A neutral particle analyser (NPA) has been used to make measurements of the ion distribution in the Alcator C-Mod tokamak. We have used the analyser to measure the energy distribution of majority deuterons and minority hydrogen (up to 20 keV) at 0.4⩽r/a⩽0.6, during minority ion cyclotron range of frequencies (ICRF) heating. These energy spectra were also simulated by using the predicted minority ion distribution from a combined Fokker Planck ICRF code in a model for the neutral particle flux. The model predictions for neutral flux were found to be in qualitative agreement with the measured energy spectra. The energy spectra for two different ICRF antenna configurations were also measured and found to be very similar.
Fast-ion distributions from third harmonic ICRF heating studied with neutron emission spectroscopy