Seasonal variation of background counting rates in liquid scintillation counting

Abstract

A liquid scintillation background sample was measured daily in a custom-built TDCR counter for more than 17 months. The double and triple coincidence counting rates exhibit an annual sinusoidal fluctuation with a maximum in winter and a minimum in summer. Possible correlations with air temperature, air humidity, radon concentration and secondary cosmic radiation were investigated. The observation of a correlation with the ambient dose equivalent rate [Formula: see text] originating from the charged component of secondary cosmic radiation and an anti-correlation with the effective atmospheric temperature T_eff suggest that the seasonal fluctuations in the background counting rate may be primarily driven by temporal variations in the muon flux at ground level. Additionally, a correlation was found with the indoor ²²²Rn concentration in air.

Keywords: Liquid scintillation counting; Radon; Seasonal background variation; Secondary cosmic radiation; TDCR.