High-pressure sheath to glow transition in a plasma-filled gap

Results are presented which support the predictions of a simple theory of sheath breakdown. The usual sheath equations are modified to allow for field-induced ionisation and secondary emission. The theory predicts that with increasing voltage the sheath expands to a certain point and then collapses catastrophically to a thickness determined by the external load. Measurements of the impedance of a plasma-filled gap reveal that a marked (~ 102 times) decrease in the magnitude of the impedance occurs as predicted by the theory.