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Study of sawtooth oscillations on the HT-7 tokamak using 2D tomography of soft x-ray signal 总被引:1,自引:0,他引:1
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It is the first time so far as we know that two arrays of multi-channel soft x-ray detectors are used to generate twodimensional (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. 相似文献
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Tomographic analysis of the central magnetohydrodynamic oscillations on the HT-7 tokamak 总被引:1,自引:0,他引:1
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Multi-channel soft x-ray (SX) detectors are applied to generate images of
magnetohydrodynamic (MHD) oscillation on the HT-7 tokamak, and the data
from SX cameras are analysed by using the
Fourier--Bessel harmonic reconstruction method and the singular value
decomposition. The image
reconstruction of SX emissivity is obtained on the assumption of plasma
rigid rotation. One of the important phenomena in the HT-7 discharge is the
transition from the sawtooth oscillations to the MHD oscillations when the
plasma density grows higher. The MHD structure
observed in the SX tomography is featured as follows: the magnetic surface of MHD
structure is made up of the crescent-shaped ``hot core' and the circular
``cold bubble'. The structure of the magnetic surface is relatively stable.
It rotates in the direction of the electron diamagnetic drift at a
frequency being the oscillation frequency of the MHD oscillations. 相似文献
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上海光源软X射线谱学显微实验站(BL08U)可实现30nm空间分辨的元素探测功能.实验中,对样品内要标识元素的吸收边附近两个能量(E1和E2,且E1E2)分别进行扫描成像,然后将这两幅吸收图上对应像素点的光密度相比,得到的相比双能衬度图像可有效地显示该元素的空间分布信息.相对于另一种常用的相减双能衬度图像分析法,这种方法对元素空间分布的显示更为灵敏、精确,判断空间点是否含有要标识元素的阈值的定义更为简单,物理意义更为清晰.通过对聚丙烯腈预氧化纤维截面氧元素分布的测量结果的分析计算,比较了这两种分析方法的差异,验证了相比双能衬度法的有效性.该方法为快速标识样品中的微量元素提供了一种很好的新型分析手段. 相似文献
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