Plasma effect in tape helix traveling-wave tube

A linearized relativistic field theory of aplasma-loaded helix traveling-wave tube is presented for aconfiguration where a solid electron beam propagatethrough a sheath helix enclosed within a loss-free wall inwhich the gap between the helix and the outer wall is filledwith a dielectric. Numerical study of the effect of plasmadensity on the phase velocity and growth rate has beendone. Numerical results show that the plasma have differentbehaviors in different density limits.