Characterization of the QUartz Photon Intensifying Detector (QUPID) for noble liquid detectors

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 (Q upid ), 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 Q upid and the testing measurements on Q upid s from the first production line. Screening of radioactivity at the Gator facility in the Laboratori Nazionali del Gran Sasso has shown that the Q upid s safely fulfill the low radioactive contamination requirements for the next generation zero background experiments set by Monte Carlo simulations. The quantum efficiency of the Q upid at room temperature is > 30 % at the xenon scintillation wavelength. At −100 °C, the Q upid shows a leakage current smaller than 1 nA and a global gain of 10 5 . In these conditions, the photocathode and the anode show > 95 % linearity up to 1 μ A 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 Q upid s have a good timing response: 1.8 ±0.1 ns rise time, 2.5 ±0.2 ns fall time, 4.20 ±0.05 ns (FWHM) pulse width, and 160 ±30 ps (FWHM) transit time spread. The Q upid s have also been tested in a liquid xenon environment, and scintillation light from 57 Co and 210 Po radioactive sources was observed.