| A high-speed Vacuum Ultraviolet (VUV) imaging telescope system has been developed in the Experimental Advanced Superconducting Tokamak (EAST). The VUV imaging system is composed of three main parts: a telescope system consisting two multilayer mirrors made of Mo/Si, a micro-channel plate (MCP) and a high-speed visible CMOS camera. The certain line emission of CVI (13:5 nm in wavelength p?q = 4?2 transition) is selectively measured by the Mo/Si multilayer mirrors.According to one-dimensional (1D) impurity transport equation, the peaking position of the C VI emission locates at a relative edge region[about ??(0.8,0.95)). Hence, it is possible to investigate the edge plasma behaviour with the VUV imaging system. This thesis is focused on to evaluation of imaging quality, code development certain techniques for data analysis, and code calculation results for experimental data in different plasma conditions.For the experimentally measured fluctuation data, the noise level is often comparable or even higher than the coherent fluctuation component. The singular value decomposition (SVD) method is employed to split the coherent component from the fluctuation data. And fast Fourier transformation method (FFT) is applied to extract the information of fluctuation frequency and plasma mode structure.Since the imaging data are line integrated measurement, developments of certain techniques for data analysis are required to obtain the information of the local emissivity. A new method is proposed to construct the so-called geometry matrix for the imaging system. The geometry matrix links the local emissivity and line-integrated measurement. The basic idea is to approximate the magnetic surfaces are by the trigons. The intersection of the line of sight and the trigons are calculated.Contribution from each layer to the all pixels can be estimated, and make it matrix-form. In addition, another method is proposed to construct geometry matrix for the tangentially viewing VUV imaging system on Large Helical Device (LHD). The basic idea is to convert the three-dimensional problem to be a two-dimensional one by project the sightlines onto a target plane. And the equilibrium code named HINT2 is employed. With HINT2 code, the magnetic field lines can be traced with finite beta.And the traces of magnetic field line which localizes outside the last closed flux surface (LCFS) can also be obtained with HINT2. Synthetic images can be made after the construction of geometry matrix. Consequently, the local emissivity can be estimated by comparing the assumed emission profile and line-integrated images.In order to evaluate imaging quality, a detailed image quality analysis of the VUV imaging optical system is performed by using ZEMAX software. Analysis of Modulation Transfer Function (MTF), spot diagram (SPT), encircled energy, ray fan and tolerance are conducted analysis will be discussed. From the Zemax analysis and calculation results, it is obvious that the requirements can be satisfied with acceptable imaging performance in this design.MHD instabilities with a poloidal / toroidal mode number m/n = 2/1 are often observed in EAST. And fluctuations with low-frequencies of? 2.3 kHz have been successfully observed by the VUV imaging system, which and it are consistent with the measurement results from by magnetic probes. The temporal (Chronos) and spatial (Topos) fluctuating component are obtained by performing applying SVD analysis on the VUV imaging data. The mode structure has been estimated by comparing the synthetic image to experimentally measured data. And the observed mode has a tearing-like structure.MHD instabilities with m/n = 2/1 have been observed successfully by the upgrade tangentially viewing VUV imaging system in LHD. From the Topos components, it is realized that MHD instability has an m=2 poloidal spatial structure. And by comparing the synthetic image and experimentally measured data, it is found that the observed mode may be the interchange mode.ELMs and disruptions are reported, as well. It indicates the VUV imaging system is a potential tool which can be applied successfully in various plasma conditions.However, the system can just view the plasma with its major optical axis parallel to the major radius at present, an upgrade of the optics to realize a tangentially view is scheduled, which is better for pedestal studies. The upgrade proposal is discussed in this paper, as well. |
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