Characterization of Monoenergetic Neutron Reference Fields with a High Resolution Diamond Detector

TL;DR

This paper demonstrates the use of a novel diamond-based detector to precisely characterize monoenergetic neutron fields, resolving detailed spectral structures and contamination effects without time-of-flight methods.

Contribution

The study introduces a high-resolution diamond detector for detailed neutron spectrometry, capable of resolving fine spectral features and contamination in monoenergetic neutron fields.

Findings

Resolved neutron line structures of about 80 keV at 9 MeV.

Measured energy shifts and broadening related to target pressure.

Identified contamination of 14 MeV neutron fields with high-energy protons.

Abstract

A novel radiation detector based on an artificial single crystal diamond was used to characterize in detail the energy distribution of neutron reference fields at the Physikalisch-Technische Bundesanstalt (PTB) and their contamination with charged particles. The monoenergetic reference fields at PTB in the neutron energy range from 1.5 MeV up to 19 MeV are generated by proton and deuteron beams impinging on solid and gas targets of tritium and deuterium. The energy of the incoming particles and the variation of the angle under which the measurement is performed produce monoenergetic reference fields with different mean energies and line shapes. In this paper we present high resolution neutron spectrometry measurements of different monoenergetic reference fields. The results are compared with calculated spectra taking into account the actual target parameters. Line structures in the order of 80 keV for a neutron energy of 9 MeV were resolved. The shift of the mean energy and the increasing of the width of the neutron peak with increasing pressure in the gas target in the order of 30 keV were measured. Another result is the determination of the contamination of the neutron field at 14 MeV with high energy charged particles (protons) from side reactions inside the T-target. The experiments have shown that this detector is an easy to operate compact neutron spectrometer with extremely good energy resolution and that detailed structures in the line shapes of monoenergetic neutron fields can be resolved without using time of flight techniques.