Optimization study with respect to the point of excitation in coaxial TE<inf>11</inf> vircator

Abstract

The vircator is a compact and robust narrow band HPM source with a simple geometry. In the most basic version of the vircator, the operating frequency depends only on the distance between the anode and cathode and the applied voltage. In a compact system the vircator is often powered by a marx generator resulting in a frequency chirp caused by the double exponential voltage pulse generated by the marx. An experimental series with a coaxial TE11 vircator has been performed in which the excitation point and the applied voltage have been varied. Experimental evidence is presented showing that the frequency shift during the pulse can be avoided by choosing the proper excitation point. The highest radiated fields were recorded when the bandwidth of the microwave radiation was narrow and only one mode was present. Both far field and waveguide measurements were in agreement with the TE11 mode. At the optimum positions the input impedance of the vircator was lower, indicating improved coupling between electron beam and microwave field. To verify the experimental findings on optimum excitation point, electromagnetic simulations were performed. Even though the simulation model was greatly simplified by replacing the electron beam with a current sheath at the position of the emitters, the results were in good agreement with experiments.

Innovative Mode Enhancement for High Power Coaxial Vircators

“…For this reason, the TE 11 mode is preferred [34]. Before the innovative solution to use an elliptic DT (EDT) that we will show later, a coaxial vircator can be designed to enhance the TE 11 mode using an SE [18], [34], [35], [36], [37], [38], as shown in Fig. 8.…”