Table of Content

15 December 2024, Volume 44 Issue 4

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Nuclear Fusion Engineering

Numerical analysis of liquid metal MHD effects in U-turn duct

LÜ Xin-ting, ZHANG Xiu-jie, WANG Lei, SUN Zhen-chao, ZHAO Yao

2024, 44(4):  373-379.  DOI: 10.16568/j.0254-6086.202404001

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Numerical simulations on the three-dimensional (3D) magnetohydrodynamic (MHD) flow of liquid metal in a U-turn duct with conducting walls was carried out by using a self-developed program under the low magnetic Reynolds number. The velocity, induced current, and pressure distributions in the U-turn duct were obtained under the magnetic field with different incline angles. The results show that the pressure drop in the U-turn coupling duct is about 2.4 times compared with the single duct under the same conditions due to the strong MHD coupling effect. A reversal flow appears in the part of the core fluid region at the flow turn of the ducts,which may adversely affect the heat transfer of the liquid blankets. In addition, the pressure gradient increases with the incline angles, but it decreases slightly when the inclination is initially increased.


Micro-structure and properties of TiN film deposited on the barrel surface by DC cathodic vacuum arc technology

LÜ Ling , HUA Cheng, LIANG Xin , LIAO Guang-qi

2024, 44(4):  380-387.  DOI: 10.16568/j.0254-6086.202404002

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TiN films were deposited on Cu plate and TC11 titanium alloy embedded in the barrel surface by DC cathodic vacuum arc technology. The structure and mechanical properties of TiN films were investigated by optical microscope, scanning electron microscopy (SEM), stylus profiler, X-ray diffraction(XRD) and micro-hardness tester. It was shown that all films are 2.7~3.0 micron thick. The film thickness uniformity is 94.7%. All films have coarse surface and large particles with magnitude of microns. The surface roughness Ra of all films increases by about 0.2~0.3 microns. Under the same deposition temperature, the particles on the film surface are refined with the nitrogen pressure. The films are composed of TiN with (111), (102), (200), (220), (311)and (222) planes. The microhardness of the film increases and the preferred orientation of TiN (111) is more distinct with the nitrogen pressure at the same deposition temperature. Moreover, the microhardness of the film increases and the preferred orientation of TiN (111) is more distinct with the deposition temperature at the same nitrogen pressure.


Experimental study on modification of HS/6 glass fiber for insulation of Nb3Sn superconducting magnet

XIONG Qiu-yue, , LIU Zhi-hong, SUN Jing, , CHEN Wen-ge, YAN Chao-hui

2024, 44(4):  388-393.  DOI: 10.16568/j.0254-6086.202404003

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The decarbonization and surface modification treatments of HS/6 glass fibers were performed to promote their electrical insulation performance to meet the requirements for use in Nb3Sn superconducting magnets. The results show that the carbon content on the surface of the HS/6 high-strength glass fibers was reduced by approximately 80% after a decarbonization process at 500℃ for 4 hours and the carbon content on the surface of HS/6 high-strength glass fibers, which were treated by palmitic acid with a mass ratio of 8:100 for surface modification after decarburizing, increased by 26.93% compared to that of the decarburized fibers. This modification significantly improved the mechanical properties of the HS/6 high-strength glass fibers more than the decarbonization ones with the tensile strength increased by approximately 10% and interlaminar shear strength improved by about 40%, and their compressive strength was also to meet the requirements for Nb₃Sn superconducting magnets.


