Table of Content

15 March 2008, Volume 28 Issue 1

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Plasma Physics

Numerical simulation of MHD equilibrium configuration for the HL-2A modification

CHEN Qian, WANG Ai-ke, LI Fang-zhu, ZHANG Jing-hua

2008, 28(1):  1-5. 

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Numerical simulation is employed for the HL-2A modification, which includes the optimum design of zero-field in the start-up phase, the limiter equilibrium configuration, the single/double null divertor equilibrium configuration, and the equilibrium configuration evolution from gas breakdown to current plateau. Results show that the new program can satisfy the design requirement.

Numerical simulation of lower hybrid wave coupling to plasma on high density edge

QIN Yong-liang, DING Bo-jiang, ZHANG Li-zhi, KUANG Guang-li

2008, 28(1):  6-10. 

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The “step plus ramp model” has been accepted to calculate the coupling of lower hybrid wave with plasma, in which the edge plasma density is assumed to be higher (large than the cut-off density) in the front. The reflected power coefficient and the power spectrum of lower hybrid wave have been validated by solving the wave equation in the areas of vacuum, density plateau and density gradient, respectively, under the conditions of electromagnetic continuity and impedance matching at the edge. The optimal coupling condition of lower hybrid wave with plasma has been explored, and the results obtained from “step plus ramp model” and Brambilla theory has been discussed.

Results of soft X-ray spectra measurement using silicon drift detector on the HL-2A tokamak

ZHANG Yi-po, YANG Jin-wei, SONG Xian-ying, LIU Yi

2008, 28(1):  11-16. 

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Measurements of soft X-ray spectra during Electron Cyclotron Resonance Heating (ECRH) has been achieved on HL-2A tokamak using two independent silicon drift detector (SDD) systems. Electron temperatures are derived from the measured soft X-ray energy spectra. A comparison indicates that the results measured by SDD are consistent with ECE measurements. Experimental results of soft X-ray spectra measure- ment using SDD show that the increment of electron temperature is larger at z=0 than that at z = 16.4cm chord, so, we can conclude that the energy of ECW is deposited dominantly in the core of plasma and electron temperature profile become peaked during on-axis ECRH (B_T=2.4T). The statistic survey of ECRH discharges (2.41T ≤B_T≤2.43T,1.5×10¹⁹m^-3≤n_e≤2.5≤10¹⁹m^-3,300kW≤ECRH power≤600kW) shows that plasma electron temperature rises obviously during on-axis ECRH, especially, in the core of plasma (z=0). It has been observed that the on-axis ECRH can make electron temperature increase up to 30%～80% at z=0 chord and 15%～55% at z=-16.4cm chord.

Experiments of the divertor detached plasma in the HL-2A tokamak

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

2008, 28(1):  17-21. 

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The divertor plasma characteristics is studied by using the fixed flush probe arrays located on the 4 neutralization plates and the electromotive-scanning 4-probe system placed in the outer chamber at the same cross-section in the HL-2A tokamak. Some important information on plasma parameter distribution and its asymmetry, and the detached plasma properties has been obtained. The fast reciprocating probes are used to measure the edge plasma temperature, density, floating potential and corresponding fluctuation profiles. These results are very useful to investigate the divertor physics, and show that the radiation divertor discharge can improve the particle confinement.

Effect of the motion of ions on rotating magnetic field current drive in Rotamak

CHEN Long-xi, ZHONG Fang-chuan, ZHANG Hai-hua, HAN Jing

2008, 28(1):  22-27. 

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Effect of the ion motion is studied in the theoretic model of rotating magnetic field as a current drive mechanism. On the basis of 2-D MHD model, the ion and electron motion equations are applied in infinitely long cylindrical geometry, and therefore a new 2-D MHD theory is built by taking account of ion radial motion. The calculated results are compared with ones obtained from fixed ion model, and the corresponding physical processes are discussed. This improved theoretic model can be adapted to the parallel flow (along the magnetic field line) effects and the axial pressure balance.

Numerical simulation of MHD effect of liquid metal free surface film flows

ZHANG Xiu-jie, XU Zeng-yu, PAN Chuan-jie, KANG Wei-shan

2008, 28(1):  28-33. 

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Numerical simulation is implemented to analyze magnetohydrodynamics (MHD) instabilities of liquid metal (LM) free surface film-flow, which is flowing in a strong magnetic field. The shape, velocity and electrical potential profile in the cross-section of the film-flow are also given. Thereby the MHD behavior of LM free surface film-flow can be well explained. The numerical simulation results are in good agreement with experimental data. The results show that the magnetic field may hinder the liquid metal film-flow from motion when it flows through a strong magnetic field.

