Microwave resonator probe for localized density measurements in weakly magnetized plasmas
Abstract
A simple diagnostic tool for performing spatially resolved density measurements in a large, weakly magnetized, low-temperature plasma is described. The principle is based on a microwave technique to determine the cold plasma dielectric property ɛ=1-ωp2/ω2, where ωp is the electron plasma frequency. A parallel-wire quarter-wavelength resonator is immersed into the plasma, the resonance frequency (ωres≳ωp) is measured and the density derived from the simple relation ωp2=ω2res-ω2res(ɛ=1). In contrast to the familiar cavity resonance shift method, the present method is suited for localized density measurements. The spatial resolution is comparable to the size of the resonator (2-mm width×8 mm length, fres=7.45 GHz). The microwave technique is largely independent of sheath and thermal effects and is thus more reliable than probe measurements in nonuniformly rf-heated magnetoplasmas. A comparison with independent density diagnostic tools is presented and additional applications are pointed out.
- Publication:
-
Review of Scientific Instruments
- Pub Date:
- May 1976
- DOI:
- 10.1063/1.1134697
- Bibcode:
- 1976RScI...47..603S
- Keywords:
-
- Density Measurement;
- Magnetic Fields;
- Microwave Probes;
- Microwave Resonance;
- Plasma Density;
- Plasma Diagnostics;
- Afterglows;
- Cold Plasmas;
- Dielectric Properties;
- Electron Plasma;
- Plasma Frequencies;
- Radio Frequency Heating;
- Instrumentation and Photography;
- 52.70.Gw;
- Radio-frequency and microwave measurements