Variations of gamma-ray background in the Belgrade shallow underground low-level laboratory.

During the last three years we investigated the variations of background simultaneously in two laboratories, the ground level (GLL) and the underground laboratory. The Forbush-like effect from March 2010 was observed in the GLL using a Ge detector and plastic veto scintillator. The underground plastic scintillator saw the same effect but the coincident veto spectrum did not detect the decrease of cosmic-ray intensity. Using a time series analysis of prominent post-radon lines, a significant radon daily variability was detected in the Ge detector background spectrum, but only in the GLL.