Nuclear Fusion and Plasma Physics

Design and test of magnetic probe for parallel wave-number measurement of lower hybrid waves in EAST

WANG Yun-fei1, 2, LI Miao-hui1, DING Bo-jiang1, Baek S G3, Bonoli P T3, Shinya T3,WANG Mao1, ZHAO Lian-min1, LIU Liang1, LI Yong-chun4, WU Chen-bin1, 2

2020, 40(2): 97-103. DOI: 10.16568/j.0254-6086.202002001

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The design, simulation and test of the magnetic probe for the measurement of parallel wave-number spectrum of lower hybrid waves at 2.45GHz in EAST have been performed. Using the software COMSOL Multiphysics 5.2 based on finite element simulation, the size of the magnetic probe is simulated and optimized. Especially, some key dimensions that affect the coupling performance of the magnetic probe, such as dimension of the loop and the slit on the shield, the thickness of ceramic are determined. The test results show that the magnetic probe has good coupling performance for 2.45GHz lower hybrid waves and the ability for identifying wave polarization, which are in consistence with the theoretical simulation results. This work provides an important reference for the establishment of parallel wave-number measurement diagnosis system in EAST, which is critical for further high-density LHCD experiments.

Preliminary experimental results of encapsuled pellet injection on the HL-2A tokamak

XU Hong-bing1, CAO Zeng1, CHEN Cheng-yuan1, ZHU Gen-liang1, CAI Xiao1, LIU Liang1, LI Yong-gao1, YANG Zeng-chen 1, ZHONG Yun-ke1, ZHANG Zan-wen2, LIU De-quan1

2020, 40(2): 104-108. DOI: 10.16568/j.0254-6086.202002002

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Preliminary experiments of encapsuled pellet injection are carried out on the HL-2A device. Basic construction of the encapsuled pellet and manufacture technology are introduced. The encapsuled pellet is with the diameter ~0.76mm, thickness of polystyrene shell ~20μm and internal deuterium pressure ~1.5MPa. Experimental results show that the encapsuled pellet is intact during its flight path, and can be injected to the depth of ~12cm with the velocity of 200m•s^-1. The fuelling efficiency is about 60%.

Reactor core parameter study of fusion nuclear science facility based on normal conductor Tokamak

WANG Jun1, WANG Xiao-yu1, ZHANG Guo-shu2

2020, 40(2): 109-116. DOI: 10.16568/j.0254-6086.202002003

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Core parameters of the fusion facility based on the concept of copper coil tokamak are designed with self-developed zero dimensional system code, ZEROCODE. Based on the neutron peak wall load and related physical and engineering requirements, a set of core parameters with optimal cost is determined for the fusion facility.

Effect of impurity ions on the surface potential of dust particles in fusion plasma

TANG Yi-jia, ZHAO Xiao-yun, WANG Chun-xiao

2020, 40(2): 117-123. DOI: 10.16568/j.0254-6086.202002004

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The influence of multi-charged positive ions on charging process of dust particles and the surface potential in charge balance are discussed with the orbit motion limited theory in fusion plasma. It is shown that the greater the concentration is, the more the charge number is and the greater the mass of other positive ions is in hydrogen plasma, the more negative charges the dust particles carry rapidly during charging, and the greater electron negativity the dust particles have in the charge balance. In addition, the surface potential of dust particles is negatively linear correlated with the concentration of other multi-charged positive ions in the hydrogen plasma. The presence of multi-charged positive ions also affects the extreme value of the surface potential of the dust particles with the change of the hydrogen ion temperature.

Study on the feasibility and technical scheme of power synthesis of two high power klystrons

CHEN Ya-li, LU Bo, BAI Xing-yu, ZENG Hao,LIANG Jun, WANG Jie-qiong, WANG Chao

2020, 40(2): 124-128. DOI: 10.16568/j.0254-6086.202002005

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The feasibility of a 1MW low hybrid current drive (LHCD) microwave synthesized by two 500kW high power klystrons is analyzed, and the scheme is designed. Through the MW level power synthesizer combining with the phase feedback technique to synthesize four channels 250kW microwave of two tubes, the MW level LHCD source is obtained on the HL-2A LHCD experimental platform. The feasibility analysis shows that the synthesis efficiency decreases by about 1.8% due to the phase deviation of 15^o and 0.1% when the amplitude deviation is 10%. Therefore, the specific implementation scheme of two-klystron power synthesis technology is obtained.

