Construction and characterisation of the DarkSide-20k veto silicon photo-multiplier tiles

TL;DR

This paper details the development, testing, and successful production of SiPM-based veto tiles for the DarkSide-20k dark matter experiment, emphasizing their cryogenic stability and low radioactivity.

Contribution

It presents the design, production, and validation of SiPM veto tiles, achieving high yield and demonstrating suitability for cryogenic dark matter detectors.

Findings

High production yield of over 87% for veto tiles

Confirmed stable operation at cryogenic temperatures

Demonstrated low radioactive contamination of the tiles

Abstract

Silicon photo-multipliers (SiPMs) are state-of-the-art sensors capable of detecting a single photoelectron under cryogenic conditions, with potentially lower radioactivity than widely used photomultiplier tubes. The DarkSide-20k experiment, designed to perform direct dark matter searches using liquid argon as the target material, employs SiPM technology to detect interactions in the active detector volumes, including the central dual-phase Time Projection Chamber and the Inner and Outer Veto volumes. The vetoes are designed to discriminate against radiogenic neutron and cosmic muon backgrounds associated with the dark matter search. This paper describes the completed production and test protocols for the "Veto Tiles" (called vTiles, arrays of 24 SiPMs integrated on a printed circuit board providing the power distribution and signal amplification); 16 vTiles are grouped into "Veto Photo-Detector Units" to instrument the Inner Veto volume. Each vTile underwent detailed testing at room and cryogenic temperatures, confirming stable operation, high signal-to-noise ratio, and low radioactive contamination, demonstrating the robustness of the proposed design for cryogenic conditions. The final production yield exceeded 87%, surpassing the 80% requirement and corresponding to 1920 Veto Tiles to populate 120 Veto Photo-Detector Units, plus an additional 6% as spares.