A Theory of Cavity Ionization

Abstract

A theory of cavity ionization is presented which takes into account the travel of fast secondary electrons generated in electron-electron collisions, an effect disregarded in the Bragg-Gray theory. The problem is schematized by defining as "fast" secondaries those with energy above a threshold A sufficient to span the cavity. Calculations based on this theory show closer agreement with experiments of Attix and DeLaVergne than Bragg-Gray theory calculations. The theories differ most when the wall and gas atomic numbers are very different. The dependence of ionization on the cavity size predicted by the present theory agrees with measurements by Gray. The interpretation of extrapolation to zero cavity size is shown to be more complex than had been believed.