Measurement Of Low Energy Compton Scattering In Silicon CCDs

A better understanding of low-energy backgrounds is critical toward improving the sensitivity of the Dark Matter in CCDs at Modane (DAMIC-M) detector in its search for low-mass dark matter particles. Among such backgrounds is Compton scattering of environmental gamma rays. Although the high energy range of a Compton spectrum is very well understood in literature, ionizing and spectral features cast its low energy range into less familiar territory, calling for validations of simulation quality in this regime. A previous study was able to probe down into atomic shell ionization energy ranges for this validation, but with the development of more robust Skipper CCDs, it is now possible to study this spectrum down to electron band-gap energies of a few eV. Using a calibration chamber at the University of Chicago, we exposed a Skipper CCD to a range of gamma and x-ray sources and compared the resulting data against images that I generated based off of Monte Carlo particle simulations that I generated using the GEANT4 software package.