Solid State Neutral Particle Analyzer in Current Mode on DIII-D Tokamak

A new three-channel solid state neutral particle analyzer (ssNPA) array, with the abilities of both active and passive charge exchange (CX) measurement, has been developed and successfully tested on the DIII-D tokamak. In active measurement mode, the three near-vertical viewing chords intersect with the footprint centerline of the closest near-tangential neutral beam at major radii of 1.50, 1.65, and 1.83~m; the outer and middle channels' sightline also cross the closest near-perpendicular neutral beam at major radii of 1.76 and 1.55~m, respectively. The inside channel is blocked for background detection during diagnostic commissioning stage. Directly deposited ultra-thin foils on the detector surface block stray photons below the energy of 1~keV and also bring about a 25~keV low energy threshold for deuterium particle detection. Operation of ssNPA in current mode provides an economical and simple approach for the diagnosing of the fast-ion distribution in energetic particle relevant experiments.