The effects of light impurities, such as helium, boron or carbon, on Alfvén 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 Alfvén waves and the Alfvén continuum. It is also shown that the global Alfvén wave enters into the Alfvén 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 Alfvén wave heating is demonstrated. This effect is explored via a series of numerical calculations of the heating conditions specifically for the Tokamak Chauffage Alfvén wave heating experiment in Brazil (TCA/BR) (1996 Nucl. Fusion 30 503).

The resonant and non-resonant current drive and plasma flow produced by the Alfvén and fast waves are discussed for both collisional and collisionless magnetized plasmas. The magneto-hydrodynamics approach is used to study collisional plasma regimes, and the kinetic model is considered for the weakly collisional plasmas. Time-averaged poloidal and toroidal ponderomotive forces driven by the Alfvén waves are estimated analytically and calculated numerically. The effect of plasma flow on the driving forces is found. Balancing the ponderomotive force with the ion viscosity, strong sheared toroidal and poloidal plasma rotations are found for wave dissipated power about 400 kW in small tokamaks. In this case hollow current profiles (inverted magnetic shear) can also be achieved. This configuration can help create internal transport barriers.

The suppression of anomalous transport and/or reduction of neoclassical transport caused by the Alfvén-wave-induced shear of the radial electric field in tokamaks is investigated. The simple quantitative estimates reported in previous papers are checked by a consistent evaluation of the profile of the radial electric field created by the resonant absorption of Alfvén waves. The radial variations of the ion viscosity and heat conductivity across the mode conversion layer are evaluated both in the banana and potato regions. In agreement with previous analytical results, it is shown that the kinetic Alfvén waves may play the role of a convenient mechanism for reduction of anomalous and neoclassical transport and formation of transport barriers in tokamaks.

Theoretical results on Alfvén wave (AW) heating, current drive and plasma flow, which may be relevant for improved confinement scenarios, are presented. It is shown that a small population of light impurities, such as carbon, in a hydrogen plasma can strongly modify the dispersion of global Alfvén waves and the Alfvén continuum. The current drive and plasma flow induced by AWs are studied for magnetized weakly collisional plasmas. We find that plasma flow and ion banana orbit squeezing by the radial electric field shear induced by AWs may be a convenient trigger for the formation of transport barriers in tokamaks. These effects are explored via a series of numerical calculations for the heating conditions foreseen for the tokamak chauffage Alfvén wave heating experiment in Brazil (TCABR).

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