Table of Content

15 September 2025, Volume 45 Issue 3

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Nuclear Fusion Engineering

Study on microstructure manipulation and properties of hot pressing sintered Cu-ZrO₂ alloys

LIU Yu-hao, CHEN Xu-zhou, WANG Zi-jie, WANG Jian-bao, WANG Ying-min, DENG Xiang, QIANG Jian-bing, FENG Fan, LIAN You-yun, LIU Xiang

2025, 45(3):  249-256.  DOI: 10.16568/j.0254-6086.202503001

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Oxide Dispersion Strengthened Copper Alloy (ODS-Cu) is a candidate heat sink material for the divertor components of future nuclear fusion devices. In this study, Cu₆₄Zr₃₆ amorphous powders were prepared by arc melting and vacuum atomization methods. These powders, together with Cu₂O and Cu powders, were usedas raw materials for mixed ball milling. The ball-milled powders were sintered at 980℃ under a pressure of 70 MPa to obtain a Cu-ZrO₂ alloy sintered billet with a relative density of 95.5%. The microstructure uniformity of the alloy was regulated by combining rolling and annealing treatments. The rolling deformation amount was 86%, and the heat treatment process was annealing at 475℃ for 1 hour. The electrical conductivity of the annealed alloy at room temperature was 87% IACS. The yield strength and tensile strength at room temperature were 213 MPa and 282 MPa respectively, and the elongation after fracture was 20.2%. At 450℃, the yield strength and tensile strength were 125 MPa and 159 MPa respectively, and the elongation after fracture was 23.2%. The in-situ formation mechanism of oxides by sintering powders containing amorphous phases was proposed, and the important factors affecting the microstructure uniformity and high-temperature stability of the alloy were analyzed.

Study on breaking transient voltage balancing characteristic of multi-series thyristor stack using in quench protection system

TONG Wei, WANG Kun, LI Hua, XU Meng

2025, 45(3):  257-264.  DOI: 10.16568/j.0254-6086.202503002

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The design of the quench protection system(QPS) equipped for comprehensive research facility for fusion technology(CRAFT) adopts the artificial current zero-crossing commutation technology for the magnetic current. The safe and reliable work of the high-power thyristor stack directly determines whether the main circuit mechanical switch can successfully break the magnetic current. The voltage sharing characteristics of single device and bridge arm in the breaking process of CRRC MKPE 330-052 Pulsed power device and CRRC KPE 6900-065 ordinary thyristor are experimentally compared. The analysis of the experimental results shows that in the valve group scheme of CRRC MKPE 330-052 Pulsed power device, the voltage sharing coefficient of the series device in the reverse recovery process is extremely low (peak voltage sharing coefficient K₂=0.713, rear peak voltage sharing coefficient K₃=0.246); From the point of view of device development process and structure, it is analyzed that the deterioration of voltage sharing characteristics of multi series pulsed power thyristors in the process of breaking transient is due to the expansion of gate area and the shortening of minority carrier life. In contrast, the CRRC KPE 6900-065 model ordinary thyristor valve group scheme has excellent voltage sharing characteristics, with series devices having a voltage sharing coefficient greater than 0.9 in all stages of the breaking transient process. Therefore, considering the safety and reliability, the CRRC KPE 6900-065 model ordinary thyristor three series valve group was ultimately selected as the design scheme for the manual zero crossing circuit trigger switch of the overload CRAFT QPS.

