Virtual Instrument for automatic low temperature plasmas diagnostic considering finite positive ion temperature

Abstract

This article presents the results obtained in the diagnostics of a low pressure, low temperature plasma whose EEDF approaches to a Maxwellian one, and in which the positive ion temperature is not negligible small compared to the electron one. The diagnostic process is automatically developed by a Virtual Instrument (VI). The VI measures the I–V characteristic curve of a cylindrical Langmuir probe immersed in the plasma. From this curve the VI obtains several parameters characterizing the plasma by using theoretical models describing the different zones of the I–V characteristic curve. One of these models, which include the influence of the positive ion thermal motion, is applied in the positive ion saturation zone of the I–V probe characteristic curve, where the perturbation due to the probe immersed in the plasma is negligible. The measurement process can be developed simultaneously in several points of the discharge and the time spent in the entire automatic processes, is about one second, so, spatial uniformity and temporal evolution in the plasma conditions can be analyzed.