Table of Content

15 September 2021, Volume 41 Issue 3

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Plasma Physics

Design and development of the calibration system for multi-channel compact pinhole neutral particle analyzer

ZANG Lin-ge, QU Yu-fan, WAN Lin, FU Hong-tao, LUO Xiao-bing, LU Jie, YU Li-ming, LI Wei, SHI Zhong-bing, YANG Qing-wei

2021, 41(3):  193-198.  DOI: 10.16568/j.0254-6086.202103001

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The calibration system of multi-channel compact pinhole neutral particle analyzer (CP-NPA) is introduced, which includes a high-energy, low-current neutral beam line and a supporting rotation platform. The beam source is composed of a high-frequency ion source, a focusing electric single lens, an accelerating tube, a focusing electric quadrupole lens and a neutralization chamber. The high-frequency ion source has been built, and the plasma has been successfully established in the experiment. Simulation, manufacture and test of the single lens have been finished. In the experiment, fixing the extracting voltage at 1.0kV, adjusting the focusing voltage of the single lens, the maximum current is 36.4μA. Design of the other parts of the beam source has been finished as well.

Numerical simulation of HL-2A encapsuled pellet injection fueling

LU Xin, WU Xue-ke , HU Shi-lin, YAN Yi-fan, LI Zheng-ji, WANG Zhan-hui

2021, 41(3):  199-206.  DOI: 10.16568/j.0254-6086.202103002

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In order to improve the charging depth and efficiency of pellets in HL-2A tokamak, an original encapsuled pellet injection fueling was recently developed. Neglecting the ablation process of the non-fuel cladding of the encapsuled pellet, the transport characteristics of the new encapsuled pellet deposited at the position of radial normalized magnetic flux equaling to 0.9 and the self-consistent interaction with the background plasma are simulated in two dimensions with Trans-neut code under HL-2A tokamak configuration. The evolutions of charging particles and background plasma profile are given. The results show that deuterium ions deposit and peak in the radial inside of feeding position, and the core density increases continually under the radial diffusion. The regions of ion temperature and electron temperature reduction at fueling position expand continually during the fueling. The evolution of electron temperature profile in poloidal direction is faster than that of ion temperature profile. The normalized molecular density and radial distribution width at feeding position decrease first and then increase, which is negatively correlated with that of the molecular decomposition at the feeding place.

Plasma radiation distribution tomography based on deconvolutional neural networks

WANG Zhao-hui, XIAO Jian-yuan, QIN Hong

2021, 41(3):  207-214.  DOI: 10.16568/j.0254-6086.202103003

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A deconvolutional neural network (deCNN) which allows to implement a pixel-wise emission distribution reconstruction is developed for plasma radiation distribution tomographic reconstruction. By adopting the structural similarity (SSIM) as the loss function, the method reveals better reconstruction accuracy in phantom data experiments. The simulated experiments results show that this method could still achieve an admissible reconstruction precision and is noise robustness when the line-integrated noise magnitude is 10%, 15% and 20%.

A windowed interpolation FFT harmonic detection method based on zeroing spectral-line amplitudes

ZHENG Zhi, ZHANG Jun-min, TIAN Yun-xiang, , LU Jing

2021, 41(3):  215-220.  DOI: 10.16568/j.0254-6086.202103004

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A harmonic analysis algorithm of windowed interpolation FFT based on zeroing spectral-line amplitudes is proposed to analyze the harmonics of complex power network signals. The complex power network signals are analyzed until the harmonic analysis is completed by zeroing the amplitudes of the maximum spectral line and the three spectral lines on its left and right sides found in the discrete spectrum. Measurement accuracy is studied when the fundamental frequency is stable and influence of fundamental frequency fluctuation on the measurement accuracy is analyzed with simulation. The analysis results of the EAST experimental data verify the feasibility and high accuracy of the method.

Nuclear Fusion Engineering and Technology

Leak test of the HL-2M vacuum chamber in the pre-assembly stage

CAI Xiao, CAO Zeng, RAN Hong, HUANG Xiang-mei, ZHANG Wei, LI Rui-jun

2021, 41(3):  221-226.  DOI: 10.16568/j.0254-6086.202103005

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Based on the methods of residual gas monitoring and helium leak testing, the leak test of HL-2M vacuum chamber was performed with the leak detection system after pre-assembly in the factory and on site respectively. After the leakages were repaired, the vacuum chamber was pumped down to test the ultimate vacuum and the total leak rate. The pressure in the vacuum vessel reached 3.7×10⁻⁵Pa after 72 hours’ pumpdown, better than the expected value 1.0×10⁻⁴Pa. The total leak by static constant volume method was 2.3×10^{− 7}Pa⋅m³⋅s⁻¹, lower than the design value 5×10⁻⁷Pa⋅m³⋅s⁻¹. The test shows that the ultrahigh vacuum condition of HL-2M tokamak is achieved and satisfies the design specification.

