The LBF performs low background counting in two unique facilities-- a local surface site constructed with low activity serpentine concrete and an underground laboratory at the 4850L (~4300 m.w.e.) of the Sanford Underground Research Facility (SURF) in Lead, SD. Prior to 2014, the underground system was located in the Hyatt Power Plant (~600 m.w.e.) of the Oroville Dam in Oroville, CA.
Facility Descriptions | LBNL Berkeley, CA | SURF Lead, SD | Depth | surface, ~10 m.w.e. | 4,850 ft, 4300 m.w.e. | Vicinity | low activity concrete | low activity bedrock | Muon Suppression | 3π active muon veto | 4300 m.w.e. overburden | Radon suppression | nitrogen purge | nitrogen purge | HPGe | 115% n-type, 80% p-type | 80% p-type | Other | NaI, BF3 | |
Samples are typically screened first at the surface laboratory at LBNL. Then, pending results and sensitivity requirements, the samples are then sent on to SURF for a more sensitive count. This prioritizes the time of the underground system for samples that actually require the enhanced sensitivity. Counting Sensitivities [for ~1kg samples] | Berkeley Site [~1 day] | SURF Site [~1 week] | U series | 0.5 ppb (6 mBq/kg) | 50 ppt (0.6 mBq/kg) | Th series | 2.0 ppb (8 mBq/kg) | 200 ppt (0.8 mBq/kg) | K | 1.0 ppm | 100 ppb | Co-60 | 0.04 pCi/kg (1.5 mBq/kg) | 0.004 pCi/kg (0.15 mBq/kg) |
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