Nuclear Fusion and Plasma Physics

Predictive simulation of neutral beam injection with different density on EAST

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

2012, 32(3): 193-198.

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Accurate simulations of neutral beam injection (NBI) in the experimental advanced superconducting tokamak (EAST) are vitally important for the analysis of future experiment since NBI is an important plasma heating and current drive tool. The different plasma density profiles of EAST can lead to different target electron and ion heating, shine-through power loss, beam-driven current and neutron emission with 4MW and 80keV beam co-injection using ONETWO and NUBEAM codes. The plasma density plays an important role in the evolution of the above physical parameters. The effects of NBI due to two density cases on EAST are discussed and some advices are submitted for the future physical experiments.

Numerical simulation of two-dimensional inductively coupled plasma torch based on FLUENT

ZHU Hai-long, TONG Hong-hui, YE Gao-ying, CHEN Lun-jiang

2012, 32(3): 199-205.

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Considering plasma as magnetic fluid in which both fluid properties and electromagnetic effects are taken into account, a numerical simulation method is introduced where FLUENT software has been developed to solve electromagnetic equation continuity equation, momentum conservation equation as well as energy conservation equation. The electromagnetic field formulated in terms of vector potential, temperature and velocity profile are obtained. Numerical simulation is carried to investigate the electromagnetic field, temperature and velocity profile of inductively coupled plasma (ICP) torch. In particular, the physical mechanisms of temperature and velocity profile are emphatically analyzed, which offer a much better way to understand the spheroidization of powders by ICP torch.

The simulations of the charged particles (e, N₂⁺, N⁺) in Nitrogen radio frequency discharge by PIC-MC model

YANG Ying, FU Dong-ru, ZHANG Lian-zhu

2012, 32(3): 206-212.

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N₂ capacitively coupled rf discharge was simulated by PIC/MCC model, in which we computed the rf electric field, the density and mean energy of charged particles (e, N₂⁺, N⁺)，the energy distribution of ions (N₂⁺, N⁺) bombarding rf electrode and their variation by following different discharge parameter (p, V_rf). The simulated results show that, ions (N₂⁺, N⁺) seem to follow the electric field with a slight delay; the ions N⁺ have higher energy near the two electrode, the ions N₂⁺ have higher density, and the N₂⁺ density is about six times of the N⁺ density. With as the change of discharge parameter, the change of the energy of ions (N₂⁺, N⁺) bombarding rf electrode is obvious, but the change of their density is slightly unconspicuous. The simulated results for electron energy probability distribution function are agreement with the measured results.

Reducing of runaway electrons by increasing plasma density on HT-7 tokamak

ZHU Jin-xia, DUAN Zhuo-qi, ZHU Jun, FANG Da, CHEN Zhong-yong

2012, 32(3): 213-217.

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Using the hard X-ray (HXR) detection system during the current flat-top phase of ohmic discharge in the HT-7 tokamak, the behaviour of runaway electrons has been studied by means of measuring the HXR produced by the runaway electrons bombarding the first wall material. During plasma density increasing at the phase, we found that HXR intensity is reduced rapidly to a very low level, which implicated that the amount and energy of runaway electrons might be reduced effectively by increasing plasma density at the current flat-top phase.

Numerical simulation of a DC double anode arc plasma torch

CHEN Lun-jiang, TANG De-li, ZHU Hai-long

2012, 32(3): 218-223.

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A 2D axisymmetric numerical simulation of DC double anode plasma torch was done by the computational fluid dynamics (CFD) software FLUENT to improve the efficiency of the waste treatment, which is on the basis of the magnetic fluid dynamics (MHD) theory and uses the method of magnetic vector potential, and the simulation method is based on SIMPLE algorithm. The temperature and speed distributions of the plasma, and so on were obtained. The results show that the temperature of plasma decreases with increasing the axial distance, and increases with increasing the amplitude of the arc current. The velocity first increases and then decreases with the axial distance increase, and increase with the arc current increase. The temperature and the speed at the export of the plasma torch both decrease when the radial distance increases. Those results are in agreement with the experimental results.

Optimization of the stray magnetic field induced by the TFC feeder for HL-2M tokamak

HUANG Zhong-fa, LI Qiang, LI Guang-sheng, JIANG Jia-ming, LIU Jian, CAI Li-jun, CEN Yi-shun

2012, 32(3): 224-229.

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Optimization of the stray magnetic field in the plasma area induced by the feeder system of toroidal field coils (TFC) for HL-2M tokamak is presented. By adjusting the structural parameters of TFC feeder, such as the outer arc radius of the lead bus, the inner and outer arc radius of the return bus and the gap between return bus and TFC, etc., the stray field in the plasma area is minimized, and the maximum field is 3.69×10^-4T. The maximum temperature rise in the feeder after one shot is estimated, the results show that the feeder doesn’t need to be cooled actively Based on the optimized parameters, the mechanical structure of the feeder and its support, such as the size, connector, flexible feeders, etc., are preliminarily analyzed.

