure material on the suppression of the stress inside the magnet. According these results, an industrialized scheme on the stress inhibition for the D-type HTS magnet for 400 MJ grade SMES was summarized.

In this paper, we proposed a variable protective resistor that realizes controllable energy dissipation and temperature inhibition for the no-insulation (NI) HTS coil-systems, during sudden discharging. The resistor is paralleled with the meter-class bore NI coil, which aims to be used in a high-field magnetic resonance imaging scanner (MRI), to avoid burn-out and shorten restart time of the coil when it has to be shut-down during an accident. To establish the relationship between the value of protective resistor, the energy dissipation and the temperature increase during sudden discharging for the NI coil, in this study, a numerical analysis coupled with a partial element equivalent circuit and a thermal analysis was conducted. Based on the results, the mechanism that how a protective resistor shares energy dissipation and inhibits temperature increase, has been clarified. Meanwhile, the effects of the value of protective resistor on the discharging behavior and temperature increase of NI pancake coil during sudden discharging, were also evaluated to verify the feasibility of this protection method in the application of MRI.

A set of gas nitriding coating device suitable for the electrostatic deflector (ESD) of cyclotron is designed. Using this device, the TiN coating on small electrode of titanium alloy coupons was carried out in the mixture of nitrogen and ammonia. The effects of nitriding temperature and time on the reaction results were studied, the results of the coating experiment were analyzed, and the surface treatment parameters suitable for gas nitriding TiN coating on the surface of the titanium alloy electrode of the ESD were obtained. X-Ray Diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize and analyze the properties of nitrided coatings. And a high voltage discharge experiment was performed on the sample to measure its dark current. The results show that under atmospheric pressure, annealing temperature of 900 °C, and holding time of 8 h, the coating conditions of titanium alloy electrode materials has the best performance.

Considering the lack of space resources limits the addition of conventional cables in urban centers, a three-in-one high temperature superconducting (HTS) cable, which has three separate superconducting cables inside a cryogenic pipe, can be used for urban power supply because of its small volume, large transmission power and low electromagnetic pollution. The three-in-one HTS cable gets a lot attention to be used for urban power supply nowadays. However, the uneven distribution of layer current in three-in-one superconducting cable is a challenge that it leads to the damage of superconducting tape, increasing losses and unstable performance. Therefore, applying an improved screening algorithm, a mathematical model is proposed and its calculation process is programmed in MATLAB for optimizing a 35 kV three-in-one superconducting cable to achieve the current sharing in the conducting layer of each phase. The resistance effect on each layer and the phase-to-phase distance influence on the layer current are considered when investigating the current carrying ability based on the numerical analysis model. Finally, a 35 kV/1 kA three-in-one high temperature superconducting cable short sample is constructed, and the current carrying operational performances of one of three-phase super-conducting cable are tested to verify the effectiveness of the optimization procedure.

A high stress superconducting magnet for the 200MeV superconducting isochronous cyclotron has been constructed and operated to supply 3.6 T extraction magnetic field for proton therapy by CIM Inc. Based those experiences, A 240MeV superconducting isochronous cyclotron (so call SC240) for proton therapy is under development by CIM (F. Jiang et al. , 2019). A superconducting magnet including 2 symmetry up/down split coils would be used to supply the 3.0 T isochronous extraction magnetic fields. The NbTi/Cu WIC conductor is selected to fabricate the superconducting coil. In this paper, the radial stress, hoop stress and displacement of the coil are investigated under different winding tension, cool down and Lorentz forces. Hoop stress is the most key point, the results are shown not more than 60 MPa, which meets the 80 MPa allowable requirement. Optimizing the coil stress design of SC240 can supply sufficient safety margin about lower 50% for hoop stress compared with SC200, which will minimize the risk of training times or avoid premature quench.

