Table of Content

15 March 2009, Volume 29 Issue 1

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Plasma Physics

MHD real-time disruption prediction system of the HL-2A tokamak

QIU Yin,HUANG Yuan,ZHEN Yong-zhen,YANG Qing-wei,CUI Zheng-ying,JI Xiao-quan

2009, 29(1):  1-5. 

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A effective method has been proposed to predict the major disruptions caused by MHD instabilities and a real-time disruption prediction system on the HL-2A tokamak has been developed successfully, in which the amplitude or frequency of the MHD signal detected by a Mirnov coil is checked to predict the major disruption and the injecting-impurity method is used to mitigate the major disruption by means of the laser blow-off system. The response time of this system is 1ms and, therefore, it satisfies the experimental requirements.

Primary experimental results of MHD flow in the duct with flow channel insert

XU Zeng-yu,PAN Chuan-jie,ZHANG Xiu-jie,ZHAO Li, ZHANG Jian,YANG Guo-yi

2009, 29(1):  6-9. 

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The primary experimental results of an MHD flow in the duct with flow channel insert (FCI) are presented and the results indicate that the velocity profile in core area is quite different from the simulation and changes periodically along the duct with the distance between pressure equalization holes, but the fluid volume in core and boundary area, and the MHD pressure drop are close to the prediction given by the simplification modeling code. These experimental results are useful for the liquid blanket design and the analysis of MHD flow in the duct with FCI.

Measurement of plasma radiation on the HL-2A tokamak

LI Xue-hong,LI Wei,LIU Yi

2009, 29(1):  10-15. 

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The plasma radiation measurements under different discharge conditions, such as limiter configuration or divertor configuration, deuterium or helium discharges, have been performed on the HL-2A tokamak. The experiment results show that the radiation power in outer divertor is decreased when inert gases are injected into the divertor chamber, the transport of the injected particle from the edge to center is observed during SMBI, the ratios of radiated power between the main plasma and the input power, Prad/POH, in ohmic heated helium discharges is larger than that in deuterium discharge, and the siliconization is good for improving the wall condition.

Fast ion bootstrap current produced by neutral beam injection in tokamaks

HUANG Qian-hong,GONG Xue-yu,XIE An-ping,LIU Bo-qing

2009, 29(1):  16-22. 

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To investigate the bootstrap current due to fast ions produced by neutral beam injection into tokamak, a drift kinetic equation is established and solved by doubly expanding the fast ion distribution function in two small parameters δ=ρ_p/a (ρ_p is poloidal Larmor radius， a is the minor radius) and δ^*=τ_B/τ_s(τ_B is bounce period of trapped fast-ion，τ_s is the slowing down time), then the expression for bootstrap current is derived,and the bootstrap current density and total bootstrap current are obtained numerically in a large aspect ratio tokamak with circular cross section. The results show that the bootstrap current depends strongly on both injection angle and the ratio of v_b/v_c(v_b is birth velocity and v_b²∝E(beam energy),v_c is critical velocity), the ratio of the bootstrap current to the total current is about 10% in the perpendicular injection and is small in the parallel injection, the bootstrap current rapidly increases when the injection-angle reaches perpendicular and the beam energy increases.

Optimum on working parameters of long cavity HCN laser

TANG Yi-wu, DENG Zhong-chao, ZHOU Yan, YI Jiang

2009, 29(1):  23-26. 

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The tests and experiments of the various parameters, which affect the output power of the long cavity HCN laser, are performed. It is shown that there exists a group of optimized parameters, under which the output power of the long cavity HCN laser reaches 210mW, these parameters are: grid 250 meshes, waveguide wall temperature 130°C, mixed gas flow 21.3sccm, laser current 1.3A, working gas pressure 147Pa, the added He flow 12sccm.

Infrared measurement of the heat flux at the outer divertor target plate on the HL-2A tokamak

ZANG Lin-ge, LI WEI,YAN Long-wen

2009, 29(1):  27-32. 

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The surface temperature of the outer divertor target plate in the HL-2A tokamak is measured by an IR camera, the thermal graphs with temporal and spatial resolutions are obtained and the evolution of the heat load at the strike point is obtained by a 1-D calculation. The heat fluxes of four kinds of discharge, i.e. radiation divertor, ECRH, NBI heating and disruption are analyzed; and the results are compared with the results measured by the target probes in radiation divertor and disruption discharges.

