Simulation of a high-energy electron beam transmission through titanium and Kapton$^\circledR$ thin films

Abstract

The results of computer simulation of the high-energy electrons passage through thin layers of titanium (Ti) and polyimide Kapton$^\circledR$ in the energy range from 3 to 20 MeV are presented. Simulation is carried out using the Geant4 toolkit. The thickness of the Ti foil in the model experiment is 50 microns, the thickness of the Kapton$^\circledR$ film is 110 microns. The purpose of the calculations is to reveal the possibility of using the Kapton$^\circledR$ film in the output devices of linear electron accelerators. It was necessary to calculate the probable values of the energy absorbed in a Kapton$^\circledR$ film and in a Ti foil for each value of primary electrons energy. Another important characteristic is the divergence radius of the electron beam at a predetermined distance from the film, or the electron scattering angle. As a result of calculations, the energy spectra of bremsstrahlung gamma-quanta, formed during the passage of electrons through the materials of the films, are obtained. The most probable values of the energy absorbed in the Ti foil and in the Kapton$^\circledR$ film are calculated. The scattering radii of an electron beam for the Kapton$^\circledR$ film and also for the Ti foil at a distance of 20 cm are estimated. It is shown that the ratio of the total amount of bremsstrahlung gamma quanta in the case of use the Kapton$^\circledR$ film is approximately 0.56 of the total amount of bremsstrahlung gamma quanta when using the Ti foil. The analysis of the calculated data showed that the use of Kapton$^\circledR$ as a material for the manufacture of output devices for high-energy electron beams is more preferable in comparison to Ti films. The use of Kapton$^\circledR$ instead of Ti makes it possible to significantly reduce the background of the generated bremsstrahlung gamma quanta and reduce the scattering radius of the electron beam.