One-year measurements of -ray background using a high-purity germanium detector

Sakoda, Akihiro   ; Tanaka, Hiroshi ; Ishimori, Yuu  

In the present work, the natural -ray background was thoroughly measured using a high-purity germanium detector in a year (283.5 days in total, = 271). The data was first discussed in relation to radon concentrations in the laboratory. No correlations were found between the -ray count rates from Pb and Bi and radon concentrations, meaning that radon just around the germanium detector was reduced to the negligible level by the introduction of nitrogen gas. Also, the count rates of major nuclides appeared to fluctuate with the coefficient of variance of a few up to several tens of percent, without seasonal variations. Furthermore, summing of all -ray spectra allowed us to see neutron-induced peaks that cannot be detected in usual short-term measurements. All data obtained here would be the knowledge useful for the practice of -ray measurements.