Speaker
Description
Despite tokamaks being primarily treated as axisymmetric beasts, many aspects of actually running such a machine are inherently nonaxisymmetric. This includes error fields, magnetic ripple, and even Edge Localized Mode-suppressing (ELM-suppressing) Resonant Magnetic Perturbations (RMPs). Each of these effects are extremely important to consider while the fusion field is moving towards next generation machines. Specifically, recent SPARC studies have addressed error field mitigation [1], and magnetic ripple-driven alpha particle losses [2], additionally many ITER studies have explored the implementation of RMPs to suppress machine-killing ELMs [3].
Upon adding 3D magnetic fields, transport is strongly affected. Loss of axisymmetry breaks integrability of field line trajectories, resulting in a chaotic equilibrium magnetic field. This chaotic field changes the structure of the differential operators within the governing transport equations, and provides additional transport in and of itself [4]. In this work, these effects are studied through a transport simulation of an RMP-applied DIII-D shot, although the methodology could nominally be applied to any other machine, and any other mode of externally-applied asymmetry. The implementation methodology is walked through, highlighting difficulties, and possible pitfalls as well as interesting physics effects which become necessary when considering a chaotic equilibrium field. Finally, the results of the study, such as the effect of 3D fields on anomalous transport coefficients, and divertor heat flux patterns are presented.
[1] S. Munaretto et.al., Nuclear Fusion, (2025).
[2] S. D. Scott et.al., Journal of Plasma Physics, (2020).
[3] L. Zhou et.al., Plasma Phys. Control., (2016).
[4] A. B. Rechester and M. N. Rosenbluth, Physical Review Letters, (1978).