Test of a prototype neutron spectrometer based on diamond detectors in a fast reactor

TL;DR

This paper presents a neutron spectrometer prototype using diamond detectors, demonstrating its effectiveness in various reactor environments through calibration and spectrum measurements, with good energy resolution and background rejection.

Contribution

The study introduces a novel diamond-based neutron spectrometer prototype with dual electronic readout chains, tested and calibrated in multiple reactor settings, showing practical applicability and accurate spectrum measurement capabilities.

Findings

Successful calibration at TRIGA reactor with high neutron flux

Effective background rejection using coincidence technique

Spectrum measurements aligned with Monte Carlo simulations

Abstract

A prototype of neutron spectrometer based on diamond detectors has been developed. This prototype consists of a $^6$Li neutron converter sandwiched between two CVD diamond crystals. The radiation hardness of the diamond crystals makes it suitable for applications in low power research reactors, while a low sensitivity to gamma rays and low leakage current of the detector permit to reach good energy resolution. A fast coincidence between two crystals is used to reject background. The detector was read out using two different electronic chains connected to it by a few meters of cable. The first chain was based on conventional charge-sensitive amplifiers, the other used a custom fast charge amplifier developed for this purpose. The prototype has been tested at various neutron sources and showed its practicability. In particular, the detector was calibrated in a TRIGA thermal reactor (LENA laboratory, University of Pavia) with neutron fluxes of $10^8$ n/cm$^2$s and at the 3 MeV D-D monochromatic neutron source named FNG (ENEA, Rome) with neutron fluxes of $10^6$ n/cm$^2$s. The neutron spectrum measurement was performed at the TAPIRO fast research reactor (ENEA, Casaccia) with fluxes of 10$^9$ n/cm$^2$s. The obtained spectra were compared to Monte Carlo simulations, modeling detector response with MCNP and Geant4.