The influence of polishing and vacuum annealing on the microstructure of tungsten surface

LI Feng, LIU Ming, QIAN Wei, ZHANG Gui-hang, CHE Tong, WEI Ran, CHEN Ji-ming, ZHENG Peng-fei

2024, 44(4):  394-400.  DOI: 10.16568/j.0254-6086.202404004

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The polishing and annealing experiments are carried out for their influence on tungsten surface microstructural changes. The different effects on surface morphology and microstructure were studied by scanning electron microscopy and electron backscatter diffraction. The experimental results demonstrate that tungsten surfaces polished by mechanical method would form numerous small subgrains with low angle grain boundary in the temperature range of 800~1100 ℃ , whose size and uniformity were mainly influenced by annealing temperatures and holding duration as well as the surface deformed degree. The study found that the average size of subgrains increases with elevating annealing temperature and duration, while the uniformity of size distribution decreases when the temperature is higher than 900℃. Small subgrains more likely appear in severe deformed areas.Furthermore, partial recrystallization occurs during prolonged annealing even at temperature well below the recrystallization temperature.


Thermal analysis of toroidal field coils on HL-3 tokamak

WANG Jia-qi, MENG Jian-peng, JIA Rui-bao, LIU Xiao-long, LI Qiang, CHEN Xin, XIE Yan-feng

2024, 44(4):  401-408.  DOI: 10.16568/j.0254-6086.202404005

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The thermal analysis on the toroidal field coil of HL-3 tokamak is carried out by using COMSOL Multiphysics software. The cooling efficiency of the coil under different working conditions is studied, and the pressure, flow rate and temperature distribution of cooling water are obtained. The results show that the cooling time of toroidal field (TF) coil controlled within 900s can fully meet the requirements of the device. Under the condition of 140kA and 190kA flat top current, the maximum temperature of the coil in one discharge will not exceed 80℃, which will not damage the inter turn insulation between the coils. The main heat generation of TF coil is concentrated in the central post section. When cooling is applied to the coil, the temperature of the coil after 600s can be reduced to a lower range, and the coil can be fully cooled after 900s. The flow rate of cooling water in the internal pipe of the coil should be controlled at 2~4m·s⁻¹, and the inlet pressure cannot exceed 0.45MPa. The cooling time of TF coil can be reduced to 600s.



Design and analysis of 12kA current leads for high temperature superconducting conductor test facility

YUAN Lei, FU You-kun, ZUO Jia-xin, CHEN-Xin, LI Peng-yuan

2024, 44(4):  409-414.  DOI: 10.16568/j.0254-6086.202404006

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According to the heat transfer theory, the current leads for 12T high-temperature superconducting(HTS) conductor test facility are designed and manufactured, which are mainly composed of copper heat exchanger and HTS module. The copper heat exchanger is designed as a stacked structure with large heat exchange area. Bi-2223/Ag-Au and YBCO superconducting materials are used for current-carrying in the HTS module. The thermal load and current-carrying capacity of the HTS module are analyzed by the finite element analysis software. The current-carrying capacity of the HTS module made by Bi tapes alone and its combination with Y tapes is compared. The results show that the combination of Bi and Y tapes have a better capacity on current carrying, and the leads meet the operation requirements of the test facility with current-carrying capacity greater than 12kA and the heat leakage less than 4W at 20K.


Simulation study of megawatt-class supercapacitor energy storage system supplying power to central solenoid

WANG Hong-zhi, PENG Jian-fei, WANG Ying-qiao, LI Hua-jun, XUAN Wei-min

2024, 44(4):  415-422.  DOI: 10.16568/j.0254-6086.202404007

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 In order to meet the high parameter power supply demand of HL-3 tokamak, the preliminary design of 150MW supercapacitor energy storage system (SESS) and the matching simulation study of power supply to the central solenoid (CS) power system were carried out. The energy storage system is designed with cascaded H-bridge structure based on carrier phase-shift modulation. After verifying the rationality of the overall parameter design of the energy storage system through modeling and simulation, the virtual discharge experiment of the energy storage system supplying power to the central solenoid power supply is carried out. The experimental results show that the AC output side of the energy storage system needs to be connected with a filter with appropriate parameters in series, which can not only reduce the AC harmonic content, but also facilitate the successful large current inversion of the CS power converter and realize the four quadrant operation of the CS power supply; In addition, the designed super capacitor energy storage system can absorb the energy fed back during the CS power inverter process, and the output voltage fluctuation is less than 7%. All parameters during the discharge operation meet the system performance requirements. The simulation model can be used as a research platform for subsequent verification of complex control strategies.


