USE OF RF BRIDGE FOR REENTRY PLASMA DIAGNOSTICS.
Abstract
Flight measurements of plasma sheath properties are essential for confirming predictions and guiding future research. One important plasma sheath property, electrical conductivity, sigma, can be measured by use of an rf bridge. The electrical conductivity can be related to electron density and collision frequency. RF bridges have been used in the laboratory, but have not been used as flight instruments. To measure, signma, an electrostatically shielded coil is placed next to the plasma. The alternating magnetic field due to the alternating current in the coil drives currents in the conductor (the plasma), changing the impedance of the coil. If the coil is part of a bridge circuit, the change in impedance causes unbalance of the bridge. The bridge unbalance, which manifests itself as a voltage, can be related to sigma by suitable calibration. Calibration constants for the bridge can be theoretically predicted. A formula was derived for power dissipation, which is related to the resistance change due to the presence of the plasma; the equation was programmed for a computer. Allowance was made for variation of sigma through the boundary layer and shock layer. Measurements were made to check the validity of the theory. Curves of the theoretical and experimental results are presented. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1966
- Accession Number
- AD0484577
Entities
People
- A. E. Fuhs
- O. L. Gibb
- W. R. Grabowsky
Organizations
- The Aerospace Corporation