The Ubitron, a high-power traveling-wave tube based on a periodic beam interaction in unloaded waveguide

Abstract

The Ubitron is a high-power traveling-wave tube which makes use of the interaction between a magnetically undulated periodic electron beam and the TE01mode in unloaded waveguide. The electron-wave interaction exhibits the same type of first-order axial beam bunching characteristic of the conventional slow-wave traveling-wave tube; hence, it can be used in place of conventional O-type interaction in extended interaction klystrons and electron accelerators, as well as traveling-wave tubes. Experimental results are presented for the simplest physical embodiment of the Ubitron, which consists of an undulated pencil beam in a rectangular waveguide. Two of the unique features of this tube are very broad interaction bandwidth which results from the absence of a dispersive slow-wave circuit, and variable interaction phase velocity--hence, variable saturation power level. Among the physical embodiments of the Ubitron are a number of higher-order mode waveguide and beam configurations. These include plane, coaxial, and circular waveguides, all supporting the TE01mode, interacting with magnetically undulated sheet, hollow and cylindrical beams, respectively. The advantage of these configurations, which have not yet been tested experimentally, is that they provide a very large interaction area for beam placement. This property, plus the fact that the peak interacting field is far from the waveguide walls, makes the Ubitron an interesting prospect for high-power millimeter wave amplification.