Magnetically levitated planar motor (MLPM) with moving-magnet has the advantages of no electric cable interference and no cooling for moving part. In this paper a novel superconducting magnetic levitation planar motor (SMLPM) whose stator uses high-temperature superconducting coils is proposed. Based on the traditional design, the cooling system and thermal shield are added. The copper coil used in the traditional magnetic levitation planar motor cannot provide large current density and have very low force-to-mass ratio. As superconducting technology has the advantages of low energy consumption and high current density, SMLPM could provide greater driving force and torque. Based on the new system, an analytical model was used to calculate the electromagnetic force/torque acting on the Halbach permanent magnet array. The heat load to the cryogenic system is calculated. The finite element method (FEM) for full model has been used to benchmark the magnetic field and force of the theoretical result.

A 10 kA high-temperature superconductor current lead (HTS-CL) using a double-tube stainless steel (SS) shunt has been designed, fabricated, and tested at Institute of plasma physics, Chinese Academy of Sciences (ASIPP). The current lead consists of 80 parallel the second generation HTS coated conductor with critical current of 220 A at 77 K in self-field, a double-tube SS shunt, and Cu connectors. The 80 YBCO tapes are divided into 20 so-called panels, which are soldered into the 20 grooves on the surface of the double-tube SS shunt and Cu connectors, each panel contains four parallel YBCO tapes. A double-tube shunt consisting of two coaxial tubes is designed. A series of tests were performed to verify the feasibility of the HTS-CL. The measured joint resistance is about 0.3–0.4 μ Ω/cm2. The transport current of 10.515 kA was carried between 5 and 65 K for 1010 s with no quenching. The LOFA time of 569 s and the burnout time over 15 s meeting the design requirements.

The SC200 cyclotron is the critical component of the proton therapy system, which is being jointly developed by the Institute of Plasma Physics Chinese Academy of Sciences (ASIPP), Hefei, China, and the Joint Institute for Nuclear Research (JINR), Dubna, Russia. It is an isochronous cyclotron to accelerate H+ ions and extract proton beam energies of 75–200 MeV with the maximum beam intensity of $1~\mu \text{A}$ . The maximum magnetic field intensity of the SC200 cyclotron is 4.6 T, and the accuracy of measurements for the average isochronous field is required to be better than $10^{-4}$ . The magnetic gap decreases from 37 mm at cyclotron center to 9 mm at the pole edge. Hence, the difficulty of designing a magnetic field measurement system is increased because of the required magnetic field accuracy and the narrow gap between the poles. A measurement system has been developed to measure the magnetic field distribution in the median plane of the cyclotron by the SENIS Hall probe. After the Hall probe is calibrated by NMR, the measurement accuracy can reach $\pm 4\times 10^{-4}$ under the magnetic field intensity of 5 T. The position of the Hall probe will be monitored by grating and optical encoder, respectively, so as to ensure its correct positions. To verify the performance of the mapping system, it has been tested in the SC200 cyclotron with the designed vacuum degree. The test results showed that the mapping system can run smoothly and meet the measurement requirements of the SC200 cyclotron.

The SC200 superconducting cyclotron is developed by the collaboration between ASIPP (Hefei, China) and JINR (Dubna, Russia). The SC200 cyclotron will deliver 200 MeV beam for proton therapy and research. The influence of the time-dependent magnetic field created by the acceleration system of SC200 should be taken into account in beam dynamics simulations and during the shimming procedure, as two conditions are present together: first — due to the spiral shape of the accelerating cavities, there is no vertical plane of symmetry through the middle of the dee; and second — second harmonic mode of acceleration in four-sector magnet structure imposes that the RF phase shift from beam entrance of the dee to its exit is not 180 degrees. Particle tracking was performed with 3D maps of electromagnetic fields obtained from computer modelling of the magnet system and the accelerating RF cavities using CST Studio Suite. We have calculated particle dynamics taking into account RF magnetic field and have estimated a value of additional mean field needed for the compensation of beam phase lag induced by RF magnetic field. And finally, we designed a shim that should form the required additional field.

In this paper, we propose a numerical method for ideal isochronous field calculation for the SC200 isochronous cyclotron based on the Nelder-Mead simplex algorithm. In this method, the radial field...

