Measurement of radioactive contamination in the high-resistivity silicon CCDs of the DAMIC experiment

ALEXIS AGUILAR-AREVALO; DAN AMIDEI; XAVIER BERTOU; BOLE, D.; BUTNER, M.; GUSTAVO CANCELO; CASTAÑEDA VAZQUEZ, ALEJANDRO; ALVARO E. CHAVARRIA; MELLO NETO, J.R.T.; DIXON, S.; D'OLIVO, JUAN CARLOS; ESTRADA, JUAN; FERNÁNDEZ MORONI, GUILLERMO; HERNANDEZ TORRES, PAMELA; FEDERICO IZRAELEVITCH; KAVNER, ALEXANDER; BEN KILMINSTER; LAWSON, IAN; JUNHUI LIAO; LÓPEZ, M.; MOLINA, JORGE; MORENO GRANADOS, G.; PEÑA, J. R.; PAOLO PRIVITERA; YOUSSEF SARKIS; SCARPINE, V. ; TOM SCHWARZ; MIGUEL SOFO HARO; JAVIER TIFFENBERG; TORRRES MACHADO, D; TRILLAUD, F.; YOU, X.; ZHOU, J.

JOURNAL OF INSTRUMENTATION

IOP PUBLISHING LTD

Lugar: Londres; Año: 2015

1748-0221

We present measurements of radioactive contamination in the high-resistivity silicon charge-coupled devices (CCDs) used by the DAMIC experiment to search for dark matter particles. Novel analysis methods, which exploit the unique spatial resolution of CCDs, were developed to identify α and β particles. Uranium and thorium contamination in the CCD bulk was measured through α spectroscopy, with an upper limit on the 238U (232Th) decay rate of 5 (15) kg−1 d−1 at 95% CL. We also searched for pairs of spatially correlated electron tracks separated in time by up to tens of days, as expected from 32Si ?32P or 210Pb ?210Bi sequences of β decays. The decay rate of 32Si was found to be 80+110−65 kg−1 d−1 (95% CI). An upper limit of ~35 kg−1 d−1 (95% CL) on the 210Pb decay rate was obtained independently by α spectroscopy and the β decay sequence search. These levels of radioactive contamination are sufficiently low for the successful operation of CCDs in the forthcoming 100 g DAMIC detector.