Corrosion of low activation ferritic/martensitic steel CLF-1 in liquid tin

HE Ping-ni1, 2, WEI Jian-jun3, WANG Zhi-jun4, ZHANG Kun1, GOU Fu-jun1

2020, 40(2): 129-134. DOI: 10.16568/j.0254-6086.202002006

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Corrosion behavior of the reduced activation ferritic/martensitic steel CLF-1 was investigated in liquid tin at temperatures of 300 up to 700℃ for 24 hours with backscattered scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Attack of liquid tin to the surface of CLF-1 was observed at all temperatures, the main corrosion mechanism was compound dissolution corrosion. Cr was considered to be dissolved and precipitated, and a corrosion layer of Fe stannate was formed at the surface of CLF-1 by reaction between Sn and Fe. Up to 500℃ the chemical composition of the corrosion layer was FeSn₂, and the thickness of the corrosion layer is a constant of about 8μm. Above 500℃ the chemical composition of the corrosion layer changed to FeSn at the border to CLF-1, forming a two-layer structure of the FeSn layer and the outer FeSn₂ layer. The thickness of the corrosion layer increased linearly with the increased temperature.

Tribological property of pulsed magnetron sputtering MoS₂-Ti coating at room and elevated temperatures in vacuum

ZHOU Yi, CHEN Ji-ming, WANG Ping-huai, DAN Min, JIN Fan-ya

2020, 40(2): 135-141. DOI: 10.16568/j.0254-6086.202002007

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MoS₂-Ti composite coatings were deposited by pulsed magnetron sputtering system on silicon wafers and aluminium bronze (C63200) substrates. Ti content was controlled by different current applied on Ti target. Morphology, composition, tribological properties and structure were respectively investigated by SEM, EDS, ball on disk tribometer and XRD. Results show that with increasing of Ti from 0% to 23%, the compactness of coatings increased gradually and structure were changed from high crystallinity of dominant orientation on basal panels (002) to amorphous forms. Friction and wear test showed that with increasing of Ti fraction, tribological properties were improved firstly and then degraded, 3%Ti coating has friction coefficient as low as 0.015 at room temperature in vacuum, while 23%Ti coating showed no lubrication. As elevated temperature to 400°C, higher friction coefficient and wider wear scar were brought about, even friction coefficient were increased from 0.015~0.04 to 0.07~0.1, 13%Ti coating damaged after 800s at 400°C in wear test. Wear debris and particles were observed on the friction pairs of pure MoS₂ and 13%Ti coating at 400°C.

Study of early stage surface evolution of molybdenum coated tungsten bombarded by helium plasma

QIAN Wei, ZHENG Peng-fei, WANG Lian, XU Li-sha,LIU Xing, WEI Ran, BAI Quan, CHE Tong

2020, 40(2): 142-147. DOI: 10.16568/j.0254-6086.202002008

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The sample of molybdenum coated tungsten (Mo-W) has been prepared by magnetron sputtering to investigate the process of fuzz formation as well as the physical mechanism. The surface morphology evolution of W, Mo blocks and Mo-W sample under the 773K or 1073K temperature plasma treatment and the action of helium plasma were observed by using various microstructure characterization methods. The results show that the behaviors of surface evolution of Mo, W and Mo-W samples under the action of helium plasma are almost the same, and the fuzz and coral-like precursor grow from the cone-like structures having relative larger dimension.

Microstructure characteristics and property in joint of graphite/copper alloy brazed by Ag-Cu-Ti liquid solder

LIU Yan-wei1, 2, CAO Lei1, XU Tie-jun1, HAN Le1, ZI Peng-fei1, YAO Da-mao1

2020, 40(2): 148-154. DOI: 10.16568/j.0254-6086.202002009

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Two kinds of graphite are brazed to copper alloy by Ag-Cu-Ti liquid solder via vacuum brazing technology. Experiments are conducted to investigate the influence of brazing temperature, intermediate layer and the size of bases on property of joints. Shear strength of joints are tested via self-designed mold by tensile testing machine. Microstructure characteristics and phase composition are observed and analyzed by scanning electron microscope and the build-in energy dispersive X-ray analysis. Experiment results reveal that continuous and tight joint interface organization of graphite/copper alloy is obtained in the condition of 910℃ brazing temperature holding for 10 minutes. Compared with GA graphite, joints of Artech graphite/copper alloy have higher shear strength. When oxygen-free copper of 1mm is used as the intermediate buffer layer, the brazing thermal stress can be effectively relieved and the joint strength can be significantly improved.

