Development of a High-Speed VUV Camera System for 2-Dimensional Imaging of Edge Turbulent Structure in the LHD

概要

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To clarify the role of edge turbulent transport, measurements of fluctuations with high temporal and spatial resolution are necessary. In this case, if 2-dimensional structures are observed, more detailed characteristics of edge turbulence can be clarified, since the propagation direction of the fluctuations and the mode number are directly visually studied. Therefore, a high-speed vacuum ultraviolet (VUV) camera system for 2-dimensional imaging of edge turbulent structures was developed and installed in the Large Helical Device (LHD). This optical system is composed of two multi-layer mirrors made of Mo/Si and a micro-channel plate (MCP). VUV emissions from plasmas are reflected at the multi-layer mirrors with high reflectivity and imaged on the MCP. The VUV emission of impurity carbon (n = 4-2 transition of C VI) near 13.5 nm can be observed with this system. In this paper, the components of this VUV camera system and the analytical method and calculations are described in detail. Moreover, preliminary results observed in the LHD are presented.