Nuclear Fusion and Plasma Physics

Numerical study of heat transport across single magnetic island

YANG Jin-hong, CHU De-lin, OU Jing, YE Lei, WANG Ping

2012, 32(4): 289-294.

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The heat transport across single magnetic island is analyzed numerically by solving two- dimensional energy transport equation. For the background heating, when the magnetic island width is less than the critical magnetic island width, magnetic islands impact on the energy confinement is not obvious, when the magnetic island width is greater than the critical magnetic island width, the energy loss increases linearly with the magnetic island width, and the effective radial thermal conductivity coefficient is in a Gaussian distribution and the maximum value is at the rational surface. For both the background heating and the ECRH heating, temperature distribution and heat energy confinement are different from that of background heating, it provide a basis for further study of the ECRH stabilizing tearing mode.

Thermal analysis of Langmuir probes for ITER divertor

ZHAO Wei, ZHONG Guang-wu

2012, 32(4): 295-300.

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ITER divertor Langmuir probes are important diagnostic devices on the divertor, working at harsh thermal nuclear reaction conditions with the highest thermal flux density. In order to optimization of designing the Langmuir probes, ANSYS software was employed to simulate the working condition, through different simulation comparison, the basic characteristics of the thermodynamic condition of probe is more clear, and it is benefit to engineering design of ITER divertor Langmuir probes.

The effect of cathode shape in magnetically dispersed arc plasma

BAI Bing, ZHA Jun, ZHANG Xiao-ning, CHEN Tang, WANG Cheng, XIA Wei-dong

2012, 32(4): 301-306.

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The arc plasma in the coaxial magnetically dispersed arc plasma generator exhibits typically dispersed uniform arc column as well as diffusive cathode root. The arc root characteristic depends on the boundary condition as well as the cathode shape. Magnetically dispersed arc plasma coupled with different shape of cathode is numerically simulated by simplified cathode sheath model with FLUENT. The result shows that the cathode arc root appears to be dispersive, the order of magnitude of which is 107A•m^-2. The configurations and the current density of arc root which has an effect on the plasma distribution highly rely on the cathode shape. With the apex angle of the cathode increase, the cathode arc root moves from the tip to the side of the cathode. The plasma moves downstream and the thickness of the cathode decrease.

Influence of Compton scattering on the defect mode in time-varying magnetized plasma photonic crystals

WEN Hua, HAO Xiao-fei, HAO Dong-shan

2012, 32(4): 307-311.

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Using the model of the multi-photon nonlinear Compton scattering and the parts electric current density cirrus finite-different time-domain method(PLCDRC-FDTD), a new mechanism of the defect mode formed by the incident light and Compton scattering optical is given out, and the influences of Compton scattering on the defect mode in the one-dimension time-varying magnetized plasma photonic crystals with a defect layer are studied. The results show that comparing those before Compton scattering, when the incident light frequency is lower than the plasma frequency, the clear defect modes are taken place in the band gap, the frequencies of the defect mode are slowly increased along with the increasing of the plasma relaxation times. Under the plasma relaxation times are the same, the band gap transmission coefficient crests of the even plasma are smaller than those of the Epstein distribution plasma, their defect mode characteristics are clearer, but the band gap widths and defect mode characteristics are clearly decreased between the even plasma and Epstein distribution.

Experimental investigation on nanosecond pulsed discharge under static air condition

ZHANG Bai-ling, CHEN Feng, LI Yi-wen, ZHANG Yang, ZHU Tao

2012, 32(4): 312-316.

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Experiment investigation on nanosecond pulse discharge under static air and big volume condition has been performed under different air pressure, discharge distance and voltage. Research shows that under the condition of the length of 200mm and the pressure of 250Pa, as voltage increases the discharge region extend from near of the conical electrode to the whole channel. When the voltage is 12kV, discharge can fill the whole channel; and with the pressure rise the initial discharge voltage increases. It is found that nanosecond pulsed ionization instability appears when the voltage is increased to a certain extent, as the radial fluctuations in the plasma when the pressure is relatively low, and the discharge tends to break initially uniform nonequilibrium plasma into narrow hot arcs at relatively high pressure. Analysis indicates that shorter rise time, shorter pulse width and higher voltage for the source are needed to realize long distance, large volume homogeneous plasma.

Langmuir-probe diagnostics of large-scale magnetically rotating arc plasmas

JIAO Ling-yun, ZHA Jun, BAI Bing, ZHANG Xiao-ning, XIA Wei-dong

2012, 32(4): 317-322.

