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Chinese Physics, 2005, Vol. 14(10): 2061-2067    DOI: 10.1088/1009-1963/14/10/023
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES Prev   Next  

Study of sawtooth oscillations on the HT-7 tokamak using 2D tomography of soft x-ray signal

Ma Tian-Peng (马天鹏)a, Hu Li-Qun (胡立群)a, Wan Bao-Nian (万宝年)a, Ruan Huai-Lin (阮怀林)b, Gao Xiang (高翔)a, Zhen Xiang-Jun (甄香君)a, Zhou Li-Wu (周立武)a, Sun You-Wen (孙有文)a, Chen Zhong-Yong (陈忠勇)a, Lin Shi-Yao (林士耀)a, Kong Wei (孔伟)a
a Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China; b Institute of Electronic Engineering, Hefei 230037, China
Abstract  It is the first time so far as we know that two arrays of multi-channel soft x-ray detectors are used to generate two-dimensional (2D) images of sawtooth oscillation on the HT-7 tokamak using the Fourier--Bessel harmonic reconstruction method, and using the singular value ecomposition to analyse the data from soft x-ray cameras. By these two arrays, 2D image reconstruction of soft x-ray emissivity can be obtained without assumption of plasma rigid rotation.Tomographic reconstruction of the m=1 mode structure is obtained during the precursor oscillation of the sawtooth crash. The crescent-shaped mode structure appearing on the contour map of the soft x-ray emissivity is consistent with the quasi-interchange mode. The characteristics of the m=1/n=1 mode structure observed in the soft x-ray tomography are as follows:the magnetic surface is made up of the crescent-shaped ``hot core'' and the circular ``cold bubble''. The structure of the magnetic surface rotates in the direction of the electron diamagnetic drift and the rotation frequency is the oscillation frequency of soft x-ray signals.
Keywords:  soft x-ray tomography      sawtooth oscillation      singular value decomposition (SVD)  
Received:  24 March 2005      Revised:  25 June 2005      Accepted manuscript online: 
PACS:  52.35.Fp (Electrostatic waves and oscillations (e.g., ion-acoustic waves))  
  52.55.Fa (Tokamaks, spherical tokamaks)  
  29.40.-n (Radiation detectors)  
  52.25.Os (Emission, absorption, and scattering of electromagnetic radiation ?)  
  52.30.Cv (Magnetohydrodynamics (including electron magnetohydrodynamics))  
Fund: Project supported by the National Natural Science Foundation of China (Grant Nos 10375070 and 10305012).

Cite this article: 

Ma Tian-Peng (马天鹏), Hu Li-Qun (胡立群), Wan Bao-Nian (万宝年), Ruan Huai-Lin (阮怀林), Gao Xiang (高翔), Zhen Xiang-Jun (甄香君), Zhou Li-Wu (周立武), Sun You-Wen (孙有文), Chen Zhong-Yong (陈忠勇), Lin Shi-Yao (林士耀), Kong Wei (孔伟) Study of sawtooth oscillations on the HT-7 tokamak using 2D tomography of soft x-ray signal 2005 Chinese Physics 14 2061

[1] Tomographic analysis of the central magnetohydrodynamic oscillations on the HT-7 tokamak
Ma Tian-Peng (马天鹏), Ruan Huai-Lin (阮怀林), Hu Li-Qun (胡立群), Wan Bao-Nian (万宝年), Gao Xiang (高翔), Zhen Xiang-Jun (甄香君), Zhou Li-Wu (周立武), Sun You-Wen (孙有文), Gao Wei (高伟), Chen Zhong-Yong (陈忠勇), Lin Shi-Yao (林士耀), Kong Wei (孔伟). Chin. Phys. B, 2006, 15(3): 593-599.
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