Effects of energetical particles on ballooning modes in high temperature tokamaks

This report describes the work done by Science Applications International Corporation to study the effects of energetic particles on the microstability of a high temperature tokamak. The effects of an energetic population on ballooning modes in a large aspect ratio, shifted circular flux surface tokamak equilibrium are investigated with the newly developed gryokinetic numerical technique. The gryokinetic equations for the background ion and electron, as well as that of the energetic population are solved directly as an initial problem. The energetic particles are modeled with a slow-down distribution in energy. It is found that the ballooning mode stability of the plasma with an energetic species of increasing concentration does not differ much from an increase in the background plasma beta, except for possible energetic particle drift resonances. This result is encouraging to the idea that energetic particles such as alphas may be used to stabilize the ballooning modes in a fusion reactor