An Analysis of the Free-Air Ionization Chamber for Extended Sources of Radiation

Abstract

A mathematical analysis of how source and diaphragm dimensions affect the accuracy of free-air chamber measurements of X-ray dosage is presented. On the basis of the derived analytical criteria it is concluded that (1) the dimension of the focal spot of the X-ray tube and (2) the length of the-cylindrical hole in the diaphragm should be kept to a mimimum.