Estimation of Absorbed Dose Rates in Air Based on Flux Densities of Cosmic Ray Muons and Electrons on the Ground Level in Japan

Flux densities of cosmic ray muons and electrons were estimated from the pulse height spectra of cosmic ray charged particles observed using a spherical plastic scintillation detector. In order to obtain the pulse height spectrum of cosmic ray electrons separately from that of cosmic ray muons, the pulse height spectrum of cosmic ray electrons was derived by calculating the probability distribution of energy deposited in a plastic scintillator by electrons alone, utilizing the spectrum of cosmic ray electrons given in literature. Calculation was corroborated by measurement with spherical plastic scintillator detector of cosmic ray muons alone, obtained by passing the particles through a lead shield to eliminate electrons and photons. The aggregate absorbed dose rates in air imparted by cosmic ray muons and electrons thus derived proved upon further adding the contribution of cosmic ray photons to come quite close to the total absorbed dose rate given in literature from measurements performed in Japan.