Simulation analysis of the reasons for the formation of temperature difference between the divertor and the vacuum vessel in the HL-3 baking experimen

BAI Yu-jie, XIE Yan-feng, JIA Rui-bao, CAI Qiang, MENG Jian-peng, QIU Li-yuan, WANG Jia-qi, LU Yong, LIU Xiao-long

2025, 45(3):  265-272.  DOI: 10.16568/j.0254-6086.202503003

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According to the first two campaigns of baking experiments on HL-3 tokamak, the temperature rise of the divertor lagged behind that of the vacuum vessel, and their temperature difference exceeded 20℃ after reaching the high baking stage. The baking process of the lower divertor is simulated by combining 3D simulation methods with one-dimensional ones. The results of the baking experiments between the vacuum vessel and divertor are compared. Furthermore, the factors for affecting the baking temperature change of the divertor are analyzed using the control variable method. The results indicate that the main reasons for the large temperature difference between the vacuum vessel and divertor are the low mass flow rate and the thin insulation layer at the distribution pipes. In addition, the analysis elucidated that reducing the mass of the divertor and the diameter of the manifold section of the divertor piping circuit helped increase the baking temperature, which provided a reference for the next stage of the upper divertor design.

The design of coherence imaging spectroscopy system on J-TEXT tokamak

NIE Lin, WU Jun-bin, LONG Ting, LEI Chi, YAN Wei, LI Yang-bo, ZHANG Xiao-yi, J-TEXT Experimental Team

2025, 45(3):  273-279.  DOI: 10.16568/j.0254-6086.202503004

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Coherent imaging spectroscopy (CIS) is a diagnostic technique that employs high-speed cameras to capture two-dimensional images of impurity ion flow velocities at the plasma boundary. It plays a significant role in studying toroidal rotation and impurity ion distribution in boundary and divertor plasmas. A coherent imaging diagnostic system based on the CⅢ line (464.88 nm) has been successfully developed and deployed on the J-TEXT tokamak. The system features an optical view field of 12°, specifically designed for observing the edge plasma region on the high-field side of J-TEXT tokamak. In terms of performance specifications, the system achieves a high temporal resolution of 2 ms while maintaining vertically spatial resolutions of 11 mm. The diagnostic system has completed experimental test and successfully acquired key data of the plasma boundary, providing a new experimental tool for boundary physics research.

Simulation study on AC loss of second generation high temperature superconducting tape and stacked cable

ZHOU Xiao-meng, LAI Xiao-qiang, ZHU Yun-peng, HOU Bing-lin, ZUO Jia-xin, LI Peng-yuan

2025, 45(3):  280-287.  DOI: 10.16568/j.0254-6086.202503005

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Based on the H equation and using finite element method, the AC loss characteristics of the second generation high-temperature superconducting single and multi band stacked cables are simulated and studied. The results indicate that the simplified model of non magnetic substrate single band has good consistency with the actual model's AC loss values, but the former can further shorten the simulation time and improve efficiency. In addition, the spacing and quantity of stacked cable strips have a significant impact on the AC loss between the entire cable and each strip. The loss value is inversely proportional to the spacing of the strip arrangement and directly proportional to the number of stacked layers.

Analysis of magnetostatic shielding system for ground detection device of superconducting magnet

YE Bei, GAO Ge, WANG Shu-sheng

2025, 45(3):  288-294.  DOI: 10.16568/j.0254-6086.202503006

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During the operation of the superconducting magnet ground detection device of the comprehensive research facility for fusion technology (CRAFT), shielding the external strong magnetic interference is the key to ensure the reliability of the device. The magnetostatic shielding design of the detection device is carried out, and the influence of different materials, shielding thickness, interference field and other parameters on the shielding effect is analyzed by ANSYS. The simulation results show that the 5 mm electrician pure iron shielding scheme fitted on the inner surface of the detection device has high space utilization and good economic efficiency. Under the static magnetic field condition of 20~90 mT, the shielding efficiency is above 21 dB, and the magnetic field intensity after shielding is less than 10 mT, which meets the design and operation requirements of the grounding detection device. Some references are provided for the design of magnetostatic shield for ground detection device of superconducting magnet.

