Electron density and temperature in the CDX-U low aspect ratio tokamak
are too low to allow observation of fast magnetohydrodynamic activity
using soft x-ray continuum emission. However, spectroscopic measureme
nts show that extreme ultraviolet (XUV) line emission of intrinsic imp
urities is bright enough to observe such activity. In addition, a fast
monitoring system for local temperature changes in the plasma core is
required for planned auxiliary heating experiments. We present a spec
trally resolved tomographic system for fast imaging of O VI 2s-np, 2p-
nd (n greater than or equal to 3), C V 1s(2)-1s(2)p and C VI 1s-2p XUV
transitions. Using this emission, we can study both core and edge MHD
activity, while the C VI to C V intensity ratio can indicate local ch
anges in electron temperature. To achieve maximal throughput together
with the needed spectral resolution, we use arrays of surface barrier
diodes filtered with bandpass elemental filters. Using M edge filters
(Zr, Pd, and Ag), we achieve both good discrimination between the abov
e charge states and large transmission at the wavelengths of interest.
Preliminary results obtained from CDX-U are presented. (C) 1997 Ameri
can Institute of Physics.