Initial tests of the NRL ubitron

An experimental program to study the potential of the ubitron interaction mechanism [1] is underway at the Naval Research Laboratory. The single stage/single pass amplifier configuration of the present ubitron experiment has been designed to match, as closely as possible, the assumptions of the NRL. developed 3-D ubitron theory. This experiment utilizes a high-quality solid cylindrical electron beam inside a smooth wall circular waveguide that is confined by a uniform solenoidal guide field. The interaction relies on the coupling between the LHCP TE11RF mode and the wiggler shifted beam negative energy space charge wave. The wiggler field is generated by a double taper RHCP bifilar helix. A comparison of the small and large signal gains, efficiency, and bandwidth to be obtained from this experiment with theoretical predictions will allow a meaningful assessment of the ubitron as a viable high-power millimeter-wave tube. The goals of the experiment are to demonstrate that the ubitron is a high gain, high efficiency, wide bandwidth source of microwave or millimeter wave radiation. Specifically, this experiment is expected to realize a total gain between 20 and 30 dB, at an efficiency greater than 10%, and a bandwidth exceeding 20% at a center frequency of 14.5 GHz. The results of individual component cold tests and initial results of ubitron performance tests will be reported.