Nuclear Fusion and Plasma Physics

Preliminary design and analysis of floating coil for dipole field magnetic confinement experimental device, China Astro-Torus No.1

LIU Teng, ZHANG Guo-shu, DU Jun-jie, YANG Qin-xi, HUANG Shu-long, LIU Yun-hui

2022, 42(3): 271-278. DOI: 10.16568/j.0254-6086.202203001

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Based on the overall design parameters of the dipole field magnetic confinement experimental device, China Astro-Torus No.1 (CAT-1), the structure and parameters of both Nb₃Sn low temperature superconducting suspended dipole field coil and REBCO high temperature one are designed respectively. The finite element analysis results show that the design parameters of the suspension coil, such as the large radius 0.5m, the small radius 0.25m and the current carrying capacity of 5.0MA and 6.5MA respectively, are feasible in structure and engineering. These parameters can provide the maximum background magnetic field strength of 12.7T and 14.8T, which can meet the requirements of CAT-1 experiments.

Preliminary design for process of tritium decontamination of CFETR blanket in hot cell

LUO Rong-rong, PAN Chuan-jie, WANG Cai-wang, LI Peng-yuan, WANG Xiao-yu, DENG Hua-lin, YAN Teng-fei, XU Fa-yong, XU Wan-yun

2022, 42(3): 279-284. DOI: 10.16568/j.0254-6086.202203002

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The systems and process of tritium decontamination for helium cold solid blanket module in the hot cell are considered, three-layer cladding design was used to make sure the safe consideration, among them the second containment system includes the vacuum furnace and glove box, the principle of the vacuum furnace and process of tritium decontamination steps of the blanket is carefully described, high temperature baking and catalytic oxidation technology are employed to remove the tritium. Until the content of tritium lower than the standard of national emission after repeatable tritium removal，which is detected using the method of ionization chamber. The preliminary process of tritium decontamination for the helium cooled solid-state blanket of CFETR is completed, which provides a reference for the design and construction of CFETR hot cell in the future.

Study on the magnetic permeability in support system component welding of HL-2M tokamak

QIAO Tao, LIU De-quan, LIN Tao, ZHENG Xiao-zhou, XU Wen-feng

2022, 42(3): 285-289. DOI: 10.16568/j.0254-6086.202203003

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The support system of HL-2M tokamak is composed of more than 500 non-standard components with different sizes and shapes. More than 400 of these components are welded parts, which are made of SS304 plates. According to the design and operation requirements of HL-2M, the support system must meet the magnetic permeability μ≤1.03, especially the parts prepared by welding process should also fully meet the requirement. Based on repeated welding test comparison and process evaluation, the magnetic permeability can be controlled by increasing the nickel content in the welding wire and adding proper amount of nitrogen into the protective gas (argon).

Thermal hydraulic analysis of the cooling system for the photodiode detectors on the HL-2M tokamak

GAO Jin-ming, LU Jie, DENG Wei, DONG Yun-bo, LIU Yi

2022, 42(3): 290-294. DOI: 10.16568/j.0254-6086.202203004

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A cooling system for the HL-2M bolometer is designed and optimized with the ANSYS software. The performance of the cooling system is estimated and the results show that, the cooling system can protect the detector from the high baking temperature.

Study on compression performance of helium cooled ceramic breeder blanket pebble bed based on discrete element method

WANG Kai-song, YANG Hao, WANG Jian, LEI Ming-zhun

2022, 42(3): 295-300. DOI: 10.16568/j.0254-6086.202203005

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Based on the open source discrete element software LIGGGHTS-PUBLIC, the uniaxial compression tests were simulated on Li₄SiO₄ pebble bed with different crushing ratio to study the compression performance of the pebble bed. The results show that under the same pebble bed strain, the pebble bed stress decreases with the increase of broken particles. The crushing ratio and the restitution coefficient affect the overall strength of the pebble bed together. When the overall strain of the pebble bed is small, the average packing fraction of the pebble bed increases linearly with the increase of the strain of the pebble bed. The average coordination number of the pebble bed increases with the increase of the strain of the pebble bed, and decreases with the increase of the crushing ratio of the pebble bed.

