Progress on the liquid metal 'divertorlets' concept: experiments and simulations*

The liquid metal (LM) plasma-facing component (PFC) is one of the most promising ways to realize a PFC capable of operating for long periods. Concept designs called ‘Divertorlets’ have been presented as a non-evaporative liquid metal solution for heat removal and low-recycling regime operation[1]. Toroidal divertorlets utilize adjacent narrow channels, separated by slats, along the magnetic direction with alternating vertical velocity. Interconnecting rods (significantly more conductive than the LM) within every other channel partially remove current from the liquid metal in the channels they pass through. Differences in current density between channels lead to J × B pumping.

A prototype was designed through COMSOL simulations and tested with Galinstan alloy in the Liquid Metal eXperiment platform at PPPL, obtaining successful operation: (1) cyclical flow pattern around the slats, (2) uniform flow pattern along the magnetic direction, (3) free surface deformations increased gradually with increasing current, (4) deformed free surface will not cause heat flux issues from tokamak plasma. Flow measurements are a high priority for flow characterization and comparison with simulation. Future designs at reactor scale aim to reduce liquid metal inventory and power requirements.