Modelling the radioluminescence of alpha particles in the air by the Monte Carlo method

In the last period, the alpha-induced luminescence of air was proposed to be utilized for remote detection of alpha emitting from radioactive waste sources or for rapid radon detection. The aim of this study is to investigate the possibility to discriminate between the radioluminescence signal and Cherenkov photons due to the simultaneous presence of alpha and beta sources in the same container. Alpha particles induce radioluminescence when absorbed in air. The photons are emitted in the near ultraviolet region by nitrogen molecules excited by secondary electrons. The accurate knowledge of the radioluminescence yield is of the utmost importance for novel radiation detection applications utilizing this effect. On the other hand, the energetic electrons from the beta spectra can produce Cherenkov radiation in air in the same wavelengths as the photons emitted by deexcitation of nitrogen molecules. When alpha and beta emitting radionuclides are simultaneously present in the sample, the detector must be able to discriminate between these contributions. We determine the number of photons produced per unit area (photon flux) by deexcitation of nitrogen molecules and also the number of photons in the same wavelength range produced by beta particles when passing through air. Monte Carlo method is used to simulate the experimental setup and to calculate the sensitivity of the detector as a function of the activities of alpha and beta sources, of the energies of the emitted radiations, of the distances between detector and sources, and also of the sensitivities of the detector in different spectral ranges. (author)