Table of Content

15 September 2013, Volume 33 Issue 3

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Plasma Physics

Third kind ballooning theory of two dimensional tokamak local modes

ZHANG Yang-zhong, XIE Tao

2013, 33(3):  193-199. 

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The ballooning theory of the third kind is constructed in parallel to the ballooning theory of the first and the second kind by making use of the 2-D ballooning representation. Compared to the ballooning theory of the first kind, the restriction to applicability due to solvability condition is found greatly relaxed to wider parameter domain; and compared to the ballooning theory of the second kind, the solution with higher growth rate is obtained because the destabilization from “bad curvature” is well included within the framework of the theory, which in turn, makes the numerical results more comparable with those from initial value simulations. The fluid model equation for ion temperature gradient mode in toroidal coordinate is adopted to calculate growth rate and eigen frequency as well for selected profile parameters. The results are presented graphically, compared and discussed with the two previous ballooning theories; also discussed is the implication with regard to improved confinement in tokamaks.

The statistic-thermodynamically calculations of magnetic thermodynamically functions for nuclear magnetic moments

ZHU Zheng-he, LUO De-li, FENG Kai-ming

2013, 33(3):  200-205. 

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The present work is to calculate the magnetic thermodynamically functions, i.e. energy, the intensity of magnetization, enthalpy, entropy and Gibbs function for nuclear magnetic moments of T, D and neutron n at 2T and 1, 50, 100 and 150K from partition functions. It is shown that magnetic saturation of thermonuclear plasma does not easily occur for nuclear magneton is only of 10^-3 of Bohr magneton. The work done by magnetic field is considerable.

The propagation of blobs in the scrape-off layer of tokamak

XU Jian-qiang, PENG Xiao-dong

2013, 33(3):  206-213. 

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The propagation of special coherent structures (blobs) in the tokamak scrape-off layer (SOL) is studied numerically. Considering that the hypothesis which assumes that electrostatic potential φ <<1 in existing model is not self-consistent with numerical results, thus modification is done to blob dynamics. Results show that the symmetry of the blob in the poloidal direction is broken and the reason for the symmetry break is discussed briefly. The blob velocity increases with its initial relative amplitude, while decreases with the rising of plasma sheath dissipation near the divertor plate. It should be emphasized that a new type of coherent structures with density lower than the bulk plasmas referred to as holes appears in the presence of strong sheath dissipation.

Mechanisms of the negative synergy effect between electron cyclotron current drive and lower hybrid current drive in tokamak

CHEN Shao-yong, HONG Bin-bin, YANG Wen, TANG Chang-jian, ZHANG Xin-jun

2013, 33(3):  214-218. 

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The synergy current drive by combining electron cyclotron wave (ECW) with lower hybrid wave (LHW) can be used to either increase the noninductive current drive efficiency or shape the plasma current profile. In this paper, the synergy current drive by ECW and LHW is studied with numerical simulation. The nonlinear relationship between the wave powers and the synergy current of ECW and LHW is revealed. When the LHW power is small, the synergy current reduces as the ECW power increases, and the synergy current is even reduced to lower than zero, which is referred as negative synergy in the this context. Research shows that the mechanism of the negative synergy is the peaking effect of LHW power profile and the trapped electrons effect. The present research is helpful for understanding the physics of synergy between electron cyclotron current drive and lower hybrid current drive, it can also instruct the design of experiments.

Scattering H atoms on first wall material Be by molecular dynamics simulation

TIAN Shu-ping, CAO Xiao-gang, ZHANG Jing-quan, PAN Yu-dong, GOU Fu-jun

2013, 33(3):  219-225. 

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The scattering behaviour of H atoms on Be surface by molecular dynamics simulations was reported in this paper. When the incident energy increases from 1 to 9eV, the outcome shows the H atoms scattering rate decrease with incident energy increasing, and increase with incident angle increasing. When incident energy is 1eV, all of incident H atoms scatter above the Be surface. When incident energy are 5 and 9eV, 14.7% and 35.8% of H atoms inject into the Be sample and then scatter, respectively, and incident depths increase with energy increasing. Scattering density and energy as function of scattering angle were also discussed.

