Application of natural diamond detector to energetic neutral particle measurements on NSTX

Two natural diamond detectors have been installed on the National Spherical Torus Experiment (NSTX) to look at escaping neutrals at or near the neutral beam injection energy. Time resolved measurements have been obtained from these detectors at various tangency radii. The close proximity of the detector to the vessel required the development of a very fast low-noise preamplifier, which has been shown to be superior to similar commercial units. With this amplifier arrangement, electromagnetic pick-up noise was reduced to acceptable levels. However, radiation shielding was required to reduce the background levels from neutron-induced pulses in the detector. Calibration data along with the measured energy resolution is presented in the useful energy range. for NSTX. Example data from plasma discharges is also presented. (C) 2003 American Institute of Physics.