Gyrokinetic turbulence simulation of profile shear stabilization and broken gyroBohm scaling

A newly developed continuum gyrokinetic code GYRO has been formulated on a radial grid to operate at finite relative gyroradius in a noncyclic radial annulus with profile variation. The code is used to simulate ion temperature gradient mode turbulence and to demonstrate that gyroBohm scaling can be obtained well above the instability threshold but sufficiently strong profile shear stabilization can break gyroBohm scaling down to Bohm scaling (or worse) near threshold. An adaptive source technique is used to maintain profiles. Clear evidence for nonlocal transport is also found in which the local diffusivity depends on the plasma gradients at some considerable radial distance. (C) 2002 American Institute of Physics.