Design of high-speed data acquisition system for key signals of NNBI breakdown

BAN Ting, WU Bin, ZHAO Yuan-zhe, CUI Qing-long, XIE Ya-hong, WANG Ze

2024, 44(4):  423-428.  DOI: 10.16568/j.0254-6086.202404008

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Given the low-speed data acquisition system can not accurately characterize the electrical signal, a high-speed data acquisition system for key signals of negative ion source neutral beam injection system (NNBI)breakdown is designed to acquire reliable and accurate data for key signals during the breakdown. This system consists of a high-speed data acquisition board, an acquisition host computer and a data server to achieve microsecond-level acquisition speed. In terms of the transient and randomness of breakdown, pre-trigger and random-trigger are adopted to measure key signals, which can obtain complete data at the moment of breakdown and greatly save the cost during long pulse data acquisition and storage of NNBI.


Experimental study on discharge improvement of KTX with dual-biased electrodes

CAI Hu, WU Jia-ren, LAN Tao, ZHUANG Ge, MAO Wen-zhe, WEI Zi-an, WEN Xiao-hui, ZHOU Chu, LIU A-di, WU Zheng-wei, XIE Jin-lin, LIU Wan-dong

2024, 44(4):  429-435.  DOI: 10.16568/j.0254-6086.202404009

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The impact of single-bias and dual-bias electrodes on the confinement characteristics of a toroidal plasma in a KTX device was studied. The experiments found that bias voltage affects the discharge duration, and by adjusting the bias voltage, the discharge duration can reach the magnetic flux limit. The mechanism by which the bias electrode changes the discharge duration may be by changing the boundary radial electric field Er and the plasma displacement. During the biasing, an increase of the plasma electron density was observed, accompanied the appearance of electromagnetic coherent modes. From the frequency resolved spectrum of the particle transport flux, the influence of biasing electrode on particle transport was studied, and it was found that the particle transport, caused by the fluctuation in the frequency range of the electromagnetic coherent mode, is enhanced.


Electromagnetic-structure analysis of the resonant magnetic perturbation coils on J-TEXT

SONG Qiang, YANG Jin-hong, GUI Teng, CHEN Kai-jie, XI Xu-yao, JIANG Zhong-he, WANG Wei-hua, YANG Qing-zhi

2024, 44(4):  436-443.  DOI: 10.16568/j.0254-6086.202404010

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In order to study the stress of dynamic resonant magnetic perturbation (DRMP) coils on the J-TEXT tokamak at the time of discharge disruption, the J-TEXT plasma discharge is simulated by TSC program,whose data of plasma current and poloidal field coil current during discharge disruption are obtained. The simulation results are consistent with the experimental data. The J-TEXT simulation model is established using the finite element analysis software ANSYS, and the simulated disruption discharge data are imported into the software. The current data are applied to the simulation models such as plasma current wire and polar field coil as a load. The electromagnetic-structure coupling analysis of the DRMP coils is carried out to obtain a more real and accurate stress condition.


Motion control of CRAFT TF coil turn insulation wrapping machine

HE Jian, , WU Jie-feng, WEN Wei, YAN Zhao-hui, , WU Yu, WEN Jun

2024, 44(4):  444-449.  DOI: 10.16568/j.0254-6086.202404011

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Based on the requirements about size, insulation structure, constant pitch and constant tension wrapping of CRAFT toroidal field (TF) coil, the D-shaped helix equation of single turn conductor was deduced.Aiming at the uniform motion of the wrapping machine along the conductor, based on the traditional three-phase PMSM vector control, an adaptive neuro-fuzzy inference controller (ANFIC) was designed to optimize the motion control of the wrapping machine. The simulation results showed that the three-phase PMSM by ANFIC had better speed and torque following ability and the three-phase current fluctuations were small, which provided the reference for the debugging and optimization of the CRAFT TF coil turn insulation wrapping system.


