Nuclear Fusion and Plasma Physics

EM scattering analysis of laser plasma channel antenna in a finite magnetic field

XIA Xin-ren, YIN Cheng-you

2009, 29(2): 97-103.

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The scattering characteristic of an obliquely incident plane electromagnetic wave by laser plasma channel antenna (LPCA) in a finite magnetic field is discussed and the electromagnetic model of LPCA in a finite magnetic field is created. Using the cylindrical coordinate and anisotropic magnetized plasma model, the wave equations of the longitudinal components and the relationships between transverse and longitudinal component are derived, the electromagnetic fields in LPCA and in the medium are given, and the equations of scattering coefficient are deduced. The calculation shows a good agreement with the result given in the reference and a possible application in the study of high power microwave weapon.

Prediction and mitigation of disruption on the HL-2A tokamak

ZHENG Yong-zhen, QIU Yin, ZHANG Peng, YANG Qing-wei, HUANG Yuan

2009, 29(2): 104-110.

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The method of ameliorating the plasma current quench in major disruptions using laser ablation of high Z impurity is described and the preliminary results on HL-1M and HL-2A tokamak are presented. The experimental results show that a resistive, highly radiating plasma can be formed prior to the thermal quench due to the rapidly-increased radiation caused by the high-impurity, both the thermal and magnetic energy are dissipated significantly and thereby the major disruption can be mitigated.

Numerical simulation of ohmic discharges in the HL-2M tokamak

LI Jia-Xian, BO Yu-Dong, ZHANG Jin-Hua

2009, 29(2): 111-115.

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The first ohmic discharge simulation of HL-2M tokamak has been done with TSC (tokamak simulation code) code and the PFC (poloidal field coil) system has been designed conceptually. This simulation achieves a stable configuration evolution from limiter to lower single-null divertor by using the vertical and horizontal displacement feedback and the current feedback. In addition, some key results provide the important reference to the physics and engineering design.

Study of particle transport on HL-2A tokamak

LI Lian-cai, ZHOU Yan, DENG Zhong-chao,YI Jiang, LI Yong-gao, FENG Bei-bin

2009, 29(2): 116-120.

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The plasma particle transport is studied by two different ways of density modulation, gas-puffing and SMBI. The particle diffusion coefficient (D) and convection velocity (v) are obtained by solving the particle balance equation with the finite difference method and Nagashima’s matrix technique, and the relation between the particle transport coefficients and the line-average-density is investigated in the routine ohmic discharge of HL-2A tokamak. Experimental reults show that the direction of particle convection velocity is always inward in the center, the particle transport coefficients (D and v) are larger for the lower line-average-density, and the particle transport coefficients become smaller when the line-average-density is higher.

ECW assited ohmic start-up experiments on the SUNIST spherical tokamak

TAN Yi, HE Ye-xi, XIE Li-feng, GAO Zhe, WANG Wen-hao

2009, 29(2): 121-125.

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The experiments of ECW assisted ohmic start-up performed on the SUNIST spherical tokamak are presented. With the injection of ECW (2.45GHz/20kW/10ms), a small plasma current (<1kA) is initialed by the combination of the induction of vertical field and the asymmetry of the helical field. Consequently, plasma current is rampped up by the ohmic field with a higher speed than those in normal discharges. In this start-up mode, the utilization of volt seconds mainly provided by ohmic field is improved; extra capability of adjusting plasma equilibrium is obtained without any modification to the hardware. The duration of discharge is increased.

Hall effect on energy decay in MHD turbulence

DUAN Shu-chao

2009, 29(2): 126-130.

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The Hall effect, correction to Ohm’s law, on the energy decay of MHD turbulence is studied by using high-resolution numerical simulations, and the energy decay law with t^–1 exponent is derived for the case of small or zero magnetic helicity.

Splitting scheme of tri-temperature equations in studying the collision problems of the compact plasma toroid

WANG Zhen-tao, WANG Shang-wu, XIAO Ya-bin

2009, 29(2): 131-135.

