A novel active veto prototype detector with an inner target for improved rare event searches

TL;DR

This paper presents a new cryogenic germanium veto detector with an inner target, significantly reducing backgrounds in rare event searches like dark matter and neutrino experiments, with experimental results matching simulations.

Contribution

The paper introduces a novel active veto detector with an inner target for improved background suppression in rare event searches, validated by experimental results.

Findings

Background reduction > 90% for gamma interactions

Baseline resolution of 1.24 keV for veto detector

Inner target resolution of 147 eV

Abstract

We report the fabrication and performance of an annular, cryogenic, phonon-mediated veto detector that can host an inner target detector, allowing substantial reduction in radiogenic backgrounds for rare event search experiments. A germanium veto detector of mass $\sim$500 g with an outer diameter of 76 mm and an inner diameter of 28 mm was produced. A 25 mm diameter germanium inner target detector of mass $\sim$10 g was mounted inside the veto detector. The detector was designed using inputs from a GEANT4 based simulation, where it was modeled to be sandwiched between two germanium detectors. The simulation showed that the background rates (dominantly gamma interactions) could be reduced by $>$ 90$\%$, and that such an arrangement is sufficient for aggressive background reduction needed for neutrino and dark matter search experiments. During testing at the experimental site the veto detector prototype achieved a baseline resolution of 1.24 $\pm$ 0.02 keV while hosting a functional inner target detector. The baseline resolution of the inner target detector was 147 $\pm$ 2 eV. The detectors were operated at mK temperatures. The experimental results of an identical detector arrangement are in excellent agreement with the simulation.