Nuclear Fusion and Plasma Physics

Influence of the tearing mode instability of plasma axial motion

HAN Zui-jiao1, PENG Xiao-dong2

2015, 35(4): 289-295. DOI: 10.16568/j.0254-6086.201504001

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From the point of view of resistive MHD theory, the linear resistive tearing mode model in the low β plasma with macroscopic axial motion of plasma was deduced in a cylindrical geometry. Numerical study shows that the axial velocity of the plasma itself has a stable effect on tearing mode and the axial velocity shear role is not obvious. Analyses indicate that the axial motion reduces the tearing mode growth rate by changing the phase difference between the plasma potential perturbation and magnetic flux perturbation (deviating from π/2), and results in a lower tearing mode frequency.

Fishbone modes excitied by energetic particles in fusion plasmas

ZHAO Kang, HE Zhi-xiong, JIANG Hai-bing, HE Hong-da

2015, 35(4): 296-301. DOI: 10.16568/j.0254-6086.201504002

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A general dispersion relation for fishbone mode is obtained when spatial density profile and pitch angle profile are taken into account. The fishbone modes can be driven into the second stable regime by barely passing energetic particles in high β_hregion. The nonresonant fishbone mode can be induced by trapped energetic particles. Similar to the resonant fishbone modes, the nonresonant fishbone modes can also be driven into the second stable regime by trapped energetic particles and the real frequency linearly increases with increasing β_h.

Design of ERD diagnostic system on EAST tokamak

LI Ying-ying1, YIN Xiang-hui2, ZHANG Yi2, FENG Shuang-yuan2, FU Jia1, Lü Bo1

2015, 35(4): 302-307. DOI: 10.16568/j.0254-6086.201504003

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A new edge rotation diagnostic system (ERD) was developed to measure the edge plasma rotation velocities and ion temperature profiles toroidally and poloidally. The collective optics adopts the ‘plug-in’ concept and is very flexible for additional system adjustment and maintenance after installation. For the spectrometer, a multi-slit entrance is used to effectively improve the capacity of the spectrometer and accommodate more optical fibers. A back-illuminated EMCCD is adopted as the photon detector for its high sensitivity and wide dynamic range. The high OH-radical concentration fused silica fibers are adopted to resist the neutron radiation. The system is in the visible wavelength range (350~800nm), the achieved temporal and spatial resolution is 15ms and 1cm respectively. Experimental results during the LHW phase are consistent with the collaborative experimental results from the XCS and fast reciprocating probe.

Phase shift real-time calculation method for J-TEXT polarimeter-interferometer signal

ZHANG Ming1, 2, YUAN Tao1, 2, ZHENG Wei1, 2, LIU Yang1, 2, LI Qiang1, 2, CHEN Zhi 1, 2

2015, 35(4): 308-313. DOI: 10.16568/j.0254-6086.201504004

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To calculate the phase shift, zero-crossing detection, digital correlation method and FFT are commonly used. Tests on the three algorithms show that, they can obtain phase shift accurately in dozens of microseconds delay, but resources and time cost are different. Zero-crossing detection needs more resources, but less time. FFT has large resource occupancy and latency. Digital correlation method is just the opposite to FFT, but detecting phase reverse is difficult.

E1 and M1 transitions of Au⁵⁰⁺ in Au laser plasma

XU Min1,2 , YAN An-ying1 , JIANG Gang2

2015, 35(4): 314-319. DOI: 10.16568/j.0254-6086.201504005

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Using the fully relativistic configuration interaction (RCI) method and the multi-configuration Dirac-Fock (MCDF) method and taking quantum electrodynamical (QED) effect and Breit correction into account, wavelengths, transition probabilities and oscillator strengths were calculated for electric dipole (E1) transitions and magnetic dipole (M1) transitions in Au⁵⁰⁺ ion. The obtained energy levels of some excited states and wavelengths of transitions in Au⁵⁰⁺ ion from the method were compared with other theoretical and experimental results, and a good agreement with other results was shown. The calculated transition probabilities and oscillator strengths in E1 transitions using the velocity and length gauges respectively confirmed the accuracy of our calculations. The calculation results indicated that for high-Z highly ionized atom, some forbidden transitions could be very important.

