Experimental studies of lithium-based surface chemistry for fusion plasma-facing materials applications

Lithium coatings on NSTX plasma facing components and its effects on boundary control, core plasma performance, and operation

“…In NSTX, recycling of deuterium species from plasma contact with ATJ graphite surfaces contributes to a secular density rise observed in most H-mode, neutral beam injection (NBI) heated plasmas. Lithium has the potential for control of this density rise due to its ability to absorb the atomic and ionic deuterium eflux through formation of lithium deuteride and lithiated compounds [14], which sequesters deuterium, making it unavailable for recycling. Due to the range of deuterium in lithium, and the immobility of the lithium deuteride formed in solid lithium, the absorption can saturate in the near surface layer [15], limiting the deuterium pumping capability of solid lithium.…”

“…Under NSTX vacuum conditions, with a base pressures in the range of about 3-5x10 -8 [14]. After an annual 12-18 week experimental campaign, NSTX is vented with the local atmosphere, and purged with humidified air for at least 1 week prior to the first personnel entry.…”

NSTX plasma operation with a Liquid Lithium Divertor

“…Lithium evaporated on plasma facing components (PFCs) has the potential for control of density through its ability to absorb the atomic and ionic deuterium efflux through formation of complex chemical bonds which sequester deuterium, making it unavailable for recycling [5,6].…”

Surface chemical/binding reaction of coated Li layer by lithium vapor injectors in LIGHT-1

“…Because the coating was performed before the discharge, the coating effect could be limited. If sufficient lithium vapor is continuously injected to the diverter, then there is a possibility that an un-saturated diverter will be realized [4]. At the NIFS, the Lithium Injection Gettering of Hydrogen and its Transport experiment (LIGHT-1) has begun demonstrating the use of future fusion devices [5] that are suitable for steady-state discharge.…”

“…Previous works on chemical binding for lithium in NSTX were also analyzed by XPS, and the characteristics of lithium binding are found in Refs. [4,6].…”