Numerical simulation for X-ray radiation emitted from a rapidly translating CT stagnated against a rigid wall

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

2008, 28(1):  34-39. 

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The physical process of X-ray radiation emitted from the rapidly translating CT (compact toroidal plasma), consisting of Ar plasma, colliding against an ideal stationary wall is numerically simulated by resolving the 1-D RHD equations. The time-dependent physical parameters during collision are presented by means of splitting scheme, and the optimized values of mass and initial velocity of the CT as an efficient radiation source are investigated when the kinetic energy of CT is fixed. The results show that the numerical scheme conserves total energy with the relative error less than 1%.

Numerical simulation of the interaction between dust particles and plasma sheath

WU Jing, ZHANG Peng-yu, WANG De-zhen

2008, 28(1):  40-44. 

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Through the solution of the one-dimension steady dust plasma sheath model, more information of the dust plasma can be gained as follows: the sheath potential, the positive ion density, the electron density, and the dust particles density distributions in the sheath; the Bohm criterion and the Bohm velocity in the sheath boundary as a function of dust particle density; the relationship between dust particle charge and density; and the effect of dust particle temperature on its distribution in the sheath boundary. The results show that with the increase of dust particle density the plasma sheath thickness, electron density, dust particle charge decrease; and with the increase of dust particle temperature the dust particles density near the sheath boundary increase gradually.

Study of 3s²3p and 3s²3d transition in Al-like ions Cr⁺¹¹, Mn⁺¹² and Fe⁺¹³

WEI Hui-ling1, ZHANG Hong1, ZHANG Ji-yan2, CHENG Xin-lu1

2008, 28(1):  45-48. 

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Transitions between 3s23p and 3s23d configurations of Al-like ions CrⅫ-FeⅩⅣ have been studied theoretically using the multi-configuration Dirac-Fock (MCDF) method. The configuration interaction and its influence to the transition properties have also been validated; meanwhile, the transition energies, transition probabilities and absorption oscillator strengths of Al-like ions have been obtained. Compared with available experimental results, the calculations are in good agreement with them.

Nuclear Fusion Engineering and Technology

Feedback control research of the HL-2M plasma vertical instability

LIU Lin1, 2, ZHANG Jin-hua1, XIA Fan1, LI Fang-zhu1, CHEN Qian1, XIE Qing-guo2

2008, 28(1):  49-53. 

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The passive stabilization plates and active coils are used to control the HL-2M plasma vertical instability. The plasma vertical instability growth time is calculated and a linear-model for controlling the vertical instability is constructed, and then the control system is simulated with MATLAB and using the PID algorithm. The results show that the plasma vertical instability can be stabilized quickly and this means that the design is feasible.

Power measurement of microwave for ECRH system on the HL-2A tokamak

LU Zhi-hong, YI Liang-bi, BAI Xin-yu, RAO Jun

2008, 28(1):  54-59. 

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Spurious mode power absorbed by MOU of the gyrotron is measured by detecting increment of the temperature difference between inlet and outlet of cooling water flowing through MOU with a calorimetric system, which consists of temperature sensors, timing power supply, electronic processing unit and data gathering and handling unit etc. The output power of gyrotron, therefore, is calorimetrically monitored based on the measured spurious mode power and its contents. In this way, four gyrotrons are measured during commissioning and ECRH experiments, and the results show that over 1.6 MW of the total output power provided by ECRH system on the HL-2A tokamak is obtained.

Intensity distribution measurement and analysis of microwave beam for ECRH system in the HL-2A tokamak

HUANG Mei, CHEN Gang-yu, RAO Jun, ZHOU Jun, LIU Yong, KANG Zi-hua

2008, 28(1):  60-64. 

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The intensity distribution, measured by IR camera at three different positions along the propagation routine, is used to calculate the first and second order moments of the radiation patterns and to retrieve the phase information, and then the propagation direction of the microwave along the waveguide can be determined. The alignment of two ECRH subsystems has been analyzed by using this method and the results show that the power distribution of two subsystems is Gaussian, the tilt angle of No.3 transmission line (7m) is about 0.05° and No.4 (6m) is about 0.14°.

Numerical simulation of static stress for ITER gravity support

HOU Bing-lin, PAN Chuan-hong, ZHOU Cai-pin, LI Peng-yuan, JIAN Guang-de, LIU De-quan

2008, 28(1):  65-68. 

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The static stress analysis of ITER magnet gravity support has been performed with ANSYS, and the variation of stress is simulated under various load cases. The calculation results reveal that the stress is lower than the allowable limits of the component materials, and therefore the gravity support, especially the 21-flexible-plate component, have enough mechanical strength and can safely withstand the various operation scenarios.

