Performance of a Large Area Photon Detector For Rare Event Search Applications

Abstract

We present the design and characterization of a large-area Cryogenic PhotoDetector (CPD) designed for active particle identification in rare event searches, such as neutrinoless double beta decay and dark matter experiments. The detector consists of a $45.6$ ${\mathrm{cm}}^2$ surface area by 1-mm-thick $10.6$ $\mathrm{g}$ Si wafer. It is instrumented with a distributed network of Quasiparticle-trap-assisted Electrothermal feedback Transition-edge sensors (QETs) with superconducting critical temperature $T_c=41.5$ $\mathrm{mK}$ to measure athermal phonons released from interactions with photons. The detector is characterized and calibrated with a collimated ${}^{55}$Fe X-ray source incident on the center of the detector. The noise equivalent power is measured to be $1\times 10^{-17}$ $\mathrm{W}/\sqrt{\mathrm{Hz}}$ in a bandwidth of $2.7$ $\mathrm{kHz}$. The baseline energy resolution is measured to be $\ddot{I}{ƒ}_E=3.86\pm 0.04$ $(stat.{)}_{-0.00}^{+0.23}$ $(syst.)$ $\mathrm{eV}$ (RMS). The detector also has an expected timing resolution of $\ddot{I}{ƒ}_t=2.3$ $\hat{I}¼\mathrm{s}$ for $5$ $\ddot{I}{ƒ}_E$ events.

6 pages, 5 figures