Nuclear Fusion and Plasma Physics

Radial profile measurement and absolutely calibration of VUV spectroscopy in HL-2A tokamak

CUI Zheng-ying, GAO Ya-dong, FU Bing-zhong, SUN Ping，LU Ping

2011, 31(1): 1-7.

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A vacuum ultraviolet VUV spectrometer with spatial and temporal resolutions was presented in this paper. The sensitivity of the spectrometer has been calibrated in situ by using the VUV bremsstrahlung continuum radiation of the HL-2A plasma. The sensitivity coefficients of two gratings were given. The absolute density profile of carbon radiation was thus obtained based on the absolutely radial profile measurement of carbon radiation.

Linear behavior of double tearing mode mediated by parallel electron viscosity

HE Zhi-xiong, DONG Jia-qi, HE Hong-da, LONG Yong-xin, MU Zong-ze, LIU Feng, JIANG Hai-bin, GAO Zhe

2011, 31(1): 8-14.

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The linear behavior of the double tearing mode (DTM) mediated by parallel electron viscosity in cylindrical plasmas with reversed magnetic shear is numerically investigated. The mode structures and dispersion relations for linearly unstable modes are calculated. A detailed analysis of linear instability characteristics of DTMs with various roles, including the inter-resonance distance, the electron viscosity Reynolds number and poloidal mode number, is performed.

Linear gyrokinetic simulation of trapped electron mode in edge plasma of the HL-2A tokamak

LIU Feng, HE Zhi-xiong, HE Hong-da, DONG Jia-qi

2011, 31(1): 15-18.

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The global gyrokinetic toroidal code (GTC) simulation and the data of HL-2A experiments were used to study the trapped electron mode, search and understand the possible mechanism of the microinstabilities which existed in the edge plasmas of HL-2A tokamak. In the GTC linear simulation, the trapped electron mode (TEM) is strongly unstable and distributes in the week magnetic area regularly in the edge plasma of the HL-2A tokamak. The unstable TEM instability is related with the intensity of density and temperature gradients. The results also shows that the TEM frequency is smaller than the drift frequence. This is in consistent with the theoretical results.

Nonlinear interaction of transverse plasmons with pair plasmas

LIU Yong1, 2, LIU San-qiu1

2011, 31(1): 19-23.

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Nonlinear governing equation for the interactions of transverse plasmons with pair plasmas is derived from the dispersion and fluid equations. Using field theory, Lagrangian density function for the nonlinear equation is constructed and the conserved plasmon number and total energy are obtained. By scale transformation, it is shown the multidimensional transverse plasmons will undergo collapse and form a localized structure with small scales due to modulational instability. During collapsing, the ponderomotive force will be enhanced for the increase of the field strength. Eventually, there will be small scale density cavitons which are produced by ponderomotive expulsion.

Numerical study of synergetic effects for electron cyclotron wave and fast wave

ZHENG Ping-wei, GONG Xue-yu, LIU Wen-yan, HE Li-hua

2011, 31(1): 24-27.

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The problem of electron cyclotron wave and fast wave current drive is studied by solving the Fokker-Planck equation in a numerical method for tokamak plasma. Effects of both bounce-averaging and relativity for electrons are considered in the process of solving. The Fokker-Planck equation is discretized by nine points difference technique, and solved by incomplete LU factorization. The results are shown that high synergetic effects are existed by combined current drive of electron cyclotron wave and fast wave, and the size of current density driven by the two waves is higher than total of the two single one.

Photonic band gap properties of magnetized plasma photonic crystals by the applied magnetic field based on the transverse magneto-optical effect

LIU Song 1, LIU Shao-bin2

2011, 31(1): 28-32.

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The photonic band gap (PBG) structures of plasma-based photonic crystals (PPCs) can be turned after adding a perpendicular magnetic field. The PPCs consisting of intrinsic plasma layers and other dielectric material layers stacked alternately, is taken as an example in studying photonic band gap structures and transmission spectra within the magnetic field using finite-difference time-domain algorithm. The numerical results illustrate that the dielectric constant of the plasma is modified differently in different frequency ranges and the PBG characteristics of the PPCs are turned correspondingly.

