Year
2011
Abstract
Various detector types were investigated in the past for fast-neutron detection. Recently, C6D6 detectors have been studied for applications such as nuclear nonproliferation and nuclear safeguards. These detectors are based on C6H6 detectors where hydrogen is replaced with deuterium. Standard liquid organic scintillators have been investigated as neutron spectrometers for the detection of special nuclear material. The neutron pulse-height distribution (PHD) from a standard liquid scintillator contains information about the energy spectrum of the incident neutrons. However, there is no unique, non-probabilistic relation between incident neutron energy and measured pulse height. Therefore, the energy-spectrum unfolding results in an ill-posed, inverse problem which has been approached in numerous ways with some success. One difficulty with unfolding spectra using standard hydrogen-based scintillators is that neutron scattering on hydrogen is isotropic, and has no “preference” regarding energy transferred in a collision. Neutron scattering on deuterium, on the other hand, is non-isotropic, often preferring back-scattering which transfers 8/9 of the incident neutron energy to the deuteron, which might lead to more accurate unfolding results. In order to reveal full potential of C6D6 detectors their detailed properties need to be accurately obtained. In this paper, detailed measurement results with monoenergetic neutron beams with energies between 5 and 20 MeV are presented for a particular C6D6 detector. The beams were produced at the Van de Graaff facility of the Institute for Reference Materials and Measurements in Geel, Belgium. The main objective of this work is to characterize the detector’s response to various neutron energies. In addition, these measured results were used to obtain an appropriate energy-to-light-output conversion curve, which is essential for performing high-fidelity Monte Carlo simulations. Only limited information is available in the literature on the light output of C6D6 detectors. An available conversion function is compared to the measured function to assess the differences. The measurement results are supported by MCNPX-PoliMi simulations performed for various experimental configurations, using experimentally obtained energy-to-light conversion curve.