Commissioning of the NUCLEUS Experiment at the Technical University of Munich

TL;DR

This paper reports on the commissioning and testing of the NUCLEUS experiment's detector systems at TU Munich, laying groundwork for future neutrino detection near nuclear reactors.

Contribution

It presents the first comprehensive commissioning results of cryogenic detectors and shielding systems for the NUCLEUS experiment at a shallow underground lab.

Findings

Stable detector operation over two months

Background measurements for reactor site modeling

Progress towards detector upgrade for future neutrino detection

Abstract

The NUCLEUS experiment aims to detect coherent elastic neutrino-nucleus scattering of reactor antineutrinos on CaWO$_4$ targets in the fully coherent regime, using gram-scale cryogenic calorimeters. The experimental apparatus will be installed at the Chooz nuclear power plant in France, in the vicinity of two 4.25 GW$_{\text{th}}$ reactor cores. This work presents results from the commissioning of an essential version of the experiment at the shallow Underground Laboratory of the Technical University of Munich. For the first time, two cryogenic target detectors were tested alongside active and passive shielding systems. Over a period of two months all detector subsystems were operated with stable performance. Background measurements were conducted, providing important benchmarks for the modeling of background sources at the reactor site. Finally, we present ongoing efforts to upgrade the detector systems in preparation for a technical run at Chooz in 2026, and highlight the remaining challenges to achieving neutrino detection.