Table of Content

15 March 2014, Volume 34 Issue 1

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Plasma Physics

A simplified model of the transport barrier formation

SUN Tian-tian , PENG Xiao-dong , TANG Chang-jian

2014, 34(1):  1-5. 

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A simplified nonlinear model of the plasma transport based on the plasma transport characteristics of the L-H mode transition in tokamak experiments has been made. The steady-state temperature profiles which illustrate the formation of the externaltransport barrier (ETB) and the internal transport barrier (ITB) phenomena with the high auxiliary heating power have been obtained by the numerical solutions of the transport equation. A comparison of the ETB energy confinement efficiency with the non-ETB case will be discussed.

Gas target thickness and neutralization efficiency in HL-2A neutral beam injection

YANG Xian-fu, XIE Wei-min, WEI Hui-ling, LIU He, ZOU Gui-qing, ZHANG Xian-ming, LI Ming, CAO Jian-yong

2014, 34(1):  6-11. 

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Gas target thickness for neutralizer is theoretically calculated for the 1MW NBI of HL-2A tokamak with iterative method, and the correspondingly neutralization efficiency is obtained, it is turned out that it is unable to make the neutralization efficiency reach its optimum value only depending on the flowing gas from the ion source, thus it is necessary to add a complementary gas puff in the neutralizer to increase the gas target thickness. The complementary gas puff system has been successfully operated in the 1MW NBI on HL-2A tokamak and the neutralization efficiency can be increased about 10% for the samedischarge parameters.

Yield and energy conversion efficiency of the forward hot electrons from laser-foil target

CAI Da-feng 1, 2 , GU Yu-qiu 2 , ZHENG Zhi-jian 2 , ZHOU Wei-min 2 , JIAO Chun-ye 2 , WEN Tian-shu 2

2014, 34(1):  12-16. 

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The distribution and the energy spectrum of forward hot electrons produced by the interaction of fs-laser with foil target were measured. The results show that the forward hot electrons jet with a large angle width is mainly along the direction of rear normal of target; the energy spectrum of forward hot electrons is a Maxwellian-like distribution. The yield and energy of forward hot electrons is about 1.23×10⁸ shot ^-1 and 4.65×10¹¹ keV . shot ^-1 , which were deduced from the distribution and the energy spectrum of forward hot electrons. The conversion efficiency of laser energy to forward hot electrons energy is about 5.72×10 ^-4 , which is better consistent with that from the reference [17].

Inverse integration of one-dimensional quasi-isentropic compression flow field

XUE Quan-xi , JIANG Shao-en, WANG Zhe-bin , ZHANG Huan , YE Xi-sheng , ZHANG Yong-sheng

2014, 34(1):  17-21. 

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Inversion codes were completed based on principles of backward integration, and simulations were performed by the codes. The results inverted from the particle velocities of interface are in consistent with the ones from MULTI. Moreover, the loading pressure curves, free surface velocities inverted from some free surface velocities are the same as the experiments results obtained from Saturn accelerator, and those both obtained by WONDY codes, and deduced from current shapes of the accelerator. This work can provide important supports for laser-driven ramp compression experiments in future.

3D simulation J-PARC multi-cusp ion source

YANG Chao, LIU Cheng-an

2014, 34(1):  22-26. 

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The theory calculation of the rectangle permanent magnet was studied. The PIC-MCC simulation algorithm was analyzed in-depth. A 3D PIC-MCC simulation algorithm was developedusing the PIC software. Based on this algorithm, the discharge characteristics of multi-cusp ion source, J-PARC, were simulated and the electron energy deposition process and the generation mechanism of volume in multi-cusp ion source were analyzed. Also, the advantages of the ion source in optical characteristics and design ideas were discussed. The results showed that the ion source can produce space uniformly negative hydrogen ion beam, and the volume negative hydrogen ions were produced high efficiently.

Nuclear Fusion Engineering and Technology

The design of the 3.7GHz microwave exciter for LHCD system on HL-2M tokamak

ZENG Hao , FENG Kun , YANG Peng-yi , ZHANG Zhi-yong

2014, 34(1):  27-32. 

