Table of Content

15 December 2008, Volume 28 Issue 4

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Plasma Physics

Experimental investigation on MHD instabilities of free surface jet and film flow for liquid metal divertor/limiter options

XU Zeng-yu, PAN Chuan-jie, KANG Wen-shan

2008, 28(4):  289-292. 

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The experiments of liquid metal (eutectic alloy NaK) free surface flows, which involve jet and jet-film flows crossing one-dimension gradient magnetic field, are conducted at SWIP LMEL facility and are reported. The objective of this study is to understand the magnetohydrodynamics (MHD) features of liquid metal (LM) free surface flows and to supply the options of LM divertor/limiter. It is observed that jet flow is in a stability-shortened and fatten structure, and jet-film flows are in three different structures, or laminar, rivulet and turbulence. In the point of MHD effect, four-type structures of free surface flow are drawn up for the LM divertor/limiter design options; and then a discussion on physics understanding is presented.

Transmission characteristics of the kinematics of the high power laser-plasma wave in solid under Compton scattering

HAO Xiao-fei, HAO Dong-shan

2008, 28(4):  293-297. 

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Using the model of inelastic scattering between electron and photon-groups, we have studied in the frame of quantum mechanics the transmission characteristics of the kinematics of the coupling laser-plasma wave, this is formed by the scattered light, the incident light, the electron vibration radiation wave and the high frequency branch of ILOTW (ion long optics transverse wave) in solid under nonlinear Compton scattering. The results show that the transmission velocity of the electromagnetism coupling phonon in the laser-plasma in the sold is raised along with the increase of the magnetic field intensity，the decrease of the electron screening action and the decrease of the plasma vibration frequency. But this increase of transmission velocity is resisted by the scattering light, and will be slowly reduced.

Detachment characteristics with gas puffing and fuelling in the HL-2A tokamak

HONG Wen-yu, YAN Long-wen, CHENG Jun, ZHAO Kai-jun, QIAN Jun, WANG Ming-xu

2008, 28(4):  298-302. 

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The detachment characteristics has been achieved in the H-2A detached divertor experiments, in which the supersonic molecular beam injection (SMBI) and gas puffing have been used to increase the main plasma density，to reduce the edge electron temperature and to increase the radiated power density, meanwhile, the fixed flush 3-probe arrays have been mounted on the 4 divertor neutralization plates to measure the profiles of the electron temperature, the electron density and the float potential. The detachment plasmas is obtained with SMBI for the first time in the HL-2A tokamak. The experimental results provide important physical parameters to investigate radiation divertor, detached divertor, as well as the abilities of impurity resident, concentration and removal efficiency.

Electron heating through fast wave mode conversion

ZHANG Xin-jun, ZHAO Yan-ping, QIN Chen-ming

2008, 28(4):  303-308. 

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By using full wave method, the mechanism of electron heating through fast wave mode conversion in general toroidal axial-symmetric tokamak plasma is discussed, and then the scenarios in the future EAST ICRF experiments are simulated. The results are very beneficial for optimizing the EAST ICRH performances.

EAST plasma boundary reconstruction based on active contour model

LIU Lian-zhong, XIAO Bing-jia, LIU Cheng-yue, SHU Shuang-bao

2008, 28(4):  309-313. 

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By analyzing the iso-flux feature of edge plasma and making use of active contour model, the plasma boundary was re-constructed; the contour energy, the algorithm steps, the method of edge-flux calculation and the method of initial-contour definition were introduced. Compared with EAST experimental data, this method shows a favorable accuracy and high real-time performance.

Study on electron density and average degree of ionization for the non-ideal argon plasmas

JIANG Ming, ZHOU Yi-su, WANG Cai-xia, HUANG Hua

2008, 28(4):  314-317. 