Design and analysis on the electrodes of glow discharge cleaning system for the HL-2M initial plasma discharge

LI Bin-bin, , CAO Cheng-zhi, CAO Zeng, CUI Cheng-he, GAO Xiao-yan, MAO Shi-feng, YE Min-you

2021, 41(3):  227-233.  DOI: 10.16568/j.0254-6086.202103006

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 The electrodes of the DC glow discharge cleaning system were designed for the initial plasma discharge of HL-2M. The system load of the glow discharge cleaning system under different working conditions was analyzed and defined, and the design and analysis standards of the electrode structure were determined. According to the structural characteristics of the electrodes, combined with the system load specifications and analysis standards, the failure analysis of the electrodes was performed in a variety of failure modes. The analysis results show that the electrodes design for the initial plasma discharge can operate safely and reliably, satisfying the design requirements.

Central controller design of electronic cyclotron resonance heating system for EAST

YANG Yong

2021, 41(3):  234-239.  DOI: 10.16568/j.0254-6086.202103007

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The design of the central controller of electron cyclotron resonance heating (ECRH) system based on FPGA chip is introduced. The processing and control logic of the central controller's input total control trigger signal, plasma current signal, ECRH system status signal, high-voltage power output status signal, wave output status signal, various stop signals, and each output control signal are described. The FPGA program is timed simulation. The simulation results show that the controller can respond to the total control trigger signal in real time, accurately control the switching of the cathode and anode high-voltage power supply, handle various abnormal conditions, meet the control requirements of the ECRH system, and is highly reliable.

Evolution of W/Fe interfacial microstructure and shear performance for W/Fe/RAFM-steel joint in process of normalizing and tempering heat treatment

HUANG Pan, WANG Yi-ming, CHEN Ji-ming, WANG Ping-huai

2021, 41(3):  240-246.  DOI: 10.16568/j.0254-6086.202103008

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Normalizing and tempering heat treatment were carried out for the HIP bonded W/Fe/RAFM-steel joints to recover the microstructure and properties of the RAFM-steel. The evolution of W/Fe interfacial microstructure were analyzed by Electron Probe Micro-analyzer (EPMA) and Grazing Incidence X-ray Diffraction (GIXRD), the evolution of bonding performance for the joint was characterized by Shear Test and Scanning Electron Microscope (SEM). The results showed that after normalizing heat treatment, the C element in RAFM-steel diffused into W/Fe interface and the content of W and C in Fe₂W phase was increased, which increased the shear strength of the joint. While the strengthening of Fe interlayer led to a shorter shear displacement. After tempering heat treatment, a W/Fe₂W/Fe3W3C/Fe interfacial structure was formed at W/Fe interface. As its composition of Fe₂W phase and strength of Fe interlayer were almost the same with the HIP bonded joint, the shear performance of the joint at room temperature was almost the same with the HIP bonded joint.

Research on HL-2M timing synchronization network  based on precision time protocol

LIU Pan-le, REN Lei-lei, ZHANG Jin-hua, LUO Cui-wen, ZHAO Li

2021, 41(3):  247-251.  DOI: 10.16568/j.0254-6086.202103009

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According to the requirement of timing accuracy of HL-2M tokamak and referring to the design scheme of ITER, the HL-2M timing synchronization network based on precise time protocol is designed, the accuracy of clock synchronization and event triggering of HL-2M tokamak is improved from microsecond level to sub-microsecond level, and is ultimately better than 100 nanoseconds.

Study of pulse-step-modulation high voltage power communication and feedback control system

CHEN Yong, WANG Ying-qiao, LI Hua-jun, LI Wei-bin, YAO Lie-yin, LI Chun-lin

2021, 41(3):  252-257.  DOI: 10.16568/j.0254-6086.202103010

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A high voltage pulse supply control system was developed to control HL-2A pulse-step-modula-tion (PSM) high voltage supply of the secondary heating system. The power supply control system of PSM adopts DSP and FPGA combination control mode, with a total output of 112 pulses. DSP chip realizes the functions of calculation, feedback and remote communication. FPGA is mainly responsible for data transmission with DSP and timing control function of 112 channel pulse output. The CAN bus is used to realize the remote communication between the host computer and DSP, and the LABVIEW software is used to realize the setting of relevant parameters and remote communication. The test results show that the control system can realize remote communication with rapid feedback control function, and meets the experimental requirements.