Investigation on the generation of runaway electrons on the HT-7 tokamak with low hybrid current drive

LEI Hong-wei,HU Li-qun,LIN Shi-yao,HT-7Shi-yan-qu

2009, 29(1):  33-38. 

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The runaway electron detection system composed of NaI detector is used to detect the hard x-ray emission which occurs when the runaway electrons impinge on the first wall and a tangentially arranged multi-channel CdTe detector array is adopted to measure the fast electron bremsstrahlung (FEB) emission on the HT-7 tokamak. And then the critical energy and critical electronic field of runaway electrons are calculated according to the experimental data.

PIC/MCC simulation of the plasma dynamics in nitrogen glow discharge

ZHAO Shu-xia, ZHANG Lian-zhu

2009, 29(1):  39-43. 

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A self-consistent hybrid model of PIC/MCC (particle-in-cell / Monte Carlo Collisions) for nitrogen glow (NG) discharge is established, in which the movement of charge-particles and the self-generated field are described by the electrostatic particle-in-cell method and the collision processes are simulated by the Monte Carlo method. The discharge processes, the behavior of charge-particles (e、N₂⁺、N⁺) and the self-consistent electric field are simulated in the whole discharge space, the behavior and distribution of charge-particle (e、N₂⁺、N⁺) in NG are discussed through the calculation of electron/ion energy probability function (EEPF/IEPF). The N₂⁺ density simulated agrees well with the experimental result.

Study on propagation properties of laser guiding EMP in a finite magnetic field

XIA Xin-ren, YIN Cheng-you

2009, 29(1):  44-50. 

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The geometric model of laser plasma channel (LPC) guiding electromagnetic pulse (EMP) in a finite electromagnetic field is created; when LPC is in lossy gas the propagation properties of the normal modes of LPC guiding EMP are studied; and then the wave equation of longitudinal electromagnetic field and the relationship between transverse and longitudinal electromagnetic field in anisotropic medium are derived under the generalized cylindrical coordinate system. By applying the boundary conditions of electromagnetic fields, the strict characteristic equation of mode propagation for LPC guiding EMP is deduced, and the effects of plasma parameter, surrounding material and external magnetic field on propagation are discussed. The results show that the propagation properties of magnetized LPC guiding EMP are easy to be controlled compared with those without external magnetic field or an infinite external magnetic field applied.

Nuclear Fusion Engineering and Technology

Operation without circulating current of HL-2A ohmic power supply

WANG Ying-qiao, YAO Lie-ying, XUAN Wei-min

2009, 29(1):  51-54. 

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The ohmic power supply of HL-2A tokamak and its operation mode without circulating current are described and the converter status detector is also introduced, which can be used to monitor the status of all thyristors and then to judge the zero-crossing of load current. The disadvantages such as low precision and low reliability of current measurement have been overcome and the response time of this detector reaches 1ms. The volt-second of ohmic transformer (5Vs) is fully used and the plasma current is up to 420kA because of the operation mode without circulating current.

The effect of the variation in discharge parameters on the discharge characteristics in the ion source with multi-magnetic pole cusp field

YU Li-ming, ZHONG Guang-wu, JIANG Shao-feng, LEI Guang-jiu, LU Da-lun, CAO Jian-yong

2009, 29(1):  55-58. 

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The effect of the variation in discharge parameters on the discharge performance in the HL-2A tokamak bucket ion source with cusp field is described, discussed and analysed. This is very useful for improving the operation reliability and stability, increasing the saturation ion current density, and enhancing the beam current and arc efficiency of the ion source.

3-D neutronics calculation of the 2×6 HCSB TBM model

LI Zeng-qiang, FENG Kai-ming, ZHANG Guo-shu, YUAN Tao

2009, 29(1):  59-61. 

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The neutronics calculations for the new 2×6 HCSB TBM model has been performed with the Monte Carlo code MCNP/4C and the FENDL-2.0 data library. The calculation shows that the generated tritium is about 0.0123g.d^-1 and the total energy deposition in HCSB TBM is 0.587MW under the ITER standard operation condition. A maximum power density of 6.26MW.m^-2 under an average neutron wall load occurs in the first wall.

Three-dimensional activation analysis for ITER solid test blanket module

CAO Qi-xiang, FENG Kai-ming, ZHANG Guo-shu

2009, 29(1):  62-66. 

