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X-ray poloidal array

90 R-1

The x-ray diagnostic consists of 5 separate arrays of x-ray sensitive diodes (2 keV to 20 keV). The signals are sensitive to electron density, electron temperature and impurity radiation both from impurity lines and from enhanced Bremsstrahlung and recombination. DIII-D has carbon walls and all of the carbon lines have energies below the cut-off of the x-ray arrays, thus there is normally very little impurity line radiation contribution to the x-ray array signals. The continuum radiation goes roughly as ne**2 Z**2 e(-Ec/Te) *sqrt(Te), where Ec is the low energy cut-off of the array of about 2 keV, determined by the thickness of the beryllium window and characteristics of the detector.