Photomultiplier tube having an electron multiplier cage assembly with

Abstract

A photomultiplier tube comprises an evacuated envelope having a photoemissive cathode, a shield cup spaced from the cathode and an electron multiplier cage assembly abutting the shield cup. The cage assembly includes a pair of transversely spaced support plates having a plurality of support slots formed therethrough. Each of the support plates has a distal end and a proximal end, with the proximal ends being attached to the shield cup. A light shield is disposed between the distal end of the support plates. An anode and a plurality of dynodes, at least one of which has a field mesh attached thereto, are disposed between the support plates and attached thereto by end tabs. The end tabs extend from the side of the anode and the dynodes. The aforementioned shield cup includes flaps which establish a minimum transverse spacing between the proximal ends of the support plates. The light shield has a transverse dimension substantially equal to that of the flaps to establish a minimum transverse spacing between the distal end of the support plates. The flaps and the light shield thus act, in combination, to provide a uniform minimum transverse spacing between the support plates which is greater than the transverse dimension of the anode and the dynodes to prevent distortion of the field mesh. The tab ends of the dynode and the anode are bifurcated so that one portion of selected ones of the tab ends can be formed to secure the dynodes and the anode between the support plates.