LXXIV. The control of a wilson cloud chamber by means of an internal counter

Abstract

Abstract A technique is described for controlling a Wilson cloud chamber by an internal counter whose cathode consists of a hexagonal array of rods and whose sensitive volume is not separated from the main cloud chamber volume by any wall and in fact forms part of the usable chamber volume. The counter has no stopping power beyond that of the gas unless the incident particle chances to hit one of the rods. Events in which heavily ionizing particles are produced in the cloud chamber and events in which low energy particles traverse the chamber can thus be photographed. Discrimination between single fast particles or events of high ionization can be made at will. Altogether 26 slow particles (excluding electrons) have been photographed—corresponding to a vertical intensity of 9·3 × 10−5 slow particles cm.−2 min.−1 sterad.−1 at sea level. Details of a proposed arrangement for photographing nuclear stars in the gas of the chamber are given. The technique is applicable to the study of the discharge phenomena of counters and some preliminary photographs of these phenomena are presented. The counter is quite stable and the technique of operation is not unduly difficult.