Preliminary result of dust investigation on HL-2A tokamak

HUANG Zhi-hui, LIAN You-yun, HONG Wen-yu, YAN Long-wen

2011, 31(1): 33-37.

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Existence of flying dusty objects during plasma discharges was observed by a visible CCD UC-610 camera on HL-2A tokamak, and morphologies and impurity elements of irradiated graphite samples have been analyzed by scanning electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDX), respectively.

Influence of granular growth in plasma by multi-photon nonlinear Compton scattering

PI Xiao-li, SUN Fu-zhao, HAO Dong-shan

2011, 31(1): 38-42.

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Using the model of the granular growth in the plasma and the model of the multi-photon nonlinear Compton scattering, the influence of granular growth by the multi-photon nonlinear Compton scattering has been studied. A new mechanism of the granular growth formed by the incident light and the multi-photon nonlinear Compton scattered optical has been given out. The formulas of the coagulation section of granular, coagulation coefficient, the electron current and ion current collected by the granular have been revised. The result shows that the changes of the plasma parameter have the relations with the inelastic scattering composition between electrons and multi-photon groups, the initial speed of the electron before the scattering, its incident angle and the photon numbers of the action at the same time with electrons, et al. The mechanisms of the collecting ions and coagulation are increased by the scattered. The coagulation section and radius rate of rise of the granular are increased, and the granular radius is quickly and no-evenly increased.

The experimental method of measurement for spatial distribution of full aperture backscatter light by circular PIN-array

ZHAO Xue-feng, WANG Chuan-ke, KUANG Long-yu, WANG Zhe-bin, LI San-wei, LIU Shen-ye, JIANG Gang, HU Feng

2011, 31(1): 43-47.

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The spatial distribution of backscatter light is very important for understanding the production of backscatter light. The experimental method of spatial distribution of full aperture backscatter light is based on the circular PIN array composed of concentric orbicular multi-PIN detectors. The image of backscatter light spatial distribution of full aperture SBS is obtained by measuring spatial distribution of full aperture backscatter light using the method in the experiment of laser hohlraum targets interaction at “shenguang II”. A preliminary method to measure spatial distribution of full aperture backscatter light is established.

Design of TE10 taper in the LHCD antenna for HL-2A tokamak

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

2011, 31(1): 48-52.

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Based on PAM, the 3-dB power splitter, the mode converter, the coupler and the water load are developed into an integrated module. The coupled wave thoery is used to design the TE₁₀ taper. The parameters is optimized with HFSS code. Finally the results are obtained, the length is 370mm; the VSWR is 1.0012 and the reflection loss is -65.81dB。

Optimization of the ICRH antenna design for tokamak

DU Dan1, GONG Xue-yu2, LIU Wen- yan1, LI Wei-jun1, YIN Lan1, CHEN You1

2011, 31(1): 53-56.

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The coupling of the ICRF antenna to the plasma in tokamak is studied by using a plasma slab model and a three-dimensional antenna model. The simulation results show that under the same conditions, the antenna of symmetric current distribution and a long feeder may have more effective power coupling than the antenna of antisymmetric current distribution and a short feeder.

Design and simulation for the support legs of the ITER transfer cask system

LI Shao-qing1, CAO Lei2, LI Ge2

2011, 31(1): 57-61.

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Based on the virtual prototype technology, a new concept design of support leg for ITER transfer cask was introduced. The support legs on the transfer cask system have to withstand Max 50t loads and can adjust their height on the distance of 150mm. The results of kinematical simulation and FEM analysis showed that the designed mechanism could not only meet the required functions but has very good characters like unchanged load and linear relation of control variables.

Correction of poloidal field coils and magnetic diagnostic system on EAST

YANG Shu-kai, XIAO Bing-jia, LUO Zheng-ping, GUO yong

2011, 31(1): 62-67.

