Steady state gyrokinetic PIC simulation of ITG turbulence

We will report the implementation of the two-weight scheme [1] in the global gyrokinetic PIC code - GTC [2], for studying turbulence transport in tokamak plasmas along with our initial attempts to also include the neoclassical transport physics. With the two-weight scheme, which is based on multiscale expansion $F = F_0 (\epsilon {\bf x}) + \delta f({\bf x})$, where $\epsilon$ is a smallness parameter and $F_0$ is the background Maxwellian, we are able to simulate the transition from $\delta f$ particles in the linear stage to a certain percentage of full $F$ particles in the nonlinear stage in the same run. Such a scheme would help us to assess the correctness of $\delta f$ runs when $\delta f$ becomes large as well as for the cases where there are sources and sinks in the simulation. The behavior of the entropy for the new scheme and the effect of collisions will also be reported along with the comparisons with the size scaling obtained earlier [3] using only the $\delta f$ simulation. \\[4pt] [1] W. W. Lee, T. G. Jenkins and S. Ethier, Comp. Phys. Comm. {\bf 182}, 564 (2011).\\[0pt] [2] Z. Lin, T. S. Hahm, W. W. Lee, W. M. Tang, and R. White, Science {\bf 281}, 1835 (1998).\\[0pt] [3] W. W. Lee, S. Ethier, R. Kolesnikov, W. X. Wang, and W. M. Tang. Comp. Sci. \& Disc. {\bf 1}, 015010