Additive Manufacturing of Near Components for Background Reduction and Structural Supports in LEGEND-1000

Detection of 0νββ decay establishes neutrinos as Majorana particles. LEGEND-1000 is the next generation ton-scale effort to detect 0νββ decay in ⁷⁶Ge using isotopically-enriched high purity (≥ 90%) germanium detectors. This experiment aims for an unprecedented discovery sensitivity of T^1/2 > 10²⁸ yrs, exposure of 10 ton·yr, and background goal of < 10⁻⁵ cts/(keV kg yr). A dominant source of external background arises from ⁴²K β-decay, produced by trace ⁴²Ar in the natural liquid argon cryostat where the detectors are submerged. To shield the HPGe detectors from this background, we study the possibility of custom radiopure encapsulations of individual detectors via additive manufacturing and Monte Carlo simulations. Tensile strength and cryogenic stability tests were performed on various Formlabs 3D printable resins and polyethylene naphthalate (PEN). Further efforts were made in filament extrusion and FDM custom filament printing. Additionally, simulations of radiation transport were used to study the optimal thickness for the encapsulation using a Julia-based Geant4 wrapper, SolidStateDetectors.jl, to produce Monte Carlo simulations of the ⁴²K decay products.