Transportation of Electronic Flows in Magnetic Periodic Focusing Systems with an Anharmonic Magnetic Field Distribution Designed for Millimeter-Range Wave Traveling Lamps

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Abstract—The paper considers theoretical and practical problems on developing electron-optical systems of traveling wave tubes (TWTs) that focus an intense electron flow via a magnetic periodic focusing system (MPFS) upon advancement into the millimeter-wave range. An analytical solution has been found for the magnetic field distribution in an MPFS TWT combined with a retarding system with magnetically soft inserts that form a passage channel with a diameter substantially less than the internal diameter of the tip. The stable focusing zones of the electron flow are determined for the considered MPFS, which makes it possible to focusing the flow with magnetic field parameters exceeding the critical values of a conventional MPFS.