S-Band Coaxial Vircator With Electron Beam Premodulation Based on Compact Linear Transformer Driver

A two-section coaxial vircator with radial electron beam injection and electrodynamic feedback was developed. The use of electron beam premodulation in the vircator allows an increase in efficiency and ensures single-mode oscillation. The vircator operates with no external magnetic field, features a comparatively low operating impedance of the vacuum diode (10-15 Ω), and makes feasible wide-band frequency tuning through varying the resonator parameters. The vircator was simulated using the PIC-code KARAT. It is shown that, in a wide range of electron beam power (10-25 GW), the oscillation efficiency is 12%-15% and the frequency tuning bandwidth is 15 %. In the experiments on a compact linear transformer driver at a cathode voltage of 300 kV, diode current of 20 kA, and driving pulse duration of 250 ns, the single H11mode oscillation at 2.2 GHz with a 300-MW microwave peak power and 130-ns pulse duration at half the power level was realized.