GB514297A - Improvements in or relating to electron multipliers and circuits therefor - Google Patents

Abstract

514,297. Circuits for electron-multipliers. WALTON, G. W. Dec. 10, 1937, No. 34300. [Classes 39 (i) and 40 (v)] In a circuit arrangement employing an electron multiplier with grid-like secondary electron emitting electrodes, a varying voltage superimposed upon a steady potential difference is applied between a control electrode adapted to emit substantially no secondary electrons and a preceding secondary electron emitting grid. In Fig. 2, a carrier wave is applied by coil 11 and tuned circuit 12, 13 between the anode 7 and the preceding grid 6 of the multiplier tube 1. The electron stream from the cathode 2, which may be photo-electric or thermionic, is varied in the rhythm of the modulating signal, and a modulated carrier is taken from the anode circuit at the terminals 16. The steady voltage difference between the electrodes 6, 7 is so chosen that the tube operates midway along the rising portion of the characteristic showing anode current against this voltage difference. Capacity effects within the tube are neutralized by means of a centre tapping on the input coil 12 and a balancing condenser 15 and resistance 14. The carrier may be applied between any of the grids and an immediately-preceding secondary-emitting electrode. Fig. 3 shows an amplifying or modulating circuit in which the signal or carrier is applied between a steady voltage point 18 and a secondary-emitting grid 5, the secondary emission of which is suppressed by a grid 19 situated beyond the grid 5 and held at a lower voltage by connexion to the point 20 on the potentiometer 8. Two or more control electrodes may be employed in a single multiplier so that each controls the secondary emission of a separate preceding electrode. By this means it is possible to achieve mixing of independent modulations. Specification 493,048 is referred to.