USE OF A HEAVY-ION BEAM PROBE TO MEASURE THE PLASMA POTENTIAL ON THE ADVANCED TOROIDAL FACILITY

During the last operational period of ATF, a heavy ion beam probe was used to make measurements of the plasma potential, potential fluctuations, and electron density fluctuations. Due to the limited operational time and resources these measurements were made primarily on ECH plasmas, although some neutral beam heated plasma data were taken. The general results of these measurements and a discussion of the possible mechanisms which could cause uncertainties in the results will be given. The diagnostic method will be outlined with an emphasis on issues related to the operation of a beam probe in a stellarator environment.