Shielding Design for the ISODAR Neutrino Experiment

TL;DR

This paper presents the design and simulation of a shielding enclosure for the IsoDAR neutrino experiment's high-intensity target, focusing on materials and configuration to minimize background and activation.

Contribution

It introduces novel shielding materials and configurations specifically optimized for the IsoDAR experiment's high neutron flux environment.

Findings

Shielding effectively reduces neutron and gamma backgrounds.

New concrete materials show promising neutron moderation properties.

Simulations indicate acceptable rock activation levels.

Abstract

The IsoDAR sterile-neutrino search requires a very high intensity neutrino source. For IsoDAR, this high intensity is produced using the high neutron flux from a 60 MeV, 10 mA proton beam striking a beryllium target that floods a sleeve of highly-enriched Li-7. Through neutron capture the Li-7 is transmuted to Li-8, which beta-decays giving the desired high neutrino flux for very-short baseline neutrino experiments. The target can be placed very close to can existing large neutrino detector, which is typically located deep underground to reduce backgrounds. With such a setup, it is necessary to design a shielding enclosure for the target to prevent neutrons from causing unacceptable activation of the rock walls close to the target. Various materials have been studied including steel to thermalize the high energy neutrons and two new types of concrete developed by Jefferson Laboratory, one very light with shredded plastic aggregate, and the other one enriched with high quantities of boron. The shielding is asymmetrical, having a larger thickness towards the detector in order to suppress the neutron and gamma background in the neutrino detector. Simulation results for rock activation and for detector backgrounds are presented.