Spatial characteristics of electron‐ and photon‐induced secondary electron cascades in CsI

Our microscopic model for electron transport in alkali halides was used for the calculation of the spatial characteristics of secondary electron cascades induced by x rays and electrons in an infinite CsI volume, in the energy range of 5–50 keV. The results show that the shape of the cascade cloud preserves the features of the primary interactions only at the core, where the cascade has an elongated, forward peaked shape for incident electrons and is spherically symmetric for photons. At the periphery the cloud is practically spherical, and of very low electron density. The maximal cascade dimensions do not exceed 10 μm at the highest considered energy. The impact of these characteristics on secondary electron emission from finite thickness CsI layers is discussed.

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