On Collisionless Energy Absorption in Plasmas: A Theoretical and Experimental Investigation in Spherical Geometry
Abstract
We are investigating the RF impedance characteristics of a small spherical probe immersed in a laboratory plasma. The experimental facility is the large Space Physics Simulation Chamber at the Naval Research Laboratory. The data taken are from network analyzer measurements of the reflection coefficient obtained when applying a low-level RF signal to the probe, which is either near-floating potential or negatively DC-biased in a low-pressure plasma. As is well known, sheaths form around objects placed inside plasmas. The electron density is smaller inside the sheath, and the reduction in density alters the plasma impedance. Surprisingly, the impedance becomes "resistive," even though the plasma is effectively collisionless, at frequencies below the bulk-plasma frequency, thus leading to collisionless energy absorption.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 28, 2005
- Accession Number
- ADA441281
Entities
People
- D. N. Walker
- David D. Blackwell
- Richard F. Fernsler
- Sarah J. Messer
- William E. Amatucci
Organizations
- United States Naval Research Laboratory