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The fast-moving electric probe designed by ourselves is used to diagnose the large-scale magnetically rotating arc plasmas in the argon under the atmospheric pressure. The signal shape of the voltage and current of the electric probe is analyzed to draw the U-I curve. The fluctuation characteristic of the plasmas on the axis of the generator is obtained, and the axial distribution of the electron temperature on the axis of the generator is found. It is found that there is a recirculation zone in the center of the generator, and the approximate volume of the arc plasmas is got.

Simulation on advanced operation mode for the compact fusion-fission hybrid reactor

CHEN Mei-xia, LIU Cheng-yue, WU Bin

2012, 32(4): 323-327.

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Reversed shear (RS) operation mode is simulated with Jsolver and TSC codes on some important issues, such as RS Plasma configuration, bootstrap current fraction and RS operation mode discharge simulation etc.. To some degree, the modeling results show that the RS operation mode is advanced and feasible for the compact Fusion-fission hybrid reactor.

The energy spectrum of ions generated by ultra-high laser and plane film copper target interaction

TANG Cui-ming, CHEN Xiao-xu, HONG Wei

2012, 32(4): 328-331.

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In the experiment of ultra-intense laser interaction with plane film copper target, ions spectrum are studied at the target rear-side normal direction. The solid nuclear detector CR39 and Thomson spectrum are used to detect the energy spectrum of protons and carbon ions. Protons and C⁴⁺, C³⁺, C²⁺ and C¹⁺ ions have been observed. In addition, the results show that the ions are cut-off at a certain energy. Moreover, the carbon ions traces are very weaker than the protons trace, so the yields of proton is much higher than carbon ions, and the protons have some screening effect on the carbon ions. And the cut-off energy of the carbon ion is increased with the charge-to-mass ratio in the same shot.

Study on suppressor gird power supply of NBI ion source on HL-2A tokamak

MA Ding-hui, RAO Jun, CAO Jian-yong, WEI Hui-ling, CHEN Wen-guang, WANG Ming-wei

2012, 32(4): 332-337.

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In order to improve the parameter and system stability, a testing suppressor grid power supply was developed based on high-frequency switching power supply technology and IGBT stacks in series technology, and all the former tetrode modulators with solid-state modulators based on IGBT stacks in series were replaced. The structure of this newly developed power supply was introduced firstly, and the operation performance of power supplies for ion source and its relationship with extraction of ion source was analyzed based on practical data of NBI debugging experiment, and the minimum voltage of suppressor grid power supply for extraction was achieved as well.

Electromagnetic analysis on China HCCB-TBM design under major disruption

CHEN Yan-jing, FENG Kai-ming, ZHANG Guo-shu, LI Zai-xin

2012, 32(4): 338-343.

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Under two major disruptions of ITER Plasma the electromagnetic loads on the updated design of CN HCCB-TBM have been performed by using ANSYS Parametric Design Language. The stress and temperature analyses have been obtained by applying multi-physical fields’ calculations such as magnet-structure and magnet-heat coupling in this paper. The results showed that the maximum stress is ~26.2MPa, which was as low as the allowable value of RAFM(CLF-1). Due to the interaction of eddy current and resistance the Joule heat caused the temperature of TBM to rise to ~0.1K, which had less influence to the thermo-hydraulic design of TBM. The evaluations of EM loads on TBM have been showed that the updated structural design of TBM was safe which can overcome the EM loads brought by two kinds of major disruptions.

Preliminary analyses of neutronics schemes for three kinds waste transmutation blankets of fusion-fission hybrid

ZHANG Ming-chun, FENG Kai-ming, LI Zai-xin, ZHAO Feng-chao

2012, 32(4): 344-350.

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The neutronics schemes of the helium-cooled waste transmutation blanket, sodium-cooled waste transmutation blanket and FLiBe-cooled waste transmutation blanket were preliminarily calculated and analysed by using the spheroidal tokamak (ST) plasma configuration. The neutronics properties of these blankets’ were compared and analyzed. The results show that for the transmutation of ²³⁷Np, FLiBe-cooled waste transmutation blanket has the most superior transmutation performance. The calculation results of the helium-cooled waste transmutation blanket show that this transmutation blanket can run on a steady effective multiplication factor (k_eff), steady power (P), and steady tritium production rate (TBR) state for a long operating time (9.62 years) by change ²³⁷Np’s initial loading rate of the minor actinides (MA).

Assembly of beam extraction system of 4MW EAST-NBI ion source

LI Jun, HU Chun-dong, XIE Ya-hong, WEI Jiang-long

2012, 32(4): 351-355.

