TFTR natural diamond detectors based D-T neutron spectrometry system

Three natural diamond detectors (NDD) based spectrometry systems have been developed and used on TFTR to perform D-T neutron spectrum and flux measurements. DT neutrons interact with the NDD through the C-12(n, alpha)Be-9 reaction to produce a narrow peak in the pulse height distribution which has 2%-3% energy resolution and is well isolated from other reactions by similar to 2 MeV in energy. The NDD detector is also highly radiation resistant (5 x 10(14) n/cm(2)) and compact in size (diameter similar to 4 mm, thickness similar to 0.2 mm). Three detectors have been installed near TFTR. One, installed in a central sight Line of the neutron collimator Views perpendicularly from below. Two other detectors placed inside radiation shields in the TFTR test cell have tangential and perpendicular cones of view. These three spectrometers provide spectrometry of D-T neutrons escaping the tokamak with angles with respect to plasma current in the ranges close to 90 degrees, 110 degrees-180 degrees, and 60 degrees-120 degrees correspondingly. The fastest standard electronics have been used to reduce the influence of pulse pileup during spectrometry measurements at count rates up to 3 x 10(5) counts/s. Results of the first D-T neutron spectra and flux dynamics measurements made with the three NDD based spectrometers during TFTR high power neutral beam injection are presented. (C) 1997 American Institute of Physics.