The breakdown of dielectrics

Saxe and Meek (1) have studied the initiation mechanism of long sparks in positive point to plane gaps. They investigated the optical and electrical characteristics of the corona discharges and leader strokes preceding the impulse breakdown in air at atmospheric pressure. Results show that initially a corona discharge forms around the point; the corona gives rise to a 0.4 micro-second pulse of light in the gap, accompanied by a similar pulse of current. The next stage in the growth of the spark is the development of a leader stroke from the corona. The characteristics of the corona and leader stroke in air at reduced pressure and in oxygen, nitrogen, and hydrogen are also briefly described.