The effect of tungsten tile size on the high cycle thermal fatigue behavior of W/CuCrZr interface

CUI Shi-yu, HUANG Pan, CHEN Yan-yu, WEI Zheng-xing, ZHANG Qi-hang, LI Qian, CHEN Ji-ming, WANG Ping-huai

2025, 45(3):  295-300.  DOI: 10.16568/j.0254-6086.202503007

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This paper presents the fabrication of small ITER W/CuCrZr first wall modules with three different tungsten tile sizes using a casting+hot isostatic pressing (HIP) bonding process with Cu as the interlayer. The modules were subjected to high heat flux fatigue testing at 4.7 MW·m⁻² for 15,000 cycles to investigate the effect of tungsten tile size on the high heat flux performance of the bonding interface. The results indicate that fatigue cracks appeared at the bonding interfaces of all three tungsten tile sizes, primarily located in the tungsten near the interface. Larger tungsten tiles exhibited faster initiation and propagation of fatigue cracks, but the cracks tended to stabilize after reaching a certain size. None of the tungsten tiles experienced melting or detachment failure. The high heat flux led to grain refinement and increased hardness in the Cu interlayer.

Study on the effect of SLM process parameter on microstructure and microhardness of SLMed ODS-CLF-1 steel

YANG Guo-ping, LIAO Hong-bin, ZHANG Long, WANG Xiao-yu, XIONG Liang-yin, CHENG Yin-fen

2025, 45(3):  301-309.  DOI: 10.16568/j.0254-6086.202503008

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The SLMed ODS-CLF-1 steel was fabricated by selecting different SLM process parameters (laser power and scan speed). The effects of different SLM process parameters on the microstructure and microhardness of SLMed ODS-CLF-1 steel were studied by means of OM, SEM, TEM, EDS and microhardness test. The results show that when the laser power is 260~300 W and the scan speed is 400~600 mm·s‒1, the SLMed ODS-CLF-1 steel featured better internal quality, and fewer microdefects. The SLMed ODS-CLF-1 steel microstructure displays stacked-layers with fish scale shape and mainly consists of columnar crystals and minor equiaxed crystals, in which numerous nanoprecipitates with spherical shape and core-shell structure are dispersed in the ferrite matrix. The microhardness reaches over 240 HV0.2 and is obviously better than CLF-1 steel with tempered martensite.

Simulation and experimental verification of CFETR blanket helium cooling experiment loop based on APROS

ZHAO Zheng-ning, YE Xing-fu, YAN Yong-jiang, XU Jing-han, ZHAO Feng-chao, ZHANG Long

2025, 45(3):  310-316.  DOI: 10.16568/j.0254-6086.202503009

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The HeCEL-3 is a high temperature, high pressure and high flow-rate helium cooling experimental loop (HeCEL), mainly used for thermal-hydraulics experiments of blanket components of fusion reactor. According to the system design and layout parameters of the experimental loop, the loop was modeled using APROS software to simulate the distribution and variation of important process parameters such as temperature, pressure and flow-rate of helium under different working conditions. The simulation also includes the transient parameters of critical equipment, such as printed circuit heat exchanger (PCHE) and circulator, during operation or state transitions to generate the thermal characteristics curve. Currently, the HeCEL-3 has been constructed, and preliminary experimental studies on some operational states of the loop have been conducted. The thermal characteristics obtained from simulation are compared with the experimental parameters to verify the effectiveness and applicability of the APROS simulation method, providing references for the future design and operation of helium cooling loops for fusion reactors by means of this method.

Design and analysis of temporary support for ITER thermal shield manifold

YANG Lu-xu, YANG Yin, JIANG Tao

2025, 45(3):  317-323.  DOI: 10.16568/j.0254-6086.202503010

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In order to solve the problem of not being able to maintain the relative installation position of the pipes when installing the thermal shield manifold of ITER, a design of temporary pipes support is proposed to meet the requirements of pipes installation displacement and to improve the accuracy of installation in subsequent processes. Simulation software is used to analyze the structure of the temporary support under input and normal conditions, and the results show that the design fully meets the design requirements and ensures the progress of the subsequent installation of ITER site.