Thermo-hydraulics analysis and optimization for the module of CFETR WCCB

LING Qi-xin, MA Xue-bin, LIU Song-lin

2022, 42(3): 301-307. DOI: 10.16568/j.0254-6086.202203006

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Based on the 3D model of the Water-Cooled Ceramic Blanket (WCCB) for Chinese Fusion Engineering Test Reactor (CFETR), thermal-hydraulic analysis of the blanket module 1# was carried out by adopting the CFD-code Fluent. The feasibility of the thermal-hydraulic design was verified. To obtain the flow distribution of the blanket, the flow analysis for the whole model was accomplished. Based on the analysis results, a design optimization of the coolant system was proposed and a better flow field was obtained.

Electromagnetic structure coupling analysis of CFETR vacuum vessel under major disruption event

SUN Jin-xin, NI Xiao-jun, GE Jian, HAN Song-bo, GONG Zheng

2022, 42(3): 308-313. DOI: 10.16568/j.0254-6086.202203007

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In this paper, based on the model of the 22.5° vacuum vessel, a finite element analysis model of the CFETR vacuum vessel under the condition of plasma major disruption is established. Through simulation calculation, the eddy current and electromagnetic force distribution of the vacuum vessel under major disruption working conditions are obtained，and the electromagnetic load is introduced into the structure field. The stress and deformation of the different PS sections of the vacuum vessel are analyzed. The calculated maximum film bending stress is in the first section, about 53.9MPa, which is far less than the allowable stress value. The results show that the design of the vacuum vessel meets the structural strength requirements under plasma major disruption conditions.

Study on the effect of the manufacturing tolerance of WCCB blanket first wall on the heat transfer and thermal stress

CHEN Chang, JIANG Ke-cheng, WANG Wan-jing, LIU Song-lin

2022, 42(3): 314-321. DOI: 10.16568/j.0254-6086.202203008

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To study the effect of manufacturing tolerance on the heat transfer and thermal stress, based on the manufacturing samples of first wall (FW) for the water-cooled ceramic breeder (WCCB) #3 blanket, the manufacturing tolerance is divided into three classes: size, site and shape tolerance. The simulation results show the influence of manufacturing tolerance on heat transfer and thermal stress is acceptable. However, considering the coupling of three kinds of tolerance, compared with the ideal design, the mass flow rate reduces by 72.5% and pressure drop increases by 24.2% due to the change of channel size and shape; the maximum temperature of structural steel is 532.6°C, which meets heat transfer requirement, but it increases by 119.2°C and the temperature allowance is only 17.4°C. Therefore, in actual manufacture, the first wall flow channel size should not less than 6mm, the depression depth should not exceed 2.5mm and the front wall distance should not exceed 5mm.

Study on the influence of structural parameters on AC loss of high temperature superconducting CICC conductor

WANG Jian, SONG Yun-tao, ZHENG Jin-xing

2022, 42(3): 322-326. DOI: 10.16568/j.0254-6086.202203009

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Based on the multiple physical field finite element software COMSOL, the influence of conductor cross section structure on AC loss of cable in conduit conductor (CICC) with 10kA transmission current in high temperature superconducting tube is analyzed. It is found that the cross-section structure and torsional pitch of the conductor have great influence on the AC loss of the conductor. The more the number of YBCO stacked strands on the cross-section is and the more uniform the distribution of magnetic field around the conductor is, the less the AC loss of cable is. The AC loss of the 6-strand is about 1% of that of the 1-strand. The smaller the torsional pitch of the conductor is, the smaller the AC loss of the conductor is, but the current penetration on one side of YBCO strip is also worse. The uniform cross section structure and torsion under the external magnetic field can also greatly reduce the AC loss of the conductor.

Ring forming technology for vacuum vessel of HL-2M tokamak

WU Xiao-qiang, RAN Hong, ZHANG Dang-shen, RONG Hua, SONG Bin-bin, HOU Ji-lai

2022, 42(3): 327-330. DOI: 10.16568/j.0254-6086.202203010

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The welding deformation of 20 sectors in the vacuum chamber of HL-2M tokamak and the precision control of the ring forming dimension are realized by combining the group welding platform with a large numerical control machine tool. High vacuum helium leak detection was carried out on the weld seam of the vacuum chamber after the ring was formed. The size, shape and position accuracy of the vacuum chamber were detected by large numerical control machine tool combined with theodolite, and the results met the design requirements.

