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 300 nm lithium pre-shot deposited coating will strongly pump impinging D+ ions. This yields a low-recycle SOL plasma with high plasma temperature, Te ∼ 200–400 eV, low density, Ne ∼ 1–3 × 1018 m−3, and peak heat loads of ∼8–20 MW/m2, for 2–4 MW 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 (10 cm/s) using a carbon (for 2 MW) or Mo/Cu or W/Cu substrate (2–4 MW). Erosion/redeposition analysis shows acceptable coating lifetime for a 2 s pulse and low core plasma contamination by sputtered lithium.