Table of Content

15 March 2025, Volume 45 Issue 1

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Nuclear Fusion Engineering

Design and application of Faraday screen fora new ICRH antenna in EAST

LIANG Qi-chao, ZHANG Wei, LIU Lu-nan, QIN Cheng-ming, MAO Yu-zhou, YANG Hua

2025, 45(1):  1-6.  DOI: 10.16568/j.0254-6086.202501001

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To achieve the long pulse high power target of experimental advanced superconducting tokamak (EAST) and improve the coupling efficiency between ion cyclotron wave and plasma, and reduce the thermal load on the Faraday screen of the ICRH antenna, the Faraday screen of ICRH antenna is optimized. Using the RAPLICASOL ICRH antenna computational model, the structure of the Faraday screen was analyzed, and synthetically considering the maximum electric field strength, coupling impedance and the limited internal space of ICRH antenna the dimensions of the Faraday screen structure was determined ultimately. Subsequently, the heat flow distribution of the Faraday screen was optimized and analyzed. After simulation and optimization, under 300-second operational conditions, the highest temperature of the Faraday screen was 300℃, meeting the thermal design requirements of the Faraday screen. This antenna was successfully applied in the EAST experiments in 2021. The experimental results showed that the coupling and heating efficiency of the new ICRH antenna significantly improved. The experiments completed include 1.5MW/30s and 0.5MW/300s long-pulse operations, and the maximum temperature of the Faraday screen was 330℃, meeting the design requirements of the ICRH antenna.


Skyshine simulation of HL-3 tokamak and shielding analysis based on cosRMC

ZHANG Yi-heng, ZHAO Zi-qiang, LI Zai-xin, CAI Lai-zhong

2025, 45(1):  7-12.  DOI: 10.16568/j.0254-6086.202501002

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The next plan for HL-3 tokamak will be DD/DT fusion experiments, the ionizing radiation damage of fusion neutrons to the human body can not be ignored, and the radiation protection is the guarantee for fusion experimental research. Using Monte Carlo method, the skyshine problem of DD fusion neutrons in the core of HL-3 within a radius of 1000m around the main hall is calculated by the three-dimensional particle transport code cosRMC. The effective absorbed dose of the human body resulting by neutron irradiation is evaluated under skyshine and direct penetration circumstance, making sure that radiation protection in the main hall is now within a safe range. For DT fusion experiment in HL-3, the skyshine circumstance of DT fusion neutrons at an energy of 10MJ is estimated, and reasonable suggestions to strengthen the shielding are proposed on the basis of the existing shielding measures, which could be used for the environmental assessment and protection design of future experiments in HL-3.


Development of metal film resistance detector of Bolometer in the HL-3 tokamak

HE Zong-yu-hui, GAO Jin-ming, HAO Guang-zhou, LIANG Shao-yong, CAI Lai-zhong

2025, 45(1):  13-18.  DOI: 10.16568/j.0254-6086.202501003

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To meet the requirements of radiation power measurement and two-dimensional radiation profile inversion for the HL-3 tokamak, a metal film resistance Bolometer system and its detectors were designed. The layout of the system's sightlines and the development of the detectors are described. The detectors mainly consist of an absorption film, a ceramic base plate, a thermistor and a stainless steel casing. The metal absorption films use gold and nickel to match the different parameters of the device discharges. The ceramic base plate is processed with magnetron sputtering to ensure its insulation and thermal conductivity, enhancing the time resolution of the detector. The thermistors are connected via a bridge structure to suppress errors caused by ambient temperature. The resistance wire is etched onto a silicon nitride substrate using photolithography techniques, which improves the detector's sensitivity and measurement range. The ceramic circuit board and the non-magnetic stainless steel casing are capable of withstanding high temperatures and baking. Each detector integrates four measurement channels, has a low space occupancy rate, and is easy to install inside the HL-3 vacuum chamber. The detector power and signal connections use spring-loaded pins for high reliability. The test results show that the detector resistance values are uniform and change linearly with temperature. This system will provide a reliable technical means for measuring plasma radiation power in the HL-3 tokamak in future.


