PNNL

Abstract

PNNL has developed two very low-background gamma detectors housed in a new shallow underground laboratory. This new capability significantly improves our ability to detect trace amounts of airborne particulate that may be present in samples from the IMS field stations. The detectors were custom ordered to be fabricated using very low background materials. The combination of cosmic veto panels, dry nitrogen gas to reduce radon, low background shielding, and the shallow underground laboratory results in a reduction of the background count rate by a factor of 100 compared to an off –the-shelf commercial gamma detector operating above ground at our laboratory. Detection limits are thus reduced an order of magnitude.