A method to measure electric field strengths in an argon glow discharge plasma using laser spectroscopy

A method for electric field measurement based on laser spectroscopy of argon atoms has been developed and calibrated. Measurements were made using both laser optogalvanic spectroscopy and laser-induced fluorescence spectroscopy. Measurements using several different transitions in argon were carried out, and it was found that the 4s→7f and 4s→8f transitions were the most suitable for measurements in the sheath region of glow discharges. The lower limit for electric field measurements was estimated to be 500 V/cm. A minimal pressure of about 100 mtorr was required to detect optogalvanic signals and about 1 torr was required for the fluorescence signals to be detectable. These detection limits make this method applicable for measurement of sheath electric fields for a wide range of discharge conditions