Research and development of gas analysis and testing system of quadrupole mass spectrometer

CAI Xiao, CAO Zeng, HUANG Xiang-mei, XU Zheng-hua, CUI Zheng-he, GAO Xiao-yan

2012, 32(3): 229-234.

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The gas analysis and testing system of quadrupole mass spectrometer was designed to research leak calibration, discrimination between helium and deuterium, and leak testing technology. The paper describe the structure of vacuum chamber, selection of pumping equipments, choice of measuring instruments, and working mode of control protection subsystem. The performance experiments of the system, including ultimate vacuum, mass spectrometric analysis of residual gas, leak and outgassing rate, and performance of mass spectrometer, are given. The experimental results show that the gas analysis and testing system satisfies our design requirements.

Electromagnetic and structure analysis for EAST vacuum vessel under major plasma disruption

LI Jun, XU Wei-wei, SONG Yun-tao, JI Xiang

2012, 32(3): 235-239.

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The eddy current, electromagnetic force and stress are computed using the ANSYS finite element software for the vacuum vessel during the major plasma disruption. The model contains the basic plasma facing components to learn the structure strength of the vacuum vessel under the transient electromagnetic force more accurately. The results indicate that high transient stress on vacuum vessel is brought by the high field plate and the inner plate, but the vacuum vessel is still strong enough to bear the electromagnetic loads. This analysis can help to check and improve the design of plasma facing components.

Study on the optical property of the first mirror exposed in EAST

YAN Rong, CHEN Jun-ling, ZHU Da-huan, LIU Yang

2012, 32(3): 240-245.

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Three different kinds of metal first mirrors made from the stainless steel, tungsten and molybdenum materials were installed on the windows of the puffing, boronization, limiter systems of EAST tokamak, and exposed during the spring experiments of the 2010 to first investigate the influence of the exposure environment on the optical property of the first mirrors. After exposure, the thick contaminant deposit layers were formed on the mirror surface and the optical property degraded seriously because of the deposit layer. Thus, to ensure the lifetime of the first mirror, the effective protective system for the mirror and the in situ cleaning of the mirror surface must be applied.

Study on low-frequency resonance of the reactive compensation system of EAST

LI Min, XU Liu-wei

2012, 32(3): 246-249.

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The power supply of EAST contains a reactive compensation system, which consists of the fixed condenser and TCR. In order to prevent negative effects of parallel-resonance on EAST experiment and power net safety, the low-frequency resonance between the reactive compensation system and distributed inductance of the 10kV grid is analyzed, which shows that the low-frequency resonance point varies from 2.04 to 2.24 with the variance of TCR, and the 2nd harmonic current of EAST power supply will meet up to the national standard after amplified. The simulation on the entire system with MATLAB and PSCAD verifies the results above.

Stress analysis and optimization design of S-bend for ITER feeder

XU Wei-wei, SONG Yun-tao, LU Jian-wu, WANG Zhong-wei, CHENG Yong, LIU Xu-feng

2012, 32(3): 250-254.

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Based on the energy principle, by means of the unit force method and the Castigliano theorem, the moment and stress distribution along the S-bend under the given displacement deformation are calculated analytically. According to the calculation, the moment and the stress along the S-bend arise mainly due to the thermal contract, but the gravity effect is nonnegligible. The maximum stress along the S-bend will increase by over 10% after the gravity effect is taken into account. Based on the premise that the height of S-bend is limited, it is found that the smaller the radius of the circles, the smaller the maximum stress along the S-bend, so we can choose the appropriate radius according to the required stress strength and the processing technology during the detailed design. Results shows that the analytical method proposed here is effective and useful for the structure optimization of the practical engineering design.

Effect of electrical ring on ion temperature after magnetoelectric heating

SHEN Wu-lin, MA Zhi-bin, TAN Bi-song, WU Jun, WANG Jian-hua

2012, 32(3): 255-259.

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The magnetoelectric heating system had been introduced on a non-symmetric magnetic mirror field ECR plasma apparatus. The effects of radius of electrical ring, axial position of the ring and double electrical ring on the ion temperatures had been studied. The results indicated that a suitable radius of electrical ring could improve ion temperature effectively and the optimal size of electrical ring depended on the cyclotron radius of ions mainly. The axial location of electrical ring was dependent on configuration of magnetic mirror field. It was the most advantageous to improve ion temperatures when electrical ring was set at a region where it had a weaker magnetic field strength in the middle of magnetic mirror field. Double electrical ring could further improve the ion temperature and the ion temperature was increased twice as the one of the single ring after heating.

Effect of bias voltage applied to target in hybrid- acceleration ion implantation system

ZHU Zong-tao, GONG Chun-zhi, WANG Zhi-jian, TIAN Xiu-bo, YANG Shi-qin, Ricky Fu

2012, 32(3): 260-264.

