NEUTRON YIELDS FROM SELECTED MATERIALS IRRADIATED WITH HIGH-ENERGY PHOTONS

Photoneutron yields from hydrogen, carbon, nitrogen, oxygen, water, polyethylene, tissue substitute and CR-39 have been calculated for the photon energy range of 2 to 30 MeV, using a previously established method. The data are useful for estimating neutron production in these and other similar materials located in the vicinity of a megavoltage radiotherapy beam. Such substances are often used as filtration, phantom or scattering material and as components of neutron dosimetry detectors. It is pointed out that photoneutrons produced in such materials may need to be taken into consideration when carrying out neutron dosimetry in the presence of even relatively low energy photons.