Abstract: The present disclosure provides a magnetic immersion electron gun and a method of generating an electron beam using a magnetic immersion electron gun. The electron gun includes a magnetic lens forming a magnetic field, a cathode tip disposed in the magnetic field, and a multi-filament heater configured to directly heat the cathode tip to emit electrons through the magnetic lens. The multi-filament heater includes a first filament connected at each end to first and second positive terminals of a power source and a second filament connected at each end to first and second negative terminals of the power source. The first positive terminal, the second positive terminal, the first negative terminal, and the second negative terminal are arranged alternately around the cathode tip such that the first filament and the second filament intersect at the cathode tip and a resultant magnetic force applied to the cathode tip is reduced.

Abstract: The present disclosure provides a magnetic immersion electron gun and a method of generating an electron beam using a magnetic immersion electron gun. The electron gun includes a magnetic lens forming a magnetic field, a cathode tip disposed in the magnetic field, and a multi-filament heater configured to directly heat the cathode tip to emit electrons through the magnetic lens. The multi-filament heater includes a first filament connected at each end to first and second positive terminals of a power source and a second filament connected at each end to first and second negative terminals of the power source. The first positive terminal, the second positive terminal, the first negative terminal, and the second negative terminal are arranged alternately around the cathode tip such that the first filament and the second filament intersect at the cathode tip and a resultant magnetic force applied to the cathode tip is reduced.

Abstract: One embodiment relates to a thermal field emission electron gun. The electron gun includes a high-vacuum chamber, a thermal field emission cathode including a filament and a tip, a suppressor electrode, an extraction electrode, and a high-voltage power source. The high-voltage power source is coupled to the filament and to the suppressor and extraction electrodes such that the suppressor electrode is at a negative voltage potential in relation to the filament and the extraction electrode is at a positive voltage potential in relation to the filament. A current-limiting resistor is electrically coupled in series with the suppressor electrode. Applicant has determined that such a current-limiting resistor substantially reduces undesirable discharges and improve the reliability and lifetime of the electron gun. Other embodiments, aspects and features are also disclosed.