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The effect of bias voltage applied to target on the ion dynamic behavior of hybrid acceleration ion implantation based on target-acceleration is investigated by PIC/MCC simulation. Our interests are mainly focused on the variations of ion energy, implantation dose, and incident angle, as well as implantation region on target with different amplitudes of bias voltage. The results show that the potential contours above the target with negative pulse bias voltage become curved because of downstream movement of beam-line ions. Simultaneously, the gradually changing electric field also affects the trajectories of flying ions. The potential edge (0V) expands forward and the region influenced by electrical field of target increases with increasing the amplitude of bias voltage. The dose and average energy of ions implanted into the surface of target increase due to the increasing velocity of ions, which are effectively accelerated by the bias voltage applied to the target. Although some of ions within curved electric field lines deflect, the average incident angle is still relatively low and the amplitude of bias voltage has no significant influence on the incident angle. Due to the deflection of beam-line ions induced by the electric filed of target, the area of implantation region on the surface of target with higher bias voltage is larger than that with lower bias voltage.

Numerical study on plasma flow control to enhance the aerodynamic characteristic of the aerofoil on propeller root region

CHENG Yu-feng, NIE Wan-sheng, CHE Xue-ke

2012, 32(3): 265-271.

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Based on the body force aerodynamic actuation mechanism of dielectric barrier discharge (DBD) plasma, the effect of DBD plasma flow control to enhance the aerodynamic characteristics of aerofoil on propeller root region under the negative angle of attack condition was numerically studied at two kinds of actuator location schemes. The results show that the plasma induce body force imparted by the actuator located at down surface of the aerofoil is bigger than that imparted by the actuator located at front or behind of the aerofoil. When DBD actuator is located at down surface of the aerofoil, the separate flow phenomenon can be entirely restrained, but the negative thrust of propeller will increase, so the torque of propeller will decrease. When the actuator is located at front and behind of the aerofoil, the thrust generated by the aerofoil of propeller root region under the negative angle of attack condition will increase, but the separate flow phenomenon cannot be restrained, so the torque of propeller will also increase.

Reaction of dielectric barrier discharge plasma with crude oil

YU Hong, LING Wei, ZHAO Ming, WANG Jie-xiang, LIU Yan-min

2012, 32(3): 271-277.

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Heavy oil was treated in dielectric barrier discharge (DBD) plasma reactor with air and argon used as the work gas respectively. When air was used, the oil became more viscous. Results from Fourier transform infrared spectroscopy measurement and the SARA analysis showed that the oil colloidal system was destroyed, a lot of gas was produced, and heavier components (Resin and asphaltene) left in oil. To make the analysis and explanation easier, argon was used as work gas. Gas chromatography (FID and TCD) was used to analyze the gas production, there were lot of C₁−C₅ hydrocarbons, and H2 was also of great concentration. Total content of hydrogen and methane is more than 70% of gaseous product. This showed that the cracking of heavy oil occurred. Heavy oil mobility was deteriorated by plasma, this indicated that polymerization reaction occurred as well as heavy oil was cracked.

Research of the emission spectrum of methane plasma in MPCVD

ZHENG Xiao-yi, XU Wei, WU Zhi-liang, XU Bai-ru

2012, 32(3): 278-282.

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The emission spectroscopy of the hydrogen and methane plasma which induced by microwave plasma in a chemical vapor deposition reactor was detected by multichannel spectrometer. It shows that the CH, CH^-, C₂ groups were main cracking production of methane in the plasma. The intensity of emission spectra of these groups was strongly impacted by the power and pressure during discharge process. With increasing microwave power the spectrum intensity was enhanced, with increasing discharge pressure, however, the spectrum intensity was first risen and then dropped. These experimental results provide a reference to comprehend various reactions in the microwave plasma chemical vapor deposition (MPCVD) and, therefore, to improve film preparation.

Low temperature DBD linear plasma jet

SHI Dan-dan, HUANG Xiao-jiang, ZHONG Fang-chuan

2012, 32(3): 283-288.

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A co-axis cylindrical dielectric barrier discharge (DBD) linear plasma jet generator is developed. The linear plasma jets with 50mm width are produced. The effect of gas pressure, flow mass, discharge voltage, absorption power and discharge chamber structure on the plasma jet length are investigated. It is found that the linear plasma length is lengthened and then saturated when gas pressure and flow mass is increased, and the linear plasma length is enhanced when the discharge voltage is increased. The nitrogen plasma jets is diagnosed by using optical emission spectra and the plasma component are analyzed. It is found that the main component existing in N₂ plasma jet are N₂ and a little of N. As the gas temperature equal to the rotational temperature in the plasmas, it is obtained that the gas temperatures are from 290K to 350K in the plasmas.

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