Space‐resolving flat‐field vacuum ultraviolet spectrograph for plasma diagnostics

A spatial imaging vacuum ultraviolet (VUV) spectrograph has been constructed for simultaneous observation of spatial and spectral distributions of plasma radiation in the wavelength range 150–1050 A. The spectrograph consists of an entrance slit of limited height which provides spatial resolution, an aberration‐corrected concave grating with varied spacing grooves which gives a flat‐field spectral output plane, and an image‐intensified two‐dimensional detector system. The basic characteristics of the spectrograph have been investigated by ray‐tracing calculations. The expected performance has been confirmed through experiments using a dc glow discharge source on the reciprocal dispersion, the spatial resolution, or the incident angle dependence of spectral images. VUV spectra with spatial and time resolution have been obtained successfully in the GAMMA10 tandem mirror experiment.