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The design of 3.7GHz microwave exciter for LHCD is presented. The system is composed of 11 modules: the single frequency solid-state source, the power divider, the power amplifier and the controller. There are 8 outputs in the microwave exciter, each output power range is within 0~10W and can be controlled continuously and remotely. The sampling phase detector and the phase-lock loop are used in the microwave exciter so the low phase noise, high frequency stability and high spurious rejection ratio of the microwave output signal can be realized. The phase noise are -115dBc/Hz at 1kHz, -117dBc/Hz at 10kHz, -122dBc/Hz at 100kHz, the frequency stability is ≤0.03ppm/30min and the spurious rejection ratio is ≤-80dBc.

Design of 3.7GHz 3dB power splitter for the new LHCD antennaon HL-2A tokamak

WEI Sen, BAI Xing-yu, ZHOU Jun, LIANG Jun, ZENG Hao, RAO Jun

2014, 34(1):  33-39. 

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The structure design of 3dB power splitter is finished based on the microwave superposition principle, impedance matching and phase compensation theory. High frequency electromagnetic simulation software HFSS has also been used to simulate and optimize the parameters of the design. The test results of manufacturing device are obtained as below: the reflection loss in input port is -31.12dB; isolation is -34.35dB; the power splitting in output port are -3.09dB, -3.07dB; the phase difference is 1.8°; input VSWRis 1.070. All of the above results show our design is reasonable.

Excitation control system of pulse generator on HL-2A tokamak

LI Wei-bin, BU Ming-nan, LIU Xue-mei, XU Li-rong

2014, 34(1):  40-46. 

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The HL-2A pulse generators outputs are controlled by their excitation feed back control systems, which adopt PID algorithm and the phase-shifted digital trigger circuit based on FPGA (field programmable gate array), and the safety of the excitation system is protected by Siemens PLC logic control system. The actual operation results show that these excitation control systems have high control precision, stable and reliable advantages.

Simulation of digital filtering proposal for converter’s synchronous signal

ZHAO Xin, YAO Lie-ying, WANG Ying-qiao

2014, 34(1):  47-52. 

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To deal with the serious waveform distortion and frequency variation of the synchronous signal of the HL-2A poloidal field SCR power supplies, a multistage digital filter for thyristor trigger system is raised by analyzing and comparing the filtering effectiveness of eachkind of filter. The simulation model of the filter is built using MATLAB and the feasibility of the method is proved through simulation analysis. By calculating the time delay, it is proved that the digital filter also satisfies real-time process.

Preliminary study on transient thermal shock behavior of high purity tungsten

CHEN Lei, LIU Xiang, LIAN You-yun

2014, 34(1):  53-56. 

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The thermal shock performances of ITER-like high purity tungsten were examined by an electron beam heat load test and finite element code simulation. Experiments under ITER-like plasma major disruption instability happening condition with test sample background temperature at room temperature were simulated by an electron beam facility EMS-60 newly constructed. Recrystallization, cracking and melting behaviors of test sample after irradiation tests were observed by a scanning electron microscopy (SEM) and their formation mechanisms have been discussed. Finite element simulation has been carried out by ANSYS code and the result shows that the cracking threshold of ITER grade tungsten is about 1.5M•Jm ^-2 for 5ms pulse loading, which is in accordance with experimental results.

Numerical simulation of EAST discharge with NBI

LI Hao, WU Bin, WANG Jin-fang , WANG Ji, HU Chun-dong

2014, 34(1):  57-62. 

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Using 1.5D tokamak discharge simulation code(TSC) combined with NUBEAM code, the heating and beam-driven current of EAST-NBI in the next experimental campaign were studied. Under different background plasma density, the efficiency of EAST-NBI heating and current drive was discussed. Numerical simulation results show that the effect of EAST-NBI heating and current drive is quite good under the condition of the typical EAST experimental parameters. Proper lowering the background plasma density will improve NBI heating and current drive efficiency.

