Validation of NSFsim as a Grad-Shafranov Equilibrium Solver at DIII-D

TL;DR

This paper validates NSFsim, a new plasma equilibrium and transport simulator, by comparing its Grad-Shafranov solver outputs against real DIII-D measurements and other models across various plasma shapes.

Contribution

The paper introduces and validates NSFsim's Grad-Shafranov solver for accurately recreating plasma shapes and signals in DIII-D, demonstrating robustness across different configurations.

Findings

NSFsim accurately reproduces plasma shapes and flux distributions.

The simulator's results closely match EFIT reconstructions and experimental signals.

NSFsim performs reliably across diverse plasma configurations.

Abstract

Plasma shape is a significant factor that must be considered for any Fusion Pilot Plant (FPP) as it has significant consequences for plasma stability and core confinement. A new simulator, NSFsim, has been developed based on a historically successful code, DINA, offering tools to simulate both transport and plasma shape. Specifically, NSFsim is a free boundary equilibrium and transport solver and has been configured to match the properties of the DIII-D tokamak. This paper is focused on validating the Grad-Shafranov (GS) solver of NSFsim by analyzing its ability to recreate the plasma shape, the poloidal flux distribution, and the measurements of the simulated diagnostic signals originating from flux loops and magnetic probes in DIII-D. Five different plasma shapes are simulated to show the robustness of NSFsim to different plasma conditions; these shapes are Lower Single Null (LSN), Upper Single Null (USN), Double Null (DN), Inner Wall Limited (IWL), and Negative Triangularity (NT). The NSFsim results are compared against real measured signals, magnetic profile fits from EFIT, and another plasma equilibrium simulator, GSevolve. EFIT reconstructions of shots are readily available at DIII-D, but GSevolve was manually ran by us to provide simulation data to compare against.