Experimental validation of the Gaseous Proton Recoil Telescope for quasi-absolute neutron flux measurements

TL;DR

This paper presents the development and validation of the Gaseous Proton Recoil Telescope (GPRT), a device designed for precise, quasi-absolute neutron flux measurements below 1 MeV, crucial for nuclear data accuracy in reactor safety.

Contribution

The paper introduces the GPRT, a novel detector with verified 100% intrinsic efficiency and low dead-time, enabling accurate neutron flux measurements essential for nuclear data improvements.

Findings

GPRT achieves intrinsic efficiency of 100%.

Dead-time of the detector is 7.3 ms.

Validated the detector's performance with alpha source and proton micro-beam.

Abstract

The accuracy of neutronics simulations of actual or future reactor cores is nowadays driven by the precision of the nuclear data used as input. Among the most important neutron-induced fission cross sections to understand well are the actinides. It is, indeed, of primary importance to know accurately these cross sections around 1 MeV for the safety of Generation IV reactors. High accuracy measurements of neutron flux are essential for accurate cross section measurements; measurements of this flux with respect to the 1 H(n,n)p cross section can be made with the proton recoil technique. For an accurate measurement below 1 MeV, the Gaseous Proton Recoil Telescope (GPRT) is developed and characterized, with the aim to provide quasi-absolute neutron flux measurements with an accuracy better than 2%. This detector is composed of a double ionization chamber with a Micromegas segmented detection plane. The pressure of the gas can be adjusted to protons stopping range -and therefore to neutrons energy. An accurate neutron flux measurement requires that the GPRT has an intrinsic efficiency of 100%, and thus an important effort has been made to verify this. An alpha source and proton micro-beam have been used and the intrinsic efficiency is confirmed to be 100%. Additionally, the dead-time of the detector has been investigated on a test bench, and is found to be 7.3 ms.