Grazing incidence time-resolving spectrograph for magnetic fusion plasma diagnostics

A time-resolving grazing incidence spectrograph based on an image intensified photodiode array detector has been constructed and has demonstrated its utility as a fusion plasma diagnostic. The total wavelength coverage is 15–360 Å with 0.7 Å resolution (line profile FWHM); portions of this range may be observed during a single plasma discharge with a bandwidth of ∼40 Å when the detector is centered at 40 Å and ∼80 Å with it centered at 200 Å. Integration times from 5.4 to 13.1 ms are available when the entire photodiode array is read out; integration times as short as 1 ms can be obtained for a few lines of interest through the readout of selected photodiodes. The spectrograph has been radiometrically calibrated over the 60- to 360-Å range at the NBS SURF II electron storage ring and is currently in operation on the Princeton Large Torus (PLT) tokamak.