On Improving Impedance Probe Plasma Potential Measurements
Abstract
In earlier works we used spheres of various sizes as impedance probes in demonstrating a method of determining plasma potential, p, when the probe radius is much larger than the Debye length, D. The basis of the method in those works 1-4 relies on applying a small amplitude signal of fixed frequency to a probe in a plasma and measuring the complex reflection coefficient, , for varying probe bias, Vb. For a given frequency, Re(Zac) (the real part of the complex plasma impedance determined from ) is plotted versus Vb , and a minimum predicted by theory occurs at p for a large range of electron density, ne 3. However, the frequency range of the applied signal is restricted as we briefly review in this paper. As ne decreases, or the sheath grows to the order of the probe radius, the frequency range becomes even more restrictive and, in addition, the minimum in Re(Zac) in experimental data at Vb = p becomes difficult to discern.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 21, 2014
- Accession Number
- ADA597426
Entities
People
- D. N. Walker
- David D. Blackwell
- Richard F. Fernsler
- William E. Amatucci
Organizations
- United States Naval Research Laboratory