Table of Content

15 March 2012, Volume 32 Issue 1

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Plasma Physics

Analysis of characteristic quantities along shock Hugoniot curves

DUAN Yao-yong, GUO Yong-hui, QIU Ai-ci

2012, 32(1):  1-7. 

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Firstly, the equation of state in the form of three-term type which embodies electron-shell structure effect, in combination with the Hugoniot relation, is used to calculate the pressures and temperatures of Al and Ag along the shock Hugoniot curve, and the computational results are compared with the experimental ones and data given by other codes. Secondly, some characteristic quantities including pressure, temperature, mean ionization degree, Fermi degeneracy factor, and effective adiabatic exponent for Be, Al, Fe, Ag, Au and Pb along shock curve are studied systematically and analyzed physically in detail. Finally, the general trends for the characteristic quantities as the function of the compression ratio of mass density are summarized.

Discrete Alfvén eigenmodes in present tokamaks

YAO Long-bao, HU Shuang-hui, WANG Yi-ru, CHEN Shu-ping

2012, 32(1):  8-14. 

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The α-induced toroidal Alfvén eigenmode (αTAE) is investigated upon the operation parameters of JT-60U. The radial s and α profiles (s=rdq/qdr, α=–q²Rdβ/dr) are obtained via the data from experiments. There exists the α maximum, especially in the reversed shear plasmas and high performance configurations, which supports the globally trapped condition of the αTAE in tokamaks. Mutiple branches of αTAEs are found in present tokamaks. Furthermore, the time-variation of αTAE during neutral beams injection presented.  

Numerical analysis of liquid metal MHD flows in rectangular duct

ZHANG Xiu-jie, MAO Jie, Pan Chuan-jie, XU Zeng-yu

2012, 32(1):  15-20. 

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A code has been developed for analyzing MHD duct flows under low magnetic Reynolds number condition based on induced magnetic field formulation. For benchmark of this code, two different cases were simulated, they were electric conductive fluid in rectangular duct with all insulated walls and Hunt's case of conductive walls. Numerical results matched well with Hunt's and Shercliff's analytical solutions, it shows very good accuracy of this code. Finally the case of liquid metal Na-K alloy flowed in rectangular duct with all conductive walls made of 304 stainless steel was simulated utilizing this code, numerical results of velocity profile in the cross section of the duct and MHD pressure drop were compared with our experimental results, the comparison shows they were in good agreement with each other.

Upstream and downstream sheath structures near a metal plate in the flow of a diffusive plasma

ZHENG Yao-bang, MA Jin-xiu, LI Yi-ren, LI Wei

2012, 32(1):  21-26. 

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The potential distributions in the sheath and presheath in the upstream and downstream sides of a metal plate immersed in the flow of diffusive plasma were measured using a fine structured emissive probe. Combining the Child-Langmuir(CL) law and one-dimensional fluid model, the sheath thicknesses and edge electric fields were analyzed. It is shown that the sheath in the downstream side is thicker than that in the upstream side, while the measured edge electric field of the upstream sheath is stronger than that of the downstream sheath. Both experimental and numerical results show that the thicknesses of the CL sheath in the two sides of the plate satisfy a linear relation, with a fitting proportionality of 1.2 between the down- and upstream thickness. The electric field at the CL sheath edge in both up- and downstream sides is consistent with the value given by T_e/(eλ_D), while the measured electric field at the Bohm sheath edge in the upstream side is close to Te/(eλ_D^3/5λ_i^2/5). However, the Bohm sheath edge electric field in the downstream side shows a significant deviation from available models.

Influences on the band gap of time-varying un-magnetized plasma photonic crystals produced by Compton scattering

HAO Xiao-fei, KONG Yin-chang, HAO Dong-shan

2012, 32(1):  27-31. 

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Using the model of multi-photon nonlinear Compton scattering and finite-difference time-domain (FDTD)analysis, the influences on the band gap of time-varying un-magnetized plasma photonic crystals induced by Compton scattering have been studied, and a new mechanism of the photonic band gap induced by the multi-photon nonlinear Compton scattering optical and incident electromagnetism wave has been advanced, and the amending equations of Maxwell equation group on electromagnetic field and the iteration equation have been given out and simulated. The results show that the widths of the plasma band gap are clearly decreased along with the increase of the plasma climb time than before the scattered by the multi-photon nonlinear Compton scattering optical, and these widths will finally be constants. The increases of the transmission crests of the homogeneous distribution plasma are bigger than the increases of the transmission crests of the linear distribution plasma, and the control to the photonic band gap can be reached through using Compton scattering.

