Analysis of the spent beam of a high-power TWT

In this study, 3 independent analytical tools were used. 1) A large-signal, 3-dimensional computer program, capable of predicting rf performance and spent beam parameters of a coupled-cavity type TWT. 2) A conventional pin-hole type beam analyzer for measuring the current density j vs. radius r at various axial distances z. From the r95vs. z-curve, the ratio of transverse/axial momentum, , is determined by a new, improved method. 3) An electron-velocity spectrometer of the magnetic lens type is used for determining the axial velocity (energy) spread of the beam. The resolution of this instrument is approximately 100 volts. Experimental and theoretical results are presented for both modes of a dual-mode TWT, at various frequencies and drive levels.