Temperature-limited electron bombardment heating method

A temperature-limited electron bombardment heating method capable of heating LaB/sub 6/ cathodes to 1800 degrees C has been developed. This method heats LaB/sub 6/ cathodes in a Pierce-type electron gun which is pulsed to 115 kV; 1.9-cm-diameter LaB/sub 6/ cathodes have been heated to 1800 degrees C, with 370 W/cm/sup 2/ of heating power. This method has been successfully used in a pulsed power environment where the bombardment filament and LaB/sub 6/ cathode were simultaneously pulsed to high voltages to produce electron beams. The heating system has produced cathode temperatures in excess of 1750 degrees C, while the electron gun has been pulsed up to voltages of 115 kV. A dynamic model of the bombardment heating system is developed. This model shows that the temperature-limited bombardment heating system is open-loop unstable. A digital control method is presented which stabilizes the heating system.<
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