High power microwave generation from a tunable radially extracted vircator

Abstract

High power microwaves in the dominant TE10 mode emitted from the radially extracted vircator were studied experimentally at the diode voltages from 660 kV up to 1.2 MV and at diode currents from 37 up to 88 kA. The dominant microwave source is in the region of the virtual cathode. The return-current rods on the virtual cathode side of the anode narrows the output microwave frequency. There are dominant frequencies observed in the experiments. For example, three dominant narrow-band microwave pulses were observed at 8.63±0.05, 9.75±0.03, and 10.53±0.03 GHz. They are tunable and scaled linearly with the diode current at the inflection point. All the observed dominant frequencies are in good agreement with the scaling law f=(4.77/d)ln[γ0+(γ20−1)1/2] derived either from the two-dimensional virtual-cathode oscillation or from the one-dimensional harmonic reflexing-electron oscillation. This agreement also confirms that these two oscillations in our vircator generate nearly the same frequency. The maximum observed powers are 120 MW at 8.63 GHz, 75 MW at 9.75 GHz, and 60 MW at 10.53 GHz.

Two-dimensional theoretical analysis of the dominant frequency in the inward-emitting coaxial vircator

“…When , (36) becomes the same with the planar Brillouin flow solution [11] and the result derived by the 1-D harmonic oscillation of the reflexing electrons [13]. This conclusion is consistent with the computer-simulation result which reveals that the microwave frequency in a coaxial vircator is similar to that produced by a planar vircator with the same anode-cathode gap distance [14], provided that the gap distance is relatively smaller than the cathode radius.…”

“…(12) Region (13) Here, and are constants to be determined from . and are the first and second kinds of the modified Bessel function.…”

Efficiency Enhancement of Reflex Triode Virtual Cathode Oscillator Using the Carbon Fiber Cathode

“…However, it has a critical drawback, which is the low efficiency. Many experimental studies have been carried out on the vircator in order to improve its beamwave energy conversion efficiency [3]- [10]. Despite these efforts, the highest efficiency is still limited to several percent.…”