Refraction and reflection of obliquely incident electromagnetic wave by inhomogeneous collisional plasmas

YUAN Zhong-cai, SHI Jia-ming, XU Bo

2012, 32(1):  32-37. 

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The effective refractive indices of collisional plasma are proposed, which are adopted to calculate the refractive angles. The angles are compared with those using traditional Snell’s theory and plasma complex refractive indexes. The dependences of discrepancies on plasma electron density and collision frequency are analyzed. The refraction and transporting properties of obliquely incident wave in inhomogeneous collisional plasmas are investigated. As an example, the reflection coefficients of obliquely incident wave by an inhomogeneous plasma slab are calculated and discussed. The results show that the influence of the incident angle is considered in the effective refractive indices of collisional plasma which are suitable to investigate the refraction and reflection of obliquely incident electromagnetic wave by inhomogeneous collisional plasmas.

Nuclear Fusion Engineering and Technology

Development of the microwave components for LHCD antenna on HL-2A tokomak

ZENG Hao, CHEN Gang-yu, BAI Xing-yu

2012, 32(1):  38-43. 

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Based on the even-odd mode theory, wave superposition and impedance matching theory，the microwave components including the 3-dB power splitter and the fixed phase shifter have been designed，then the HFSS has been used to simulate and optimize the parameters of the design. Finally the microwave components have been developed. The test results show that the design is reasonable.

Optimization the heat loads on divertor target plates and first wall with B2.5-EIRENE

CUI Xue-wu, PAN Yu-dong, ZHANG Jin-hua, LI Jia-xian

2012, 32(1):  44-50. 

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The numerical simulation code of B2.5-EIRENE is used to design and optimize of the divertor target plates. The divertor targets geometrical structure influences the neutrals recycling and surface area of the heat loads on the target plates, and further influences the heat loads on the target plates. New designed divertor structures are assessed through analyzing the peak heat loads and the electron and ion heat flux on the target plates, the distribution of total heat loads along the target plates and first wall of the main vacuum chamber.

Preliminary experimental study on the uniaxial-diffusion welding for CN HCSB TBM

ZHAO Zhou, CHEN Mao-ai, WANG Ping-huai, FENG Kai-ming, ZHANG Guo-shu

2012, 32(1):  51-55. 

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Preliminary experimental study on the CLF-1 steel of structural material of CN HCSB TBM was performed using U-DW setup. Experimental results show that the tensile strength and ductility of welding joint are identical with base material if the bonding ratio of joint can reach a certain degree; however the toughness of welding joint is very sensitive, the best testing value is only 48% the corresponding value of base material, which mainly depends on the joint gap defects caused by the sources of the contaminations in the welding surface.

Harmonic analysis of EAST large power fast control power supply

LIU Hui, GAO Ge, FU Peng, HUANG Hai-hong

2012, 32(1):  56-60. 

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The multiple structure of three-level inverter is presented to satisfy the requirement of large current and quick control for the fast control power supply in the EAST tokomak, which applies carrier phase-shift PWM technology to realize multi-inverters parallel. The design scheme is analyzed, and the output harmonic characteristic of parallel inverters is studied, the analytic expression of harmonic of the output voltage is obtained by means of dual Fourier transformation. The simulation and experimental results confirm that the power supply system has a perfect performance on harmonic feature, can supply large current and has ability of fast response.

Design and analysis of the support structure for EAST ICRF antenna

YANG Qing-xi, SONG Yun-tao, SHI Shan-shuang, BIAN Hong-bo, ZHAO Yan-ping

2012, 32(1):  61-65. 

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In view of the vacuum sealing importance and the movable requirement of EAST ICRF antenna, the movable support structure is designed to uphold the weight from the fore part of ICRF antenna. Based on the importance of the support structure of ICRF antenna, the calculations for the support structure using the formula have been carried out at first. Results of calculation are shown the stresses and the deformations of the support rod are varied with different section dimension and different length of the support rod. In addition, finite element method (FEM) was applied to perform structural analysis for the support rod under the same conditions, results of analysis are very similar to the results of calculation using formula and meet the design requirements. The results obtained will guide the optimization design for the EAST ICRF antenna support structures, the methods will be useful reference for the same structure of other device.

Analysis of the stability for Nb₃Sn superconducting magnet

XU Shao-feng, LIU Xu-feng

2012, 32(1):  66-69. 

