Ion species mix and ion density measurements using radio frequency waves

Radio frequency wave applications have demonstrated great versatility in tokamak plasmas. Two applications, using the same diagnostic design, can make use of a fast Alfven wave to make ion species mix and ion density measurements. A discussion and derivation, using the cold plasma approximation, is given for a fast Alfven radio wave used for making an interferometry density measurement, a two ion species mix reflectometry measurement, and a three ion species mix reflectometry measurement.; Utilizing the dependence of the fast Alfven wave upon density, the mass density evolution of a plasma can be tracked via interferometry. In addition, new antennas were installed where the graphite tiles were converted to be part of the receiving antenna, increasing reception by at least one order of magnitude. Density evolution measurements with these new antennas (∼100 MHz, 20mW) were made for the first several hundred milliseconds until tracking was lost. When tracking was successful, the density evolution observed from the new antennas shows reasonable agreement with existing diagnostics.; 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. In addition, it is demonstrated 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.