Extended MHD studies of ELM-free negative-triangularity plasmas and the CETOP SciDAC-5 project

The CETOP (Center for Edge of Tokamak OPtimization) project is a SciDAC-5 project for the development of high-fidelity simulation capabilities for ELM-free design. In CETOP, we employ a fidelity hierarchy of global models, ranging from XGC to NIMROD, M3D-C1, and MARS-K/Q. Our objectives are: 1- inclusion of non-ideals effects, plasma shaping, multi-species, nonlinear physics, coupling of extended MHD, XGC via transport coefficients, as well as performing a full nonlinear benchmark between extended MHD, gyrokinetics and NIMROD DK, 2- to develop advanced time discretizations and transition to GPU-accelerated architectures for our MHD codes, 3- to apply ML techniques for ELM-free optimization. Our extended MHD studies of negative-triangularity (NT) plasmas in DIII-D will be presented. We model the entire plasma, including the core, edge, SOL and vacuum regions, using NIMROD with 2-fluid and gyroviscosity effects. Our linear and nonlinear NIMROD simulations of two strongly shaped NT plasmas (\delta =-0.54) in DIII-D show a persistent reconnecting global n=1 mode. We compare the saturated nonlinear mode amplitudes with the measurements. The linear stability scaling of these plasmas using the MARS-F and NIMROD codes will also be presented. This work was supported by the DOE SciDAC program under Award Number DE-AC02-09CH11466 and by US DOE awards DE-SC0022270 and DE-FC02-04ER54698.