The key alignment and metrology technology during ITER PF6 large superconducting magnet coil lifting

GU Yong-qi, ZHENG Yuan-yang, YUAN Zhong, WANG Lin, DENG Lei, LI Zhi-hu, ITER TAC Project Consortium Team

2025, 45(1):  19-26.  DOI: 10.16568/j.0254-6086.202501004

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The PF6 superconducting magnet coil is the first lifting and the heaviest magnet coil on ITER, so the lifting accuracy will directly affect the installation of subsequent components. According to the structure status, fiducial distribution and visual conditions of ITER assembly workshop and Tokamak Hall, the simulation measurement analysis was carried out through the load deformation test, lifting trial, coil orientation adjustment, lifting path and precise positioning, therefore the measurement scheme was simplified and the key steps of alignment and metrology were optimized to ensure the progress of ITER TAC1 project. The one-time accurate lifting and landing position of PF6 coil meets the requirement of ±4mm, the measurement uncertainty is 0.66mm, and the ratio of the tolerance and the measurement uncertainty is not less than 5, which meets the ITER standard requirements. 


Effect of Ti coating on hot-isostatic pressing bonding of Be/CuCrZr

WANG Hai-long, TANG Jiang-ke, ZHU Ying-xi, HU An-de

2025, 45(1):  27-33.  DOI: 10.16568/j.0254-6086.202501005

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Be and CuCrZr alloys are connected by the hot isostatic pressing bonding technique, and ultrasonic nondestructive testing (UT), SEM, EDS, XRD, hardness tester and material performance testing machine are used to analyze the interface bonding, microstructure, element distribution, phase composition, micro hardness and shearing strength. The results show that the effective connection of Be/CuCrZr alloys can be achieved at 580℃/150MPa/2h, and its shear strength is up to 110MPa, the joint exhibits a good bonding between Be and CuCrZr, and no visible cracks. The Ti transition layer on the surface of Be can effectively prevent the formation of brittle phases between the Be-Cu interface, the thickness of Ti diffusion layer in Cu is about 4μm, and the diffusion layer thickness in Be is about 2μm. Cu₄Ti、CuTi₃、Cu₄Ti₃、Be₁₀Ti、Be₁₂Ti、Be₁₇Ti₂ etc. various Cu-Ti, Be-Ti intermetallic compounds exist at the diffusion interface, and the shear fracture occurs at the Cu-Ti diffusion interface.


Research of the 105GHz/1MW ECRH boron nitride ceramic window

WANG Chao, HUANG Mei, CHEN Gang-yu, CHEN Cheng

2025, 45(1):  34-38.  DOI: 10.16568/j.0254-6086.202501006

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Dielectric parameters of the 105GHz/1MW ECRH boron nitride (BN) ceramic window are measured by open cavity, and the impact of permittivity and mechanic tolerance on performance of the window are calculated. The temperature distribution after power deposition was obtained with finite element analysis, thereby the pulse duration for BN ceramic under 1MW condition was confirmed. The proper thickness of the BN ceramic for next welding work was chosen by low power test. 


Design of joint three-motor control system for ITER-like multi-purpose deployer

QI Guo-dong, YAO Da-mao, ZHONG Chong-feng

2025, 45(1):  39-44.  DOI: 10.16568/j.0254-6086.202501007

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The multi-purpose deployer remote handling system is the main component of tokamak remote handling systems, which is mainly used for internal inspection and internal components maintenance of tokamak. The multi-purpose heavy-load manipulator is an important part of the multi-purpose deployer remote handling system. The key rotary joint control system of the manipulator has large output torque, high positioning accuracy and limited installation size. To solve these problems, a cooperative drive method of three motors is adopted. Therefore, a three-motor synchronous control system based on EtherCAT real-time bus was designed for key joint of ITER-like multi-purpose deployer and tested. Under the present experimental conditions, the position and speed tracking test of a single motor is carried out under no load. The experimental results show that the control system can run normally and the maximum tracking error at the given point is less than 2', which meets the requirements of positioning accuracy. The design and construction of the control system lay a foundation for the no-load synchronous test and loading experiment of the following three motors.


Analysis of critical current degradation of CICC superconducting joint under cyclic force load

ZOU Chun-long, LIU Xu-feng, DU Shuang-song

2025, 45(1):  45-48.  DOI: 10.16568/j.0254-6086.202501008

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The critical characteristics of CICC superconducting joints under cyclic force load are analyzed respectivly from mechanics and electrical aspects to explore the transformation of critical characteristics of CICC superconducting joints under the service conditions of fusion reactors, expected to provide theoretical basis and reference for the design of CICC superconducting joints of fusion reactors in future, and make a more accurate prediction for the performance degradation of joints during operation.