Design and analysis of the first wall on the NBI shine-through area of high magnetic field side of EAST

YANG Xian-ke, , YIN Lei, YAO Da-mao

2024, 44(4):  450-455.  DOI: 10.16568/j.0254-6086.202404012

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The first wall at high field side is an important part of the plasma-facing component in the experimental advanced superconducting tokamak (EAST), and its function is to withstand high thermal load and protect the vacuum inner components. With the increase of neutral beam injection (NBI) power and plasma operation parameters, the existing first wall in the NBI shine-through area of high magnetic flied side cannot meet the high power and long pulse requirements of EAST. Therefore, a modular pattern NBI shine-through area panel has been designed, each panel contains inlet and outlet water module, standard and connection modules. Each module has a three-layer structure, the carbon fiber composite (CFC) is used as the plasma-facing layer and the oxygen-free copper (OFC) is used as the intermediate layer and the CuCrZr/316L bi-metallic plate used a the heat sink layer. The heat transfer and thermal stress analysis of NBI shine-through area panels are carried out by the simulation software Ansys. The analysis results show that the material temperature and thermal stress are within the allowable range. Based on the structural design and thermal-hydraulic analysis, the design feasibility of the first wall on the NBI shine-through area panels is verified.

Conceptual design of magnetic deflector shape for deflector neutral beam

WANG Xue-chun, ZOU Gui-qing, YU Qi, SUN Yu-long, ZHANG Yu-xian, ZHAO Zi-qiang, LEI Guang-jiu, ZHENG Guo-yao, GENG Shao-fei

2024, 44(4):  456-463.  DOI: 10.16568/j.0254-6086.202404013

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The core component of the current linear neutral beam injector, i.e. the strong current ion source,cannot operate in the strong neutron radiation region for a long time. Facing the demand of the future fusion reactor, the concept of the deflecting neutral beam is proposed. Using the transverse magnetic field of the two coils perpendicular to each other to change the direction of the ion beam transmission path, the beam injection channel is deflected away from the ion source in the longitudinal direction, so that the radiation problem in the ion source region is alleviated. By analyzing the effects of different shapes and angles of magnetic deflection coils on the beam deflection angle and convergence, the Helmholtz coil structure to meet the demand is determined, and the advantages of parallelogram coil and trapezoidal coil magnetic field distribution to make the beam converge in different directions are integrated to optimize the coil structure to present a fan shape, which finally realizes the dual-focusing design of the beam in the transverse and longitudinal directions to ensure the negative ion beam deflection at a large angle and convergence for injection into the tokamak windows.


Plasma Physics

Observation and quantitative study of blob structures using a gas puff imaging diagnostic on the HL-2A tokamak

YUAN Jin-bang, YUAN Bo-da, XU Min, YU Yi, NIE Lin, HL-A Experimental Team

2024, 44(4):  464-469.  DOI: 10.16568/j.0254-6086.202404014

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On the HL-2A tokamak, a gas puff imaging (GPI) diagnostic system was developed for the measurement of plasma fluctuations in edge and scrap-off layer (SOL). This diagnostic covers a 160mm×160mm plane near the mid-plane. The poloidal-radial spatial resolution was 2.5mm×2.5mm and temporal resolution is 3~10μs. The GPI line intensity data are compared with ion saturation current data by Langmuir probe, and the results verify that GPI diagnostic can measure plasma density perturbations with high spatial and temporal resolution. In this paper, an elliptic fitting algorithm is developed to analyze the experimental data collected by GPI to quantitatively study the structure and motion of blobs. On this basis, key parameters such as blob location,spatial scale (including poloidal and radial scale length) and motion velocity are calculated, respectively. The titling and splitting effects of poloidal shear flow on blobs are observed, and it is observed that the blob’s poloidal motions are dominated by E_r×B flow. The radial velocity of blob is toward the first wall, consistent with the analysis. These results verify the successful application of elliptic fitting algorithm in GPI data analysis, and provide an important method and experimental basis for the future study of blob evolution.