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Electron density and average degree of ionization of the non-ideal argon plasmas under different plasma temperature and density are calculated by using SHM model. It comes to a conclusion that the average degree of ionization is less than 0.5 for the non-ideal argon plasmas at temperature T≈ 2.0eV and plasma density ρ≈ (0.01~0.5)g•cm^-3, and the average degree of ionization is reduced with the increase of plasma density ρ. This indicates that the non-ideal argon plasma has a very low degree of ionization so that most argon has not been ionized. In addition, the discussion on the ionization decrease with the increase of plasma density ρ is given.

Nuclear Fusion Engineering and Technology

FEM static analysis of ITER overall gravity supports

JIAN Guang-de, LI Peng-yuan, HOU Bing-lin, WANG Ai-ke

2008, 28(4):  318-323. 

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The static structural analysis of the ITER (international thermonuclear experimental reactor) overall gravity support is performed by using the ANSYS software of finite element method (FEM); and the stress distribution and displacement under the loads of magnet dead weight, thermal load, seismic load and electromagnetic force are obtained. The maximum stress intensity and maximum displacement of overall gravity support are within the allowable stress limit and displacement limit. This provides an important reference basis to optimize the ITER overall gravity support.

Real-time measure and control of MHD on the HT-7 tokamak

MAO Jian-shan, LUO Jia-rong

2008, 28(4):  324-327. 

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The MHD instabilities can be suppressed real-timely with the method of initiative feedback modulating low hybrid waves (LHW) in the HT-7 experiments. The implement of the real-time measure and control of MHD with DAQ2010 data acquisition card on the HT-7 tokamak is introduced.

Design of the H-bridge high current fast control power supply

WANG Ying-qiao, YAO Lie-ying, XUAN Wei-min, XU Wei-dong

2008, 28(4):  328-332. 

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The preliminary scheme of the H-bridge power supply of the fast radial field of the new machine (the modified device of HL-2A) is introduced, which includes the simulation of operation mode of the fast power supply, the selection of switching components and the way of improving the static current sharing for paralleled IGBTs. The experiment results show that the current sharing can be improved by adjusting the layout and the parameters of circuit, and the mismatch rate of paralleled IGBTs can be reduced from 16.5% to 6.8%. In addition, the maximum power loss is calculated and the cooling method of IGBT is given.

Quench-protection system design and analysis of superconducting dipole magnet for FAIR

LONG Feng, LIU Fang, SHI Yi, WU Yu

2008, 28(4):  333-336. 

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The methods of balancing-bridge voltage quench detection and protection in the superconducting dipole magnet experiments are introduced. The quench-detection circuit is analyzed and the principle of voltage quench-detection by means of balancing-bridge is brought out.

Design and application of power supply distributed-control for accelerating pole

BU Ying-nan, XUAN Wei-min, YAO Lie-ying

2008, 28(4):  337-341. 

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To achieve the distant management and supervisory control of NBI (neutral beam injection) accelerating-pole power supply in HL-2A tokamak, the distributed-control system is designed under ethernet, in which key components are composed of PC-104 embedded industrial computer, numerical interface card, and analogy interface card as well as control software. The design requirements of the control system including hardware and software are proposed to guarantee the operation of NBI accelerating-pole power supply system, and then a discussion of “how to realize the distributed control strategy” is given. The experimental results show that the control system not only satisfies the distant management and real-time control, but also ensures the stability of power supply and improves the experiment level.

Design of arcing protection for ECRH system on the HL-2A tokamak

WANG Xue-yun, LI Bo, ZENG Jian-er

2008, 28(4):  342-346. 

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ECRH arcing protection system consists of arcing detector, A/D converter and logical processing unit. The response time of the arcing detector is less than 2μs, and the response time of the A/D converter and logical processing unit is less than 1μs. The system could switches off all related power supplies within less than 20μs from outputting the protection signals.

Double seal door design and analysis for ITER transfer cask

CHENG Tao, LIU Chang-le, YAO Da-mao

2008, 28(4):  347-351. 