The ITER high temperature superconducting current lead is a critical component for the magnet system, which has the benefit of reduction in the heat load of the cryogenic system compare with the conventional lead. The current lead is located in the coil terminal box and dry box at the end of the ITER feeder system. As a warm to cold transition section, the current leads feed the huge current from the power supply system into the coils. At the outer surface of the current lead, one layer of a composite insulation is applied to isolate the high voltage potential of the current lead to the ground potential of the environment. The main body of the current lead is that of a long cylinder, but at the cold termination and the cooling inlet, the local geometry is much more irregular. So the insulation wrapping and curing technology of the current lead had to be developed to acquire its uniform mechanical and electrical performance. Now, the multi-stage autoclave curing technology has been qualified in ASIPP and the series ITER current leads are being manufactured based on the qualified procedure. In this paper, the latest insulation progresses for the ITER current lead are introduced, the high voltage testing results as part of the formal qualification are presented and discussed.

The SC200 superconducting cyclotron for hadron therapy is under construction based on an agreement of the Institute of Plasma Physics Chinese Academy of Sciences and the Joint Institute for Nuclear Research in Russia. The cyclotron will provide a 200-MeV proton beam with maximum current of 400 nA. Thanks to the superconducting magnet, the cyclotron is very compact and light. The yoke weight is about 35 tons. The Hefei team took the responsibility to develop this laser-triggered switching magnet in the past two years. Early this year, the magnet was tested with the iron system. The operating current is 140 A. The magnetic energy is about 4 MJ. In order to decrease the quench risk of the switched capacitor coil, an FEM quench model that can perform quench dynamics simulations of the main magnet system is developed. A quench test is performed to verify the safety of the coil. The hotspot temperature is about 60 K, the max voltage is less than 800 V, and the energy extraction time is about 15 s. The magnet system is, therefore, safe during a quench.

The level of the fault current is enlarged against the capacity of conventional circuit breaks in some urban power grids with the rapid increase of power load. Thus, a high-temperature superconducting fault current limiter (HT SFCL) has been suggested to provide effective and reliable protection of power devices against fault currents. This paper deals with the design of a prototype hybrid SFCL, which is integrated by a double-split reactor with asymmetric noninductively wound copper windings and a noninductive HTS magnet in series to one branch of the reactor. There is a fast switch in series to the magnet as well. The role of non-inductive magnet is for reducing the fault current in the first swing and the double-split reactor further decreases the fault current. The noninductive HTS unit is designed based on the magneto-thermal coupled model. A noninductive superconducting unit prototype is constructed using a YBCO-coated conductor and is immersed in the liquid nitrogen. A high-speed Data Acquisition System of National Instruments based on LABVIEW is built. The critical current and current impact performance for this prototype under the operating temperature of 77 K are investigated experimentally. The experimental results validate the current limiting effectiveness of the noninductive unit for the SFCL with bias magnetic field.

International Thermonuclear Experimental Reactor (ITER) is the largest global cooperation project, which will be built as the world's largest tokamak to explore the commercial production of fusion-based electricity. In order to connect the busbars electrically and hydraulically, the “shaking hands” twin-box type joint was designed and implemented for ITER project. Different from the conventional method, the indium bonding technology was developed instead of the Tin soldering method for the joint connection. In order to qualify for the ITER correction coil (CC) feeder joint structure and the manufacturing technology, Institute of Plasma Physics, Chinese Academy of Science (ASIPP) has launched the joint qualification on the manufacture process and the cryogenic performance. By means of the indium bonding, the joint resistance can be lower than 1 nΩ before and after the mechanical fatigue. This paper reports the structure and manufacturing process of CC feeder joint, describes the establishing of the testing setup, and finally discusses the cryogenic testing results. Besides the joint resistance, the pressure drop and the critical temperature are reported.

