DISTINCTION BETWEEN DD AND DT NEUTRONS IN THE TFTR NEUTRON COLLIMATOR

A difficult part of the analysis of the neutron collimator data is the distinction between contributions from DD and DT neutrons. This is im portant for the majority of TFTR discharges, which use neutral deuteri um heating beams and relatively small amounts of tritium. At present, the DT-neutron contribution is determined from a comparison of the cho rd-integrated neutron collimator data with measurements of the DT-neut ron source strength from general wide-angle detectors, using an iterat ive computational method. A more satisfactory solution should be obtai ned with detectors that measure the contributions from DD and DT neutr ons, and gamma radiation, directly. Purse-shaping techniques are insuf ficient, since the detectors in the neutron collimator are operated in current mode. The presently used data analysis is described and the c oncept of a new multilayered plastic detector that makes use of the di fferences in the attenuation of the various radiation components is pr esented. The dimensions of the detector are based on calculations of t he attenuation for the expected neutron energy spectrum. (C) 1997 Amer ican Institute of Physics.