Discrimination of gamma rays due to inelastic neutron scattering in AGATA

TL;DR

This paper investigates methods to discriminate between neutrons and gamma rays in the AGATA spectrometer to reduce background noise from neutron inelastic scattering, using simulations to develop and test three identification techniques.

Contribution

The study introduces three novel methods for identifying neutron interaction points in AGATA detectors, improving neutron-gamma discrimination in simulations.

Findings

Peak-to-background ratio improved by factor of 2.4

Photopeak efficiency reduced by only 1.25 times

Effective neutron rejection demonstrated in simulated environment

Abstract

Possibilities of discriminating neutrons and gamma rays in the AGATA gamma-ray tracking spectrometer have been investigated with the aim of reducing the background due to inelastic scattering of neutrons in the high-purity germanium crystals. This background may become a serious problem especially in experiments with neutron-rich radioactive ion beams. Simulations using the Geant4 toolkit and a tracking program based on the forward tracking algorithm were carried out by emitting neutrons and gamma rays from the center of AGATA. Three different methods were developed and tested in order to find 'fingerprints' of the neutron interaction points in the detectors. In a simulation with simultaneous emission of six neutrons with energies in the range 1-5 MeV and ten gamma rays with energies between 150 and 1450 keV, the peak-to-background ratio at a gamma-ray energy of 1.0 MeV was improved by a factor of 2.4 after neutron rejection with a reduction of the photopeak efficiency at 1.0 MeV of only a factor of 1.25.