Computational applications of Multiple Region relaXed MHD (MRxMHD)

Controlled magnetic confinement fusion offers the possibility of an inexhaustible supply of energy with zero greenhouse gas emissions. At the very high temperatures needed to initiate a fusion reaction, the fuel (a mixture of deuterium and tritium) exists in the plasma state. A way to confine the hot plasma is by applying a strong magnetic field.

Magnetohydrodynamics (MHD) is an electromagnetic fluid model of magnetized plasmas, with applications ranging from solar flares through to fusion experiments in the laboratory. In an ANU/ Princeton Plasma Physics Laboratory collaboration, a new MHD model is being developed: multi-region relaxed MHD (MRxMHD). This is based on the use of a topological invariant called the helicity, which is used in conventional plasma relaxation theory to constrain the evolution of a relaxing plasma towards a minimum energy state. In MRxMHD the plasma is divided into multiple regions, each with its own helicity invariant, thus allowing the description of a richer variety of phenomena.

MRxMHD, and its numeric implementation through the supercomputer SPEC code developed by Princeton Plasma Physics Laboratory, has been applied to describe a rippled boundary perturbed field of the US DIII-D tokamak (http://link.aip.org/link/doi/10.1063/1.4765691?ver=pdfcov) , and the spontaneous helical state of RFX-mod (http://dx.doi.org/10.1103/PhysRevLett.111.055003). Opportunities exist to apply this code to describe sawteeth reconnection, and new data from a reverse field pinch which constrains the rotational transform profile (https://doi.org/10.1063/1.5038430), and the fully helical state of Heliotron J plasmas.

The project is suitable for third year special projects through to Honours and Masters.  Suitable project extensions to a PhD are also possible.

Illustrative Poincéare sections of double helical axis (left) and single helical axis (right) states of RFX-mod.

Illustrative Poincéare sections of double helical axis (left) and single helical axis (right) states of RFX-mod.

The solutions are predicted minimum energy states using the MRxMHD SPEC code.