Experimental observation of non-resonant divertor resiliency in the Compact Toroidal Hybrid experiment

The first experimental measurements of a novel non-resonant divertor (NRD) magnetic topology, to exhaust particles and heat in stellarator plasmas, yields an order of magnitude improvement in strike line resiliency when compared to an island divertor. The NRD concept leverages resilient invariant manifolds near sharp flux surface boundaries in an otherwise chaotic magnetic field to decouple the exhaust channels within the plasma boundary from the three-dimensional equilibrium properties of the confined plasma. Ion flux profiles are measured during two different vacuum magnetic configurations within the Compact Toroidal Hybrid experiment, allowing for investigations of the strike line response to the evolution of the ohmically driven plasma current. During the NRD portion of the discharge, the majority of the strike line locations are observed to shift poloidally by ⩽ 80 mm/ Δ − ι when varying the edge rotational transform, − ι , by ⩽ 0.24. These observations are in agreement with diffusive field line modeling of the NRD magnetic topology and promote further investigation of this concept as a possible divertor solution for an optimized stellarator fusion power plant.