A numerical solution of the Thomas-Fermi equations for mixtures

MENG Dong-yuan, ZHANG Ling-yu, YAN Xue-song, LIN Ping

2013, 33(3):  226-230. 

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Thomas-Fermi model can be applied to describe state of electrons for mixtures. A method to solve the mixture Thomas-Fermi equation is proposed. With the proper initial test solution and step length, this method searches the solution in a way that reduces the steps by half, which can get solutions with various densities and temperatures fast.

Nuclear Fusion Engineering and Technology

The real time equilibrium reconstruction algorithm for HL-2M tokamak

MAO Rui, LI Jia-xian, MA Rui, ZHANG Jin-hua

2013, 33(3):  231-238. 

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The simulation results of the plasma reconstruction were obtained and compared with the accurate balance results. With the introduction of random errors in the simulation process, robustness of the inversion procedure had been verified. The reconstruction results using the experimental data from EAST device had been compared with the inversion results from EAST’s RTEFIT to verify the correctness of the results that a single time and the continuous-time inversion. The results show that, choosing the current distribution model and magnetic diagnostic data through the equilibrium reconstruction algorithm can correctly identify the plasma shape.

Error analysis of magnetic diagnostic signal on HL-2M

MA Rui, ZHANG Jin-hua, LI Jia-xian

2013, 33(3):  239-243. 

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To decide the allowable error range of magnetic measurement system, it is assumed that the measurement errors of the magnetic probe and flux loop signals are characterized by a normal probability distribution on HL-2M. The input signals with errors are calculated using the EFIT code in fitting mode. The analysis results show that the good plasma configuration can be obtained if the measurement errors are lower than 4%.

Improved density measurement by FIR laser interferometer on EAST tokamak

CHEN Jie, JIE Yin-xian, LIU Hai-qing, WEI Xue-chao, WANG Zheng-xin, GAO Xiang

2013, 33(3):  244-250. 

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A three-channel far-infrared (FIR) HCN laser interferometer has been developed to measure the line averaged electron density on EAST tokamak. Detectors with the properties of high sensitivity, high signal-to-noise ratio, small volume and stability are needed in interferometer device. The application of new Schottky barrier diode (SBD) detector has made the density signal and the signal-to-noise ratio greatly improved. The disturbance caused by the lower hybrid wave can be eliminated by using double copper foil shield and narrow band pass filter. The improved detectors have worked well during the long pulse discharge and H mode discharge.

Wave-plasma coupling by measuring LH grill density in EAST

ZHANG Lei, DING Bo-jiang, WU Ze-ge, MA Wen-dong, LIU Liang, ZHU Wen-hua, LIU Fu-kun, SHAN Jia-fang

2013, 33(3):  251-256. 

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A triple Langmuir probe was installed at the top of the lower hybrid (LH) antenna in the experimental advanced superconducting tokamak (EAST). The probe system consists of a triple probe, a measurement circuit, data acquisition and data processing. The preliminary results show that injection of LH power increases the density in front of the LH grill. The relationship between grill densities and reflection coefficients (RCs) agrees with the theoretical prediction. The optimum density for LH coupling in EAST was measured, being in range of (4~5)×10¹⁷m^-3.

Structural design and coupled thermal-mechanical analysis for vacuum barrier of EAST

SHI Shan-shuang, SONG Yun-tao, WANG Zhong-wei, ZHANG Shan-wen

2013, 33(3):  257-261. 

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The structural design of the vacuum barrier was introduced, and then a 3D finite element model is established by using ANSYS for the purpose of coupled thermal-mechanical analysis. The temperature distribution and thermal stress in normal and fault condition is obtained from the calculation. The calculation results can verify the reasonability of the structural design of vacuum barrier and lay the foundation for the further optimization.

Upgrade of the software monitoring system for LHCD in EAST

WU Ze-ge, SHAN Jia-fang, WANG Mao, HU Huai-chuan, MA Wen-dong

2013, 33(3):  262-266. 