Based on the collaboration of ASIPP (Hefei, China)–JINR (Dubna, Russia) for proton therapy, a 200-MeV compact superconducting proton cyclotron project (SC-200 project) has been launched at ASIPP. The superconducting coil of the main magnet system for cyclotron is cooled by liquid helium. A zero rate evaporation cryogenic system has been designed and tested for the main superconducting magnet system. Three GM-cry coolers (40 W at 50 K, 1.5 W at 4.2 K) were worked as the cold source to cooling the thermal shield, a pair of high-temperature superconducting current leads (HTSCL) and liquid helium container. The test results show that the thermal shield and HTSCL can be cooler lower than 77 K, the heat load of the cryogenic system is less than 2.8 W. The detail design of the cryogenic system and test process will be described in the paper.

High temperature superconducting magnetic energy storage system (HT SMES) can be utilized to compensate voltage sag caused by grid-connected renewable energy power generation and can address power fluctuation while the fault occurs in electric power system, which effectively improves stability of power grid and quality of power supply. With the recent increased capacity requirements of SMES, improving the ampacity becomes a core for its application in renewable power grids. Therefore, a novel 100 m high temperature superconducting twisted stacked-tape in tube (TSTT) composite cable with inner spiral cooling channel is proposed and is manufactured for constructing a 3 MJ toroidal SMES in China Electric Power Research Institute. A prototype pancake using this 100 m TSTT cable is constructed. An experimental set up and critical properties measurement systems are built including a 3000 A dc current power supply, a closed-loop cooling system with LN2 and a high-precision data acquisition system of national instruments based on LABVIEW. The characteristics of critical current for the pancake under an operating temperature of 77 K are investigated in this paper. The experimental results have validated the feasibility of this TSTT composite cable for the MJ-class energy storage magnet. It provides a valuable reference to the large-scale HT SMES applied in the power grids based on a high temperature superconducting composite cable technology.

Heat conduction load test is a main and tough issue in the complex and huge general atom (GA) feeder system cold test. The GA feeder system is a superconducting system connects from the room temperature power supply system to the 4.5-K busbar of the magnet, supply 52 kA current and cryogenic provisions to the central solenoid magnet (CSM) coil, used for International Thermonuclear Experimental Reactor CSM magnet test at General Atomics Company, San Diego, CA, USA. This system have been developed and constructed at the Institute of Plasma Physics, Chinese Academy of Sciences, and completed the full cold test before transferred to the USA. In all the cold test items, the requirement of overall heat load 68 W is a big challenge, for its many leakage heat sources and cooling circuits: high temperature superconducting current lead, vacuum barrier, busbars, pipes, supports, etc. In order to get the steady results, many efforts were took to achieve the required value, such as reduce the inlet pressure of the 5-K loop as much as possible, minimize the flow rate of different 5-K cooling circuits, and at the same time, a dedicated program was developed to online calculate the density and the heat load while monitoring and analyzing the heat load. This paper will give a detail description of the 5-K overall heat load measurement.

The Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP), is in charge of the manufacturing and testing of the 60 high-temperature superconducting current lead series to be completed at the end of 2020 for the International Thermonuclear Experimental Reactor (ITER). This paper first summarizes the testing items and testing results of the ITER lead prototypes in 2015/2016, then, based on the prototypes experiences, discuss the final test piping and instrument diagram for the ITER lead series production testing. A new 5-K test platform to expedite the series testing is also introduced, and a new feature, the 30-kV high-voltage (HV) class insulation for the cryogenic temperature and voltage measurements to allow in situ HV testing, is introduced. The detailed test procedures and test items for the series are discussed finally.

In this paper, the model of electric-thermal-magnetic coupling of the high temperature superconducting (HTS) 10 kV/ 1 kA tri-axial cable is established based on Matlab/Simulink and Ansys. The current, temperature and magnetic field distribution change of the cable are showed by the simulation results. Under fault current of 10 kA last for 10 ms, the maximum temperature of the cable is 79.4 K. The results of this study can be used to evaluate the transient operating characteristics of the HTS cable under fault conditions. Besides, the design of protection system of the cable can be instructed by the results.

