LANDAU WAVES.
Abstract
The report describes a comprehensive theoretical and experimental study of Landau's electrostatic space-charge waves in isotropic hot electron plasmas. The signal spreading from a steadily oscillating dipole sheet is described by an electrostatic Green's function which is synthesized from the spectrum of Landau waves. Numerical results for a Maxwellian plasma show that this signal is rejected below the plasma frequency, penetrates deeply into the plasma slightly above it, and is strongly damped for higher frequencies. Pairs of parallel plane grids immersed into a plasma provide a scheme for launching and detecting Landau waves. This system is described by N-terminal impedance equations from which transconductances and voltage transfer ratios between gridded rf probes are calculated. Results show an optimum width of about 5 Debye lengths for modulating and detecting gaps. The experiment employs gridded rf probes to excite and detect electrostatic waves within a quiescent collision-free sodium plasma at thermodynamic equilibrium. As plasma density and rf frequency are varied the measured wavelengths and spatial damping rates are scaled to Debye length using independent Langmuir probe data. Full agreement is found between the experimental results and the fundamental solution of Landau's dispersion relation. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1967
- Accession Number
- AD0651461
Entities
People
- Thomas C. Simonen
Organizations
- Stanford University