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The first Nb₃Sn superconducting magnet model coil used in the fusion reactor in China is introduced. We applied a one-dimensional mathematical model (Gandalf) to simulate the superconductor stability of CICC. The relation of stability margin of CICC to magnetic field intensity and operating current is obtained, which is very important to the design and operation of the magnet.

Preliminary analysis of hydrogen risk caused by dust in ITER

CHENG Kun, TONG Li-li, CAO Xue-wu

2012, 32(1):  70-75. 

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A lot of dust will be generated during ITER operation, and hydrogen will be produced by the interaction of hot dust with water in the case of coolant ingress accident. The accumulated hydrogen will bring risk of combustion and explosion, which will damage the device. CFD method has been used to analyze the produced hydrogen in “wet bypass” scenario, and come to the results that hydrogen will burn and explode at the beginning of the accident, different hydrogen risk will be brought by different coolant leakage, and hydrogen risk will be inert if the leakage is massive. Injecting CO₂ to inert the vacuum vessel has also been discussed, the risk of hydrogen will be suppressed by injecting CO₂ with a large rate at the beginning of accident.

Optimizing design of toroidal spectrum for fast wave heating

ZHU Xue-guang

2012, 32(1):  76-80. 

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The progress of research on the antenna system ion cyclotron wave heating is presented, and the spectrum characters of conventional loop antenna, phase controllable double loop antennae and double limb single loop antenna are discussed. The single pass absorption rate is studied by digital simulation of ray tracing scheme, and the relation between single pass absorption rate and toroidal spectrum is obtained. In this way, it is verified for the double limb single loop antenna to have good coupling performance. This antenna’s structure is simple and can be used to improve coupling performance.

Performance measurement and applications of the high-precision digital light source

CHENG Shu-bo, YI You-gen, LIU Meng-si, ZHANG Hui-ge, WANG Zhe-bin, ZHANG Chen

2012, 32(1):  81-86. 

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The high-precision digital light source RS-5B from GMMA company was introduced and its performance parameters was measured. The results show that the spatial distribution of light intensity is very stable. When light intensity is stronger than 0.001μW•cm^-2, the resettability better than 1% and when stronger than 0.01μW•cm^-2, the stability better than 0.5%. The output light intensity and nominal value keep the linear relationship. These excellent parameters and characteristics meet the demands of the calibration source in the calibration test of fusion research and meanwhile provide the conditions for experiment data analysis and computer simulation.

Non-Fusion Plasma Applications

Study of density jump in helicon-wave induced H2 plasma

JIANG Fan1, WU Wei-dong2, GAO Ying-xue3, DAI Yang3, WANG Yu-ying2, CHENG Xin-lu1

2012, 32(1):  87-91. 

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Hydrogen plasmas electron density and electron energy distribution function EEDF were studied with Langmuir probe. Two jumps were observed in the variation of the electron density with the radio frequency power. The relative intensity ratio of hydrogen plasmas spectrum line H_α, H_β and H_γ validated this phenomenon. Two density jumps illuminated the transition of discharge mode, which labeled as capacitive, inductive and helicon-wave mode. In this work, the density jumps are explained from two sides, one is the interaction between electrons and hydrogen molecules, the other is Nagoya type Ⅲ (N-type) antenna-plasma coupling. With the increase of radiofrequency power, the interaction between electron and hydrogen molecule has been enhanced which causes the electron density jumps. The antenna couples well to plasmas when transverse field E_y is maximum, and the wave vector of k_z locates at π/l_a or 3π/l_a, corresponding to the first and second density jump.

Research in luminous efficacy of the mercury free plasma flat panel lamps

LI Jian, WANG Kun, WANG Shi-qing, WANG De-zhen

2012, 32(1):  92-96. 

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Influences of the gas pressures, the gas compositions and gas gaps, the structure and the phosphor printing on the luminous efficacy of the mercury-free plasma flat panel fluorescent lamps were investigated. Marked increments in the luminous efficacy of the lamps were observed by optimizing the conditions. The results showed that the130mm×90mm plasma flat panel fluorescent lamps with a luminance of 11000cd•m^-2, a luminous flux of 500lm and an luminous efficacy of above 40lm?W^-1 could be attained at 450torr pure xenon, 0.7mm gap distance, 2.8mm front glass layer thickness and 60% phosphor pattern printing 20•m layer on the front glass. Higher luminance and higher luminous efficacy were realized by the optimization. The factors influencing the luminous efficacy were discussed.