Research and design of nuclear safety system for magnetic confinement fusion reactor

WANG Fen, ZHANG Long, CAO Qi-xiang, ZHAO Feng-chao, ZHOU Bing, WANG Yan-ling

2025, 45(1):  49-57.  DOI: 10.16568/j.0254-6086.202501009

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The design of nuclear safety systems must be considered in the construction of fusion reactors. The biggest safety issue for fusion reactors is the inclusion of high-energy neutrons and tritium. The characteristics of the magnetic confinement fusion reactor are analyzed, and the nuclear safety function and its system compositions are proposed, including the confinement system, multi-layer shielding, protection and support functions of the confinement. Tritium protection measures were discussed; In view of the fact that the classification method of safety components in the existing nuclear safety standards is too complex for fusion reactors, a new classification method is proposed. For the defense-in-depth level on the fusion facility, the corresponding objectives and measures for each level are given. This paper can provide a reference for the design of nuclear safety systems for future fusion reactors.


Development of the HL-3 first wall temperature monitoring system

XU Jie, CAI Li-jun, LIU Jian, LU Yong, ZHANG Long, LIU Kuan-cheng, HUANG Wen-yu, LIU Yu-xiang, LUO Shan

2025, 45(1):  58-63.  DOI: 10.16568/j.0254-6086.202501010

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In order to meet the safe operation and experimental needs of the HL-3 first wall system, the first wall temperature monitoring system is designed and developed, mainly including monitoring point design, hardware design and development, and software development. The S7-300PLC is used as the main controller, and the ET200 remote module is used as an analog data input collector, which realizes the real-time temperature monitoring of the key positions of the first wall, mainly including the high-field-side, low-field-side, divertor, movable limiter and other heat load concentrated areas. The human-computer interaction interface is completed to realize the functions such as real-time data display, history curve looking over and the threshold alarm for the engineering temperature of HL-3 first wall. The system has been successfully invested in HL-3 baking and discharge experiments. The operation results since 2022 show that the system has realized dynamic monitoring of the first wall temperature status and ensures the safe and reliable operation of the HL-3 tokamak.


Plasma Physics

Study of the laser propagation characteristics of the vertical Thomson scattering system on HL-3 tokamak

GONG Shao-bo, ZHANG Tong-chuan, GUO Wen-ping, HOU Zhi-pei, ZHAI Wen-yan, LIU Chun-hua, DENG Bi-he, SHI Zhong-bing, ZHONG Wu-lü, XU Min, DUAN Xu-ru

2025, 45(1):  64-68.  DOI: 10.16568/j.0254-6086.202501011

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A vertical edge Thomson scattering diagnostic system on HL-3 tokamak has been developed recently. The Nd:YAG laser (1064nm, 0.6~2J, 30Hz, 15ns) is used as the probe beam. The laser beam propagates vertically through the plasma region and the scattered light is observed horizontally. The propagation characteristics of the Nd:YAG laser is studied experimentally. The experimental data are fitted by the propagation equation of non-ideal Gaussian beam, and the important parameters such as waist radius, waist position and quality factor of the incident laser are obtained. Based on the incident laser parameters obtained from the experiment, a Galileo beam expansion collimation system and a single lens focusing scheme are designed, and a laser spot with a waist radius of 2mm is successfully obtained in the center of the observation field of view. The study and development on the propagation characteristics of Nd:YAG laser is not only the key to determine the field of view of Thomson scattering system, but also the basis for the design of baffles for stray light suppression.


Effect of EAST density pedestal on linear peeling-ballooning mode stability

LIU Zhi-yang, WANG Yi-feng, LI Yong-liang, ZHANG Tao, WANG Min-rui, ZANG Qing, LIU Hai-qing, XU Guo-sheng

2025, 45(1):  69-75.  DOI: 10.16568/j.0254-6086.202501012

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To understand the effects of parameters related to the pedestal density profile (separatrix density, pedestal top density and normalized pedestal top collisionality) on the stability of linear peeling-ballooning mode in the pedestal, the simulations have been performed with the ELITE code based on the EAST experimental data. The results show that with the decrease of separatrix density(the pedestal temperature profile is kept invariant), the pedestal gradually moves from near the ballooning mode boundary dominated by high-n mode to near the peeling mode boundary dominated by low-n mode, this is mainly because the decrease of the separatrix density, increases the pressure gradient, and the ion diamagnetic frequency, resulting in a more stable high-n ballooning mode.As the pedestal top density decreases(the pedestal temperature profile remains invariant), the pedestal moves from the unstable region of the peeling-ballooning mode to the stable one. The normalized pedestal top collisionality was adjusted by changing the density and temperature. Its decrease causes the pedestal moving from the stable region of the peeling-ballooning mode to the unstable one.


