Fast ion loss diagnostic plans for the National Spherical Torus Experiment

The prompt loss of neutral beam ions from the National Spherical Torus Expe riment is expected to be between 12% and 42% of the total 5 MW of beam powe r. There may, in addition, be losses of fast ions arising from high harmoni c fast wave (HHFW) heating. Most of the lost ions will strike the HHFW ante nna or the neutral beam dump. To measure these losses in the 2000 experimen tal campaign, thermocouples in the antenna, several infrared camera views, and a Faraday cup lost ion probe will be employed. The probe will measure l oss of fast ions with E > 1 keV at three radial locations, giving the scrap e-off length of the fast ions. (C) 2001 American Institute of Physics.