#### Bulg. J. Phys. vol.45 no.1 (2018), pp. 054-066

#### Photon Beam Fluence and Energy at the Phantom Surface as a Function of Primary Electron Energy: Monte Carlo Study Using BEAMnrc Code, DOSXYZnrc and BEAMDP Code

M. Bencheikh

go back^{}, A. Maghnouj^{}, J. Tajmouati^{}*LISTA Laboratory, Physics Department, Faculty of Sciences Dhar El-Mahraz, University of Sidi Mohamed Ben Abdellah, Fez, Morocco*Abstract.The purpose of this study is to provide detailed characteristics of incident photon beams for different primary electron energy for the field size of 10×10 cm^{2}in terms of the photon fluence profile, energy photon fluence profile, and energy photon distribution, The method used in this study was the Monte Carlo calculation method, it is considered to be the most accurate method for dose calculation in radiotherapy. The Monte Carlo codes used were the BEAMnrc code to simulate the 6 MV photon beam produced by Varian Clinac 2100 and photon transport, DOSXYZnrc code to simulate the absorbed dose in a water phantom, and the BEAMDP for the photon beam characteristics at the surface water phantom. We have calculated the percentage depth dose (PDDs) for the 10×10 cm^{2}field size and the calculated PDDs was compared to the measured PDD, and the gamma index was determined as a function of depth in the phantom, the gamma index criterions used was 3% for dose difference and 3 mm for distance to agreement. The acceptance criterion was more than 95% and the statistical uncertainty was 1%. The photon beam characteristic maximum increased in a linear manner as a function of the primary electron energy. The percentage of the beam characteristic maximum was determined relative to the primary electron energy of 6.1 MeV. For example, for a primary electron energy of 6.7 MeV, the percentage of the photon fluence maximum was 23.22% of the photon fluence maximum at 6.1 MeV, the percentage of the photon energy fluence maximum was 32.69% of the photon energy fluence maximum at 6.1 MeV, and the percentage of the photon energy distribution maximum was 19.39% of the photon energy distribution maximum at 6.1 MeV. Our study can be useful to improve photon beam dosimetry and radiotherapy quality.