Time distribution measurements of prompt-delay events at the Dhruva reactor for detection of antineutrinos

The measurement of the antineutrino spectrum from reactors is an effective tool to investigate the fundamental aspects of neutrino physics and to monitor the status and composition of reactor cores. A recent reanalysis of short-baseline reactor neutrino experiments has revealed a discrepancy between observations and the predicted antineutrino flux [1]. It might be a signal of oscillation to an additional ’sterile’ flavour beyond the global 3-flavor neutrino and antineutrino picture [2]. The changes in the reactor antineutrino emission rate can be correlated with the evolution of the reactor power [3] and fissile inventory [4]. A large plastic scintillator array is planned to be installed at the Dhruva reactor hall, BARC for these investigations and reactor monitoring purposes [5]. The antineutrinos are conventionally detected via the inverse beta decay interaction  + → + , which takes place typically on a proton in the plastic scintillator detector with the energy threshold of 1.8 MeV. The positron deposits energy via ionization, and emits two gamma rays by annihilation, together providing the prompt signal. The neutron is thermalized in the plastic and captured some time later by gadolinium wrapped on the scintillators bars, and a gamma ray cascade is produced with total energy of about 8 MeV, referred to as the delayed event. The antineutrino interactions can be identified through the correlation of the prompt positron signal and a delayed neutron capture signal. However, the enhanced background due to neutrons and their radiative capture at the reactor site and the neutrons produced by cosmic muons needs to be discriminated from the true antineutrino interactions.