Simulation of a High-Energy Electron Beam Transmission Through Titanium and Kapton® Thin Films

Abstract

The results of computer simulation of the high-energy electrons passage through thin layers of titanium (Ti) and polyimide Kaptonâ (C22H10N2O5) in the energy range from 3 MeV to 20 MeV are presented. Simulation is carried out using the Geant4 toolkit. The number of primary electrons is 6.24×107 for each series of calculations. The thickness of the titanium foil in the model experiment is 50 µm, the thickness of the Kaptonâ film is 110 µm. The energies of primary electrons are chosen as following: 3 MeV, 5 MeV, 10 MeV, 15 MeV, and 20 MeV. The purpose of the calculations is to reveal the possibility of using the Kaptonâ film in the output devices of linear electron accelerators. It was necessary to calculate the probable values of the energy absorbed in a Kaptonâ film and in a titanium 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 titanium foil and in the Kaptonâ film are calculated. The scattering radii of an electron beam for the Kaptonâ film and also for the titanium foil at a distance of 20 centimeters are estimated. These calculations are performed for electron energies of 3 MeV, 5 MeV, 10 MeV, 15 MeV, and 20 MeV. A comparative analysis of the obtained results of computational experiments is carried out. It is shown that the ratio of the total amount of bremsstrahlung gamma quanta in the case of use the Kaptonâ film is approximately 0.56 of the total amount of bremsstrahlung gamma quanta when using the titanium foil. The coefficients of the ratio of the electrons scattering radius most probable value after passing through Kaptonâ to the most probable value of the scattering radius after passing through titanium are from 0.62 at electrons energy of 3 MeV to 0.57 at electrons energy of 20 MeV. The analysis of the calculated data showed that the use of Kaptonâ (C22H10N2O5) as a material for the manufacture of output devices for high-energy electron beams is more preferable in comparison to titanium films, since the use of Kaptonâ instead of titanium makes it possible to significantly reduce the background of the generated bremsstrahlung gamma quanta and reduce the scattering radius of the electron beam.

Modeling and Preliminary Experimental Results of Thin Film Heating During the Passage of a High-Energy Electron Beam

“…Taking into account the positive results of the simulation [2] and preliminary complex thermo mechanical experimental tests, it was decided to use 125 µm Kapton® [6] of two diameters, Ø56 mm and Ø36 mm, as the outlet windows of the electron beam [1]. Kapton ® thin films have been successfully tested in bench tests at an electron beam accelerator.…”

“…Previously, using the main data on the total ionization losses of electrons when passing through thin films of 50 μm Aluminum, 50 μm Titanium, and 125 μm Kapton ® were obtained [2,10]. The calculations use the following values for the deposited energy of the 15 MeV primary electron beam: 28.81 keV for Aluminum, 51.23 keV for Titanium, and 37.36 keV for Kapton ® .…”

“…Small changes in the step increase the complexity of calculations many times over. Thus the expression (2) where equals zero because the temperature is stable along the z-axis…”

“…Electron energy ranges from 3 to 15 MeV as well as different thickness of thin films were investigated. The main objectives of that work [2] were to estimate the probable values of the energy absorbed in the films, as well as the characteristics of the bremsstrahlung beam for each type of thin film.…”

Universal Experimental Facility of Ihepnp NSC Kipt for Research of High-Energy Electron Beam Interaction With Thin Amorphous and Single-Crystal Structures

“…1,a Traditionally for high energy electron beam extraction from the accelerator vacuum volume to the air for NSC KIPT electron accelerators thin titanium foil (50 µm) is used. In our case after positive results of Geant4 toolkit modeling [8] and complex thermomechanical experimental tests the new material 125 µm Kapton was applied for two diameter output windows: Ø56 mm (position 11) and Ø36 mm (position 10) respectively. During the bench tests of universal experi-mental facility the Kapton® as a material of electron beam output window shown the stable operation.…”