US Patent 7893620 Traveling-wave tube turn-off body energy circuit

An apparatus that includes a traveling-wave tube having an electron gun having a cathode. The apparatus also includes a first power supply for establishing a first electric potential between the cathode and an anode and for providing an operational current to the cathode to generate a beam of electrons. The apparatus also includes a slow-wave structure having a passage through which the beam of electrons passes. The apparatus also includes a second power supply for providing a voltage to a beam focusing electrode to establish an electric potential between the cathode and the beam focusing electrode. The apparatus also includes a switching module coupled to the first power supply and the second power supply, the switching module providing a current path between the cathode and the beam focusing electrode, wherein the current path is disabled when a biasing current is below a predetermined level.