Diagnostic for Measuring the Ion Density Ratio in a Plasma with Two Ion Species*

Understanding of turbulence and transport in multi-ion species plasmas is important for establishing predictive capability for burning tokamak plasmas with comparable densities of D and T. In order to effectively analyze plasmas with multiple ion species, a new diagnostic is needed in order to properly characterize the individual ion species. In plasmas with two ion species, an ion-ion hybrid cutoff frequency exists, from which one can estimate the ratio of the two ion densities [1]. Previous work has been able to observe this cutoff frequency on a global scale [2], although a new diagnostic is needed in order to resolve local measurements. A new antenna diagnostic was developed to measure the ion-ion hybrid cutoff locally in the LAPD machine, and the initial results were documented and will be presented.

[1] Buchsbaum, S. J. (1960), Resonance in a plasma with two ion species, Phys. Fluids, 3, 418.

[2] Vincena, S. T., W. A. Farmer, J. E. Maggs, and G. J. Morales (2011), Laboratory realization of an ion-ion hybrid Alfvén wave resonator, Geophys. Res. Lett., 38, L11101.