Structural design of vacuum vessel system of a high heat flux test facility #br#  for divertor components of fusion device

LI Bo, MAO Xin, XU Shu-ling, SHEN Jun-song, YIN Zhou, LI Qiang, WANG Wan-jing, LEI Ming-zhun

2021, 41(3):  258-263.  DOI: 10.16568/j.0254-6086.202103011

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The structural design of a high heat flux test facility for divertor components of fusion device, including vacuum vessel, vacuum pumping system, manipulator, small-scale water-cooling system, electronic gun operating platform and so on, is carried out. The rationality and reliability of vacuum vessel structure has been verified through Ansys software. The simulation results show that the max temperature of vacuum vessel outer wall is less than 50℃, and the maximum stresses of vacuum vessel and its support are 134.49MPa and 48.76MPa respectively, meeting the allowable stress intensity requirement (3S_m=620MPa).

Spreading test platform and preliminary experiment of liquid lithium limiter

WANG Ze-hui, LIU Bai-qi, YANG Juan-cheng, CHEN Long, NI Ming-jiu

2021, 41(3):  264-269.  DOI: 10.16568/j.0254-6086.202103012

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A liquid lithium limiter test platform with the same mechanical interface of EAST is designed to study the spreading characteristics of liquid lithium on the limiter. The vacuum pressure of the platform is less than 10^-4Pa and the temperature is up to 350℃ for working conditions. An external horizontal magnetic field with a maximum strength of 2T coupled with a vertical direct current up to 400A is used to generate the electromagnetic force to drive the flow of liquid lithium in the loop. The spreading characteristics of liquid lithium on the limiter surface are captured from two visual windows in the top and front of the platform. Basing on this platform, a new designed liquid lithium limiter with dual-channel is tested to study its surface spreading characteristics under different temperature and driving current. The present results show that the lithium flow rate and the limiter surface structure are two main factors that influence the spreading characteristics of lithium on the limiter surface.

Design of high voltage pulse power supply for compact torus injector

HUANG Lian-sheng, LAN Tao, HE Shi-ying, WANG Ze-jing, CHEN Xiao-jiao, CHEN Chen, ZHUANG Ge, KONG De-feng, ZHANG Shou-biao

2021, 41(3):  270-273.  DOI: 10.16568/j.0254-6086.202103013

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The theoretical model of the discharge circuit and the simulation analysis of Simulink are used to guide the design of Compact Torus Injector (CTI) high-voltage pulse power supply. The discharge experiments are performed on the CTI. The experimental results prove that the designed CTI high-voltage pulse power supply can generate a target current of 100 kA at a specific frequency, which guarantees the power supply requirements of the CTI molding field and acceleration field electrodes.

Study on performance of the vertical field coil under different connection modes

XIE Fei, WANG Xian-wei, JIN Huan, JIANG Lei

2021, 41(3):  274-279.  DOI: 10.16568/j.0254-6086.202103014

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The temperature distribution of the vertical field coil, caused by ohmic heat and plasma irradiation, is carried out based on thermal-structural coupling analysis, and the electrical parameters of the vertical coil under different connection modes are analyzed. Consequently, an optimal coil connection mode is proposed. The calculation results indicate that the optimized scheme is helpful to improve the coil response and the plasma control.

Non-Fusion Plasma Applications

Low-pressure copper vapor plasma induced by direct current supply

YAN Dong-xiao, LI Zhan-xian, CUI Ya-shuo, YU Jiang-tao

2021, 41(3):  280-283.  DOI: 10.16568/j.0254-6086.202103015

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 The atomization and excitation ionization processes in atomic vapor laser isotope separation technology are realized by direct current supply and copper plasma stabilized jet is obtained by using solder short circuit cathode and anode under low pressure. Under the pressure of 10^-3Pa and power of 0.9kW, the volt-ampere characteristic curve and spectral intensity diagram of stable discharge were measured. It was obtained that the electron density was about 109 cm^-3 and the electron temperature was about 0.69eV.

Discharge mode analysis of pulsed chemical HF laser system

YANG Nan-nan, ZHANG Jia-liang, ZHAO Yong-li, , LI Guo-fu, WEN Xiao-qiong

2021, 41(3):  284-288.  DOI: 10.16568/j.0254-6086.202103016

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The pulsed discharge mode of SF₆-C₂H₆ mixtures was investigated using plane electrode configuration assisted with pre-ionization spark array on the cathode. The results show that self-sustained volume discharge (SSVD) and arc discharge could occur and transform for different discharge conditions. The SSVD current waveform is influenced significantly by charging voltage and pressure instead of the gas mixture ratio and capacitance. The peak of SSVD current relates positively to charging voltage, while negatively to gas pressure, which indicates that synchronous electron avalanches initiated from cathode by the sliding spark and overlapped spatially into SSVD and thus SSVD is essentially Townsend discharge with a avalanche.