Characterization of the QUartz Photon Intensifying Detector (QUPID) for Noble Liquid Detectors

TL;DR

This paper introduces the QUPID, a low-radioactivity photodetector designed for noble liquid detectors, demonstrating its low background, high efficiency, and fast timing suitable for dark matter and double beta decay experiments.

Contribution

The paper presents the design, production, and comprehensive testing of the QUPID, highlighting its ultra-low radioactivity, high quantum efficiency, and fast timing performance for next-generation experiments.

Findings

QUPID meets low radioactive contamination requirements for next-gen experiments.

QUPID achieves >30% quantum efficiency at xenon scintillation wavelength.

QUPID demonstrates fast timing with 1.8 ns rise time.

Abstract

Dark Matter and Double Beta Decay experiments require extremely low radioactivity within the detector materials. For this purpose, the University of California, Los Angeles and Hamamatsu Photonics have developed the QUartz Photon Intensifying Detector (QUPID), an ultra-low background photodetector based on the Hybrid Avalanche Photo Diode (HAPD) and entirely made of ultraclean synthetic fused silica. In this work we present the basic concept of the QUPID and the testing measurements on QUPIDs from the first production line. Screening of radioactivity at the Gator facility in the Laboratori Nazionali del Gran Sasso has shown that the QUPIDs safely fulfill the low radioactive contamination requirements for the next generation zero background experiments set by Monte Carlo simulations. The quantum efficiency of the QUPID at room temperature is > 30% at the xenon scintillation wavelength. At low temperatures, the QUPID shows a leakage current less than 1 nA and a global gain of 10^5. In these conditions, the photocathode and the anode show > 95% linearity up to 1 uA for the cathode and 3 mA for the anode. The photocathode and collection efficiency are uniform to 80% over the entire surface. In parallel with single photon counting capabilities, the QUPIDs have a good timing response: 1.8 +/- 0.1 ns rise time, 2.5 +/- 0.2 ns fall time, 4.20 +/- 0.05 ns pulse width, and 160 +/- 30 ps transit time spread. The QUPIDs have also been tested in a liquid xenon environment, and scintillation light from 57Co and 210Po radioactive sources were observed.