Abstract: A structure to eliminate non-fundamental space harmonics in helical traveling wave tubes is disclosed. A sever of moderate attenuation is produced by way of a conductive surface on nonconductive rods supporting a helical conductor in a traveling wave tube. In addition, the radius and pitch of the helical conductor are simultaneously varied over a short distance to improve the efficiency and performance of the tube.

Abstract: A structure to eliminate non-fundamental space harmonics in helical traveling wave tubes is disclosed. The helix radius and pitch are simultaneously varied over a short distance to improve the efficiency and performance of the tube. This new geometry, an adverse space harmonics taper (ASHT), renders the fundamental phase velocity invariant to frequency and distance effects, while adversely affecting all other space harmonics. Another aspect of the invention reduces the temperature of the helix and further improves tube efficiency, so that electronic efficiencies approach 30% in a linear performance region.