A large-dynamic-range current probe for microsecond pulsed vacuum breakdown research

A large-dynamic-range current probe for microsecond pulsed vacuum breakdown research is fabricated. The basic principle of this probe is to turn the current signal to a voltage one via a load of fixed impedance and to test the voltage signal via a voltage divider of adjustable voltage ratio. With a segment of 40-Ω coaxial line, which is connected to the experimental chamber, and a self-fabricated two-stage resistor-capacitor voltage divider, the current probe is realized and is applied to test the vacuum breakdown current for 3-cm parallel-plate electrodes under microsecond pulses. The results show that the current probe is capable of responding to current signals with an amplitude of 10(-2)-10(3) A and a duration of 10(-2)-10(1) μs. Based on the current probe, the characteristics of the vacuum breakdown current under 30-μs quasi-sinusoidal pulses are summarized. The potential mechanisms for each type of current are also discussed in this paper.