Time-resolving extreme ultraviolet spectrograph for fusion diagnostics

Abstract

A time-resolving spectrograph for the simultaneous measurement of emissions at extreme ultraviolet wavelengths (300–2200 Å) is described. The spectrograph is a 400-mm normal incidence f/30 system with seven gratings. Together two of the gratings cover the entire wavelength range at low resolution. The other five gratings have higher dispersion and cover adjacent intervals of the spectrum. The spectral resolution varies between 0.7–4 Å. The detector consists of a windowless microchannel plate/phosphor screen image intensifier, coupled by fiber optics to a 1024-element self-scanning integrated photodiode array. The output from the array is digitized and stored by a small desktop computer which has sufficient memory to record up to 80 spectra during a single plasma discharge.