Breakdown in Triggered Spark Gaps in Air

Trigatron breakdown characteristics were studied in atmospheric air for gaps up to 15 cm in length. Under negative impulse voltages with a positive trigger pulse applied in the grounded electrode, the minimum breakdown values corresponded closely to the negative sphere-rod gap breakdown values. While under positive impulses the trigatron broke down at approximately the same voltages as the positive sphere-rod gaps. The low breakdown in trigatrons under negative impulse voltages was preceded by a positive leader identical to that observed in positive sphere-rod gaps. The higher breakdowns under the positive voltages resulted from a negative leader. The results suggest that the space charge from the auxiliary spark distorts the initially uniform field in the gap and the breakdown follows the nonuniform field breakdown mechanism.