³He-free triple GEM thermal neutron detector

¹ Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Frascati - Via Enrico Fermi 40, 00044 Frascati (Rome), Italy
² CERN - CH-1211 Geneva 23, Switzerland
³ ENEA Centro Ricerche Frascati - Via Enrico Fermi 45, 00044 Frascati (Rome), Italy
⁴ MIFP, Mediterranean Institute of Fundamental Physics - Via Appia Nuova 31, 00040 Marino (Rome), Italy
⁵ ENEA Centro Ricerche Casaccia - Via Anguillarese 301, 00123 S. Maria di Galeria (Rome), Italy
⁶ Oak Ridge National Laboratory - 2008 MS-6466, Oak Ridge, TN 37831-6466, USA

^(a) antonino.pietropaolo@enea.it

Received: 13 November 2013
Accepted: 12 January 2014

Abstract

A novel type of thermal neutron detector based on the gas electron multiplier (GEM) technology is presented in the framework of the research and development activity on the ³He replacement for neutron detection. The device relies on a series of boron-coated alumina sheets placed perpendicularly to the incident neutron beam direction. The detector, named side-on GEM (S-GEM), was tested on beam at the High Flux Isotope Reactor at the Oak Ridge National Laboratory (US) to assess its performance in terms of beam position resolution, efficiency and signal-to-background (S/B) ratio as compared to a 10 bar ³He tube for sub-thermal neutrons. Using 3 mm wide PADs, a sub-millimeter position resolution was obtained. The achieved efficiency is about 30% with a quite good S/B ratio. The obtained results demonstrate the effectiveness of the proposed detector configuration to achieve a good spatial resolution and, in the perspective, a higher thermal neutron efficiency, comparable to ³He tubes typically used for diagnostic in nuclear reactors. The main issues to be addressed to reach the goal, mostly related to boron coating procedures and characterization, are also pointed out.