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The 1-D RHD tri-temperature equations, which are critical to the numerical studies of x-ray emission caused by the collision between compact plasma toroid and ideal wall, are formulated and solved from the Lagrange viewpoint and by using the splitting scheme. The implicit method is adopted to solve the electron、ion and photon temperature equations, the splitting scheme is applied to separate the energy-exchange term from others, and then effects on temperatures are investigated.

Simulation on the HL-2A plasma equilibrium response

XIA Fan, CHEN Liao-yuan, SONG Xian-ming, ZHANG Jin-hua, WANG Ying-qiao, LIAO Min, PAN Wei

2009, 29(2): 136-141.

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A plasma equilibrium response model for the HL-2A tokamak is developed based on the laws of Newton and Kirchoff, and then a ohmically-heated plasma of this machine is simulated by using the experimental data and the matlab/simulink platform. The calculation results confirm this plasma equilibrium response model and proved that this model can be applied in the design of the plasma position and shape controller.

Structure dynamic analysis of neutron shielding component for ITER vacuum vessel

LIU Chang-le, WU Song-tao, YU Jie

2009, 29(2): 142-145.

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To study the single-point response of the neutron shielding component of ITER vacuum vessel based on the acceleration seismic spectrum of ITER site, Cadarache, France, the FEM (finite element method) analysis model was made according to its original design concept and the structure features. Modal analysis of the component was performed by using ANSYS, and based on the results, modal superposition was calculated and discussed. The analysis shows different vibrations in the different frequency ranks and the model was response to the lower ranks frequency. However, the stress and displacement was under the permission. Consequently, the assembly one is more reasonable to resist the seismic cases, and the present work maybe contributes a little to the future optimization of component and the engineering realization in next steps.

Two preliminary alternative designs for the gravity support of ITER toridal field magnet

HOU Bing-lin, PAN Chuan-hong, LI Peng-yuan, ZHANG Nian-man

2009, 29(2): 146-151.

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According to the original reference design, the gravity support pedestal (GSP) of ITER toridal field magnet will be very difficult to fabricate because of large vacuum electronic welding, and therefore, two conceptual alternative designs, “split vacuum electronic welding option” and “bolt clamping option”, are put forward. The preliminary buckling analyses with FEM (finite element method) and hand calculation show that there are enough safety margin in two options and both of them are feasible. Even though the “split vacuum electronic welding option” makes the welding easier (in which GSP is split into two halves and thereby no large vacuum-chamber is needed), there are more advantages in the “bolt clamping option” (where no welding is needed), such as the GSP fabrication is simple, the reject rate is low, the cost is much lower, and the producing time is shortened. Comparably, the “bolt clamping option” is strongly recommended.

Thermo-hydraulic design of Chinese helium cooled solid breeder blanket for ITER-TBM

YUAN Tao, FENG Kai-ming, LI Zeng-qiang

2009, 29(2): 152-155.

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To further optimize thermo-hydraulic capability of HCSB-TBM, two different thermo-hydraulic schemes would be proposed and investigated by relevant calculating and simulating of thermo-dynamics in normal and peak heat flux condition. With computational fluid dynamics (CFD) code FLUENT, the actual temperature distribution of key components of HCSB-TBM is simulated.

The input power sub-system and output power control of LHW system in HT-7 tokamak

WANG Mao, XU Han-dong, ZHAO Lian-min, LIU Liang, HU Huai-chuan, DING Bo-jiang, L

2009, 29(2): 156-160.

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The structure of the input power sub-system of klystron, the data acquisition and the output power mode control of the low hybrid wave (LHW) system in HT-7 tokamak are presented. The LHW output power modes can be adjusted to meet the experimental requirements in HT-7 tokamak by controlling the PIN switches in the input power sub-system.

Design and realization of central control system for J-TEXT tokamak

YANG Zhou-jun, ZHUANG Ge, HU Xi-wei1, ZHANG Ming, QIU Sheng-shun, HUANG Li-hua

2009, 29(2): 161-165.