Numerical simulation and analysis for the cooling of HL-2M toroidal field coils

LU Yong, CAI Li-jun, ZOU Hui, LI Guang-sheng, LIU Jian, LIU De-quan

2015, 35(4): 320-326. DOI: 10.16568/j.0254-6086.201504006

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The water-cooled model of the toroidal field coils was established calculated according to the heat conduction and the convective heat transfer equation. The results show that the thermal contact resistance and the electrical contact resistance of the interface between the finger joint and the copper plate had a larger effect on the temperature rise of the finger joint. At maximum current of 140kA and the current flattop 7s, the maximum temperature rise of the toroidal coils with the finger joint was below 40℃, so the maximum temperature of the coils wouldn’t exceed 80℃, and the temperature of the toroidal field was below 30℃ after an interval of 15min. However, at maximum current of 190kA, the current flattop time was determined by the thermal contact resistance, the electrical contact resistance and initial temperature.

Blanket design and neutronics analysis for compact tokamak test reactor

MIAO Peng1, 2, WANG Su-hao1, 2, ZHANG Guo-shu2, FENG Kai-ming2

2015, 35(4): 327-333. DOI: 10.16568/j.0254-6086.201504007

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Using Monte Carlo particle transport code MCNP, the 3D neutronics analysis as well as TBR calculation for high power compact tokamak (CT) test reactor were done. The structure design for helium cooling ceramic breeder (HCCB) blanket was carried out with Li₄SiO₄, Be and the low activated ferrite steel as the tritium breeder, neutron multiplier and structural material respectively. The variation of TBR vs the breeding unit thickness was simulated, under different breeding unit with different structure arrangement. The preliminary optimum design of blanket with tritium self-sufficiency was obtained. The related characteristics of neutron wall loading, energy deposit and power density was given, as supplies data support for the thermal hydraulics and related design and analysis in next step.

Development of high power RF ion source for NBI

CHEN De-zhi, LI Dong, LIU Kai-feng, HUANG Jiang, LIU Da-wei, YUE Hai-kun, LI Xiao-fei, ZHOU Chi, ZHANG Zhe

2015, 35(4): 334-339. DOI: 10.16568/j.0254-6086.201504008

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A radio frequency (RF) driven negative ion source for NBI purpose was established at HUST. The main parameters include: pressure of 0.3Pa, frequency of 1MHz, ceramic cylinder diameter of 300mm. With 16kW RF power input the plasma density is greater than 10¹⁸m^-3.

Structural analysis and optimization of the middle ELM coil support for ITER

LU Su, ZHANG Shan-wen, SONG Yun-tao, WANG Zhong-wei, JI Xiang

2015, 35(4): 340-345. DOI: 10.16568/j.0254-6086.201504009

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Due to the position of ITER ELM coils assembly and its working condition, these coils are subjected to large electromagnetic force and thermal expansion caused by the nuclear heat and ohmic heat. The stress analysis and optimization work within six different design schemes of ELM Coils (ELMC) support are carried out by finite element software ANSYS. The analysis results proof that when the support has the V character configuration alignment of its transversal elliptical through-holes on both ends of top and bottom, the maximum Tresca stress is at the lowest value. The final outcome brings about meaningful reference for ELMC support design.

Design and implementation of the matching unit for a high-power RF based ion source

YUE Hai-kun1, 2, LI Dong2, LIU Kai-feng2, LI Xiao-fei2, WANG Chen-re2, CHEN De-zhi2

2015, 35(4): 346-349. DOI: 10.16568/j.0254-6086.201504010

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For a RF ion source test facility, the driver is used to produce plasma, and the matching unit is the key for the driver to absorb RF power. The driver’s impedance could be equivalent to a resistance and an inductance in series. A matching unit which consisted of an RF transformer and two variable capacitances was chosen, it was analyzed by an ideal transformer model and its electrical parameters were derived under the condition of matching. When a quartz glass driver was mounted onto the test facility at HUST, a matching unit was implemented, it transmitted RF power into the driver and then plasma was successfully produced.

Calculation and determination of parameters on plane mirror’s rotating mechanism in EAST ECRH antenna

HU Ze-kai, WU Jie-feng, LI Bo, WANG Xiao-jie

2015, 35(4): 350-355. DOI: 10.16568/j.0254-6086.201505011

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To precisely control the microwave’s position parameters, the relational expression between driving motor’s displacement and mirror’s rotating angle as well as the relational expression between mirror’s rotating angle and microwave’s launching angle has been calculated. The relationship curves were also given. In addition, the determination experiment has been carried out to mark the position of launching microwave, and the result showed these relational expressions are accurate, and can be the theoretical foundation of the plane mirror’s rotating mechanism’s driving control.

