Vircanator: a reverse-magnetron type variation of vircator

Summary form only given. Vircator is plagued with low efficiency (~2-3%) despite ingenious efforts for decades. Causes for the low efficiency may include the fact that it is a high-impedance diode at the beginning stage, the vircator oscillates only a short time before the condition of exceeding the space charge current limit disappears, late and stray electrons distorts the induced field pattern, and usually operated in an un-enclosed, vastly over-mold resonator. Variations like the pre-bunched radiation-feedback two region vircator and transversely fired two cathodes vircator had reported improved efficiency in the vicinity of 10%, and higher efficiency is considered possible through optimization. Study on new dual-coaxial vircator also indicates possible 11% efficiency. Simulation on coaxial vircator suggests 50% increase of output power, though at a total 3.5% efficiency. Radial acceletron, though operating on a different principle to vircator, elucidates the advantages of low impedance from a coaxial structure. We present a MAGIC simulation of another variation of vircator, which we called vircanator. Six beams below the space charge current limit are pre-bunched by the pulsed power system externally and fired into a coaxial structure with magnetic field formed by permanent magnet. The convergence of these beams will bring the current density above the space charge current density limit and initiates an oscillation. The repelling force of adjoining electron swarm and magnetic force will push the swarm back towards the outer wall, as if there is a virtual anode, hence the term vircanator, which means virtual cathode and anode. The magnetic field is to prolong the oscillation into continuous one on a circular path, similar to the sigma mold in a magnetron if tuned correctly. This design should in principle possess some merits of the previous designs, and presents more parameter space a designer can adjust while easy to make. Electron trajectories, field plots, a- d mold frequencies interactions are discussed