GB958529A - Improvements in or relating to electron tubes - Google Patents

Abstract

958,529. Travelling-wave tubes. M-O VALVE CO. Ltd. June 13, 1962 [June 20, 1961], No. 22347/61. Heading H1D. An electron tube of the type wherein a stream of electrons travels along the length of an interaction space under the influence of perpendicularly directed crossed electric and magnetic fields, the electrons being arranged to interact by virtue of their periodic cyclotron motions with the electric field of an electromagnetic wave propagated along a transmission line which extends in a direction parallel to the length of the interaction space, comprises an electron gun 24 which includes an electron emissive cathode 22 and a further electrode 23 defining therebetween a gun space which extends transversely to the length of, and communicates with, the interaction space, the arrangement being such that with a positive potential on the further electrode with respect to the cathode and a magnetic field disposed in the same direction as in the interaction space, electrons are caused to travel through the gun space into the interaction space and injected therein with low initial velocities. In one preferred embodiment of the invention, a backward-wave oscillator tube comprises an anode 13 maintained at 3kv, and a collector electrode 14 maintained at 750V. with respect to a sole electrode 15, the electrodes 13 and 14 with electrode 15 constituting a transmission line. Waveguide 2 is connected to a reflectionless termination whilst waveguide 3 is used as an output coupler. Electrodes 13, 14 are supported by tubes 16, 17 through which cooling fluid may be passed. The tube may also be used as an amplifier, and it is stated that maximum interaction occurs at a frequency w 0 = W c /(1-R), where W c is the cyclotron frequency and R is the ratio between the general drift velocity of the electrons and the velocity of propagation of the wave along the transmission line in the direction of the electron flow.