Analysis of the methods to increase the output power and frequency of the broadband TWTs

Abstract

The limitations on the output power and operating frequency of the broadband TWTs resulting from a relatively low thermal stability of helix and the self-excitation at the backward wave at a operating voltage of greater than 10 kV are considered. The analysis yields the methods to overcome limitations: the application of a bifilar helix with the azimuthally conducting rings and the application of combined metal-dielectric supports that allow a simultaneous improvement of the heat removal from the helix and an increase in the TWT band. It is demonstrated that a decrease in the slowing caused by the rings and a smaller period of the bifilar helix make it possible to shift the threshold of the self-excitation at the backward wave to 30-40 kV.