Experimental studies of C-Mod ICRF minority tails via a multi-channel compact neutral particle analyzer*

Recent experimental results from the upgraded multi-channel Compact Neutral Particle Analyzer (CNPA) system are presented and compared with numerical simulations. The CNPA system consists of Si diode detectors and measures charge exchange (CX) induced energetic ($>$40 keV) neutral particles for ICRF hydrogen minority tail temperature diagnosis. A new long-pulse diagnostic neutral beam (DNB) provides the neutrals for active CX. The discussed data involve measurements of the Hydrogen-minority energy spectrum during low to moderate (n$_{e}$l$\sim $2x10$^{20}$/m$^{2})$ density ICRF plasmas with up to $\sim $3 MW of ICRF power and B$_{T }$from 4.4 to 6.2T. During these discharges, evidence of fast ion resonance localization and tail temperatures greater than 100keV is observed. The energy distributions are compared with a synthetic diagnostic based on CQL3D Fokker-Planck simulations. ICRF power deposition densities and efficiencies are also inferred.