PSFC / JA - 06 - 25 Plasma shaping effects on the collisionless residual zonal flow level

Plasma shaping e¤ects, such as elongation, triangularity and Shafranov shift have long been considered an important ingredient in improving tokamak performance. It is known that the growth rate of ion temperature gradient (ITG) turbulence can be regulated by these shaping e¤ects and that the ITG turbulence level can also be regulated by zonal ‡ow. Moreover, recent numerical simulation shows that the collsionless residual zonal ‡ow level can be in ‡uenced by these shaping e¤ects. An analytical approach is used to explicitly evaluate plasma shaping e¤ects on the collisionless residual zonal ‡ow. The results show that the residual zonal ‡ow level increases with elongation, triangularity and the Shafranov shift.