We proposed a method by optimizing the cross section of toroidal magnet to ‘D-type’ to maximally reduce the situation of stress concentration. Firstly, the magnetic field distribution of both toroidal and D-shaped toroidal magnet was analyzed and compared based on finite element method (FEM), and a convergence curve of maximal magnetic field act on the winding part was obtained. According to this convergence curve, we reproduced an optimized scheme of the ‘D-type’ toroidal HTS magnet for a 400 MJ grade SMES, and analyzed the distribution of electromagnetic stress including von-mises stress and hoop stress in the winding of the magnet. We then built a reinforcement structure for the ‘D-type’ toroidal HTS magnet and evaluated the influence of the material of reinforcement structure on the inhibition of the stress inside the magnet. Based on these results, we plan to summarized an industrialized scheme on the stress protection of the ‘D-type’ HTS magnet for 400 MJ grade SMES.

The performance and miniaturization of the main split magnet generated isochronous magnetic field in the 240 MeV proton cyclotron aims to apply in Hefei ion medical center, needs to be improved using high-temperature superconducting (HTS) magnet technology. In this study, we reported the optimization method of the HTS main split magnet based on using particle swarm optimization (PSO) algorithm. In the optimization, the volume of HTS tape, the current density, and the maximally experienced electromagnetic stress were set as a convergence condition to the optimization of the main split magnet. The magnetic field accuracy in the proton beam acceleration plane is converged under 1 ppm. We also evaluated the spherical harmonic components of the error of the magnetic field to verify the quality of magnet optimization. Finally, we conducted the analysis of electromagnetic field stress based on a structural finite element method to screen out the optimal scheme for the design of the HTS main split magnet for 240 MeV proton cyclotron.

The DONS code is developed for beam dynamics simulation of cyclotrons, particularly the superconducting compact ones. While few codes with full functionality are dedicated for this industry, the code DONS can be applied to facilitating the physical design and optimization of nearly all the commonly used critical electromagnetic components equipped in cyclotrons. Parallel computing and fast algorithms integrated in a user-friendly interface of the code make it efficient and convenient to perform iterations of the physical design. The accuracy of the code is benchmarked with a widely used code SNOP. At present the code DONS is employed in beam dynamics simulation of the SC200 superconducting compact cyclotron.

Mapping and shimming of magnetic field of cyclotron SC200 in Hefei, China is nearing completion. The results of magnetic field measurements are presented in the paper [1]. The beam dynamics simulation was done with the newest experimental map. It showed that beam completely lost near radius 13 cm. In order to decrease beam losses in central region, beam dynamics with different Br distribution was studied. Vertical and horizontal Br shimming coils are used to decrease Br field. These lead to an increase in beam transmission efficiency to radius 15 cm.

During the achievement of high-performance and miniaturization of magnetic resonance imaging (MRI) scanner, extremely strict indexes on magnet field, stability, and structural strength have been required. To address these problems, we applied “No-Insulation (NI) winding technology” in the magnet of 3-T all HTS MRI. However, in the process of miniaturization, electromagnetic stress becomes a technical challenge. In this study, we focus on designing a reinforcement structure for the magnet of 3-T MRI against electromagnetic stress. First, the magnetic field and electromagnetic force were calculated, and the distribution of electromagnetic stress and strain inside the winding of the designed magnet applied in 3-T MRI were analyzed, based on a finite element method. Moreover, the influence of the mechanical strength of the reinforcement materials used in the pads between sub-coils, shells and blind flanges in the magnet on the effect of stress characteristics, were evaluated respectively to clarify the optimized material and its consumption to establish the reinforcement structure of the magnet employed in 3-T MRI. Further, the influence of boundary condition on the stress characteristic of the NI HTS magnet was also evaluated. Finally, a feasible scheme of a stress reinforcement structure and its manufacture method were summarized for the NI HTS magnet applied in 3-T MRI.

