The response of CR-39 nuclear track detector (TasTrak®) to protons in the energy range of 0.92–9.28 MeV has been studied. Previous studies of the CR-39 response to protons have been extended by examining the piece-to-piece variability in addition to the effects of etch time and etchant temperature; it is shown that the shape of the CR-39 response curve to protons can vary from piece-to-piece. Effects due to the age of CR-39 have also been studied using 5.5 MeV alpha particles over a 5-year period. Track diameters were found to degrade with the age of the CR-39 itself rather than the age of the tracks, consistent with previous studies utilizing different CR-39 over shorter time periods.

A four-channel compact neutral particle analyzer ͑CNPA͒ based on operating small Si diode detectors in pulse-height analysis ͑PHA͒ mode is used to measure energetic hydrogen minority ions with energies between ϳ50 and 350 keV stemming from ion-cyclotron range-of-frequency heated D͑H͒ Alcator C-Mod plasmas with both active and passive charge exchange ͑CX͒. First core minority ion distribution results from Alcator C-Mod discharges and a detailed description of the diagnostic are presented. The diagnostic employs integrated electronics and fast digitization of the shaping amplifier voltage. The digitized data are stored for postshot PHA, which removes the constraints of real-time PHA and allows for improved performance via elimination of base line shift effects and potentially relieving pileup through Gaussian fitting routines. The CNPA is insensitive to the large gamma and neutron background in Alcator C-Mod discharges but is susceptible to the plasma's soft x-ray flux. The soft x-ray flux limits the CNPA energy resolution to ϳ15-20 keV. A simple model is used to interpret the active CNPA data which permits rapid estimates of the core hydrogen minority temperatures and anisotropy with a time resolution of ϳ100 ms. Hydrogenlike boron is identified as an important electron donor for the CX signal.