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.
Received: 24 March 2005
Revised: 25 June 2005
Accepted manuscript online:
PACS:
52.35.Fp
(Electrostatic waves and oscillations (e.g., ion-acoustic waves))
(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
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