Vircator

A viractor (VIRtual CAthode OscillatOR) is a microwave generator that is capable of generating brief pulses of tunable, narrow band microwaves at very high power levels.

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A typical viractor is built inside an evacuated resonant cavity or waveguide. An electrode at one end injects an intense electron beam, such as from a Marx generator. The electrons are attracted to a thin anode, such as an aluminized Mylar foil, that is connected to the grounded waveguide body. The unit is surrounded by a magnet. Due to the intensity of the electron beam, many electrons pass through the anode into the region beyond it, forming a virtual cathode. The electron beam must be intense enough to exceed the space charge limiting current in that region, causing oscillations that generate microwaves. The frequency, efficiency and other characteristics of the emitted beam depend on the precise physical configuration and operating parameters.

Viractors have been used as electromagnetic pulse generators and for generating X-rays. Power levels on the order of 10¹⁰ to 10¹² watts are possible.

Sources

• U.S. Patent 4,345,220 , High power microwave generator using relativistic electron beam in waveguide drift tube, to Donald J. Sullivan, 1982
• U.S. Patent 4,730,170 , "Virtual cathode microwave generator having annular anode slit," Thomas J. T. Kwan, 1988
• Donald J. Sullivan, "High Power Microwave Generation From a Virtual Cathode scillator (Vircator)," IEEE Trans. Nucl. Sci., vol. NS-30, No. 4, 3426-3428 (Aug. 1983) [1]
• Thomas J. T. Kwan, "High-Power Coherent Microwave Generation from Oscillating Virtual Cathodes," Phys. Fluids 27 (1), 228-232 (Jan. 1984)