ANALYSIS OF THE DEFLECTION SYSTEM FOR A MAGNETIC-FIELD-IMMERSED MAGNICON AMPLIFIER

A linear analysis of the electron-beam deflection system in a magnicon is presented. The system consists of identical cavities, one driven and the remainder passive, separated by a drift space and immersed in an axial magnetic field. The cavities contain a rotating TM110 mode. The length of each cavity is pi-upsilon(z)/omega, and that of the drift space is pi-upsilon(z)/omega(c), where omega is the RF frequency, omega(c) is the relativistic gyrofrequency in the guide field, and upsilon(z) is the mean axial velocity of the beam electrons. The linearized electron orbits are obtained for arbitrary initial axial velocity, radial coordinate, and magnetic field. The small-signal gain and the phase shift are determined. The special case where omega(c)/omega = 2 has unique features and is discussed in detail. For example, this special case gives rise to a constant phase of the electrons relative to that of the TM110 mode, and the passive cavity may be driven optimally for a given beam current. For the NRL magnicon design, a power gain of 10 dB per passive cavity if feasible. Results from numerical modeling of a magnicon with two passive cavities are presented. Operation of the output cavity at the fundamental and higher harmonics of the input drive frequency is briefly discussed.