Space-resolved VUV spectroscopy using the 3 m normal incidence spectrometer with back-illuminated CCD detector in the LHD

Abstract

Space-resolved VUV (300–3100 Å) spectroscopy using the 3 m normal incidence spectrometer has been developed for the study of edge plasmas in the Large Helical Device (LHD). The radial (vertical) profile is obtained with a space-resolved slit placed horizontally between the entrance slit and the grating of the spectrometer. Using a cylindrical mirror placed in the front of the entrance slit, which magnifies the vertical image five times, a full vertical distribution of the LHD plasma is projected on the back-illuminated CCD detector. The two-dimensional distribution can be measured by scanning a toroidal slit placed vertically between the spectrometer and LHD during a single discharge. Recently, first results were successfully obtained. Some examples of the vertical profile and temporal behaviors of the ion temperature are presented with a description of the instrumentation. Unfortunately, the poloidal rotation could not be measured, because the data from the CCD operated in room temperature included a lot of thermal noise. After repairing the cooling system, the S/N ratio can be much improved. The simultaneous measurement of the vertical profiles of VUV line emissions, ion temperature, and poloidal rotation will become possible.