Passage of beta particles through dielectrics in presence of an electric field

Abstract

The effect of an electric field on the passage of thallium-204 beta particles through polymethyl methacrylate, polystyrene, polyethylene terephthalate (Lavsan), and polyethylene targets was investigated. The number of transmitted beta particles and their angular and energy distributions were determined. The transmission curves were obtained with a SBT-7 counter. The angular distribution was investigated in a specially designed scattering chamber, and the energy distribution was determined with a scintillation beta spectrometer incorporating the USD-1 and AI-100 instruments. It was found that the relative change in the number of transmitted beta particles depends on the size of the entrance solid angle, depends linearly on the potential difference applied to the dielectric, and is practically independent of the dielectric material if its thickness is expressed in mass units. It was also found that the relative change in angular distribution up to 60° with potential differences of not more than 10 kV is independent of the scattering angle. The energy distribution is not only shifted on the energy scale, but its shape is also altered. The results are attributed to the effect of the electric field on both the energy of the particles and the direction of their momentum. A simple method of calculating the effect of the field on the number of transmitted beta particles is proposed. The results of calculation agree with the experimental data.