Bolometric diagnostics in Tokamak de Varennes

Abstract

Radiative power from the main and divertor plasmas of Tokamak de Varennes (TdeV) is measured using a compact bolometric diagnostic. The diagnostic is comprised of a multichannel pin-hole camera and several collimated bolometers. The electronic circuit of the bolometers permits remotely controlled in situ calibration of the detectors. The pin-hole camera, with its 17 channels of thermistor bolometers, monitors the plasma poloidal cross section horizontally. In the same camera housing reside a pair of wide angle metal film bolometers that measure the total radiative losses from the main plasma, and a 16 channel x-ray-ultraviolet photodiode array. Five collimated thermistor bolometers project the vertical view of the plasma poloidal cross section. The divertor plasma losses are monitored by six pairs of collimated thermistor bolometers installed at different toroidal locations. One pair in the lower and three pairs in the upper divertor chamber measure the global power loss from the plasma in front of the outboard divertor plates. Two other pairs of bolometers located just behind the inclined divertor plate, measure the poloidal distribution of the plasma losses from the divertor plate to the X point with an improved spatial resolution. Three divertor bolometers and one of the wide angle bolometers in the main plasma are covered with MgF2 windows, for rough spectral analysis of the radiative power loss. Examples of bolometric measurements of the radiative loss and its distribution in the TdeV during plasma detachment, plasma biasing and lower hybrid current drive and heating experiments are given.