GB518665A - Method of electron control - Google Patents

Abstract

518,665. Thermionic valves. JOBST, G. May 26, 1938, Nos. 15784, [Convention date, May 26, 1937], 15785, 15786. [Convention dates, June 1, 1937], 15787 and 15788. [Convention dates, Aug. 28, 1937]. [Class 39 (i)] A constant or modulated stream of electrons from a cathode is gathered into groups which reach the anode at regular intervals which are equal to or a multiple of the period of an oscillator circuit connected between the anode and cathode. Two methods of accomplishing this are described. In the arrangement shown in Fig. 1a electrons from a cathode 2 pass through a positively biased grid 3 to a grid 5. The grid 5 has a negative bias on which is superinduced an alternating potential such that the passage of the electrons is blocked for the greater part of the period, but during a short part of each cycle they can pass to the anode 8 ; in the interval, they oscillate between the cathode 2 and grid 5. In the arrangement shown in Fig. 2a two grids 23, 24 are provided, connected together so that the space between them is free of field. A potential increasing rapidly with the time and returning suddenly to its original value is applied to these electrodes so that electrons leaving the cathode 22 at a later period are accelerated more strongly in the space between the cathode and the electrode 23 than those leaving earlier and overtake them in the space between the electrodes 23, 24, so that they pass to the anode 25 in groups. It is stated that for the best effect the voltage applied to the electrodes 23, 24 should be proportioned to #o<2>/(#o-t)<2>, where #o is a constant and t the time but that a good approximation to this value can be obtained over a considerable part ot the period by means of a sinusoidal potential ; in the latter case the electron stream should be stopped by a grid carrying an alternating potential for that portion of the period when the approximation is not satisfactory. It is also stated that the cathode current may be modulated by a grid carrying an alternating current having a frequency less than that of the oscillating circuit, the frequency of the oscillations thus produced being increased in the ratio of the time in which a group of electrons leave the cathode to the time between the arrival of the first and last electrons of the group at the anode. The current may also be modulated by a frequency greater than that of the oscillating circuit. The application of the invention to a gas-filled tube, say at a pressure at or above 10<-5> mm. of mercury, is discussed.