Design and analyze of the displacement for cold qualitative magnet in EAST

ZOU Chun-long , XI Wei-bin , GAO Qing-sheng , LI Yu-he , ZHU Hai-sheng , SONG Yun-tao

2014, 34(1):  63-68. 

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In order to measure the displacement, computer vision processing method was used to build the three-dimensional measurement model, the pictures weredistinguished and detected by the image acquisition system, and then the displacement data was got. The displacement measure problem of cold qualitative magnets of EAST was solved.

Analysis of EAST tokamak cryostat anti-seismic performance

CHEN Wei, LIU Su-mei, KONG Xiao-ling, NI Xiao-jun, WANG Zhong-wei

2014, 34(1):  69-74. 

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A 3-D finite element model for EAST tokamak cryostat is established by using ANSYS. On the basis of the modal analysis, the seismic response of the EAST tokamak cryostat structure is calculated according to an input of the design seismic response spectrum referring to code for seismic design of nuclear power plants. Calculation results show that EAST cryostat displacement and stress response is small under the action of earthquake. According to the standards, EAST tokamak cryostat structure under the action of design seismic can meet the requirements of anti-seismic design intensity, and ensure the anti-seismic safety of equipment.

Nickel removal and post surface treatment for ITER CC joint

TIAN Ze-jun, WU Wei-yue, WANG Lin, LIU Li-ping

2014, 34(1):  75-79. 

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Two joints were manufactured. One was manufactured using mechanical grinding nickel removal method and hot tinning technique. Another was manufactured by anti-plating removing nickel method and brush silver plating technique. The measured DCresistances of the two joints are 1.98nΩand 1.53nΩrespectively. By comparison, anti-plating nickel removing and brush silver plating technique is more effective and easier to processing. All the technique researches are very useful for the fabrication of CC joints.

Design and implementation of control system for J-TEXT’s divertor power supply system

XIE Xian , ZHANG Ming , HE Yang , ZHANG Jing , ZHENG Wei , PAN Yuan, YU Ke-xun

2014, 34(1):  80-83. 

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Based on the load characteristics and power demand, the control system is designed from hardware and software according to the J-TEXT CODAC (Control, Data Access and Communication) standard. To evaluate the characteristic of the control system, a series of experiments had been carried out. The result indicates that the control system offers good control effects and reliability. It may provide an instance for control schemes in ITER and related systemof fusion reactor in future.

Non-Fusion Plasma Applications

Optimization design of slot antenna array of surface wave discharge

CAI Hong-hua, NIE Wan-sheng, CHE Xue-ke, FENG Song-jiang

2014, 34(1):  84-89. 

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In order to optimize the design of slot antenna array of surface wave discharge and provide theoretical basis for design of surface wave discharge device, the slot antennas have been calculated and analyzed. The results show that the electromagnetic field radiated by transverse slots is stronger than by longitudinal slots; the electromagnetic field radiated by co-phased antennas is stronger than by heterogeneous antennas, the former is easier to breakdown air and produce plasma. The longitudinal slot antenna array is improved based on the phase distribution of magnetic field intensity, in order to make every slot in phase to make produce plasma efficiently, longitudinal slot antennas are arranged on two sides with interval of half a wavelength.

Light scattering characteristics of Al2O3 tail plume plasmas for a spacecraft

MA Bao-ke , GUO Li-xin , CHANG Hong-fang

2014, 34(1):  90-96. 

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Based on the Mie’s scattering theory, the light scattering characteristic of Al₂O₃ tail plume plasma for a spacecraft was studied. Influences of the complex refractive index onthe extinction efficiency factor, scattering efficiency factor, absorb efficiency factor, scattering phase function and the single-scattering albedo of an Al₂O₃ particle were analyzed by using the Mie’s scattering theory. Meanwhile, based on the particle scale unimodal distribution with a polydispersity, the changes of the concerned effect factors and the scattering phase function were analyzed with considering the Al₂O₃particle size, and some numerical simulations were also given. The theoretical and numerical simulation studies show that the imaginary and real part of the refractive index of the Al₂O₃ particles, the radius and its distribution of the particles bring out great effect on the scattering phase function, extinction and scattering efficiency factors and single-scattering albedo.