PSI modeling of liquid lithium divertors for the NSTX tokamak

We analyzed plasma surface interaction issues for the planned Module-A static liquid lithium divertor for NSTX using coupled codes/models describing the plasma edge, divertor temperature, and erosion/redeposition, with input data from tokamak and laboratory experiments. A 300nm lithium pre-shot deposited coating will strongly pump impinging D+ ions. This yields a low-recycle SOL plasma with high plasma temperature, Te∼200–400eV, low density, Ne∼1–3×1018m−3, and peak heat loads of ∼8–20MW/m2, for 2–4MW core plasma heating power. This regime has advantages for the NSTX physics mission. Peak surface temperature can be held to an acceptable ⩽470°C with moderate strike point sweeping (10cm/s) using a carbon (for 2MW) or Mo/Cu or W/Cu substrate (2–4MW). Erosion/redeposition analysis shows acceptable coating lifetime for a 2s pulse and low core plasma contamination by sputtered lithium.