QUPID, a single photon sensor for extremely low radioactivity

We have successfully developed a new photon sensor, the Quartz Photon Intensifying Detector (QUPID), for experiments such as dark matter searches and observation of double beta decay. The QUPID is a type of hybrid-photo-detector (HPD), consisting of a special bialkali photocathode considering the operation under extremely low temperature such as the temperature of liquid xenon, −108 °C, and a special avalanche photodiode for electron bombardment. The QUPID is constructed solely from extremely low radioactive materials, such as quartz and Si-avalanche photodiodes (APDs), which allows it to reach radiation levels of less than 1 mBq while being able to detect single photons. In this paper, we report superior characteristics of the QUPID confirmed by the evaluation.