SENSEI: Characterization of Single-Electron Events Using a Skipper Charge-Coupled Device
L. Barak, Itay M. Bloch, Ana Martina Botti, Mariano Cababié, Gustavo Cancelo, Luke Chaplinsky, Fernando Chierchie, M. B. Crisler, A. Drlica-Wagner, Rouven Essig, Juan Estrada, E. Etzion, Guillermo Fernández Moroni, Daniel Gift, S. Holland, Sravan Munagavalasa, Aviv Orly, Darío Rodrigues, Aman Singal, Miguel Sofo Haro, Leandro Stefanazzi, Javier Tiffenberg, Sho Uemura, Tomer Volansky, T. Yu
Abstract
We use a science-grade skipper charge-coupled device (skipper CCD) operating in a low-radiation background environment to develop a semiempirical model that characterizes the origin of single-electron events in CCDs. We identify, separate, and quantify three independent contributions to the single-electron events, which were previously bundled together and classified as ``dark counts'': dark current, amplifier light, and spurious charge. We measure a dark current, which depends on exposure, of $(5.89\ifmmode\pm\else\textpm\fi{}0.77)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\phantom{\rule{0.2em}{0ex}}{e}^{\ensuremath{-}}/\mathrm{pix}/\mathrm{day}$, and an unprecedentedly low spurious charge contribution of $(1.52\ifmmode\pm\else\textpm\fi{}0.07)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\phantom{\rule{0.2em}{0ex}}{e}^{\ensuremath{-}}/\mathrm{pix}$, which is exposure independent. In addition, we provide a technique to study events produced by light emitted from the amplifier, which allows the detector's operation to be optimized to minimize this effect to a level below the dark-current contribution. Our accurate characterization of the single-electron events allows one to greatly extend the sensitivity of experiments searching for dark matter or coherent neutrino scattering. Moreover, an accurate understanding of the origin of single-electron events is critical to further progress in ongoing research and development efforts of skipper and conventional CCDs.