Temperature at the plasma boundary: a 2-D toroidally symmetric plasma (left), and a 3-D non-symmetric plasma with a magnetic field modified by ELM control coils (right). Corresponding heat loads on the outer divertor target are shown below.
The results discussed below were recently published by the Physical Review Letters in an article titled, Detachment in Fusion Plasmas with Symmetry Breaking Magnetic Perturbation Fields.
Development of a sustainable magnetic fusion reactor is contingent on the successful management of high heat and particle fluxes to plasma facing components. Therefore, a “detached” plasma state with a tightly coupled plasma-gas zone in front of exposed surfaces is an integral element of steady state divertor operation in the next step fusion energy experiment ITER (see recent ITER Newsline article, ITER Scientist Fellows make progress).
This, however, has to be combined with a solution for a different crucial challenge: the mitigation of transient heat fluxes from so-called type I edge localized modes (ELMs) that occur in high confinement (H-mode) plasmas.
Application of resonant magnetic perturbation (RMP) fields has been identified as a promising tool to control ELMs, and these will be part of the ITER baseline scenario. However, if RMP application for ELM control is compatible with the dissipative, partially detached divertor plasma of the baseline scenario in ITER remains unknown at this point. Recent extensions of the computational model have allowed for the first time to evaluate this compatibility issue, and it is found that RMPs can have both beneficial and adverse effects on divertor performance. The new results therefore open a path to include the divertor plasma in the optimization process to provide an integrated solution for ITER to control the divertor power fluxes.