Modification of Alfven wave dispersion and Alfven wave heating in multiple ion species tokamak plasmas

The effects of light impurities, such as helium, boron or carbon, on Alfven wave dispersion characteristics are studied. It is shown that a small population of light impurities in a hydrogen plasma can strongly modify the dispersion of the global Alfven waves and the Alfven continuum. It is also shown that the global Alfven wave enters into the Alfven continuum. Under these conditions, it is possible to heat the plasma core efficiently by using an antenna with a narrow toroidal wavelength spectrum. The relationship between impurity concentration and the efficiency of Alfven wave heating is demonstrated. This effect is explored via a series of numerical calculations of the heating conditions specifically for the Tokamak Chauffage Alfven wave heating experiment in Brazil (TCA/BR) (1996 Nucl. Fusion 30 503).