Measurement of Radioactive Contamination in the High-Resistivity Silicon CCDs of the DAMIC Experiment
- Universidad Nacional Autonoma de Mexico (Mexico). et al.
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 b decays. The decay rate of 32Si was found to be 80+110-65 (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. Furthermore, these levels of radioactive contamination are sufficiently low for the successful operation of CCDs in the forthcoming 100 g DAMIC detector.
- Research Organization:
- Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- Contributing Organization:
- DAMIC Collaboration
- Grant/Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1223218
- Report Number(s):
- FERMILAB-PUB-15-315-A-CD-E; arXiv eprint number arXiv:1506.02562
- Journal Information:
- Journal of Instrumentation, Vol. 10, Issue P08014; ISSN 1748-0221
- Publisher:
- Institute of Physics (IOP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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