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

• 来源期刊: 中国物理（英文版）
• 关键词: soft x-ray tomography sawtooth oscillation singular value decomposition (SVD)
• 年，卷（期）: 2005,（10）
• 页码范围: 2061-2067
• 页数: 7页
• 语种: 英文

摘要

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 decomposition 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 quasiinterchange 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.