Simple automatic initiator for microwave induced plasmas

A simple circuit is described which is used to maintain continuity of a radio-frequency or microwave induced plasma. The microwave power reflected from the discharge is monitored. Upon an increase of the reflected power which indicates that the plasma has become extinguished, a high-voltage pulse is applied to a coil wrapped around the discharge region. The repetition rate, voltage of the pulse, and threshold of reflected power are adjustible. This circuit is applicable to resonance fluorescence, atomic absorption and emission, and kinetic determinations