NEW MICROWAVE PLASMA AT ATMOSPHERIC-PRESSURE

Plasma at atmospheric pressure can be obtained by surface wave propagation with a surfatron. If the plasma is produced within a quartz tube, it is constricted to a diameter of approx. 1 or 2 mm but its length can attain some tens of centimeters with microwave power as low as 100 W. This plasma is quite uniform along the axis, with a typical electron density of 3 × 1014 electrons/cm3. Since the excitation and gas temperatures are lower than 4000 K, the plasma is far from local thermodynamic equilibrium. High stability and repeatability is achieved with an argon flow of 0.2-17 l/min. Applications are foreseen in the field of optical spectroscopy and plasma chemistry. © 1978.