Laser triggering of electric breakdown in liquids

Abstract

Electric breakdown in semihomogeneous geometries has been studied in n-hexane and transformer oil using a laser triggering method for fields far below the spontaneous breakdown field. The method uses a laser-produced plasma to initiate the breakdown. Strong self focusing in the liquids was limited by increasing the numerical aperture of the laser beam to >0.20 prior to focusing. Electrical breakdown could be triggered at fields as low as 50 kV/cm in transformer oil and 25 kV/cm for n-hexane. The time lags are between 30 and 200 /spl mu/s, depending on voltage, liquid, and gap size. Current and light emission measurements of the prebreakdown phenomena are presented and a model for the triggering process is proposed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>