Simulation of impurity transport induced by RMP stochastic magnetic field on EAST

CHANG You-you, SUN You-wen, SHENG Hui, YAN Xing-ting, LI Han-hui, XIE Peng-cheng, ZHANG Wen-min, GUO Jin, MAO Shi-feng, LIU Yue-qiang, ZHANG Ling, DUAN Yan-min, LI Ying-ying, ZANG Qing, YE Min-you

2025, 45(1):  76-83.  DOI: 10.16568/j.0254-6086.202501013

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Based on EAST experiments and a stochastic magnetic field transport theory model, the effect of stochastic magnetic field on W20+ transport caused by resonant magnetic perturbation (RMP) is simulated by considering vacuum and plasma response effect, respectively. The numerical simulation results indicate that within the stochastic layer, the impact of the stochastic magnetic field on the W20⁺ transport is greater in vacuum assumption than in plasma. When the plasma response effect is taken into account, the equivalent transport coefficient of W20⁺ in the stochastic magnetic field can reach 3~5m²·s⁻¹, which is about 3~5 times the two-dimensional neoclassical diffusion coefficient of W20⁺. The dependence of the equivalent transport coefficient of W20⁺ in the stochastic magnetic field on the RMP spectrum is in good agreement with EAST experimental observations when considering the plasma response effect, while the results taking the vacuum assumption have a phase shift of about 60°compared to experimental results. In addition, the impact of the stochastic magnetic field on W20+ equivalent transport coefficient is more significant at low toroidal mode numbers than that at high ones, which is qualitatively consistent with the results of EAST experiments.


Experimental study on the relationship between particle flow distribution and neutral gas pressure on the target plate of the upper external diverter on EAST

ZHAO Ping-an, DING Fang, ZHANG Qing, YU Lin, MENG Ling-yi, HU Zhen-hua, WANG Liang, YU Yao-wei, DING Rui, LUO Guang-nan

2025, 45(1):  84-90.  DOI: 10.16568/j.0254-6086.202501014

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The baffle structure of the tokamak divertor can enhance the particle closure of the divertor, but it may also prevent part of the particle flow in the scrape-off layer from entering the divertor, which can affect the distribution of particle flow on the divertor target Studying the relationship between target particle flow distribution and neutral pressure can help optimize plasma configuration,promote divertor to be detached, and improve compatibility with main plasma.The correlation coefficient between particle flow changes on the surface of EAST divertor and neutral pressure changes was calculated,and the dependence of the correlation coefficient on the different positions of the divertor surface is studied under the typical conditions of lower hybrid wave heating and RMP modulation. The results show that the correlation coefficient has a steep change at the position of the 6th and 7th probes of the outer target plate(The 6th and 7th probes are about 149.6mm and 126.0mm away from the upper edge of the outer target plate respectively)，which reflects that the particle flow received in the divertor target area above the position is the main contributor to the neutral pressure of the divertor and can be better confined by the divertor. The particle flow received in the lower part of the position is difficult to enter the divertor, which plays the role of baffle. The spectroscopic analysis of the divertor shows that the electron and ion recombination process in the target area is an important factor affecting the neutral pressure.


Optimization of electromagnetic forces on practical coils of CFQS stellarato

XU Jun-ming, LIU Hai-feng

2025, 45(1):  91-97.  DOI: 10.16568/j.0254-6086.202501015

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The influences of the finite-sized effects of coils on various engineering and magnetic field configuration characteristics, such as surface twist, line torsion, curvature, electromagnetic force and magnetic topology, are studied. A number of surface-twist-free three-dimensional (3D) coil systems have been designed by changing the coil configuration. By analyzing and studying the coil systems, a new optimized method for finite-size coil system is achieved. Compared to the original coil design, the new coil system possesses much lower electromagnetic forces and optimized shapes, which can produce the 3D objective magnetic field configuration to confine the plasma precisely.