Numerical simulation of edge-localized mode at the pedestal region in the HL-3 tokamak

WANG Sheng-qing, , WANG Zhan-hui, TANG Teng-fei, XU Xin-liang, CHEN Jian, WANG Zhi-bin

2024, 44(4):  470-476.  DOI: 10.16568/j.0254-6086.202404015

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Based on the peeling-ballooning model, the edge localized mode (ELM) in the pedestal region of the HL-3 tokamak was simulated by the reduced three-field program, elm-pb, in BOUT++ code. The research results show that the dominant modulus of the ELM in the pedestal of the HL-3 tokamak is around n=25, namely the middle toroidal mode number is dominant. The current-dominated peeling-ballooning mode instability is the driving force of the ELM, and the collapse of the pedestal is concentrated in the position where the pressure gradient is the maximum. In addition, the numerical simulation results show that the ELM amplitude in the pedestal region is rather small, suggesting a grassy ELM.


The development of charge exchange recombination spectroscopy diagnostic system on the HL-3 tokamak

HE Xiao-xue, CHEN Wen-jin, WEI Yan-ling, LIU Liang, WANG Shi-qin, YU De-liang

2024, 44(4):  477-482.  DOI: 10.16568/j.0254-6086.202404016

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A toroidal charge exchange recombination spectroscopy (CXRS) diagnostic system on the HL-3 tokamak is developed to measure ion temperature and rotation velocity, which are derived from the Doppler broadening and Doppler shift of the charge exchange spectral lines. The CXRS system measures the CVI (n=87,529.05nm) spectrum line, and it has 32 channels covering the low field side of the plasma from R=1.70m to R=2.43m with spatial resolution to be 1.5~2.5cm. The time resolution of the system is expected to be 5~50ms,which is determined by the spectrum intensity. Now ion temperature and rotation velocity have been obtained during the experiment.


Design and Validation of the Tritium Migration Analysis Program JD-CF in Fusion Reactors

SHAO Li-hua, LIU Ze-kang, LI Zai-xin

2024, 44(4):  483-490.  DOI: 10.16568/j.0254-6086.202404017

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The diffusion, permeation and retention of tritium in the component materials are essential for the engineering design of fusion reactor. In order to facilitate the research of tritium behavior, based on Python the tritium transport calculational program named JD-CF in one-dimensional structural materials of fusion reactor was developed. JD-CF program can calculate the tritium transport problem based on the continuous or multi-layer structure model of one-dimensional flat plate, one-dimensional cylinder and one-dimensional sphere, and realize the coupling calculation of mass and heat transfer. The JD-CF program is verified with the relevant experimental results, TMAP simulation programs, and the results of ANSYS software, which is relatively agreeable. The results show that the JD-CF program has high accuracy and could satisfy the requirements of gas/plasma injection experiment, thermal desorption experiment, transient/steady-state hydrogen and deuterium concentration and temperature distribution simulation, and flux change simulation, it has important reference value for solving the problems of tritium diffusion and tritium retention in the structural materials of fusion reactor.


Time step average method for solving current density in one-dimensional LPIC program

LI Meng-chao, GUO Yong, RONG Chui-cai, CHEN Wei, HUANG Jun, WANG Xing-quan

2024, 44(4):  491-496.  DOI: 10.16568/j.0254-6086.202404018

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In one-dimensional (1D) Laser plasma interaction simulation via Particle In Cell code (LPIC), a time-step averaged method is proposed to solve the particle weight assignment in different positions near the grid according to the effective residence time of particles. The current density in the grid distribution direction (laser propagation x direction) is calculated by the current continuity equation, and in the vertical (y, z) direction , the average density of particles is calculated by the time-step averaged method, and then the current density is calculated by J_y= ρy_y and J_z= ρv_z  in 1D LPIC program. In the case of first-order weight distribution of particle cloud, the current density obtained by this method is consistent with the first-order current density of most LPIC codes.