Addressing the anomalies in determining negative ion parameters using electrostatic probes

Abstract

The negative ion density and temperature are the two fundamental parameters that are necessary to quantify the properties of electronegative discharges. However, determining these parameters by means of electrostatic probes can be quite challenging because of the inherent inaccuracies involved in determining the electron/ion saturation currents, electron temperatures and plasma potential, which relies on charge particle collection by the probe surface; as well as on the sheath models that are originally developed for an ideal collision-less plasma. This paper briefly reviews the various limitations associated with these underlying methods and suggests useful means to correct the anomaly associated in determining the negative ion parameters based on electrostatic probes.

Equilibrium properties of inhomogeneous partially-magnetized plasma containing negative ions

“…To increase the accuracy of the obtained parameters, a cylindrical Langmuir probe was used in combination with a DC biased hairpin probe to determine plasma parameters. The specifics of this technique, however, are outside the scope of the present investigation, hence it has been presented separately [58].…”

“…Since negative atomic oxygen is the most dominant species in the discharge [57], the negative ion parameter corresponding to O − has been obtained by applying the saturation current ratio (SCR) method. The details of the procedure to derive the negative ion parameter based on the saturation current ratio method have been recently communicated [58].…”