Influence of backscattered electrons on exit beam of miniature transmission X-ray tube using Geant4

Abstract

BackgroundWhen an X-ray tube operates, a large number of backscattered electrons are generated inside the tube. Under the influence of the electric field inside the X-ray tube, these backscattered electrons are pulled back to the anode target by the electric field, generating additional X-rays, which ultimately have a negative impact on the quality of the emitted beam.PurposeThis study aims at the distribution rules of backscattered electrons in transmission X-ray tubes, and the changes in backscattered electrons caused by target materials and tube voltages as well as their impact on the outgoing beam quality.MethodsFirstly, Geant4 was used to establish the physical model of the transmission X-ray tube, and the theoretical calculations were compared with experimental data to verify the accuracy of the calculation program. Then, C, Si, Cu, Ag, and W were selected as anode target materials, and the influences of different electric field strengths and these target materials on the distribution of backscattered electrons in the X-ray tube were analyzed in details. Finally, the influence of the backscattered electrons on the outgoing beam quality under the effect of tube voltage was investigated.ResultsThe full width at half maximum, photon yield, and characteristic peak yield of the outgoing beam of the X-ray tube increase when considering the electric field, indicating that the backscattered electrons have effect on the outgoing spectrum quality. Simultanously, the backscattered electrons pulled back by the electric field in the first and second generations predominantly affect the outgoing beam quality. A change in the tube voltage alters the extent of influence of the backscattered electrons on the outgoing beam quality, and a larger tube voltage leads to a more obvious influence of the backscattered electrons on the outgoing beam quality of the X-ray tube.ConclusionsThe distribution of inside backscattered electron is closely related to the characteristics of the X-ray tube, including the tube voltage and target material. The results of this study may provide a reference for numerical simulation calculations of miniature transmission X-ray tubes.

Keywords

• transmission x-ray tube
• backscattered electron
• tube voltage
• target material
• geant4