Microwave resonator probe for localized density measurements in weakly magnetized plasmas
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 epsilon=1-..omega../subp//sup 2//..omega../sup 2/, where ..omega../subp/ is the electron plasma frequency. A parallel-wire quarter-wavelength resonator is immersed into the plasma, the resonance frequency (..omega../sub res/>..omega../subp/) is measured and the density derived from the simple relation ..omega../subp//sup 2/=..omega../sup 2//sub res/-..omega../sup 2//sub res(epsilon = 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 x 8 mm length, f/sub res/=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. (AIP)
- Research Organization:
- TRW Systems, Redondo Beach, California 90278
- OSTI ID:
- 7285246
- Journal Information:
- Rev. Sci. Instrum.; (United States), Journal Name: Rev. Sci. Instrum.; (United States) Vol. 47:5; ISSN RSINA
- Country of Publication:
- United States
- Language:
- English
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