• Develop and understand high-performance operating scenarios utilizing a liquid lithium divertor (LLD) for particle control
• Understand and minimize the sources and accumulation of plasma impurities arising from lithium conditioning of the PFCs
• Assess the relationship between lithiated surface conditions and edge and core plasma conditions (Milestone R11-3)

FY2011 Research Milestone R(11-3):  Assess the relationship between lithiated surface conditions and edge and core plasma conditions

The plasma facing components (PFC) of fusion devices play a key role in determining the performance of the fusion plasma edge and core by providing particle pumping and fueling and acting as a source of plasma impurities. On NSTX, coating the divertor carbon PFCs with evaporated lithium has resulted in transient particle pumping, increased energy confinement, and suppression of edge localized modes (ELMs). To extend the duration of particle pumping, and to investigate the impact of liquid lithium on plasma performance, a liquid lithium divertor (LLD) will be installed in FY2010, and the relationship between lithiated surface conditions and edge and core plasma conditions will be determined. To understand pumping, D retention will be studied as a function of surface conditions such as lithium coverage and LLD surface temperature, and plasma exhaust parameters such as divertor electron density and temperature, strike-point location, and flux expansion. The temperature evolution of the LLD surface will be measured to understand the heat transfer properties of the LLD, to determine the allowable peak flux onto the LLD, and to relate the LLD surface temperature to the measured influx of lithium and hydrogenic species. Recycling and retention on the divertor carbon and LLD surfaces are particularly important, so a Lyman-α AXUV diode array will be utilized for deuterium recycling measurements in the presence of the highly-reflective liquid lithium surface. Further, an in-situ materials analysis particle probe placed near the LLD will provide measurements of retention and surface composition in the outer divertor region for selected shots. These retention measurements will be compared to dynamic retention measurements and to retention models. Finally, D, Li, and C sources from the divertor and Li transport from the plasma edge to the core will be measured. This research will provide the scientific understanding of LLD operation necessary to begin to comprehensively assess liquid lithium as a possible PFC solution for NSTX and next-step ST facilities.

ITPA Participation

• DSOL-21 Introduction of pre-characterized dust for dust transport studies in divertor and SOL

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