Table of Content

15 March 2004, Volume 24 Issue 1

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Propagation of MHD modes in the HL-1M tokamak

YANG Qing-wei, DING Xuan-tong, HONG Wen-yu, YAN Long-wen

2004, 24(1):  1-6. 

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The purpose of this paper is to describe the features of propagation of the MHD instability modes observed in the HL-1M tokamak experiments．Through investigating the propagation features of the MHD modes the relationship between MHD mode propagation and plasma rotations is studied in detail at different discharge conditions with ohmic Lmode and H-mode discharges induced by biased electrode． 

Measurement of superthermal electrons during ECRH in the HL-1M tokamak

YANG Jin-wei, ZHANG Wei, ZENG Qing-xi

2004, 24(1):  7-10. 

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Experimental results of electron cyclotron resonant heating in the HL-1M tokamak show that a large number of superthermal electrons appear during ECRH．From the spectra of soft X-rays and medium energy X-rays in the energy range of 15～150keV, measured with a Si（Li） drift detector and array of HgI₂ semi-conductor detectors,the temper-ature of superthermal electrons is in the range of 30～60keV,up 30％～40％ during ECRH．Measurement results of X-ray flux indicate that the deposition of energy of ECRH is local, and the superthermal electrons have no effect on the mode of MHD．


Stabilization of tearing mode by current drive

WANG Zhong-tian, SHI Man-li, MAO Guo-ping, ZHAO Shan-zhong, ZHENG Xiao-hu

2004, 24(1):  11-14. 

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The major disruption limits the operation of present tokamaks．Experimental evidences point out that the growth of tearing modes or the magnetic islands is primarily responsible for the occurrence．Taking the non-inductive current drive effects into account, a set of 3D nonlinear equation is derived．It is shown from simulation that the growth of the magnetic island is suppressed effectively by RF current drive．It is consistent with recent experiments on the HL-1tokamak in which the plasma is stabilized by an RF current drive．

Calculation of DD thermonuclear fusion neutron yield and flux in the HL-2A tokamak

LI Wen-zhong, YANG Jin-wei, ZHANG Wei, ZENG Qing-xi

2004, 24(1):  15-18. 

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Based on an advanced MCNP3B code with the Monte-Carlo method‚the yield and flux of DD thermonu-clear fusion neutrons in the HL-2A tokamak have been calculated．For the branch of DD fusion D＋D→P＋T , when only 10％ tritium in the D（D, p） T fusion reacting with deuterium D（T , n）⁴He fusion occur , the yield and flux are higher than that of pure D（D , n）³He fusion．The results of calcultion provide basis for developing new detection systems of fusion neutron, and neutron radiation protection．

Magnetohydrodynamic instability analysis of liquid metal free-surface jet flow （II）

XU Zeng-yu, XUE Shi-hua, KANG Wei-shan, PAN Chuan-jie, ZHAO Huai-guo

2004, 24(1):  19-23. 

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The magnetohydrodynamic instability has been analyzed with the differential analysis method for liquid metal free surface jet flow both in transverse nonuniform magnetic fields BT and Br．Calculation formulas for velocity of the jet flow in its path are obtained．The jet flow will have a cordage shape in the magnetic fields．


Study of the graphite components in the HL-2A tokamak

WANG Ming-xu, XU Zheng-yu, CHEN J-i ming, WU J-i hong, YAN Long-wen, BAI Gang-yi

2004, 24(1):  24-28. 

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The first wall in the HL-2A tokamak consists of the graphite components, the divertor plates made of Cu and the internal surface of the vacuum vessel made of AISI304L stainless steel．The weight of the graphite components is 44kg, the cover area is 2．8m² and the cover fraction is 2．2％．The preconditioning of the graphite components in the HL-2A tokamak is very important, because the graphite components have experienced various experiments and have been exposed in air for a long time．We describe the experimental results for EK98, SMF-800 graphite, CFC material used in ASDEX,CFC material made in China, and the preconditioning of the graphite components of the HL-2A tokamak and its effects．


Nuclear physics for nuclear fusion

LI Xing-zhong, LIU Bin, WEI Qing-ming, REN Xian-zhe

2004, 24(1):  29-32. 

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The D-T fusion cross-section is calculated using quantum mechanics with the model of square nuclear potential well and Coulomb potential barrier．The agreement between ENDF data and the theoretically calculated results is well in the range of 0．2～280keV．It shows that the application of Breit-Wigner formula is not suitable for the case of the light nuclei fusion reaction．When this model is applied to the nuclear reaction between the charged particles confined in a lattice, it explains the “abnormal phenomena”．It implies a prospect of nuclear fusion energy without strong nuclear radiations．


Time evolution of artificial plasma cloud

LU Qi-ming, YANG Wei-hong, LIU Wan-dong

2004, 24(1):  33-38. 

