Some Effects of Magnetic Field Strength on Space-Charge-Wave Propagation

An analysis is made of the propagation of spacecharge waves in an axially symmetric electron beam originating at an emitting surface threaded by an arbitrary amount of magnetic flux. The propagation characteristics, for the fundamental radial mode with no azimuthal variations, are expressed in terms of the plasma-frequency reduction factor, graphs of which are shown. Approximate methods of evaluating the propagation characteristics of a beam in a helix are given, expressed in terms of the usual traveling-wave tube space-charge parameter Q and impedance parameter K.