Temperature-limited electron bombardment heating method

A temperature-limited electron bombardment heating method capable of heating LaB₆ cathodes to 1800°C has been developed. This method heats LaB₆ cathodes in a Pierce-type electron gun which is pulsed to 115 kV; 1.9-cm-diameter LaB₆ cathodes have been heated to 1800°C, with 370 W/cm² of heating power. This method has been successfully used in a pulsed power environment where the bombardment filament and LaB₆ cathode were simultaneously pulsed to high voltages to produce electron beams. The heating system has produced cathode temperatures in excess of 1750 °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