Cooling enhancement of front lid in the shield blanket for ITER

YAN Hui-bo, HUANG Su-yi, ZHANG Fu

2008, 28(1):  69-72. 

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The front header of one of the ITER shield blankets is studied using the FLUENT code. The calculation results indicate that the cooling of the front lid in the front header is not adequate and uniform. To meet the design requirement of ITER, the flow driver is improved, and the new structure is given in this paper. According to the analysis, the cooling of the front lid will be adequate and uniform because of the modified flow driver and this can satisfy the design requirement of ITER.

Design of magnetic probe coils in the EAST tokamak

XI Wei-bin, WU Song-tao, SHEN Biao, WAN Bao-nan, SONG Yun-tao

2008, 28(1):  73-76. 

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A detailed description of measurement theory, magnetic probes geometry, fabrication, calibration, and frequency response is introduced. The calibration error of the magnetic probe and the frequency response of Mirnov coil are given. The EAST experiments show that magnetic sensors could provide sufficient information for machine operation and plasma control.

Numerical simulation of CICC rolling process

LIU Zhi-hong, YU Jie, WU Jie-feng, LI Bo

2008, 28(1):  77-80. 

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The rolling process of cable in conduit conductor (CICC) has been simulated using the explicit dynamic finite element analysis software ANSYS/LS-DYNA. The rolling forces for different rolling passes and the influence of the rolling pass on conductor shape and conductor remainder stress have been obtained. The simulated rolling force matches the reference experimental data, and therefore the study results provide an important basis for the design of rolling equipment.

Preparation of tungsten matrix nanocrystalline powders for plasma facing materials

YU Fu-wen1, WU Yu-cheng1, CHEN Yong 1, CHEN Jun-ling2

2008, 28(1):  81-84. 

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W-30%TiC nanocrystalline composite powders for plasma facing materials were prepared by mechanical alloying. Influences of parameters of mechanical alloying process such as liquid-to-balls-and-powders ratio, ball-to-powder ratio, milling speed and milling time on characteristics of the milled powders were studied. The optimal mechanical alloying process parameters were the liquid-to-balls-and-powders ratio 2:1，ball-to-powders ratio 10:1, milling speed 200r•min^-1 and milling time 25h, respectively.

Parallel application of plasma equilibrium fitting based on inhomogeneous platforms

LIAO Min, ZHANG Jin-hua, CHEN Liao-yuan, LI Yong-ge, PAN Wei, PAN Li

2008, 28(1):  85-89. 

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An online analysis and online display platform EFIT, which is based on the equilibrium-fitting mode, is inducted in this paper. This application can realize large data transportation between inhomogeneous platforms by designing a communication mechanism using sockets. It spends approximately one minute to complete the equilibrium fitting reconstruction by using a finite state machine to describe the management node and several node computers of cluster system to fulfill the parallel computation, this satisfies the online display during the discharge interval. An effective communication model between inhomogeneous platforms is provided, which could transport the computing results from Linux platform to Windows platform for online analysis and display.

Non-Fusion Plasma Applications

Protection against high power microwave using plasma

YANG Geng, TAN Ji-chun, SHENG Ding-yi, YANG Yu-chuan

2008, 28(1):  90-93. 

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Protection against high power microwave using plasma was proposed. A reflection/absorption sandwich model of “medium slab-plasma slab-medium slab-plasma slab” was established, where the thickness for the un-magnetized uniform plasma is 50mm, the plasma frequency 30GHz, and collision frequency 70GHz. Then the transmitted power of electromagnetic wave and the minimal protecting-distance of protector were calculated. The results show that for a microwave source with 10GW power, 100ns pulse width, 100m² antenna area (with efficiency of 50%), the emitted microwave will be reflected when the frequency is less than 30GHz; or the minimal protecting-distance of protector is about 5km when the frequency is within 31～80GHz.

Dependence of thermal plasma jet temperature on discharge power and gas flow rate

QIN Pan, RAN Yi, LAN Tian-shi, DAI Xiao-yan, YIN Yong-xiang, TONG Hong-hui, CHENG Chang-ming

2008, 28(1):  94-96. 

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With the help of heat balance equation and high temperature thermodynamic function, the calibration relation of jet temperature with discharge power、gas flow rate was obtained for nitrogen thermal plasma. It was shown that the results were agreed with the principle of similarity. The jet temperature was a function of P_eff/f, instead of a general two variables function of P_eff and f, which were effective discharge power and working gas flow rate, respectively. A related discussion has been given; it will be referable to thermal plasma applications.