Collisional Physics in GS2*

Collisions are an important component of gyrokinetic systems, even in the long mean-free-path limit. In this poster, we recall the role of collisions in several interesting test cases (kinetic Alfven waves, reconnection, zonal flow damping, and neoclassical transport). Upgrades to the GS2 collision operator that proved to be necessary to obtain expected results in each area have been implemented and will be described.