A semi-automatic analyser for bubble chamber photographs

Abstract

Photographs of nuclear particle tracks can be accumulated rapidly with fast-cycling bubble chambers. This article describes a machine for measuring the photographs quickly so that the subsequent computations can be done with an electronic computer. The films are projected onto a ground glass screen bearing a reference mark, and moved by hand through a pantograph to bring interesting points onto the mark. The panthograph carries a plate with a fine square lattice of dots, and four photocells serve to digitise its X and Y coordinates. The two stereoscopic images of a point can be merged by moving one of the projection lenses; this motion also is digitised photoelectrically. After setting each point, the measured data are punched on tape, to be fed later to an electronic computer. The design, operation, and performance of the machine are described in some detail, together with the principles of measurement and some proposed improvements.