Theory of a ubitron in a corrugated waveguide

A Ka band ubitron is currently under development at NRL using a corrugated waveguide and a helical wiggler. The corrugated waveguide is used for low-voltage operation. A 3-D nonlinear formulation has been derived, and a simulation code TARANTULA has been developed. The model treats HE and EH modes in the vacuum waveguide. No wiggler average is imposed on the electron dynamics. Preliminary calculations indicate that 20% bandwidth operation in Ka band is possible at voltages of about 90 kV with a 7–8 mm period wiggler generating a 500–600 G transverse magnetic field. Detailed results of the theory and simulation will be presented.