Experimental measurements of ICRF minority-heated fast- ion distributions on Alcator C-Mod

measurements of ion cyclotron range of frequency minority-heated fast-ion distributions on Alcator C-Mod. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. ICRH (Ion Cyclotron Resonance Heating) is the primary auxiliary heating on the Alcator C-Mod tokamak and is commonly used on other devices, and is planned for use on ITER. The RF-power density on C-Mod is above 5 MW/m 3 providing for a unique opportunity to study wave-particle effects in the high RF power per particle regime. Minority heating produces a highly energetic tail in the minority distribution function which is measured using a Compact Neutral Particle Analyzer. In this paper, we present the measurements of the fast-ion spectrum between 200 keV and 2 MeV, compiled over an entire experimental campaign. We also estimate the effective tail temperatures for the fast-ion distribution. We find that the fast-ion distribution is less energetic and less dense with increasing electron density; is more energetic with increasing plasma current; and is more dense but has no measurable change in energy with increasing RF power. Some possible explanations for these findings are discussed.