TIME-RESOLVED ELECTRIC-FIELD MEASUREMENTS IN A 15 KHZ HELIUM GLOW-DISCHARGE

Time-resolved electric field profile measurements were made in a driven 15 kHz parallel plate helium glow discharge using optogalvanic spectroscopy. Electric field values in the sheath region were determined from the energy splitting of the helium Rydberg state Stark manifolds due to the local applied electric field as a function of position and phase. The measured field values in the cathode sheath region range from about 800 to 300 V/cm; the measurement accuracy of electric field values are +/-25 V/cm. The line of sight laser probe measurements have a spatial resolution of 200 mum and a temporal accuracy' of better than 1 % of the driving cycle. The low driving frequency allows for a comparison with the dc discharge approximation. The spatial electric field profile is identical to a dc discharge operating at the same peak current and voltage values and the temporal field profile is symmetric about the current wave form extremum.