Towards a new generation of solid total-energy detectors for neutron-capture time-of-flight experiments with intense neutron beams

TL;DR

This paper advances neutron-capture detection technology by developing and comparing high-sensitivity detector setups, including a new conceptual design for a gamma detector array optimized for high-flux neutron experiments.

Contribution

It introduces a novel detector array design, STAR, based on deuterated-stilbene crystals, with detailed Monte Carlo modeling and experimental validation demonstrating improved performance and discrimination capabilities.

Findings

The CERN n_TOF EAR2 setup achieved high sensitivity with nine sTED modules.

Monte Carlo simulations enhanced understanding and optimization of detector efficiency.

Deuterated-stilbene crystals showed potential for superior neutron-gamma discrimination.

Abstract

Challenging neutron-capture cross-section measurements of small cross sections and samples with a very limited number of atoms require high-flux time-of-flight facilities. In turn, such facilities need innovative detection setups that are fast, have low sensitivity to neutrons, can quickly recover from the so-called $\gamma$-flash, and offer the highest possible detection sensitivity. In this paper, we present several steps toward such advanced systems. Specifically, we describe the performance of a high-sensitivity experimental setup at CERN n\_TOF EAR2. It consists of nine sTED detector modules in a compact cylindrical configuration, two conventional used large-volume C$_{6}$D$_{6}$ detectors, and one LaCl$_{3}$(Ce) detector. The performance of these detection systems is compared using $^{93}$Nb($n$,$\gamma$) data. We also developed a detailed \textsc{Geant4} Monte Carlo model of the experimental EAR2 setup, which allows for a better understanding of the detector features, including their efficiency determination. This Monte Carlo model has been used for further optimization, thus leading to a new conceptual design of a $\gamma$ detector array, STAR, based on a deuterated-stilbene crystal array. Finally, the suitability of deuterated-stilbene crystals for the future STAR array is investigaged experimentally utilizing a small stilbene-d12 prototype. The results suggest a similar or superior performance of STAR with respect to other setups based on liquid-scintillators, and allow for additional features such as neutron-gamma discrimination and a higher level of customization capability.