Thermal hydraulic analysis of EAST W-divertor outer target

XIAO Xuan, YAO Da-mao, CAO Lei, ZHOU Zi-bo

2015, 35(4): 356-360. DOI: 10.16568/j.0254-6086.201504012

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In order to improve the anti-thermal load and heat dissipation performance of the divertor of EAST, its first wall material is changed to tungsten from graphite. In the structure, outer target adopts the ITER-like monoblock, bracing and cooling structure adopts incorporate cassette. After establishing the cooling structure of EAST tungsten divertor, the flows-solid coupling heat conduction model of water-pipes is used to analyze the heat dissipation situation of outside target in the form of turbulent flow. While the cooling system comes to failure, a series of heat flux value 3MW·m^-2, 5MW·m^-2, 8MW·m^-2, 10MW·m^-2 are applied in the hazardous area to analyze transient conditions and real temperature distribution. The results shows that if the water flows at 4m·s^-1, the cooling pipes can withstand the heat flux with peak power in 10MW·m^-2. It can well meet the needs in heat dissipation of EAST experiment.

Experimental study for thrust enhancement of stratospheric propeller blade elements by unsteady plasma

TIAN Xue-min, TIAN Xi-hui, CHE Xue-ke, NIE Wan-sheng, CHEN Qing-ya, JIANG Jia-wen, ZHOU Si-yin

2015, 35(4): 361-367. DOI: 10.16568/j.0254-6086.201504013

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Based on Reynolds similar principles of plasma-induced jet and propeller blade element theory, experiment of propeller blade element wind tunnel was conducted. The effects of constant and unsteady model were compared, effect of different duty cycle and the frequency in unsteady model were studied. The results showed that: at the same voltage, the enhancement of propeller thrust was 9.8% by steady mode, unsteady mode was greater than the steady mode in enhancement of propeller thrust, the enhancement up to 20.4% in unsteady mode. The thrust enhancement of propeller blade elements by plasma was obvious with relative radius between 0.4 and 0.85, in order to improve energy efficiency, plasma actuator could be arranged between blade relative radius of 0.4 and 0.85. At the same frequency, enhancement of propeller thrust increased with duty cycle decreasing, and in duty cycle of 10%, the enhancement was greatest. At the same duty cycle, there existed an optimal frequency, it was 30Hz in which plasma enhanced propeller thrust the most.

Numerical simulation of RF oxygen discharge characteristics at atmospheric pressure

WANG Yi-nan, DAI Yu-jie, WANG Xue-hui

2015, 35(4): 368-372. DOI: 10.16568/j.0254-6086.201504014

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Based on diffuse and drift assumption, a 1-D fluid model of atmospheric pressure oxygen RF discharge was developed. The model includes continuity equations for electrons, positive and negative ions, and energy equation, and Poisson equation for eclectic potential. The finite difference method was adopted to solve the model by numerical simulation. The simulation results show that the electron density and electron temperature were 10¹²cm^-3 and 1.23eV, respectively, and the main negative ion was O^- . As the peak of voltage increased, the electron density and electron temperature increased, however, the ratio of O^-/n_e had a maximum value at 700V.

Experimental study of the low power arc discharge assisted methane combustion

ZHANG Jun, FANG Shi-dong, SHU Xing-sheng, WANG Chuang, ZUO Xiao, MENG Yue-dong, WANG Shou-guo

2015, 35(4): 373-378. DOI: 10.16568/j.0254-6086.201504015

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Different ratios of methane/air in the low power arc discharges assisted methane combustion were studied at atmospheric pressure. Plasma emission spectroscopy was recorded by an optical emission spectrometer. The possible physical and chemical reaction process and mechanisms were discussed. With a plasma in the on or off state, the physical appearances of the methane combustion flame were observed and compared, the temperature of the flame in the main combustion zone was investigated. The gas compositions of CH₄, CO and O₂ were analyzed by the gas chromatography and flue gas analyzer. The results showed that when plasma was in the on state, the temperature of flame increased and the combustion efficiency enhanced in stable combustion due to decrease of CH₄, CO and O₂; the combustion enhancement was more obvious at low ratio of methane/air; the rich combustion limits in terms of the ratio of methane/air was extended from 16% to 21%.

Nuclear Fusion and Plasma Physics Vol.35 (2015)

2015, 35(4): 379-384.

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