The perturbation of electron beam dose distributions at medium interfaces

The perturbation of electron beam dose distributions in the vicinity of medium interfaces is calculated. Two different solutions to the Boltzmann equation, one an energy averaged solution and the other a diffusion approximation solution, are presented for the calculation of the electron distribution in the vicinity of interfaces. An extension of the energy averaged formalism is presented for media with high atomic number. A new effective depth approximation is introduced to calculate the beam conditions beneath the interface. The transformation from electron distribution to dose distribution is made and dose calculations are compared with published electron beam dose measurements.