Relativistic helix traveling wave tube amplifiers

A relativistic field theory of a helix traveling wave tube (TWT) is described for the case in which a thin annular beam propagates through a sheath helix enclosed within a loss-free wall. The theory is applied to the study of a TWT with an intense relativistic electron beam. The analysis implicitly includes beam space-charge effects and is valid for arbitrary azimuthal mode number, and the coupled-wave Pierce theory is recovered in the near-resonant limit. The results indicate that impressive gains and efficiencies are possible in this regime. In addition, the interaction is relatively insensitive to the effects of a beam energy spread