A Method to Decrease the Background Fluctuation of the Low Background Liquid Scintillation Counters Caused by Atmospheric Radioactivity (Radon and Its Daughters)

Abstract

α-Rays from atmospheric radionuclides, i.e. radon and its daughters (²²²Rn, ²¹⁸Po and ²¹⁴Po) fluctuate background counts of liquid scintillation counters, since they are sensitive to the luminescence of nitrogen molecules excited by the α-rays. The background count was decreased and its fluctuation was suppressed by passing nitrogen gas through its detector chamber; for example the count rate of tritium free water sample, which fluctuates in the range of 3-5 min^-1 without the gas flow, was decreased to 3.2±0.3 min^-1.