Speaker
Description
The DAMIC (Dark Matter in CCDs) experiment employs the bulk silicon of scientific-grade charge coupled devices (CCDs) to detect Dark Matter particles. DAMIC-100, a 41 g detector, is operating in the SNOLAB laboratory, located 2 km below the surface within the Vale Creighton Mine near Sudbury, Ontario, Canada. We present a powerful technique to distinguish and reject background events. Utilizing the exquisite spatial resolution of CCDs, discriminating between $\alpha$ and $\beta$ particles, we identify spatially-correlated decay sequences over long periods. We report measurements of the radioactive contamination of $^{210}$Pb and $^{32}$Si in DAMIC-100 CCDs, and place limits on $^{238}$U and $^{232}$Th contamination. DAMIC's capability to measure contamination has significant implications for the next generation of silicon-based dark matter experiments. For example, $^{32}$Si could become a dominant and irreducible background for future programs. We show that $^{32}$Si levels may vary significantly in high-purity silicon, and indicate feasible methods to screen materials for fabrication of future detectors in order to push experimental sensitivity to unprecedented levels.
