Experimental investigation of large-signal traveling-wave magnetron theory

Experiments conducted on a beam-type backward-wave amplifier which closely approximates the theoretical thin-beam model used in the large-signal analysis of Sedin have resulted in gain and phase shift characteristics which are in good quantitative agreement with the adiabatic portion of both the Sedin and Gandhi-Rowe theories. Efficiencies approaching the theoretically-predicted maximum have been observed. By driving the amplifier to very large signal levels a conversion efficiency for power available from the initial potential energy of the beam of 63 per cent was obtained with a corresponding value of 45 per cent for the total electronic efficiency. An important feature of this experimental amplifier is the electron gun design which is based on a theory by Kino. That this gun is capable of producing a well-confined, rectilinear-flow thin beam is demonstrated by visual observations of the beam thickness which indicate that\omega_{c}/\omega_{p}is as low as 1.17, a value close to that for a laminar-flow Brillouin beam (\omega_{c} = \omega_{p}).