Field emission behaviors under trapezoid voltage pulses with a DC bias

When a field emission cathode works under voltage pulses, remarkable charging current that is equal to the displacement current in the cathode-anode gap occurs in the circuit at the rising edges of the pulses. This charging current does not only interfere the measurement of the emissive current from the cathode but also constitutes a threat to the components in the circuit. This article describes the authors’ effort to tackle this problem using trapezoid voltage pulses with a DC bias. The DC bias was not high enough to extract a large number of electrons out of the cathode. Instead, it was devoted to reducing the amplitudes of the voltage pulses. The introduction of a DC bias considerably lowered the charging current and the emissive current was only slightly influenced. The unfavorable consequence of the DC bias was a low unwanted background current between the pulses. To minimize it, the value of the DC bias was optimized to reach a good compromise between lowering the charging current and avoiding the background current.