Effect of the Incident Photon Energy and the Thickness of the tungsten Target on the Efficiency of Photoneutron Production for the Treatment of Cancer Patients

Nowadays boron neutron capture applies as an alternative method to treat some cancers which do not respond to traditional radiation therapy. Considering that the epithermal neutron energy are useful for therapeutic purposes, achieve the maximum flux of the epithermal neutron has always been concerned. The aim of this study was to evaluate the effect of the converter thickness and the photon energy incident on the neutron flux output and energy generated.
In this study, using Monte Carlo simulation MCNPX6.2 code, a single pencil photon beam with energies 13, 15, 18, 20, 25 MeV and 2 mm diameter were employed. To optimize the design of the photoneutron target, tungsten target was tested at different thicknesses.
The maximum of the neutron flux for all thicknesses and beam energy occurred at neutron energy peak 0.46MeV. Increasing thickness up to 2 cm showed the neutron flux was increased with increases in thickness and followed a downward trend.
The photon energy and the thickness of the tungsten target have a significant impact on the total neutron energy, energy spectrum and the average energy neutrons which depending on the neutron energy spectrum required should be selected. The use of a tungsten layer with a thickness of 2 cm and the 15MeV photon energy for production of maximum neutron flux with a minimum average energy is suggested.