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    15 December 2005, Volume 25 Issue 4
    Contents
    Manufacture and application of fast-scanning probe system in the HL-2A tokamak
    HONG Wen-yu1 , YAN Long-wen1 , CONG Shu-min2, QIAN Jun1
    2005, 25(4):  241-245. 
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    A fast- scanning probe system has been installed in the HL-2A tokamak and is used to measure the edge and scrape-off layer ( SOL) plasma parameter profiles, especially the characterist ic length and fluctuations of local plasma parameters. The system has a compact pneumat ic cylinder and the pneumat ic cylinder can drive a long drive shaft with the probe array. The system can scan a horizontal distance of 8 cm in 60 ms. The SOL and edge plasma parameter profiles with spatial resolution 0. 04 mm have been obtained with a digital grating displacement measurement system.

    The HL-2A tokamak power supply
    XUAN Wei-min, YAO Lie-ying, LI Hua-jun, CHEN Yu-hong,BU Ming-nan, SHAO Kui, MAO Xiao-hui, LI Qing
    2005, 25(4):  246-250. 
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    The HL-2A tokamak power supply is presented. Three flywheel motor-generator ( MG) sets with several converters and high voltage power supplies are used for the magnetic coils and the auxiliary heating. The peak power of the power supply system is 300 MVA and the released energy is 1200MJ per shot. A new control system is implemented.Some experimental results are presented and discussed briefly.

    Numerical investigation on synergetic effects of LHW and FW
    ZHANG Gong-rang, KUANG Guang-li
    2005, 25(4):  251-256. 
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    Using a ray-tracing code combined with a fast two-dimensional relativistic quas-i linear Fokker-Planck solver, the 2D equation is discretized in momentum space using an implicit 5-point stencil and solved using the NAG l-i brary routine D03UAF. Numerical simulat ion of synergy of LHW and FW for the FTU ( Frascati Tokamak Upgrade) plasmas has been carried out. The simulation results show that the LHW power absorption distribution and the LHW driven current distribution depend on the position of antenna where the LHW is emitteed from different point, whether with or without FW, and the effect of LHW on driven plasmas current is obviously changed during the synergy of LHW and FW.

    Simulation and experiment of ohmic power supply operation without circulating current
    WANG Ying-qiao, SHAO Kui, WANG Shu-jin
    2005, 25(4):  257-263. 
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    The basic principle and realization steps of the HL-2A tokamak ohmic heating power supply running with- out circulating current are introduced in this paper. By means of the oretic analysis and simulation, a control scheme that can improve the inversion reliability of the positive thyristor rectifier is given. The control strategy that will be carried out when circulating current appears are discussed. The analysis is proven by the experiment results.

    The structural design of ECRH antenna system for the HL-2A tokamak
    RAN Hong, RAO Jun, ZHOU Jun, ZHANG Jin-song,CHEN Gang-yu, SONG Shao-dong, LIU De-quan
    2005, 25(4):  264-268. 
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    The ECRH antenna system on the HL-2A tokamak consists of shell, ellipsoidal mirror, plane mirror, rotating and pushing mechanism. The plane mirrors can be rotated toroidally and poloidally to heat plasma and drive plasma current in different regions. The variable angle ranges in toroidal and poloidal direct ions are 0°~ 37° and 0°~ 15°, respectively.The relat ions of steering poles and steering angles are presented. The assembly of ellipsoidal mirror and the pushing mechanism are introduced. The ellipsoidal surface equation is also given. The antenna system has compact structure, and can be assembled, disassembled and adjusted conveniently.

    Genetic algorithm simulation for line shape spectroscopy
    SUN Ping, PAN Chuan-hong, CUI Zheng-ying, DING Xuan-tong,WANG Quan-ming
    2005, 25(4):  269-272. 
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    Line shape spectroscopy is a valuable tool both for diagnost ic, and for understanding the basic atomic processes in the boundary region of magnetically confined fusion plasmas. The Dα line profiles are modeled with genet ic algorithm. The modeling profiles are in good agreement with the line profiles obtained in experiment .The results of this analysis suggest that there are one population of hydrogen and three populat ions of deuterium with different temperatures and population ratios.

    Solution of ionization rate equation of light impurities in tokamaks
    CHEN Wei1, YANG Qing-wei2 , LI Wei2 , HU Xi-wei1
    2005, 25(4):  273-277. 
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    Using model of coronal and non-coronal radiation, ionization rate equat ion has been solved respectively. The radiated power of impurity ions varying with time and electron temperature for given the profiles of electron temperature and density is calculated, and the corresponding physics is discussed.

    Study of liquid impedance matching for ICRF on the EAST tokamak
    WANG Peng1,ZHAO Yan-ping1, MAO Yu-zhou1,QIN Cheng-ming1,T Watar i2,R Kumazawa2,T Mutoh2,T Seki2
    2005, 25(4):  278-282. 
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    Two impedance matching systems for ion cyclotron frequency( ICRF) are introduced on the EAST tokamak. One consists of the liquid triple stub tuners, and the other is composed of liquid phase shifter and single liquid stubtuner. The result turns out that the impedance matching can be achieved by using either of the two systems.

