Theory Weekly Highlights for January 2021

January 15, 2021

An integrated modeling workflow capable of finding the steady-state plasma solution with self-consistent core transport, pedestal structure, current profile, and plasma equilibrium physics has been developed and successfully tested against a DIII-D discharge. Key features of the simulation were the self-consistent inclusion of impurity transport and the use of machine learning accelerated models for both the pedestal structure and the turbulent transport physics. The coupled workflow is implemented within a new Stability Transport Equilibrium Pedestal (STEP) physics module in the One Modeling Framework for Integrated Tasks (OMFIT) framework. STEP makes use of the ITER integrated modeling and analysis suite data structure for exchanging data among physics codes, and such technical advance was enabled by the development of a new numerical library named the Ordered Multidimensional Arrays Structure (OMAS). Simulations of an ITER baseline scenario within STEP show that although D-T fuel dilution in the core raises the core plasma temperature, this positive effect is offset by a decrease in the available fuel, a decrease in pedestal pressure, and increased radiation. The work has recently appeared in Meneghini, et al., 2021 Nuclear Fusion 61 026006.

January 08, 2021

Simulations of negative triangularity (δ < 0) plasmas predict relatively good confinement, (H-mode scaling factor H98y2 ~ 1 ) with only a small H-mode edge pedestal, consistent with DIII-D experimental observations. Profile predictions for this scenario using the TGYRO transport manager show good agreement with experiments using either the TGLF-SAT0 and TGLF-SAT1 models for prediction of nonlinear saturation of turbulent transport. Negative-δ is found to reduce the predicted pedestal pressure by a factor of 2.5. TGLF predicts that turbulence is reduced across all wave numbers, and that an increase in the electron temperature gradient scale length relates to a reduction in particle transport. In agreement with experiments, core-pedestal STEP (Stability, Transport, Equilibrium, Pedestal) modeling finds that confinement increases as δ is reduced below zero. This is attributed to the increase of electron temperature gradient scale length reducing the particle transport.

These highlights are reports of research work in progress and are accordingly subject to change or modification