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Given the deficiency of the monitoring system in 4MW/2.45GHz LHCD, a new layer-based mode of the software monitoring is formulated for 6MW/4.6GHz LHCD system, which intends to provide better scalability. Both the monitor server and monitor client are implemented after solution to inter-process and network communication was brought out by taking advantage of QProcess and QTcpSocket classes in cross-platform developing framework Qt. The response time of the new software monitoring system proves to be less than 200ms after practical test and able to fully satisfy the requirements of 4.6GHz LHCD to monitor software devices within 2s.

Structure optimization of high power microwave ceramic window

SHANG Yun-ying, WANG Xiao-jie, LIU Fu-kun, LIU Liang, ZHAO Lian-min, JIA Hua

2013, 33(3):  267-271. 

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The structure and its optimization of 2.45GHz high power microwave ceramic window are introduced in this paper. The structure optimization includes optimization of structure dimensions and coolant flowing rate. The microwave properties are sufficient when the thickness of ceramic disk is 4.4mm and the length of cylindrical waveguide is 52.3mm. The maximum thermal stress on the ceramic disk is far less than the limitation that ceramic disk could sustainable stress when the coolant flowing rate is 0.4t×h^-1 . Optimized ceramic window did not appear crack problem after several runs of experiments.

Electrical properties of solder for ITER feeder system

ZOU Chun-long, SONG Yun-tao, HUANG Xiong-yi, LIU Cheng-lian, XI Wei-bin

2013, 33(3):  272-276. 

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In ITER Feeder system, the superconducting joints and the current leads should use solder to weld. In this paper, Bi-2223/Ag iswelded with different kinds of solders, and the weld procedure and the measuring device are introduced in this paper. The electrical property of the superconducting joint under liquid nitrogen was also measured and the result showed that Bi50Sn9Pb31, In99.99 and high melting point solder Sn96.5Ag3Cu0.5 have a lower resistance under liquid nitrogen, and satisfy the requirement for temperature gradient. This can make a reference for the solder measurement and choice of ITER Feeder system.

Non-Fusion Plasma Applications

The characteristic of electromagnetic scattering by uniform unmagnetized cold plasma cylinder

HUANG Fang-yi, SHI Jia-ming, YUAN Zhong-cai, WANG Jia-chun, CHEN Zong-sheng, LIN Zhi-dan, XU Bo, WANG Chao

2013, 33(3):  277-282. 

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The characteristic of electromagnetic scattering by plasma cylinder is researched in this paper. Scattered fields of the parallel-polarized wave and vertical-polarized wave by plasma cylinder are calculated and analyzed. The calculated results show that the higher the electron density, is the greater the scattering intensity in the outside of the cylinder and the higher the plasma frequency of collision, is the smaller the scattering intensity in the outside of the column. In addition, the electromagnetic wave polarization and frequency of the incident wave also have a significant impact on the scattering intensity of electromagnetic waves, the vertically polarized wave is more likely to be scattered, and the lower frequency of the incident wave is also easier to scattering. These have certain reference value for designing and studying of the plasma antenna.

Thermal diffusivity of reduced activation ferritic/martensitic steel studied by modified photoacoustic piezoelectric technique

ZHAO Bin-xin, WANG Ya-fei, GAO Chun-ming, WANG Ping-huai, GU Ti-bo, LIU Li-xian, SUN Qi-ming

2013, 33(3):  283-288. 

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Thermal diffusivity of reduced activation ferritic/martensitic (RAFM) steel CLF-1 has been determined by the modified photoacoustic piezoelectric (PAPE) technique. Firstly, the modified PAPE theoretical model is introduced and the experimental condition with high measurement precision are identified; Secondly, the experimental system is set up and calibrated by investigating the thermal diffusivity of nickel; Finally, the thermal diffusivity of RAFM steel CLF-1 is measured by the modified PAPE method. The results show that the RAFM steel CLF-1 has good thermal diffusion properties and is a fusion reactor structural material with excellent heat conductivity. The modified PAPE technique can determine the thermal diffusivity of RAFM steel CLF-1effectively, and provides an effective way to investigate the thermal-physical property of fusion reactor structural material.