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To keep the J-TEXT tokamak running in order, it needs a central control system to coordinate the operations of all the sub-systems. The J-TEXT tokamak central control systm adopts industrial PC with some PCI control cards based on Windows and QNX operation systems. This control system has been finished the test and put into use in the first-round experiment of the J-TEXT tokamak successfully. The testing and operation show that this system is stable and reliable.

Coupled analysis between structure and heat conduction on the thermal shield support of CTB for ITER

LIU Su-mei, SONG Yun-tao, WU Song-tao, WANG Zhong-wei

2009, 29(2): 166-170.

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Based on the performance request of CTB in ITER DDD 111 magnet, the CTB cryogenic system is designed for the ITER feeder, the shape of the thermal shield support (TSS) is selected, the mechanical performance of TSS is analyzed, the heat loads of TSS are calculated，and then the coupled problem between mechanical structure and heat conduction in TSS of CTB has been analyzed by ANSYS code. The results show that the mechanical performance and the heat loss for the CTB thermal shield support could meet the requirement of ITER DDD 111 magnet.

Design and realization of the protection system of high-voltage power supply of the EAST low hybrid current drive

HU Huai-chuan, SHAN Jia-fang, ZHENG Guang-hua, YANG Chun-sheng, WU Jun-shuan

2009, 29(2): 171-173.

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Design and realization of the protection system of high-voltage power supply of the EAST low hybrid current drive are described, in which the over-current in main circuit and tube body, and the over-current and over-voltage in th high-voltage circuit are considered as the basic protection parameters for the system. Consequently，the crowbar will protect the klystron by transferring the fault current when the over-current takes place in the main circuit and tube body.

The analysis of EAST error field

LIU Xu-feng, DU Shi-jun

2009, 29(2): 174-177.

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The statistical method is used to analyze the asymmetric error field resulting from misalignment of PF and TF coils in EAST. The results show that the critical error field is beyond the scope of the physical requirement, so a set of correction coils should be designed to compensate the error field of the device.

Calibration system of magnetic probe on tokamak

SHEN Biao, LIU Dong-mei, WANG Yong, DU Xiao-ying

2009, 29(2): 178-181.

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Calibration of the effective area value of magnetic probes and RC value of integrator for the magnetic diagnostics system has been discussed. The calibration system is introduced, and two methods are presented.

Influence of operating parameters on discharge characteristics of planar DC magnetron

QIU Qing-quan, LI Qing-fu, SU Jing-jing, JIAO Yu , Finley Jim

2009, 29(2): 182-188.

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A 2D self-consistent PIC/MCC software OOPIC is used to simulate the plasma properties in the planar dc magnetron sputtering system, and then the influence of parameters such as the magnetic field, cathode voltage and gas pressure on the discharge characteristics is discussed. The results show that, in a definite range of operation parameters, the sheath thickness becomes narrower and the sheath potential fall (SPF) reduces, the ion density on the cathode(IDOTC) increases but its distribution becomes narrower as the magnetic field is strengthened, the sheath thickness becomes a little narrower and SPF increases, IDOTC increases and the distribution becomes wider as the increase of cathode voltage; the sheath thickness keeps constant almost and SPF increases, IDOTC increases firstly and then decreases, the distribution becomes a little wider as the increase of gas pressure.

Experimental investigation for structure of the shock waves influenced by the plasma

CHENG Bang-qin, LI Ying-hong, LI Jun, CAO Jun, WANG Jian, SU Chang-bing

2009, 29(2): 189-192.

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Results of recent experiments on the influence of specially organized electrical discharges on the structure of the shock waves in a supersonic wind tunnel were presented and discussed. Two discharge types were explored: dielectric barrier discharge and transverse DC surface discharge. The results show that the dielectric barrier discharge (DBD) can change the boundary layer. The intension of the shock waves decreases as the discharge obeys the flows. And it increases as the discharge disobeys the flows. In contrast to the dielectric barrier discharge plasma, the shock can be considerably weakened by transverse DC discharge plasma.

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