In-Beam Background Suppression Shield

TL;DR

This paper proposes an innovative in-beam shielding method using material blocks like sapphire and silicon within the guide system to reduce background noise for instruments at the European Spallation Source, enhancing signal clarity.

Contribution

It introduces a novel shielding configuration with material blocks directly in the guide system, modeled with Geant4, to improve background suppression without significantly reducing flux.

Findings

Sapphire and silicon blocks effectively reduce background noise.

The shielding maintains a high flux of cold and thermal neutrons.

Modeling shows promising results for instrument signal-to-noise improvement.

Abstract

The long (3ms) proton pulse of the European Spallation Source (ESS) gives rise to unique and potentially high backgrounds for the instrument suite. In such a source an instrument capabilities will be limited by it's Signal to Noise (S/N) ratio. The instruments with a direct view of the moderator, which do not use a bender to help mitigate the fast neutron background, are the most challenging. For these beam lines we propose the innovative shielding of placing blocks of material directly into the guide system, which allow a minimum attenuation of the cold and thermal fluxes relative to the background suppression. This shielding configuration has been worked into a beam line model using Geant4. We study particularly the advantages of single crystal sapphire and silicon blocks .