ELECTRON CURRENT TO A CYLINDRICAL PROBE IN A MOVING HIGH-PRESSURE PLASMA

A theoretical expression has been developed for the electron current which flows to a positively biased cylindrical probe immersed in a moving, high pressure plasma. Experimental results obtained with an atmospheric pressure plasma show good agreement with the theory and are similar to those obtained recently by other experimenters. Essentially, the theory states that under given conditions, namely, where the sheath convection mode is dominant, the electron current to a negatively biased probe is approximately equal to the ion current that would flow to a negatively biased probe multiplied by a factor equal to the ratio of the electron and ion mobilities. A separate measurement of the thickness of the electron sheath is also found to be in good agreement with the theory. Because of the much higher magnitude of the electron current to a probe (versus the ion current), electron current measurement can provide far more accurate data in many circumstances.