Performance of a large area photon detector for rare event search applications


We present the design and characterization of a large-area Cryogenic PhotoDetector designed for active particle identification in rare event searches, such as neutrinoless double beta decay and dark matter experiments. The detector consists of a 45.6 cm 2 surface area by a 1-mm-thick 10.6 g Si wafer. It is instrumented with a distributed network of Quasiparticle-trap-assisted Electrothermal feedback Transition-edge sensors with superconducting critical temperature T c = 41.5 mK to measure athermal phonons released from interactions with photons. The detector is characterized and calibrated with a collimated Fe-55 x-ray source incident on the center of the detector. The noise equivalent power is measured to be 1 x 10 - 17 W / mml:msqrt Hz</mml:msqrt> in a bandwidth of 2.7 kHz. The baseline energy resolution is measured to be sigma E = 3.86 +/- 0.04 ( stat . ) - 0.00 + 0.19</mml:msubsup> ( syst . ) eV. The detector also has an expected timing resolution of sigma t = 2.3 mu s for 5 mml:msub sigma E events.