Far-infrared scattering on ELMO Bumpy Torus and impurity study experiments

A far-infrared (FIR) laser scattering diagnostic was installed the ELMO Bumpy Torus (EBT) experiment to measure density waves and fluctuations. The system was tested and calibrated using a TPX plastic Bragg acoustic cell and was shown to be fully functional. Only low signal levels were observed during most plasma conditions including fast and slow wave ion cyclotron heating (ICH) experiments. It was demonstrated that the level of fluctuations in EBT-S was much lower than in EBT-1. Also penetration of ICH driven waves into the plasma core was evidenced. Pulsed experiments provided evidence of an instability, probably related to the rapid increase in ECH power, that had a remarkably short lifetime.

Unresolved forward scattering of FIR radiation was accomplished on the Impurity Study Experiment (ISX) by spectrum analyzing the output signals from the FIR interferometer system. MHD instabilities and fluctuation levels were observed in agreement with other plasma diagnostics.