Design of the HL-3 tokamak movable limiter displacement control system based on PLC

XU Jie, CAI Li-Jun, LIU Jian, LU Yong, LI Yun-feng, LUO Shan, HUANG Wen-yu

2025, 45(3):  324-331.  DOI: 10.16568/j.0254-6086.202503011

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Based on the principles of PLC and stepper motor, an automatic control system was designed to realize the flexible displacement control of the movable limiter on HL-3 tokamak. A two-phase hybrid stepper motor was selected, and the S7-1200 PLC was used as the stepper motor controller. The open-loop speed control and position control of the actuator driving stepper motor of movable limiter were achieved through motional axis configuration and the application of PLC-open motion function blocks. At the same time, human-machine interface interaction was implemented, which achieved real-time display of the HL-3 movable limiter displacement, parameter setting, automatic feedback control, and threshold alarm functions. The system has been successfully deployed in the operation of the discharge experiment of HL-3 tokamak. The results since its operation have shown that the designed control system can meet the control requirements and reach the desired objectives.


Plasma Physics

Progress of investigation on the interaction between tearing mode and turbulence in HL-2A tokamak

JIANG Min, XU Yu-hong, ZHONG Wu-lü, CHEN Wei, SHI Zhong-bing, LI Ji-quan, ZHANG Yi, LI Yu-cai

2025, 45(3):  332-341.  DOI: 10.16568/j.0254-6086.202503012

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Investigating the interaction between tearing modes and turbulence in plasmas is crucial for understanding the impact of tearing modes on plasma transport, which holds significant implications for developing effective control techniques for tearing modes and maintaining high-confinement plasma performance in large fusion devices. The multi-scale interaction mechanisms between tearing modes and turbulence, as well as their influence on energy transport were investigated systematically, through experiments on the HL-2A tokamak combined with numerical simulations. The key findings are as follows: (1) A strong poloidal flow shear layer is observed at the boundary of the tearing-mode magnetic island; (2) The modulation effect of tearing-mode rotation on turbulence amplitude is confirmed to exhibit a critical magnetic island width threshold, providing direct experimental evidence for Fitzpatrick’s theory; (3) For the first time, nonlinear cross-island turbulence spreading is discovered, revealing the physical phenomenon exciting quasi-coherent mode turbulence at large magnetic island boundaries, with a proposed non-local phase coupling mechanism underlying this phenomenon; (4) Thephysical mechanism, by which the turbulence near the X-point of magnetic islands triggers plasma thermal quench, is elucidated. These results suggest that active turbulence regulation may serve as a novel approach for controlling tearing mode stability and mitigating disruptions.

The turbulence eddy structure measurement and statistical parameter characteristics in the edge of HL-2A tokamak

NIE Lin, XU Min, KE Rui, LONG Ting, WU Ting, WANG Zhan-hui, HUANG Zhi-hui, HL-A Experimental Team

2025, 45(3):  342-348.  DOI: 10.16568/j.0254-6086.202503013

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A systematic experimental investigation of eddy structures in the edge plasma of the HL-2A tokamak was developed based on structural kinetic theory and conditional averaging methods, utilizing a 3×4 array probe system. Firstly, the correlation analysis of probe signals verified the feasibility of the array for measuring the characteristic scales of plasma vortices. By employing a fully floating potential measurement circuit, the rotation velocity fields of both positive and negative polarity vortices in the edge plasma were successfully measured, demonstrating good self-consistency in the results. The experiment further integrated double-probe diagnostic techniques to obtain the temperature, density, and velocity distribution characteristics in the eddy central regions. The results reveal significant coupling effects between density and temperature fluctuations as well as between radial and poloidal velocities in both positive and negative eddy structures. This discovery provides crucial experimental evidence for understanding the role of eddy structures in plasma transport processes, suggesting that vortices structures may contribute substantially to the particle, energy and momentum transport in edge plasmas.

