Evaluation of photon and neutron dose distribution from the Varian Clinac 2300EX 15 MV medical LINAC with MCNP6 Code

Abstract

The X-ray and neutron beam characteristics of the Varian Clinac 2300EX LINAC were obtained by simulation and computation using the MCNP6 software. An electron source with an energy of 15 MeV is used to produce an X-ray beam which is then directed to the phantom 100 cm distance from the electron source. With an irradiated area (10 × 10) cm2, the average X-ray dose on the phantom surface obtained was (2,91 ± 0,47) 10−15 Gy/e. For better isodosis, a triangular prism-shaped within nickel material flattening filter was installed to produce an X-ray beam profile with an average dose of (2,04 ± 0,22) 10−16 Gy/e. During LINAC 15 MV operation, the mean neutron dose was detected (8,57 ± 0,55) 10−20 Sv/e. The neutron energy spectrum has been simulated, the distribution of thermal energy intensity is 0,06%, epithermal energy is 0,74%, and the most distribution is fast energy 99,20%. The ratio of neutron equivalent dose to the central axis X-ray dose (ξ) was calculated. The value of ξ meets the allowable limit of < 1/1000 Sv/Gy, recommended by the International Electrotechnical Commission (IEC). The ξ values obtained at several phantom depths in this study indicate the values allowed by the IEC.