A new anti-neutrino detection technique based on positronium tagging with plastic scintillators

TL;DR

This paper introduces a novel anti-neutrino detection method using positronium tagging with plastic scintillators, aiming to improve background rejection especially in aboveground environments for reactor monitoring.

Contribution

It proposes a new threefold coincidence detection scheme involving positron ionization, ortho-positronium decay, and neutron capture, with experimental validation of key parameters.

Findings

Demonstrated achievable light yield in the detector setup.

Measured ortho-positronium formation and lifetime.

Discussed detection efficiency and background rejection capabilities.

Abstract

The main signature for anti-neutrino detection in reactor and geo-neutrino experiments based on scintillators is provided by the space-time coincidence of positron and neutron produced in the Inverse Beta Decay reaction. Such a signature strongly suppresses backgrounds and allows for measurements performed underground with a relatively high signal-to-background ratio. In an aboveground environment, however, the twofold coincidence technique is not sufficient to efficiently reject the high background rate induced by cosmogenic events. Enhancing the positron-neutron twofold coincidence efficiency has the potential to pave the way future aboveground detectors for reactor monitoring. We propose a new detection scheme based on a threefold coincidence, between the positron ionization, the ortho-positronium (o-Ps) decay, and the neutron capture, in a sandwich detector with alternated layers of plastic scintillator and aerogel powder. We present the results of a set of dedicated measurements on the achievable light yield and on the o-Ps formation and lifetime. The efficiencies for signal detection and background rejection of a preliminary detector design are also discussed.