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 A lfven 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 conti nuum. It is also shown that the global Alfven wave enters into the Alf ven continuum. Under these conditions, it is possible to heat the plas ma core efficiently by using an antenna with a narrow toroidal wavelen gth spectrum. The relationship between impurity concentration and the efficiency of Alfven wave heating is demonstrated. This effect is expl ored 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).