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By analyzing the time evolution of an artificial plasma cloud at high altitude‚we found that there are two zones, exponential attenuation zone and linear attenuation zone,in the spatial distribution of electron density of artificial plasma clouds．The plasma generator’s particle flux density only contributes to the exponential attenuation zone,and has no effect on the linear attenuation zone．The average electron density in linear attenuation zone is about 10^－5 of neutral particle density, and can overcast wider area．The conclusion will be valuable to the research of electromagnetic wave and artificial plasma interaction, the plasma invisibleness research of missile and special aerocraft,and the design of artificial plasma source．


Influence of the interaction of ions-dust grains on ion acoustic wave and dust acoustic wave

HUA Jian-jun, LIU Jin-yuan, MA Teng-cai

2004, 24(1):  39-42. 

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Based on a set of hydrodynamic equations and a linear time-dependent perturbation theory, the influence of the interaction of ions-dust grains on ion acoustic wave IAW and dust acoustic wave DAW in dusty plasma is analyzed．The results show that the interaction makes IAW more stable and DAW less stable．


Research on the thermal efficiency of a DC non-transfer arc plasma torch

YAN Zhi-jun, GAO Yang, AN Lian-tong

2004, 24(1):  43-48. 

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A mathematical model is presented to describe the fluid flow, the electromagnetic, heat flow phenomena in an arc plasma torch we constructed．A computing program has been developed to simulate the different factors that influence on the thermal efficiency．The results show that the thermal efficiency of the torch increases with the increase of the gas flow rate, the nitrogen or hydrogen content and decrease of the length of torch．The current and diameter of the torch have no obvious effects on the thermal efficiency．


Simulative calculation of magnetron injection gun in an mm-wave gyro-klytron

ZHAO Qing, LI Hong-fu, REN Tong, LUO Yong

2004, 24(1):  49-52. 

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The structure and characteristics of magnetron injection gun for mm-wave gyro-klytron are introduced．Properties of electron beam directly affect the parameters of gyro-klytron．In order to get high efficiency and high output
power,a code for the electron gun was used to simulate the electron trajectory, and the influence of electrode shape, magnet field and electron trajectory on the electron beam has been studied．The simulation results became the foundation for the electron gun design．


Numerical simulation of high-frequency slow wave structures of coupled-cavity TWT

YANG Hong, ZHANG Guo-shu, SUN A-i ping, PENG Xiao-dong, CAO Jian-yong

2004, 24(1):  53-57. 

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Numerical simulation of X-band Huges coupled-cavity slow-wave structures （SWS） and Kα-band tunneladder coupled-cavity SWS have been performed by using 3D electromagnetic code MWS and periodic field symmetry model of high frequency structure．The dispersion and coupled impedance in these high frequency structrues are presented．


Power supplies on SUNIST low aspect ratio tokamak

YANG Xuan-zong, FENG Chun-hua, WANG Long

2004, 24(1):  58-62. 

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The electric parameters of toroidal magnetic field coils, ohmic heating systems and vertical balance magnetic field coils of SUNIST low aseptic ratio tokamak were introduced．The capacitor current exchange type quas-i constant current charging system was used for capacitor bank storage energy systems．The discharge currents for these three coils were measured and compared with the circuit calculations．


Measurement of plasma parameters in rf-biased ECR-PECVD

XU Shu-hua, REN Zhao-xing, SHEN Ke-ming

2004, 24(1):  63-66. 

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The plasma parameters in an rf-biased ECR-PECVD have been measured using double Langmuir probes．The effect of microwave power, magnetic electrical curent and gas pressure on the plasma parameters in ECR-PECVD under rf biasing have also been measured．The results indicate that the rf biasing in our dual ECR-rf configuration enhances the electron temperature,but the plasma density is mainly affected by ECR．


The “ droop” method to measure space plasma potential with emissive probes

SUN Qiu-pu, DENG Xin-lu, MA Teng-cai, SONG Yuan-hong

2004, 24(1):  67-72. 

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A method for measuring the plasma potential with emissive probes, the “droop” method, is presented in this paper．The plasma space potential for the microwave plasma source of double “ECR” chamber has been measured in this method．The radial distribution of the plasma space potential and its variation with pressure and the microwave power has been derived∙


HL-2A control system and its discharge management

SONG Xian-ming , LI Qiang, LI Bo, JIANG Chao, FAN Ming-jie, CHEN Liao-yuan, LUO Cui-wen, LIU Li

2004, 24(1):  73-76. 

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The HL-2A control system consists of timing system , PLC logic control system and feedback control system．The hardware and software for these three systems have been introduced , together with the electric parameters of the poloidal coils that are the main controlled objects．The characteristics and function of discharge management software for the HL-2A control system are discussed．The working processes of the HL-2A control system are presented．Finally , the experimental result during the HL-2A tokamak first plasma discharge has been given．


Development of a visualized software for tokamak experiment data processing

CAO Jian-yong, DING Xuan-tong, LUO Cui-wen

2004, 24(1):  77-80. 

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With the VBA programming in Microsoft Excel,we have developed a post-processing software of experimental data in tokamak．The standard format data in the HL-1M and HL-2A tokamaks can be read,displayed in Excel,and transmitted directly into the MATLAB workspace,for displaying pictures in MATLAB with the software．We have also developed data post-processing software in MATLAB environment,which can read standard format data display picture,supply visual graphical user interface and provide part of advanced signal processing ability．