    Application of omegatron detector in the HT-7 tokamak edge ion diagnosis
    GAO Wei, LING B-i li,WAN Bao-nian
    2005, 25(4):  283-289. 
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    The configuration of the omegatron detector developed for the HT-7 tokamak is described. The detector has been employed under the condition of ohmic discharges. The detector was located near the limiter and the plasma was introduced into it through a pinhole. The biasing voltages were used to separate the ions and electrons. After being decelerated, the ions enter the cavity and resonate with the superimposing effect of RF electronic field and magnet ic field.Resonant ion current signals have been collected successfully. Analyzing the resonant peak is an effect ive method to acquire the charge-mass ratio and cyclotron frequency of the ions. The resonant peaks of the ions at the charge-mass ratio 1,0.5,0.3333 and 0.1819 were observed in the experiment.

    Design of the arcing detection and protection circuit of diagnostic neutral beam accelerator power supply
    DU Shao-wu 1 , GE Suo-liang 1 , ZHANG Jian 2 , LIU Bao-hua 2 ,HUANG He 3
    2005, 25(4):  290-294. 
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    The accelerator power supply is protected by detecting the di/dt and du/dt , when the power supply is arcing. The protection characteristics of the DNB power supply system are studied. Based on this, the detection circuit of di/dt and du/dt in the power supply arcing and the corresponding protection circuit are designed.Therefore the protection of the accelerator power supply can be achieved in advance.

    A distributed high speed data acquisition system for KT5C tokamak
    SUN Xiang, WANG Zh-i jiang, LU Rong-hua, WANG Jun, YU Yi, ZHU Zheng-hua,WEN Y-i zhi, WAN Shu-de, LIU Wan-dong, YU Chang-xuan
    2005, 25(4):  295-299. 
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    The development of a distributed data acquisition system with low cost to implement high speed data collection through the campus networks for a small tokamak, KT5C, is presented. Data of 512 k bytes at 5MHz from 5 channels for each can be collected during about 10s after three researchers at different positions demand this system for acquisitions. This system realizes long distance multiuser operations, virtually efficiency of the data acquisition is enhanced.

    Spectrum measurement and calculation of electron temperature in glow discharge with equivalent electric potential
    WANG Jian-zhong1, KUI Xiao-yun1, XU Jin-yong1, 2,LIU Yan-ping1 , GAO Yuan1 , XU Zhong1
    2005, 25(4):  300-304. 
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    A series of spectral lines of emissive spectrum with relative intensity in double glow discharge of equivalent electric potent ial under different processing parameters using SII-IV type holographic concave grating monochrometer has been acquired. Electron temperature for different processes was achieved by solving Boltzmann equation. The influence of the work piece voltage and the work pressure upon electron temperature has been analyzed. The results indicate that electron temperature reduced initially, then increased, but reduced again with the work piece voltage increase; and it increased with the work pressure increase in this process. The electron temperature change due to change of work pressure is more great than that of the work piece voltage.

    Numerical simulation of four anodes DC glow discharge by PIC/MCC
    YUAN Zhong-cai, SHI Jia-ming
    2005, 25(4):  305-310. 
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    In order to obtain the characteristics of the plasma generated in the low helium pressure four anodes DC glow discharge, numerical simulation of the discharge using the code OOPIC andMCC has been carried out . Firstly, the OOPIC calculating flow is analyzed and the boundary conditions, the mesh spacing, and the time step in the simulation are presented. Then, the results about the distributions of the plasma density and temperature are analyzed. The results show that, the gas pressure, electrical current, and the virtual breadth of the annular electrode affect the radial distribution of the plasma density and temperature. When the helium pressure is 300Pa, the electrons are distributed equally in almost radial range. But when the pressure is up to 800Pa, radical electron distribut ion varies greatly, and the total density and the average temperature of electron descend. The augmentation of the electrical current makes the plasma density and temperature higher. But the lessening of virtual breadth of the annular electrode makes the radial distribut ion of plasma density more unequal, and the total density and the average temperature lower.

    Experimental study on the ion movement law in corona ionosphere at atmosphere pressure
    BAI Min-di, YANG Bo, ZHOU Jian-gang, GU Jian-long, BAI Xi-yao
    2005, 25(4):  311-314. 
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    Ion movement law in corona discharge at atmospheric pressure has been studied. Experiment results show that ionizat ion electric field intensity, power density and ionization energy density have limited influence upon plasma transport rate in a order of magnitude in the stream or glow discharge area of corona discharge. When the speed of gas is from 5m•s- 1 to 25m•s- 1 with 0. 4mJ•cm- 3 ionization energy density, the transportation rate is from 5. 4  ×108cm- 3•s- 1 to 8 ×1010 cm- 3•s- 1 , almost increases in two orders of magnitude. The effect of momentum of charged particles on concentrat ion and transport rate of ions is far greater than that of electric field, input power density and energy.

    Nuclear Fusion and Plasma Physics Vol. 25 ( 2005)
    2005, 25(4):  315-320. 
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