A millimeter-wave tunneladder TWT

A millimeter-wave TWT was developed using a dispersive, high-impedance "forward wave" interaction structure based on a ladder, with non-space-harmonic interaction, for a tube with high gain per inch and high efficiency. The "TunneLadder" interaction structure combines ladder properties modified to accommodate Pierce-gun beam optics in a radially magnetized PH focusing structure. The development involved the fabrication of chemically milled, shaped ladders diffusion brazed to diamond cubes which are in turn active-diffusion brazed to each ridge of a doubly ridged waveguide. Cold-test data are presented, representing the and impedance characteristics of the modified ladder circuit. These results were used in small- and large-signal computer programs to predict TWT gain and efficiency. Actual data from tested tubes verify the predicted performance while providing broader bandwidth than expected.