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

TL;DR

This study uses Geant4 simulations to compare electron transmission through titanium and Kapton films, finding Kapton reduces bremsstrahlung and beam scattering, making it preferable for accelerator output devices.

Contribution

First simulation-based comparison of electron transmission through titanium and Kapton films, demonstrating Kapton's advantages in reducing bremsstrahlung and beam divergence.

Findings

Kapton reduces bremsstrahlung gamma quanta by about 44% compared to titanium.

Electron beam scattering radius is smaller with Kapton at 20 cm distance.

Kapton is more suitable than titanium for high-energy electron beam output devices.

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.