1987 calibration of the TFTR neutron spectrometers

Abstract

The 3He neutron spectrometer used for measuring ion temperatures and the NE213 proton recoil spectrometer used for triton burnup measurements were absolutely calibrated for source strength measurements with DT and DD neutron generators placed inside the TFTR vacuum vessel. Details of the detector response and generator calibration are presented. The calibrated accuracy of the NE213 system to the DD neutron source strength is ±30%, to DT neutrons ±20%, and to the ratio ±20%. Background problems made the accuracy of the 3He system calibration ±70% for the DD peak. Strong affects of local attenuation were observed. For both systems the calibrated efficiencies were 10–100 times less than the unattenuated response, consistent with removal cross sections for the intervening material. The relatively high-energy threshold of these detectors resulted in insensitivity to scattered neutrons. Within the relative calibration uncertainties, the neutron source strengths from these systems are in agreement with the source strengths measured from the calibrated fission chamber system.