Title: Studies of Algorithms for Gyrokinetics & The Effects of Shaping on Plasma Turbulence Date/Time: Monday, November 7, 2005, 9:30-10:30 am Location: Building 980, Room 95 (Sandia NM) Brief Abstract: The gyrokinetic equation is the fundamental equation describing drift-like microinstability-driven turbulence in magnetized plasmas. Presently, gyrokinetic simulations of plasma turbulence and transport are one of the primary tools used to design the next generation of experimental fusion devices with optimal neoclassical confinement and stability properties. However, solving the full 5D, nonlinear, integro-differential gyrokinetic equation in realistic geometry can be computationally intensive, requiring many hours of computing time on massively parallel machines for a single set of parameters. In this talk, I will describe various improved numerical algorithms and order-reduction models for Eulerian gyrokinetic codes, including a recently developed iterative implicit scheme based on numerical or analytic approximations to the plasma response. This method eliminates the long time to set up implicit arrays, yet still has the same larger time-step advantages of an implicit method. Various model preconditioners and iteration schemes, including Krylov-based solvers, will be compared. Applications to studies of the effects of flux surface shape on the gyrokinetic stability and transport of tokamak plasmas using the GS2 code and a new local linear trial function-based gyrokinetic code will also be discussed. CSRI POC: John Shadid, (505) 845-7876 |