Double-Tipped Impedance Probe Diagnostics for Dusty Plasmas*

Impedance probe diagnostics are a type of active resonance spectroscopy that utilize RF resonances at frequencies of the order of the electron plasma frequency, ω_pe­­. Impedance probes used for steady-state plasmas, such as most low-temperature plasmas in laboratory environments, usually operate in a frequency-swept mode, probing the plasma’s frequency-dependent response to low-power RF signals. Such measurements may be desirable for use in dusty plasmas because the probes can be designed to be only mildly perturbing to dust particles, as compared to the large perturbative effects of Langmuir probe measurements, for example. A double-tipped impedance probe may be especially useful for use in dusty plasmas because it can be separately sensitive to plasma in areas near the probe tips and areas farther away in the chamber.

In this presentation, we discuss modeling and analysis of double-tipped impedance probe diagnostics, and we present results of experiments using such a probe in capacitively-coupled RF plasmas at Auburn University. We further discuss the use of the diagnostic for dusty plasma applications. For example, we discuss a method for measuring the charge absorbed by a dust cloud by measuring the cloud’s effect on electron and ion densities in the surrounding plasma.