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According to the characteristic of extraction system of EAST-NBI and the requests of assembly, the assembly methods were studied. Several methods were used to eliminate the assemble error, and the overall error is less than 0.05mm, the leak rate of vacuum interface is less than 1×10^-7Pa.L.s^-1, and the resist pressure of cooling water pipe can reach 1MPa. Besides, the extraction system tested with 100kV static high voltage. It is meets the requirement of design of beam extraction system, and ensure the development of mage-watt high current ion source.

The fabrication of polycrystalline Si thin film by electron cyclotron resonance plasma source enhanced CVD

ZUO Xiao, WEI Yu, CHEN Long-wei, SHU Xin-sheng, MENG Yue-dong

2012, 32(4): 356-361.

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The Polycrystalline silicon thin films were directly fabricated on K9 glasses at low substrate temperatures by the use of electron cyclotron resonance plasma source enhanced chemical vapor deposition system. In order to explore the optimal deposition condition of polycrystalline silicon thin films, the influence of different deposition parameters (such as hydrogen dilution ratio, substrate temperature) on the deposition was studied. The X-ray diffraction spectra, Raman spectra and scanning electron microscopy measurements were carried out to characterize the micro-structure and the topography of polycrystalline silicon thin films. The results showed that polycrystalline silicon thin films with the maximum crystallization fraction of 62% were obtained, which was reported to be suitable to fabricate high efficiency thin film silicon solar cells. The maximum size of crystal clusters was 500 nm. It was found that columnar structure crystals were deposited on the glass substrates, however, with an amorphous incubation layer formed first; higher hydrogen dilution ratio and substrate temperature were beneficial to improve the crystallization fraction.

Nelder-Mead algorithm for inversion analysis of plasma parameters in stealth application

CHENG Li, SHI Jia-ming

2012, 32(4): 362-365.

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The multi-parameter optimization of plasma was performed by using the Nelder-Mead algorithm for getting the optimal point, and the optimal solution of plasma’s parameters in stealth application was solved. The results of the parametric inversion show that in the spans of the parameters against the nonmagnetic and uniform plasma, the attenuation level was decided by the electron density， collision frequency and the thickness of plasma layer. The optimal absorptive wavelength was decided by the thickness of the plasma layer, and when the frequency of the incident wave was greater than a threshold, the collision frequency of plasma was tended towards a stable value.

Development of atomic oxygen source for space tribology test

MA Guo-zheng, XU Bin-shi, WANG Hai-dou, ZHANG Sen, TONG Jing-yu

2012, 32(4): 366-371.

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In order to investigate the interaction mechanisms between space atomic oxygen (AO) environment and friction material, an AO beam source for space tribology test was developed on the basis of MSTS-1 vacuum tribometer. The radius of beam area is more than Æ50mm, the flux density and energy of the AO beam are 2.6×10¹⁵atoms×cm^-2×s^-1 and 5~10eV, respectively. The typical spacecraft material, i.e. Kapton, is exposed in the simulation facility, and the test results are similar to those of space flight exposure tests. In addition, the performance of the AO source is very stable and can work in high vacuum, the composition of the beam is pure. So the AO source not only satisfies all the special requirements of space tribology test, but also can be used to other space environment simulation test.

Numerical analysis of the effect of plasma flow control on enhancing the aerodynamic characteristics of stratospheric screw propeller

CHENG Yu-feng, NIE Wan-sheng

2012, 32(4): 372-378.

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Based on the body force aerodynamic actuation mechanism of dielectric barrier discharge (DBD) plasma, the effect of plasma flow control on enhancing the aerodynamic characteristics of ten blade elements equably along the stratospheric screw propeller blade was numerical studied. Then the effect of plasma flow control enhancing the aerodynamic characteristics of stratospheric screw propeller was compared that by the blade element theory method. The results show that the flow separate phenomena will easily happen in the root region and top end region of screw propeller, and the blade elements in the root region of screw propeller may work on the negative attack angle condition. DBD plasma flow control can entirely restrain the faintish flow separate phenomena in middle region of screw propeller. Although DBD plasma flow control can not entirely restrain the badly flow separate phenomena in top end region of screw propeller, it also can enhance the aerodynamic characteristics of blade elements in these regions in same degree. But effect of DBD plasma flow control on enhancing the aerodynamic characteristics of the blade elements working on the negative attack angle condition is ineffectively. It can be concluded that DBD plasma flow control can enhance the aerodynamic characteristics of stratospheric screw propeller, the thrust of the whole propeller and the propeller efficiency in the case of plasma on will increases by a factor of 28.27% and 12.3% respectively compared with that in the case of plasma off studied.

Nuclear Fusion and Plasma Physics Vol.32 (2012)

2012, 32(4): 379-384.

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