Study of microwave rectification effect by microwave-induced plasma

WANG Bei-bei, ZHANG Zhuo-yue, WANG Tao, LIU Wen-bo, HOU Jing, ZHONG Yu, CHEN Wen-qi

2022, 42(3): 331-335. DOI: 10.16568/j.0254-6086.202203011

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According to the technical idea of using microwave induced plasma for microwave rectification in microwave energy transmission, a low-pressure microwave-induced plasma fixture is presented. The fixture can generate plasma in a neon bulb with the 2.45GHz microwave. A DC signal can be detected as long as the electrodes loaded in plasma. This work has investigated the rectified voltage dependence on the microwave excitation power, and the load resistance, respectively. The rectification efficiency can reach a maximum of 0.05%.

Absolute intensity calibration for extreme ultraviolet spectroscopy by use of helium plasma in EAST tokamak

XU Zong, LI Lei, ZHANG Ling, CHENG Yun-xin, CHEN Ying-jie, WANG Shou-xin, ZHOU Tian-fu, LIU Hai-qing

2022, 42(3): 336-341. DOI: 10.16568/j.0254-6086.202203012

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The continuum bremsstrahlung in extreme ultraviolet (EUV) wavelength range with high signal to noise ratio is observed at high electron density in EAST helium plasma discharge density limit experiments, which is used to perform the in-situ absolute intensity calibration of EUV wavelength range. Consequently, the sensitivity curve of a fast-time-response EUV spectrometer is obtained in 10~65Å, and the absolute intensity of several impurity emission lines in the plasma is measured, and the time evolutions of CVI, NVII and OVIII lines intensity are obtained.

Development of Langmuir probe diagnostic system in radio frequency negative ion source

PENG Xu-feng, XU Yong-jian, YU Ling, LIU Wei, GU Yu-ming, WANG Ri-xin, XIE Ya-hong, XIE Yuan-lai, HU Chun-dong

2022, 42(3): 342-346. DOI: 10.16568/j.0254-6086.202203013

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A set of Langmuir probe diagnosis system is designed to diagnose the plasma parameters in the radio frequency negative ion source. The probe was tested on the test platform, and the V-I characteristic curve of the probe was obtained. Therefore, the electron density distribution and electron temperature distribution of the plasma were calculated and compared with those from the microwave interferometer (MWI). It shows that the diagnostic results of the probe can describe the changes of plasma parameters.

Research of the divertor heat flux on the HL-2A tokamak

MIAO Xiang-gan, GAO Jin-ming, YAN Long-wen, HUANG Zhi-hui, WU Na, WANG Wei-ce

2022, 42(3): 347-353. DOI: 10.16568/j.0254-6086.202203014

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The plasma deposition power distribution on the divertor plate was measured by infrared temperature measurement system and Langmuir probe system in the lower divertor chamber of HL-2A tokamak. The distribution characteristics of the radial and toroidal deposition structures of the heat flow of the target plate in the outer divertor were analyzed. The results show that the heat flow of the target plate on the HL-2A tokamak basically presents an exponential decay distribution in the radial direction, and its decay length is about 5~7mm.

Discharge simulation and volt-second consumption analysis of neutral beam injection on CFETR

LU Ye, YANG Jin-hong, GUI Teng, REN Zhen-zhen, LIU Sheng, NING Hong-wei, XU Jing-kun, SONG Qiang, DENG Hai-fei, WANG Wei-hua

2022, 42(3): 354-360. DOI: 10.16568/j.0254-6086.202203015

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The free boundary axisymmetric tokamak code (TSC) evolving with time is used to numerically simulate the discharge in the current ramping stage of China fusion engineering experimental reactor (CFETR), and the main plasma parameters, plasma configuration and coil current evolutions are given. The volt second consumption of plasma current in the ramping process of CFETR current under the conditions of neutral beam injection (NBI) assisted heating and no auxiliary heating, and the effects of different neutral beam injection conditions are analyzed. The results show that about 10%-25% volt seconds can be saved by properly controlling the injection time and energy deposition profile of neutral beam particles. The simulation results have certain reference value for the engineering design of CFETR.

Design of CFETR hybrid quasi-snowflake configuration

LI Hang, XIE Hai, LI Guo-qiang, QIAN Jin-ping, GAO Xiang, HUANG Jian-jun

2022, 42(3): 361-366. DOI: 10.16568/j.0254-6086.202203016

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The position of the second X-point of the QSF+ was optimized to reduce the currents in the central solenoid (CS) and poloidal field (PF) coils. The results indicate that the PF coil system has the capacity to sustain a 13MA hybrid QSF+ with a long flattop, but the capabilities of the PF2L and PF3L must be enhanced by 2.5 and 3 times, respectively.

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