Derivation of Second Order Geometric Factor G

Abstract

The geometric factor G is a major parameter in determining differential cross sections with a gas target. Silverstein has calculated G for several detector aperture geometries with a finite sized, but parallel incident beam. Critchfield and Dodder have calculated G for a parallel‐edge front aperture and circular back aperture with a divergent incident beam. In this article, G is calculated for a parallel edge front aperture and a rectangular back aperture with a divergent incident beam. The present calculation follows the method outlined by Critchfield and Dodder and employs a convenient combination and slight modification of their notation and that of Silverstein.