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The design concept of double seal door (DSD) for ITER transfer cask was introduced and the 3-D model design was performed in three typical regions, such as upper port, equatorial port and divertor port. The numerical analysis and optimization for some typical components were carried out based on finite element method (FEM) by using ANSYS code. The rescue scheme of DSD was discussed and this could benefit a little for the future engineering implementation.

Central control system for the EAST tokamak

SUN Xiao-yang1, LUO Jia-rong1, 2, JI Zhen-shan1, WU Yi-cun1

2008, 28(4):  352-356. 

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The architecture, the main function and the design scheme of the central control system and the collaboration system of EAST tokamak are described. The main functions of the central control system are to supply a union control interface for all the control, diagnoses, and data acquisition (DAQ) subsystem and it is also designed to synchronize all those subsystem.

Application of three-level large power paralleling inverter in EAST system

HUANG Hai-hong1, GAO Ge1, FU Peng1, WANG Hai-xin2, YAN Shi-chao1

2008, 28(4):  357-361. 

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The multiple structure of carrier phase-shift three-level inverter is presented to meet the requirement of the large-current fast control of plasma displacement in EAST superconductor tokamak, which can realizes the parallel operation of multi-converters, the enhancement of equivalent switch-frequency control of converters and the improvement of current control. To verify the design idea, the design scheme and control method are analyzed and the simulation based on Matlab is carried out. The experimental result confirms the validity of the proposed scheme and the control strategy，and the fine capacities of supplying large current and fast response.

Non-Fusion Plasma Applications

Dynamics model and theoretical calculation of tritium enrichment by Pd-Ag membrane electrolysis

XIE Bo, HU Rui, LIU Yun-nu

2008, 28(4):  362-367. 

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A dynamics model is established to simulate the tritium enrichment process and to optimize the electrolysis parameters in the Pd-Ag alloy membrane electrolytic cells, and then the theoretical calculation is performed and compared with the experimental results. The analysis shows that the behavior of tritium absorption, desorption and enrichment depends on many conditions, besides a fine seal property, the Pd-Ag membrane electrolytic cell consists of at least three sub-systems: the tritium water circuit, the anode gas eliminating facility and the cathode tritium recovery facility. In addition, a cascade design could improve the separation performance of the device. It is found that higher electrolysis temperature, stable OH^- concentration, suitable current, reasonable thickness and metallographic structure and strictly-deposited palladium black for membrane, are demanded.

A tunable radio-frequency magnetic probe

YUAN Guo-yu, GAO Wei, DING Zhen-feng

2008, 28(4):  368-374. 

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A tunable center-tapped transformer is proposed to improve the sensitivity of an RF (radio-frequency) magnetic probe. The transformer involves two variable capacitors: one is parallel with the primary winding and another is in series with the secondary winding. In addition, a planar faraday shield, which consists of two discrete slotted metal plates, is installed between two windings to suppress the electrostatic coupling. It is found that the capacitive coupling of the probe is effectively reduced and the resonance of the probe output voltage can be achieved by tuning the parallel or the series capacitor. It is also found that the resonant output-voltage obtained by tuning the parallel capacitor is larger than that with the series capacitor, and the largest output under typical conditions is higher than the conventional probe by one order of magnitude. A circuit model of the tunable RF magnetic probe is established and the calculation results are in good agreement with the measurements.

Analysis of the absorption property of low power laser in underdense cold plasma

YUAN Zhong-cai1, WANG Long2, SHI Jia-ming1, HUANG Yong1

2008, 28(4):  375-378. 

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The laser energy absorption in underdense cold plasma, where the electron density is much lower than the critical value corresponding to the incident low power laser, is very different from that of the hot plasma with high electron concentration. In this plasma, the collision frequency between electrons and neutral particles is dominant and much greater than that between electrons and ions. This results in the change of the character of collision absorption, and therefore the collision absorption of low power laser in the band of visual light and infrared is negligible because of the low electron density and the low collision frequency. However, the effects of abnormal absorption mechanism need to be studied deeply.

Nuclear Fusion and Plasma Physics Vol.28 ( 2008 )

2008, 28(4):  379-384. 

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