Dependence of Secondary Electron Emission upon Angle of Incidence of 1.3-Mev Primaries

Utilizing a high-energy beam and targets sufficiently thin to permit the primary electrons to pass through with negligible scattering and energy loss, the secondary electron yield has been observed to vary with the angle of incidence of the primaries in accordance with the relationship $\delta \left(\theta \right)={\delta }_{0}sec\theta$. This angular dependence is predicted theoretically on the basis of the single assumption that the secondary electrons can be treated as though they were produced with an isotropic velocity distribution. At large angles of incidence, the variation is slightly greater as a consequence of scattering effects which are larger in Ni than in an approximately equal thickness in mg ${\mathrm{cm}}^{\mathrm{—}1}$ of Al. The experimentally observed equality of the yields in the forward and backward directions is consistent with the conclusion that the angular distribution of the secondaries is effectively isotropic.