Development of a small Time-Projection-Chamber for the quasi-absolute neutron flux measurement

¹ Institut Pluridisciplinaire Huber Curien, 23 rue du Loess, 67200 Strasbourg, France
² Laboratoire de Physique des 2 infinis, 33170 Gradignan, France
³ National Technical University of Athens, Department of Physics, Zografou Campus, Athens, Greece
⁴ CEA, DES/IRESNE/DER/SPRC/LEPh, 13008 Saint Paul Lez Durance, France

^* Corresponding author: carole.chatel@iphc.cnrs.fr

Published online: 26 May 2023

Abstract

Accurate actinides fission cross sections around 1 MeV are of primary importance for the safety of generation IV reactors. To have accurate measurements, the neutron flux must also be accurately estimated. This is usually done with respect to the ²³⁵U(n,f) cross section. It is however possible to measure the neutron flux with respect to the ¹H(n,n)p cross section which is a primary standard, providing an independent and precise measurement. Typically, the usual proton recoil technique uses a silicon detector for neutrons of energy between 1 and 70 MeV. However, the high electron and gamma background due to neutron production under irradiation makes the use of this or any other detector not suitable for an accurate measurement below 1 MeV. To this end, the Gaseous Proton Recoil Telescope is developed and characterized. The goal is to provide quasi-absolute neutron flux measurements with an accuracy better than 3%. It consists of a double ionization chamber with a Micromegas segmented detection plane and the gaseous pressure can be adjusted to protons – and hence neutron – energy. The sensitivity to gamma and electrons background, the intrinsic efficiency as well as the resolution of this detector have been investigated.