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An efficient method is given to correct the position and scales of poloidal field coil, flux loop, magnetic probe by using meshes to calculate magnetic field and least square approximation. The result reduces the different between calculated data and experiment signal. And then it provides a more accurate green function for equilibrium fitting algorithm.

Finite element analysis of bottom correction coils structure for ITER

CUI Xiang-bin, NIU Zhong-rong, CHEN En-wei, TONG Yong-yao, LIU Zheng-shi, WU Wei-yue

2011, 31(1): 68-74.

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The mechanical property of the bottom correction coils(BCC) structure in ITER was analyzed by finite element method (FEM). A strategy by combining the simplified profile BCC structure model and the partly entire profile model was proposed for the considerable difference in the three-dimension size of the component in the BCC structure. The displacement fields and stress fields in the BCC structure and the results of every material in the weak region were obtained by FEM. On the other hand, the method determining the pretightening forces in the bolts of support components was proposed for the BCC structure and the rational pretightening forces of bolts were obtained by FEM. The pretightening forces will be used in installing the BCC structure.

External n=1 magnetic field system on SUNIST spherical tokamak

JIANG Yan-zheng1, ZHONG Fang-chuan1, WU Yan-bin1, TAN Yi2, ZENG Long2, GAO Zhe2

2011, 31(1): 75-80.

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An external n=1 magnetic field system is set up on the spherical tokamak SUNIST, in order to research the MHD instability control. The power supply of this system could steadily and reliably generate a specified discharge, which could reach the highest value in 1ms and keep a 3ms current platform, meanwhile the current could shut down instantly. Experimental results demonstrate that this system could create a majority of n=1 mode magnetic field at the centre of vacuum chamber, which is an essential foundation for the researches of controlling MHD instability.

Interdigital cavity filter design

CHEN Li-yan, LIU Fu-kun, SHAN Jia-fang, JIA Hua, LI Jun

2011, 31(1): 81-84.

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The lower hybrid current drive system will be interferenced by jamming signal in the EAST experiment site, so a interdigital cavity filter with passband centered at 2.45GHz is designed to repress the jamming signal.This paper gives the particular description of a theoretical analysis and practical design for interdigital cavity filter, and the filter is simulated by HFSS-software which greatly improves the efficiency and accuracy of the design.

Molecular Dynamics Simulation of incident energy effects of H2+ interactions with SiC surface

SUN Wei-zhong, ZHAO Cheng-li, LIU Hua-min, ZHANG Jun-yuan, Lü Xiao-dang, PAN Yu-dong, GOU Fu-jun

2011, 31(1): 85-90.

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Molecular dynamic simulations were performed to study H₂⁺ ions bombarding SiC with incident energies of 1, 5, 10 and 15eV. The simulated results show that the retention of H atoms on the surface increases with increasing energy. During the initial stage, the amount of retention H atoms sharply increases and then the retention of H atoms reaches saturation. Si and C atoms are removed from the surface with energies of 10 and 15eV. The number of removed Si atoms is larger than that of C atoms. For the products, H, H₂ and SiH₄ are dominant. And with increasing incident energies, the number of H₂ species decreases and the other species increase.

Research of extraction mechanism for microplasma reactor

WANG Hai, TONG Yun-hua, WEN Li

2011, 31(1): 91-96.

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An extraction mechanism based on micronozzle in the bottom of the microhollow cathode and applied bias electrical field is proposed, and digitally simulated with a two dimensional fluid model. When the operating gas is SF₆and its pressure is 2~9kPa, radius of the micronozzle is 0.25μm, maximum F atom flux density is between (1.53~5.62)×10¹⁴cm^-³·s^-1, maximum SF₅⁺ flux density is between (2.46~7.83)×10¹⁶cm^-³·s^-1. When gas pressur is 5kPa,average energy of F atom at sample surface is 3.82eV, dispersion angle is −14º~14º; average energy of SF is 25eV, dispersion angle is −13º~14º. When applied voltage across hollow cathode and sample is between 10~50V (sample as cathode), average energy of SF is between 52~58eV. The density of F and SF in the simulation result could satisfy the requirement for silicon etching, and the feasibility of scanning plasma etching validated.

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