Development of Neutron Detectors for the Next Generation of Radioactive Ion-Beam Facilities

TL;DR

This paper discusses the development and characterization of neutron detector arrays, Neutron Wall and NEDA, for next-generation radioactive ion beam facilities to improve detection efficiency and neutron-gamma discrimination.

Contribution

It introduces new neutron detector arrays and evaluates digital pulse-shape discrimination techniques for enhanced neutron detection in high-background environments.

Findings

Neutron Wall's efficiency can be increased by higher photomultiplier high voltage.

A 12-bit ADC at 100 MS/s is sufficient for neutron-gamma discrimination.

NEDA is designed to operate effectively in high gamma-ray background conditions.

Abstract

The next generation of radioactive ion beam facilities, which will give experimental access to many exotic nuclei, are presently being developed. These facilities will make it possible to study very short lived exotic nuclei with extreme values of isospin far from the line of beta stability. Such nuclei will be produced with very low cross sections and to study them, new detector arrays are being developed. At the SPIRAL facility in GANIL a neutron detector array, the Neutron Wall, is located. In this work the Neutron Wall has been characterized regarding neutron detection efficiency and discrimination between neutrons and gamma rays. The possibility to increase the efficiency by increasing the high voltage of the photomultiplier tubes has also been studied. For SPIRAL2 a neutron detector array, NEDA, is being developed. NEDA will operate in a high gamma-ray background environment which puts a high demand on the quality of discrimination between neutrons and gamma rays. To increase the quality of the discrimination methods pulse-shape discrimination techniques utilizing digital electronics have been developed and evaluated regarding bit resolution and sampling frequency of the ADC. The conclusion is that an ADC with a bit resolution of 12 bits and a sampling frequency of 100 MS/s is adequate for pulse-shape discrimination of neutrons and gamma rays for a neutron energy range of 0.3-12 MeV.