Bolometric measurements in ATF

Bolometer measurements are made under various plasma conditions in ATF. Each bolometer module includes four pairs of detectors; each pair consists of a sensor and a reference detector. Two or three detector pairs in each module were installed with various types of aperture masks to serve as radiation detectors. The rest were completely shielded from plasma emissions and used as blind detectors to measure background levels. When electron cyclotron heating (ECH) power was applied to ATF, the radiation signal was more than 10 times higher than that expected for 100 kW of radiated power. Surprisingly, similar signal levels were observed on the blind detectors. It is hypothesized that the bolometers are sensitive to ECH power at 53 GHz. (This problem may be general in near-term fusion experiments, in which microwave power will be an important tool for plasma heating). In this paper, experiments aimed at proving this hypothesis are reported; bolometric signals before and after chromium gettering are discussed; and measurements of the microwave power deposition profile around the torus, made by using the observed microwave interference with the blind detectors, are presented. (author). 4 refs, 4 figs