Effect of magnetic perturbations on the 3D MHD self-organization of shaped tokamak plasmas

TL;DR

This paper investigates how magnetic perturbations influence the self-organization and sawtooth oscillations in shaped tokamak plasmas using 3D MHD simulations, confirming experimental observations and previous circular tokamak results.

Contribution

It demonstrates that specific magnetic perturbations can mitigate sawtooth oscillations in shaped tokamak plasmas through nonlinear 3D MHD modeling.

Findings

Magnetic perturbations significantly affect sawtooth activity.

Mitigation of sawtooth oscillations by specific MPs is confirmed.

Results align with experiments in RFX-mod and DIII-D.

Abstract

The effect of magnetic perturbations (MPs) on the helical self-organization of shaped tokamak plasmas is discussed in the framework of the nonlinear 3D MHD model. Numerical simulations performed in toroidal geometry with the \textsc{pixie3d} code [L. Chac\'on, Phys. Plasmas {\bf 15}, 056103 (2008)] show that $n=1$ MPs significantly affect the spontaneous quasi-periodic sawtoothing activity of such plasmas. In particular, the mitigation of sawtooth oscillations is induced by $m/n=1/1$ and $2/1$ MPs. These numerical findings provide a confirmation of previous circular tokamak simulations, and are in agreement with tokamak experiments in the RFX-mod and DIII-D devices. Sawtooth mitigation via MPs has also been observed in reversed-field pinch simulations and experiments. The effect of MPs on the stochastization of the edge magnetic field is also discussed.