Design, calibration and testing of the NRCAM fast neutron spectrometry system

Abstract

This paper describes the design, calibration and testing of all aspects of an NE-213 detection system which was built for measuring neutron spectra from 1 to 30 MeV . To cover the whole energy range two detectors are required. A smaller detector is usually used for the lower energy range, but for the upper energy limit, in which we are interested, a larger detector is needed. Particular attention has been paid to cell construction and reflective paint covering. Decisions on the length of light guide which leads to optimum resolution have been made on the basis of experiment and Monte Carlo simulation of the photon transport within the cell and light guide, previously reported. Response matrix information for the detector has been prepared with the codes 05S (A Monte-Carlo code for calculating the pulse-height distributions due to monoenergetic neutrons on organic scintillators. Oak Ridge National Laboratory ORNL-4160) and SCINFUL (SCINFUL: a Monte Carlo based computer program to determine a scintillator full energy response to neutron detection for En between 0.1 and 80 MeV : program development and comparisons of program predictions with experimental data. Oak Ridge National Laboratory ORNL-6463), with validation at a few energy points against quasi-monoenergetic neutron sources available at the cyclotron of NRCAM. The unfolded spectra obtained by the detector when exposed to Americium–Beryllium, 15.2 and 28.2 MeV neutron fluences are shown as overall validation of the performance of the detector.