Study on the cooling channel dimension control in the manufacture of CFETR WCCB blanket

GAO Qing-ran1, 2, WANG Ji-chao1, 3, WANG Wan-jing1, WANG Xing-li1, 2,GENG Xiang1, CHEN Zhen1, 2, LI Qiang1, XIE Chun-yi1, 2, LUO Guang-nan1, 2

2020, 40(2): 155-161. DOI: 10.16568/j.0254-6086.202002010

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Uniaxial diffusion welding (U-DW) technique was used to solve channel deformation in fabrication of water cooled ceramic breeder (WCCB) blanket on China Fusion Engineering Test Reactor (CFETR). Under the optimized welding condition the flat-type first wall mockup with cooling channels was fabricated by using two-step hot isostatic pressing diffusion welding (HIP-DW). The experimental results show that the temperature of solid phase bonding needs to be higher than 950℃, and the mechanical properties of post-weld samples can be effectively recovered with tempering at 760℃ for 60 minutes.

Demonstration and calculation of rupture discs in vacuum vessel pressure suppression system of CFETR

TAO La-bao1, 2, YANG Qing-xi1, XU Hao1, LI Ning1,CHEN Jian1, LU Kun1, ZHOU Cai-pin3

2020, 40(2): 162-167. DOI: 10.16568/j.0254-6086.202002011

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The selection of the rupture disc in vacuum vessel pressure suppression system (VVPSS) of CFETR is carried out according to the relevant standards. The design and the calculation of the rupture disc are completed under the VVPSS working conditions, and the preliminary results show that the diameter of disc is 882mm and its thickness is 1mm. The structural analysis and the comparison of the various rupture discs are carried out with the finite element analysis software, the anti-arched rupture disc with toroidal seam is selected finally. The finally selected rupture disc is optimized to meet the design requirements.

Design of high precision and high power bidirectional adjustable power supply

HUANG Hai-hong1, ZHENG Xiao-peng1, WU Yi-bing2, SHENG Zhi-cai2

2020, 40(2): 168-173. DOI: 10.16568/j.0254-6086.202002012

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To meet the high steady-state accuracy, high voltage and high current performance requirements of the power supply for the ITER sensor test steady-state platform, the high power supply is designed with H bridge cascaded carrier phase shifting method. Meanwhile, harmonic analysis is carried out, which can effectively improve equivalent switching frequency of converter and improve output waveform. The supply has been verified by experiments and achieved good results.

New advances in fault diagnosis method of arc power supply for MW neutral beam injector heating system

LI Song-ping1, GONG Xue-yu1, 2, YANG Pu-qiong1, YU Pei-xuan3, LUO Huai-yu3

2020, 40(2): 174-181. DOI: 10.16568/j.0254-6086.202002013

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According to the characteristics of arc power supply (APS) on HL-2A tokamak and the conditions and present status of the fault diagnosis of APS, this paper proposes a scheme which combines the relevant functional modules of the NBI control system and the fault dictionary constructed based on the Matlab/Simulink simulation technology so as to realize the on-line monitoring for the real time state and diagnosis of fault mode of APS. After monitoring the fault of APS, the NBI control system would call the stored output signals of APS for analysis, extracting eigenvalues of signals, and then diagnosing the possible fault modes by APS fault dictionary lookup. Finally, this paper combines experimental data to demonstrate that the fault diagnosis method is accurate for the simple fault location of APS, and can narrow the positioning range for complex faults. It has the advantages of simple principle and strong operability.

Current situation of tritium-related valve technology for China Fusion Engineering Test Reactor

HU Jun, YU Bin, JIANG Fei, DENG Li, ZHANG Zhi

2020, 40(2): 182-187. DOI: 10.16568/j.0254-6086.202002014

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In this paper, the technical requirements and current situation of the tritium-related valve for China Fusion Engineering Test Reactor (CFETR) are described. All-metal valves should be selected for CFETR, which have along service life and a fast response, as well as the overall leakage rate lower than 10^-9Pa·m³×s^-1 under the pressure of 0.25MPa.

Influence of magnetic boundary effect on the trajectory of plasma beam in radial magnetic field

ZHAO Hai-long, LIN Zhong-ying, YANG liu-xiang

2020, 40(2): 188-192. DOI: 10.16568/j.0254-6086.202002015

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According to the confinement relationship between ion and radial magnetic field, the movement of plasma beam in uniform and non-uniform radial magnetic field on plasma optical mass separation (POMS) is simulated with object-oriented particle-in-cell (OOPIC) code. The distribution of diverted electric field in the azimuthator under the magnetic boundary effect is obtained, and its effect on the mass separation is estimated. The results provide reference to the development of some devices, such as mass separator, mass spectrometer and material purification, and the research in related fields such as multi-mass beam flow control with special electromagnetic field configuration.

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