SciDAC-5 : Development of High-Fidelity Simulation Capabilities for ELM-free Design Optimization 

CETOP: A Center for Edge of Tokamak OPtimization (ELM-SciDAC) 

 Abstract: 

For the advanced tokamak concept, the focus of the US fusion community is based on two major objectives: 1) sustained operation at the pressures and temperatures to achieve the conditions needed for the fusion reaction to occur and 2) closing the technological gaps needed to integrate a high performance plasma into a viable fusion power plant (FPP) system. One of the key challenges to these objectives is the occurrence of periodic instabilities at the plasma edge. Transient Edge-Localized Modes (ELMs) are one of the most concerning phenomena in burning plasmas as they could pose a risk to plasma facing components (PFCs). We propose to develop the simulation capability and to perform extended MHD and kinetic simulations of non-ELMing (and some ELM-ing) regime operating points in an FPP, projected from multi-machine databases. High performance computation (HPC) using the extended MHD codes, NIMROD and M3D-C1, as well as the XGC, and MARS-K/Q codes, together with existing multi-machine databases of ELM-free scenarios will be used for AI/ML based design extrapolation. This will enable optimization of future devices for ELM-free operation. Our physics goals are to obtain new high-fidelity-based ELM stability boundary maps by including non-ideal and multi-species physics, as well as stability analyses and nonlinear simulations of non-ELMing regimes due to plasma shaping (negative triangularity). In addition to AI/ML contributions, SciDAC Institute research necessary for the high fidelity MHD simulations also includes advance time-integration methods and transition to GPU-accelerated architectures.

Purpose: 

The project overarching objective is to develop the simulation capability and to perform extended MHD and (drift-gyro) kinetic simulations of non-ELMing (and some ELMing) regime operating points to close gaps in understanding, prediction, and optimization of edge stability for an FPP.

To achieve our overarching goal, our ASCR objectives are therefore,

Approach: 

Due to multi-physics and multi-scale challenges, a multi-hierarchy approach is essential. In this SciDAC, for both understanding and reliable prediction of ELMing and non-ELMing discharges, we therefore utilize a hierarchy of models and methods, from comprehensive first-principle/high-fidelity to reduced linear models, as described below. Our physics goals are to obtain new high-fidelity-based ELM stability boundary maps by including non-ideal and multi-species physics, as well as stability analyses and nonlinear simulations of non-ELMing regimes due to plasma shaping (negative triangularity). We focus on physics challenges of 1-ELM onset prediction, 2- Reproduction of complete ELM cycles, 3- Prediction of ELM-induced heat loads, and 4- Optimization for ELM-free plasmas.


Finally, to meet challenge of prediction of ELM-induced heat loads, full nonlinear calculations also are needed for understanding and reliable prediction and optimization for non-ELMing regimes. Magnetic reconnection effects as well as multiple species in the SOL region will be studied via full nonlinear extended MHD and kinetic simulations.

SciDAC team members and institutions: 

SciDAC-5 Principal Investigator : Fatima Ebrahimi (PPPL)