Study of neutron response using time of flight technique in ISMRAN detector

TL;DR

This paper measures the fast neutron energy response and capture time in the ISMRAN detector using the time-of-flight technique, aiding background discrimination in reactor anti-neutrino detection.

Contribution

It introduces a novel TOF-based method to determine neutron energies and capture times in the ISMRAN detector, enhancing background suppression capabilities.

Findings

Neutron capture time measured as 68.29 ± 9.48 μs, matching GEANT4 simulations.

Validated the use of TOF technique for neutron energy and capture time measurements.

Results improve background discrimination in reactor anti-neutrino experiments.

Abstract

We report the measurements of the fast neutron energy response in Indian Scintillator Matrix for Reactor Anti-Neutrinos (ISMRAN) detector consisting of an array of 9$\times$10 Plastic Scintillator Bars (PSBs) at BARC, Mumbai. ISMRAN is an above ground detector setup at $\sim$13 m from the Dhruva reactor core for the detection of reactor anti-neutrinos (${\overline{\ensuremath{\nu}}}_{e}$) via the inverse beta decay (IBD) process. The dominant sources of reactor-related background in the vicinity of the detector are high energy $\gamma$-rays and fast neutrons. Therefore, a good understanding of fast neutron response in PSB is an essential pre-requisite for suppression and discrimination of the fast neutron background from IBD events. Kinetic energies of the fast neutron were determined using the Time-of-Flight (TOF) technique, which is used to get the scintillation light yield due to recoiling proton in PSB. We also measured the fast neutron capture time distribution in ISMRAN array using a novel technique involving TOF of the measured fast neutrons. The observed characteristic neutron capture time ( $\tau$ ) of 68.29 $\pm$ 9.48 $\mu$s is in good agreement with GEANT4 based MC simulation. These experimentally measured results will be useful for discriminating correlated and uncorrelated (accidental) background events from the true IBD events in reactor ON and OFF conditions inside the reactor hall.