A method for simulating radiative Bhabha scattering for configurations where one or both electrons do not scatter appreciably is presented. Double radiative Bhabha scattering is included by using the equivalent photon approximation. Results from a Monte Carlo event generator are shown for two experimental configurations. When an electron and photon scatter at large angles, the contribution from...

The characterization of the incident photon beam is usually divided into its dependence on collimator setting (head-scatter factor) and off-axis position (primary off-axis ratio). These parameters are normally measured "in air" with a build-up cap thick enough to generate full dose build-up at the depth of dose maximum. In order to prevent any influence from contaminating electrons, it has been...