Plasma Species Mix Diagnostic Using Hybrid Layer Reflectometry
Abstract
A heterodyne reflectometer could provide a direct and inexpensive measurement of ion species mixes with different charge to mass ratios. Using the cold plasma dispersion relation for multiple ion species, the ion-ion hybrid cutoff frequency is uniquely determined by the density ratio and cyclotron frequencies of those two species. The phase of a ∼20 MHz wave that travels from the launching point to the cutoff layer to the receiving antenna provides a direct measure of the hydrogen:deuterium species mix. In the first experiment, a fast Alfven wave was launched perpendicular to a hydrogen-deuterium plasma from the low field side of the DIII-D tokamak. Quantitative measurements observed a hydrogen concentration range of 3%-67% and a maximum penetration depth of 0.60 m. Corroborative values were obtained from two independent diagnostics. In the second experiment, the fast Alfven wave was launched from the high field side during a hydrogen puffing experiment. Results again show agreement with other diagnostics, demonstrating that a wave launched from the high field side is able to tunnel through the resonance layer and be reflected back to the receiving antenna.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2003
- Bibcode:
- 2003APS..DPPQP1050W