MHD simulation of different sawtooth crash models with comparison to DIII-D experiments

Core electron temperature drops rapidly during the sawtooth crash in tokamak plasmas, which causes heat loss and may lead to fast particle losses or even a disruption. Several models have been proposed for the fast relaxation, including (1) fast magnetic reconnection provided by two-fluid effects or the plasmoid instability; (2) growth of higher-mode-number pressure driven instabilities. We have performed 3D MHD simulations of the sawtooth crash for different models with the M3D-C1 code. The magnetic field, parallel current density profile, electron density and electron temperature have different behaviors in the original Kadomtsev’s resistive reconnection model, (1) the extended model with two-fluid effects, and (2) the quasi-interchange model with higher-mode-number instabilities. The 2D poloidal structures of electron density and temperature evolution are compared with that near the q=1 surface during sawtooth crashes in DIII-D measured by Beam Emission Spectroscopy (BES) [Bose et. al. submitted to Rev. Sci. Instrum. (2022)] and Electron Cyclotron Emission Imaging (ECEI) to distinguish between these models.