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Using the codes of MCNP and FDKR, the activation analysis for CH HCSB TBM (China Helium-Cooled Solider Breeder Test Blanket Module) has been performed. The calculation results show that after a continuous irradiation over 0.53 years with 500MW fusion power, the total radioactivity inventory, decay heat and BHP are 1.182×10¹⁷Bq, 2.463×10^-2MW and 5.651×10³km³·kW^-1, respectively, which are attributed mainly to the structure materials. In order to realize the automated routing of the neutron flux spectra from MCNP to FDKR, the two codes are linked through the automated interface code.

Neutronics calculations of neutron flux monitor for ITER

YUAN Guo-liang, YANG Jin-wei, ZHANG Guo-shu, YANG Qing-wei

2009, 29(1):  67-71. 

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A simplified model for the ITER neutron flux monitor (INFM) is developed, the energy-response and time-response of INFM with different moderators and different types are calculated by using MCNP code, the kinds and quantities of moderators used in INFMs are determined, and the preliminary physical understanding on INFM is presented.

Non-Fusion Plasma Applications

Simulation investigation on boundary layer of a plate flow control by plasma aerodynamic actuation

LIANG Hua, LI Ying-hong, WU Yun, MA Qing-yuan, WU Wei

2009, 29(1):  72-77. 

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Simulation investigation on boundary layer flow controlled by plasma aerodynamic actuation is performed, in which the influences of the plasma actuation on the boundary layer are regarded as added momentum and thermal energy. The body force of the plasma actuation is obtained by solving a two-dimensional fluid model of the surface discharge; from the body force the momentum and thermal energy acting on the boundary layer are induced, and then introduced into the Navier-Stokes equation as the source term. The influence of the intensity of the plasma aerodynamic actuation, the electrode number and position, as well as the thermal energy is investigated, the results agree with experiments.

PIC simulation of super hot electrons emitting out of the rear side of metal target

KUANG Long-yu, WU Shun-chao, JIANG Shao-en, WANG Chuan-ke, WANG Zhe-bin

2009, 29(1):  78-81. 

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The kinetic features of super hot electrons emitting out of the rear side of metal target is simulated and the reflux is studied by a two-dimension PIC code in cylindrical coordinates. The results show that the emission ratio oscillates when the super hot electron beam is mono-energetic, and the oscillation is smoothed when the electron energy distribution is Maxwellian.

Characterization of Raman spectroscopy of DLC films deposited on inner surface

WANG Jun, WEN Xiao-qiong, YIN Li-yong, WANG De-zhen

2009, 29(1):  82-86. 

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Diamond-like carbon (DLC) films deposition on inner surface of a stainless steel tube with 100mm in length and 10mm in inner diameter is carried out in direct current glow discharge plasma of Ar/CH4 mixed gas with a flow ratio of 20% CH₄, and the influence of pressure and deposition time on micro-structure of the films is investigated by Raman spectroscopy. It is found that the position of both G and D line, the width (FWHM) of both G and D line and the I_D/I_G ratio all drop firstly and then rise along with the pressure increase, the lowest values occur when the pressure is 20Pa. On the other hand, along with the time evolution the position of both G and D line shift to the lower wave-number, the width (FWHM) and the I_D/I_G  ratio of both G and D line decrease. These results reveal that the DLC films become harder, more ordered and more diamond-like with higher sp³ content, and the size of sp³ cluster grows larger along with the time evolution.

Study on high growth-rate deposition of nanocrystalline silicon thin film with VHF-PECVD

ZHUANG Juan, WANG De-Zhen, GAO Xin-xin, WANG Yan-hui

2009, 29(1):  87-91. 

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Using the self-consistent one dimensional fluid model, equations of particle-balance, momentum, charged particle flux and current continuum have been established to study the behavior of chief particles in low-pressure very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD). The influence of VHF (very high frequency) has been analyzed and the profiles of SiH₃^- negative, electrons, SiH₃⁺ positive density have been obtained. The simulation results show that the density of SiH₃^- negative changes with frequency and consequently the frequency controls the particle nucleation and growth; meanwhile, the densities of electron, SiH₃⁺ positive and the electric field intensity also vary with frequency, so that the chemical reaction and the nanoparticle deposition are accelerated.

Characteristics of the low power cylindrical anode layer ion source

ZHAO Jie, TANG De-li, CHENG Chang-ming, GENG Shao-fei

2009, 29(1):  92-96. 

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A low power cylindrical anode layer ion source and its working characteristic, and the beam distribution are introduced. This ion source has two working states, emanative state and collimated state, and the  normal parameters of this system are: working voltage 200～1200V, discharge current 0.1～1.4A, air pressure 1.9×10^-2～1.7×10^-1Pa, gas flow 5～20sccm.