Design of a photoneutron source based on 10Â MeV electrons of radiotherapy linac

The optimization of a compact, economical and simple photoneutron production, by using the tungsten as bremsstrahlung production target and heavy water serving as the dual purpose of photoneutron production and heat exchange medium, has been studied. The Monte Carlo code MCNPX has been used to optimize the targets geometry and reflectors geometry to increase the photoneutron yield as the highest possible rate. The process of bremsstrahlung production extremely heats up the tungsten target, making it necessary to be cooled down to below 350 K. The MATLAB code and jet impingement cooling method were used to obtain the temperature of tungsten target versus the electron current and also the velocity of heavy water coolant. The jet impingement cooling method was used to control the temperature of tungsten target versus the electron current and the jet velocity. Results showed that for the temperature of 350 K, the radius of tungsten was obtained to be 15.7 cm in accordance with the maximum electron current for 10 MeV electrons. Applying the optimized dimensions of the targets and a beryllium layer of 50 cm thick as a reflector and γ-contamination converter, the neutron yield was found to be 1.25 × 1011 n/mA/s for 10 MeV electrons.