Calibration of the compact neutron spectrometer at PTB

TL;DR

This paper details the calibration process of a compact neutron spectrometer using PTB's neutron source, demonstrating accurate energy measurement, good resolution, and efficiency consistent with theoretical models.

Contribution

It presents a novel calibration of a diamond-based neutron spectrometer with detailed experimental validation and comparison to simulations, enhancing neutron detection precision.

Findings

Neutron energy reconstructed within 11 keV of reference values.

Energy resolution approximately 100 keV (RMS).

Detection efficiency matches simulations within 4% systematic error.

Abstract

In the present article we describe the calibration measurements of the compact neutron spectrometer at certified PTB neutron source. The spectrometer is based on two diamond detectors enclosing the Li-6 neutron converter. The incident neutron energy is measured through the sum of energies of the two conversion reaction products: t and alpha. The prototype used in this work was based on two 4x4 mm2, 100 um thick single crystal CVD commercial diamond plates. The measurements were performed in the fission spectrum domain at five different neutron energies varying from 0.3 up to 2 MeV. The obtained data showed a very good neutron energy reconstruction, i.e. in agreement with its reference values within statistical uncertainties or with deviation below 11 keV in absolute scale. The energy resolution of the spectrometer was found to be about 100 keV (RMS) with a small (about 9 keV/MeV) rising trend towards higher energies. The measured detection efficiency was found to be compatible with expectations based on analytical calculations and on Geant4 simulations within 3% statistical and 4% systematic precision.