Transport of fast electrons through thin foils

We investigate both experimentally and theoretically the energy and angular distribution of fast monoenergetic electrons penetrating very thin foils with a thickness of the order of a few ${\lambda }_f$, the mean free path for free-electron scattering. The measured distribution functions display three distinctive components of zero scattering, single scattering, and multiple scattering, in both angle and energy. The description in terms of a kinetic equation (or equivalently, phase-space master equation) is discussed. Its numerical application is facilitated by a multiple-scattering expansion. Good agreement between experiment and theory is found.