Analysis of deuterium-induced blistering in tungsten after plasma exposure

YUAN Meng-hui, LUO Zhong-fan, KE Zhen-hua, ZHU Xiu-li

2025, 45(3):  349-356.  DOI: 10.16568/j.0254-6086.202503014

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In this work, the intra-granular and inter-granular deuterium-induced blistering behavior of tungsten materials exposed to low-energy and high-flux deuterium plasma was investigated under different sets of exposure parameters via scanning electron microscope and professional image analysis software. The changes in deuterium retention with exposure parameters were also compared after thermal desorption spectroscopy (TDS) measurements. The present experimental results show that in the low-temperature exposure, the increase in exposure fluence leads to a significant increase in the intra-granular blister density with little change in the size distribution trend and average size, while for the inter-granular blisters, the increased exposure fluence gives rise to a significant increase in blister density, a wider range of size distribution and even the appearance of micrometer-sized blisters. For a given exposure fluence, the increased exposure temperature leads to a significant increase in the number density and a decreased average size of both intra- and inter- granular blisters. It is evident that the behavior of deuterium-induced blistering is more sensitive to the exposure temperature than to the fluence. The TDS results show that the deuterium retention increases slightly with increasing irradiation dose at low irradiation temperatures; when the irradiation temperature is increased above 500 K, the deuterium retention increases significantly, which is mainly reflected by the increase in the intensity of the medium and high-temperature peaks. The comparison between blistering and deuterium retention shows that the significant increase in intra-granular blistering contributes very little to the total deuterium retention, whereas the increase and growth of intergranular blistering can significantly affect the deuterium retention, mainly due to the enhancement of the deuterium diffusion depth and the significantly increased amount of the high-energy trapped deuterium.

Experimental observation of electromagnetic instabilities under the density limit condition in the HL-2A tokamak

HU Li-wen, CHEN Wei, SHI Pei-wan, XU Jian-qiang

2025, 45(3):  357-364.  DOI: 10.16568/j.0254-6086.202503015

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The density limit is one of the mechanisms of plasma disruption, and there is no very well-developed theory that can explain all the density limit disruptions. Core-located electromagnetic instability excited in high-density plasma may be one of the physical mechanisms of the density limit. In this paper, we show the electromagnetic instabilities observed in the high-density plasma of the HL-2A tokamak. These pressure gradient-driven instabilities are very easily excited in high-density plasmas and are localized in the plasma core, where their frequency is positively correlated with the ion temperature, and they often exhibit "staircase" frequency-hopping behavior with fixed frequency intervals. Simulations based on the GENE program show that the electromagnetic instabilities excited in high-density plasmas are Alfven ion temperature gradient modes (AITG). The growth rates of these electromagnetic instabilities are closely related to the pressure, ion temperature gradient, and magnetic shear, which implies that their effects on the confinement performance of high-density/high-pressure plasmas can be effectively controlled and further minimized by adjusting the relevant parameters in future burning plasmas.

Simulation study of fast electron bremsstrahlung imaging in the HL-3 tokamak

GUAN Shuai, CHENG Shi-kui, ZHANG Yi-po, ZHANG Jie , ZHU Yu-xuan

2025, 45(3):  365-372.  DOI: 10.16568/j.0254-6086.202503016

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In response to the diagnostic needs of high parameter physics experiments, the HL-3 tokamak plans to develop a two-dimensional hard X-ray (HXR) imaging system for fast electron physics experiments. A fast electron bremsstrahlung radiation model for the HL-3 tokamak has been constructed using the Monte Carlo code Geant4. The input source was based on the experimentally measured electron temperature and density distribution, while considering the plasma toroidicity and the forward fast electron bremsstrahlung radiation. The calculation shows that although the plasma distribution is asymmetric due to the toroidicity, the energy deposition of HXR radiation on the detectors exhibits a symmetrical distribution under the mutual effect of pinhole imaging

and the forward fast electron bremsstrahlung, which is consistent with the fast electron density profile. The simulation results of this article provide theoretical support for the system design and optimization of two-dimensional HXR imaging diagnosis, and also help to further analyze the experimental data of fast electron bremsstrahlung, in order to carry out energetic electron physics research.