VACUUM PHOTODIODE DETECTORS FOR BROAD-BAND VACUUM-ULTRAVIOLET DETECTION IN THE SAHA-INSTITUTE-OF-NUCLEAR-PHYSICS-TOKAMAK

We report on the application of the vacuum photodiode to detect vacuum ultraviolet (VUV) radiation emitted from the Saha Institute of Nuclea r Physics (SINP) Tokamak. It is simple to fabricate and provides broad band spectral response in the VUV and ultrasoft x ray (10 eV-1 keV). I n our design, a stainless steel photocathode is used, which has a resp onse identical to tungsten in the wavelength range 100-1200 Angstrom. Its surface is passivated, to minimize contamination and monolayer dep osition, by electropolishing it. Some representative experimental resu lts illustrating the range of applicability are presented with special emphasis on its performance in disruptive shots. (C) 1997 American In stitute of Physics.