Patent GB-982179-A (GB)
Title: Improvements in or relating to electron discharge devices
IPC: H01J25/49
Filed: 1961-05-18
Abstract: 982,179. Electron beam parametric amplifiers. WESTERN ELECTRIC CO. Inc. May 18, 1961 [May 26, 1960], No. 18161/61. Heading H1D. Electron discharge apparatus comprises means for forming and projecting an electron beam, means for producing an axial magnetic focusing field throughout the beam thereby creating an inherent angular cyclotron frequency within and of the beam, means for modulating the beam with signal wave energy by producing transverse signal frequency electric fields along a portion of the beam, and means for producing a quadrupole electric field along another portion of the beam, the spatial and time alternations of the quadrupole electric field being substantially determined by the relationship where #p is the angular frequency of time alternations of the quadrupole electric field, #p is the angular frequency of longitudinal spatial alternations of the quadrupole electric field, U o  is the mean velocity of the beam, and #c is the angular cyclotron frequency. The quadrupole electric field effects energy interchange between the sychronous and cyclotron wave modes, and is used to obtain a substantially noisefree cyclotron wave mode on the beam in a parametric amplifier. As shown, Fig. 1, such an amplifier, having an axial magnetic field 8, comprises in axial order between an electron gun 11 and a helical slow wave structure 22, a fast cyclotron wave noise stripper 29 for removing to an appropriate load 33 noise associated with the fast cyclotron wave mode which exists on the beam by virtue of the magnetic field B, a " high frequency" quadrupole couple 31 for transferring energy from the fast cyclotron mode to the slow synchronous mode, and a " low frequency " coupler 30 for transferring energy from the slow synchronous mode to the slow cyclotron mode. The beam thus enters the interaction region 10 with a substantially noise free slow cyclotron wave mode, and the amplified output delivered to a load 23 will be a noise free amplified signal wave originating from source 21. The high frequency coupler 31, as shown in Fig. 5, comprises a pump signal source 37 delivering energy to the quadrupole structure 38 at a frequency approximately equal to the cyclotron frequency. The low-frequency coupler, Fig. 4, comprises a series of quadrupoles 34 biased by a D.C. source 35, the distance d between the quadrupoles being equal to the distance the beam travels in one-half a cyclotron rotation. In a further embodiment, Fig. 8 (not shown), an amplifier comprises in axial order a highfrequency coupler which produces noise-free fast and slow cyclotron wave modes, an input resonator for coupling a signal to the fast cyclotron wave mode of the beam, a plurality of electro-statically charged quadrupoles for converting D.C. beam kinetic energy into fast signal cyclotron wave energy, and an output resonator for delivering an amplified signal to a load. The device shown in Fig. 9 amplifies wave energy through the principle of frequency " up-conversion." Energy from source 56 at frequency #s is coupled to the fast synchronous mode of the mode by input helix 58 which also extracts fast synchronous wave noise. Quadrupole coupler 60 excited with pump energy at a frequency #p equal to the cyclotron frequency serves to transfer energy between the cyclotron and synchronous modes. An amplified upper sideband wave is extracted from the cyclotron mode in the output cavity 62.