Estimation of Neutron Production from Accelerator Head Assembly of 15 MV Medical LINAC using FLUKA Simulations

For the production of a clinical 15 MV photon beam, the design of accelerator head assembly has been optimized using Monte Carlo based FLUKA code. The accelerator head assembly consists of etarget, flattening filter, primary collimator and an adjustable rectangular secondary collimator. Accelerators used for medical radiation therapy generate continuous energy gamma rays called bremsstrahlung radiations by impinging high energy electrons on high Z materials. The electron accelerators operating above 10 MeV can result in the production of neutrons, mainly due to photo nuclear reaction ( ,n) induced by high energy photons in the accelerator head materials. These neutrons contaminate the therapeutic beam and give a non negligible contribution to patient dose. The gamma dose and neutron dose equivalent at the patient plane were obtained at different field sizes and maximum neutron dose equivalent observed near the central axis of of 30 30 cm.