Because high-temperature superconductors have good electrical conductivity and low thermal conductivity in the superconducting state, the China Fusion Test Reactor (CFETR) under construction will use high-temperature superconducting current leads. Under this background, the relevant numerical calculation and design analysis of the 100 kA high-temperature superconducting current lead were carried out. The resistive section consists of a phosphorus de-oxidized copper conductor and heat exchanger and the HTS section is constructed from SEI's Bi2223 tapes. The analysis results show that the overcurrent capability of the current lead is more than 120 kA, the 5 K cold-end leakage heat is less than 25 W, the LOFA time is about 580s, and the overheating running time is about 35s, which meets the design requirements.

Proton therapy is one of the most advanced cancer treatment methods, the study of proton therapy equipment has received increasing attention in China. Hefei CAS Ion Medical and Technical Devices Co., Ltd. (HFCIM) is developing a proton medical device based on the superconducting proton cyclotron (SC200). The extracted proton beam energy of SC200 is designed to be 200 MeV and the beam current is higher than 400 nA. The electrostatic deflector (ESD) is used as the key extraction component to bend the proton beam from the track. Due to the volume limitation of the cyclotron, the ESD shall provide an electrical field up to 150kV/cm to obtain a higher extraction efficiency. However, the extremely high-intensity electric field brings great challenges to the structure optimization, the fabrication technology, and the commission strategy of ESD. HFCIM has completed the engineering design, the material selection, and the technique exploration of the whole ESD system of SC200, and several prototypes have been manufactured. A testing setup with the maximum 1.6 T magnetic field background and the 10−4 Pa magnitude vacuum condition has been established. The commission and the aging experiment is proceeding. From the latest testing results, the ESD can reach to an electrical field of 150 kV/cm, but the stability and the repeatability still need to be improved. Meanwhile, the research of the surface modification of the ESD electrode is in progress, TiNx will be grown on to the electrode surface by the high temperature annealing, which may limit the electron emission.

The SC200 proton therapy system commissioned by the Hefei CAS Ion Medical and Technical Devices Co., Ltd. (HFCIM; Hefei, China) and the Joint Institute for Nuclear Research (JINR; Dubna, Russia) has made significant progress. A main radial beam diagnostic system (MRBDS) equipped with a new type of train probe was developed to satisfy the requirements of beam diagnosis. In this paper, the detailed design of the mechanical structure and electronics system of the MRBDS is presented. The electronics system, which includes hardware and software components, was tested and calibrated. The results show that measurement errors can be significantly reduced by the designed calibration procedures. The repeatability of the mechanical structure was also verified, and the experimental results indicate that the unidirectional repeatability of the positioning is better than 0.3 mm. Finally, the MRBDS was used to measure the phase lag of the particles in the beam, and the results showed a high degree of agreement with theoretical calculations, which proved the applicability and high efficiency of the MRBDS.

The Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) is responsible for the construction and performance testing of the 30 pairs of the international thermonuclear experimental reactor high-temperature superconducting (HTS) current leads. The first pair of poloidal field (PF) coil type, 52-kA HTS current lead prototypes was built and cold tested in ASIPP in mid-2016. The test results demonstrated their excellent performance on low joint resistance, long loss of flow accident time, and high current-sharing temperature. The overheating time, mass flow, and heat loads to 5-K ends also meet the requirements. This paper summarizes the major test results for the PF 52-kA HTS current lead prototypes.

General Atomics has commissioned the final test facility at the central solenoid module (CSM) manufacturing site in Poway, CA, USA. The facility includes a number of critical subsystems including the feeder system (FS), supplied by the Institute of Plasma Physics Chinese Academy of Science (ASIPP), that connects the test chamber to the cryogenic and electrical systems. It includes a coil termination box, high-temperature superconducting current leads, and a feeder duct. The FS carries the current (50 kA) and supercritical helium (4.5 K, 5.5 bara) to the CSM and its supporting structure, while monitoring and controlling the temperature, pressure, flow, and voltage drop through all elements of the superconducting components. It functions as an integral part of the system to rapidly (6-s decay time) dissipates 1-GJ energy stored in the coils, and to protect the cryogenic system. The system is complex, requiring multidisciplinary engineering including: high-temperature superconductivity, cryogenic-temperatures (77, 50, and 4.5 K), high vacuum (1.0 × 10−5 Pa), redundant quench detection (voltage, temperature), high-voltage insulation (15 kV), low thermal loads (70 W), low electrical joint resistance (2 nΩ), Paschen testing, high-voltage signal measurements, and high-current electronics. The system presented significant challenges for design and analysis, complex manufacturing assembly processes, measurement and control, and stringent quality and safety requirements.

