Current Density Limitations in a Fast-Pulsed High-Voltage Diode

Abstract : An investigation into the limitations on the enhanced field-emitted current density in a fast-pulsed (rise-time on the order of ns), high voltage (>106V), 1-inch vacuum diode was conducted using a computer simulation based on the Fowler-Nordheim equation. Oscillations in the emitted current density (due to the change in the amount of space charge within the gap) were found to quickly decay into a final steady-state for the voltages applied. Steady-state values for a wide variety of work functions, electric field enhancement factors (based on the theory that whiskers on the cathode surface experience varying degrees of enhancement), and applied potentials were compare to two benchmarks: the amount of current density required to explode a whisker in <10 ns by joule heating (JE =10 9 A/cm2); and the Child-Langmuir (C-L) space-charge-limited current density.