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.
|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]
|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)|