First tests of the applicability of $\gamma$-ray imaging for background discrimination in time-of-flight neutron capture measurements

TL;DR

This paper demonstrates the first use of gamma-ray imaging with a pinhole camera to improve background discrimination in neutron capture experiments, achieving a twofold enhancement in signal-to-background ratio.

Contribution

It introduces a novel gamma-ray imaging technique for background suppression in neutron capture measurements and characterizes its performance.

Findings

Achieved a twofold increase in signal-to-background ratio.

Successfully assembled and tested a gamma camera with spatial and energy resolution.

Validated the technique with measurements on a $^{197}$Au sample at n_TOF.

Abstract

In this work we explore for the first time the applicability of using $\gamma$-ray imaging in neutron capture measurements to identify and suppress spatially localized background. For this aim, a pinhole gamma camera is assembled, tested and characterized in terms of energy and spatial performance. It consists of a monolithic CeBr$_3$ scintillating crystal coupled to a position-sensitive photomultiplier and readout through an integrated circuit AMIC2GR. The pinhole collimator is a massive carven block of lead. A series of dedicated measurements with calibrated sources and with a neutron beam incident on a $^{197}$Au sample have been carried out at n_TOF, achieving an enhancement of a factor of two in the signal-to-background ratio when selecting only those events coming from the direction of the sample.