Plasma shaping effects on the collisionless residual zonal flow level

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