Investigation the trend of different magnetic fields types on linac photon beam mode by Monte Carlo method using Geant4 toolkit

The present study is aimed at investigating the behavior of the secondary particles due to the photon beam interaction at the presence of the longitudinal, radial, tangential (angles), and uniformly springy magnetic fields with different intensities. The photon mode of a 15 MV Siemens Primus linac is used as an example. On the validity of the accelerator simulation, the percentage of depth dose and dose profile were also measured in the water phantom in 5-Azar hospital. The simulation has been performed by the Geant4.10.3 version in order to assess investigate the effect of different magnetic fields with a variety of intensity on dose profiles. Based on the profile dose distribution obtained for magnetic fields with different types and intensities it can be realized that the field of 3 T has the optimal condensation of the dose profile distribution. The striking feature the flux of electrons dramatically decreases for the tangential field compared to other magnetic fields, as in the dose profile graphs of this filed were shown.