Study of Radon-induced Background Mitigation in an HPGe Counting System

The spectrum of gamma-rays emitted from a material can be used to measure or place limits on the presence of contamination with radioisotopes. High purity germanium detectors are a powerful tool for such spectroscopy due to their relatively high probability to absorb gamma rays and typically excellent energy resolution which aids separation and identification of gamma rays characteristic of the contamination. In the case of 238U, a long-lived radioisotope of importance in low-background rare event searches, sensitivity to the contamination is often impeded by the presence of 222Rn, a relatively long-lived noble gas daughter of 238U, emanating from materials in the counting lab and diffusing into the sample volume. In this poster, we report on the 222Rn background in a HPGe counting setup and efficacy of techniques such as nitrogen gas purging to mitigate this background.