Neutron Cross Section Measurements with Diamond Detectors

Abstract

Diamond is one of the most robust, versatile and radiation tolerant material for use in beam diagnostics with a wide range of applications in beam instrumentation. Diamond detectors are successfully used with charged particles, photons and neutrons. They are used as neutron monitors using two different measurement techniques. In the case of the measurements with thermal neutrons, a neutron converter is used. Fast neutrons directly interact with carbon nuclei of the diamond detector, so the detector simultaneously acts as a sample and as a sensor. Single-crystal diamond detectors were used in the measurement performed at the Van de Graaff facility of EC-JRC, Geel, Belgium. A dedicated method of the ionization current pulse-shape analysis allowed to measure the cross section of ¹³C(n, α₀)¹⁰Be reaction relatively to ¹²C(n, α₀)⁹Be reaction. This method is based on the unique property of sCVD diamond sensors that the signal shape of the detector current is determined by the initial ionization profile. It allows discrimination between different types of interactions in the detector and a background rejection. In the measurement presented in this report the pulse-shape analysis method was used to obtain the spectra of the two nuclear reactions of interest in order to calculate the cross sections. This pulse-shape analysis method is especially relevant for neutron diagnostics in harsh radiation environments, e.g. fission and fusion reactors. It allows the separation of the neutron spectrum from the background, and it is particularly useful in neutron flux monitoring and neutron spectroscopy.