The Institute of Plasma Physics, Chinese Academy of Sciences was contracted by General Atomics Company to develop a superconducting feeder system containing a pair of 50-kA high-temperature superconducting (HTS) current leads for ITER central solenoid magnet test. These HTS current leads (HTSCL) are based on the previous ITER lead design experiences. However, the vertical assembly design of HTSCL which is different from ITER's horizontal assembly causes the water leakage in the insulation flange during the initial phase. Some improvements were recognized and expected to avoid the potential risk for further prototypes and series production of ITER leads. Some development experiences are shared in this paper. The HTS current leads contain BiSCCO AgAu matrix tapes to minimize the heat load to 4.5 K end. Its resistive part is cooled by 50-K helium. In the HTS part, the conduction cooling is adopted. The HTS current leads were integrated in the feeder system to perform 4.5-K full current test. The factory acceptance test was implemented to verify the high-voltage and thermodynamic performances. The maximum current of 55 kA was achieved. The test indicates that the helium mass flow consumption is 3.3 g/s per lead and the loss of flow accident time is approximate to 10 min at the nominal current with the stoppage of 50-K helium. The insulation flange passed the high-voltage test of 15 kV, while the leakage current is less than 1 mA after the improvement. More detailed test results will be shown in this paper.

Transverse oscillation is an important issue in beam dynamics of cyclotrons and can be described by the Mathieu equation. We review the standard form of the Mathieu equation, d^{2}u/dθ^{2}+(δ+ϵ·cos2θ)u=0, and propose a modification of the method of multiple scales (i.e., a perturbation method) so that the asymptotic analytical solutions of the Mathieu equation can be computed in the stable and unstable regions for both δ≥0 and δ

The realization of high-field generation and high operational reliability for a next-generation magnetic resonance imaging (MRI) scanner has been a worldwide endeavor for highresolution medical imageology. Our purpose is to apply the recently proposed no-insulation winding technique to achieve high engineering current density (>500 A/mm2) as well as high operational reliabilities (defect irrelevance and self-protection) of HTS pancake coil-systems in the application of static magnetic field such as in meter-class bore MRIs. In this paper, we report our investigation concerning the development of the design scheme for a meter-bore 3-T grade all high-temperature superconducting MRI. Moreover, we compare our design scheme to the conventional design of the 3-T MRI and evaluated the operational reliabilities of designed NI pancake coil-system of MRI.

The SC200 proton therapy superconducting cyclotron was developed by ASIPP (Hefei, China) and JINR (Dubna, Russia). A measurement system was designed to assess the average radial component of the magnetic field (Brav) with 15 search coils in the median plane. The winding differences of the search coils affect the measurement accuracy of the Brav. Based on the electromagnetic induction principle, to measure the Brav accurately, this paper focuses on the design and commissioning of the Brav measurement system. The preliminary results confirm that the system design is reasonable and suitable. After testing the search coil at different speeds, the optimal speed was determined as 2.5 mm/s. The relative error was approximately 0.1% under the maximum radial component of the magnetic field Br of 7 G. The measurement precision was up to 1.0 × 10−3, which can provide the required measurement tolerance of 3–7 G for Br in the median plane. The commissioning of the Brav measurement system is an important step for Br measurement. It can check and adjust the asymmetry of the superconducting coils (SCs).

er to detect the beam quality of the SC200 superconducting cyclotron,measure the beam at the extraction reference and the acceptance of the accelerator is realized.This article mainly introduces the design that use the scintillation screen at the extraction reference to measure the beam profile,position and use the Faraday cup to measure the current intensity with 2.5 level accuracy.The remoted controlling of probes and the acquisition and processing of signal based on LabVIEW and PLC.