HIGH POWER RF PLASMA HEATING AND WAVE PROPAGATION NEAR THE FUNDAMENTAL AND HARMONICS OF THE ION CYCLOTRON FREQUENCY.
Abstract
Generation, propagation, and damping of fundamental and harmonic ion cyclotron waves were investigated experimentally and theoretically. A magnetic beach geometry is used and the waves are excited by a Faraday-shielded Stix coil from a 30 kW, 5.8 MHz driver. The Stix coil has four sections with a periodicity (wavelength) of 16 cm. The plasma is subjected to an axial magnetic field which is uniform in the Stix coil region and which has a 45 cm long, 16.5% magnetic beach for wave propagation studies. Maximum magnetic field in the Stix coil region is 10.6 kG. The plasma loading of the Stix coil, the cut-off conditions for the fast wave, and optimum coupling conditions were calculated and measured. Grounding of the beach end of the plasma tube led to apparent plasma fluctuations which are related to the onset of axial rf currents in the plasma. A new wave phenomenon was observed during the experimental investigation. It was observed that for certain experimental conditions the ion cyclotron waves propagate for frequencies above the ion cyclotron frequency f sub c. The harmonic number G at which the waves attenuate is found to be pressure dependent such that G increases for increasing gas pressure. Both hydrogen and deuterium plasmas were investigated. Attenuation at harmonics up to the 8th was observed. Spatial measurements of the wave magnetic fields were made with magnetic probes for several plasma densities and confining magnetic fields in a magnetic beach geometry. Axial measurements of the wave magnetic fields demonstrate the wave propagation and wave damping. Radial measurements of the wave magnetic fields indicate a higher order transverse mode structure.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 20, 1966
- Accession Number
- AD0803584
Entities
People
- Arwin Adelbert Dougal
- Magne Kristiansen
Organizations
- University of Texas at Austin