Note on the Theory of Cavity Ionization Chambers

In 1955, a paper on cavity ionization focused attention on a function fz(To, A), which was interpreted as the ratio of energy dissipation per gram of cavity gas to the energy dissipation per gram of wall material (1). Among the expressions presented there for fz(To, A), probably the most useful was equation (3b), here given as equation (28).1 This expression was not derived in ref. 1 but was stated without proof. There have since been requests for a derivation; and my purpose is to present one here. The following three short sections review the terminology to make this manuscript internally complete, and contain essentially no new material. The derivation itself is quite short and is given in a manner suggesting possible corrections.