GB865431A - Beam-type tube - Google Patents

Abstract

865,431. Travelling-wave tubes. HEWLETTPACKARD CO. June 20, 1958 [July 18, 1957], No. 19922/58. Class 39(1). An E-type beam tube has a slow wave circuit comprising an even number of part cylindrical conductors 12 round which an electron beam 26, from a gun 15, describes a helical path between the slow wave circuit and a concentric cylindrical conductor 19. Cylinder 19 is maintained at a negative D.C. potential with respect to the D.C. potential of the slow wave circuit and the electron velocity is chosen so that the outward centrifugal force on the electrons is balanced by the inward electrostatic force. As the electrons travel in their spiral path they can give up potential energy to the R.F. field by moving inwards to the region of higher D.C. potential. By controlling the electron velocity the frequency with which a given electron. crosses the gaps 13 between conductors 12 and hence the output frequency may be controlled. One end of the slow wave circuit may be terminated as at 21, the output being obtained from the other end of circuit 11, the electron beam thus being coupled to the backward wave component of the R.F. field. Alternatively the end 21 may serve as an input terminal whereby a signal applied there is amplified and the amplified signal is available at the other end of circuit 11, or the beam may be coupled to the forward wave component by reversing the roles of the input and output ends. The electron beam may be collected by inserting a collector member through a hole in cylinder 19, the member being at the same potential as the slow wave circuit, thus forming a field free region which when reached by the electrons causes them to move outwards and strike the collector.