Exploration of New Materials for Background Mitigation and Construction of LEGEND-1000

Background mitigation is one of the most important requirements for the success of experiments searching for neutrinoless double-beta decay. The ton-scale ⁷⁶Ge-based LEGEND-1000 experiment is currently in the design stage, with several options under study to optimize background rejection and enhance detector performance. Indeed, to reach an anticipated half-life of T_1/2>10²⁸ years of ⁷⁶Ge neutrinoless double-beta decay, extreme care must be taken in the hardware design to minimize background. For LEGEND-1000, one of the most powerful background suppression tools will be the use of liquid Ar (LAr) instrumentation as an active shield to reject backgrounds. LAr sourced from atmospheric Ar, however, by itself presents a risk of backgrounds from the decay of ⁴²K, which results from the decay of ⁴²Ar contained in atmospheric Ar. This background must be mitigated unless pure underground-sourced LAr is used. Additionally, it is highly desired to use ultra-low background materials for experimental construction, especially parts that are near the Ge detectors. In this presentation, we investigate materials that could be potentially used to build detector enclosures to mitigate the ⁴²Ar/⁴²K background, and for on-demand underground manufacturing of detector parts. Various tested properties of investigated materials will be presented.