Investigations of magnetic fluid flow in ferromagnetic RAFM steel rectangular duct under inclined transversal magnetic field

DONG Kai-wei, WANG Jun, WANG Xiao-yu, WU Xing-hua, GUO Li-kai

2025, 45(1):  98-103.  DOI: 10.16568/j.0254-6086.202501016

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In order to study the magnetic fluid characteristics of the liquid metal blanket in a strong magnetic field, based on the multi-physics simulation software COMSOL, a two-dimensional MHD calculation program was developed. Using this program, the numerical simulation of the flow of liquid metal in a rectangular duct under the influence of a transverse magnetic field was simulated. Through the fully developed flow model, the effect of RAFM steel on the state of flow used as duct material was studied. Furthermore, the influence of the direction and strength of the transverse magnetic field upon the average velocity was also studied. The results show that the velocity distribution characteristics is insignificantly affected when RAFM steel is used as the duct wall material. A smaller Hartmann number accompanied with a larger magnetic field tilt angle has a greater influence on average velocity. The effect of distribution of magnetic field on fluid pressure drop can be ignored when the magnetic field direction is almost perpendicular to the pipe wall under a big Hartmann number. The conclusions provide theoretical supports for the design of liquid metal blanket.


Research of the instability of internal interchange mode with different magnetic configurations

GAO Zheng-kun, YANG Wen-jun, GONG Xue-yu, ZHONG Yi-jun

2025, 45(1):  104-110.  DOI: 10.16568/j.0254-6086.202501017

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Four magnetic configurations with different plasma current and safety factor distributions based on the parameters of the J-TEXT tokamak were designed with the VMEC code. The Mercier criterion is used to figure out the instability of the internal interchange mode under different magnetic configurations, and the source of the instability is also analyzed. It is found that the magnetic shear term plays a dominant role in the Mercier criterion and the positive magnetic shear has the dominant effect on suppressing the instability of interchange modes. The stronger the positive magnetic shear is, the better the suppression effect on the instability of the interchange mode.


Experimental study on the thrust of corona discharge ion wind

CHEN Zhen, MA He, LI Shan, LIU You-jiang, CHEN Chi-lai

2025, 45(1):  111-116.  DOI: 10.16568/j.0254-6086.202501018

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In order to study the influence of different gas mediums on the corona discharge ion wind, selecting Air, Nitrogen and Helium as the discharge gas mediums the changes of thrust and wind speed of ion wind generated by pin-ring corona discharge with the electrode voltage are studied under the same condition. Experimental results show that the thrust of corona discharge ion wind has a saturation trend with the change of current in all three gases, but the saturation point of each gas is different. The saturation current of Helium is the smallest, which has a positive corona saturation thrust of 0.98mN. The thrust for Nitrogen is 1.96mN, and Air is the slowest gas to saturation. The maximum thrust before the change of discharge property reaches 11.76mN. For the thrust per unit power, we find it decreases with the voltage. Among three gases, for Helium its decrease is the fastest, while for Air its decreases the slowest and shows a non-linear relation. The wind speed across three gases is quite different. The maximum speed in Helium reaches 4.4m·s^‒1, but that in Nitrogen can only reach 1.4m·s^‒1. Existing ion exclusion theory is too simple to explain these phenomena clearly. This study shows that these phenomena are closely related to the property of electron participation, gas viscosity and density. Therefore, this study has a profound meaning for the research and application of the ion wind mechanism.


Study on the influence of external magnetic field and antenna configuration on radio-frequency plasma microdischarge

ZHANG Jin-heng, CHANG Lei, YANG Xin, ZHOU Hai-shan, LUO Guang-nan

2025, 45(1):  117-124.  DOI: 10.16568/j.0254-6086.202501019

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Effects of magnetic field and antenna configuration on radio-frequency (RF) microdischarge are studied with the HELIC program. The power deposition and electromagnetic wave parameters affected by the external magnetic field were studied under two typical modes, m=0 and m=1, of antenna modulus. For the half helix antenna with m=1, when the critical magnetic field is 10mT, the axial power deposition and RF electric field distribution change from single peak to dual peaks, and the peak value is mainly distributed on both sides of the antenna. However, when the external magnetic field reaches 1mT, the loop antenna with m=0 mainly presents a single peak distribution, and the peak value is located directly below the antenna. Simultaneously, it is found that the critical magnetic field values of loop⁺⁺ antennas are different at two axial positions (1mT at z=0mm and 9mT at z=±60mm). Finally, the power deposition of loop⁺⁺ antenna is higher than that of the other two antennas without magnetic field.