A Simplified Lithium Vapor Box Divertor Design

UEDGE simulations give the remarkable result that a divertor plasma acts nearly like a mirror for lithium vapor. In lithium-detached plasmas the rates of lithium ionization and recombination at the cold ends of each flux tube are nearly in local balance. This suggests the possibility of simplifying the lithium vapor box divertor concept by using the plasma itself as one of its side walls, and perhaps forgoing distinct baffles. Since there is much less heat flux on the private-flux side of a divertor leg, it should be easier to detach the divertor leg all the way to the separatrix from that side, so we choose to evaporate lithium into the private-flux side of the divertor leg. This creates a vapor-box-like configuration where the lithium vapor is emitted from near the target end of the divertor leg, on the private flux side, and is recondensed along the “dome” closer to the main plasma as well as on the outer wall of the divertor channel. Configurations of this sort, without material baffles, may be easier to test on existing experiments and may be geometrically attractive for future devices. We will examine engineering parameters, including lithium liquid flow rates and cooling rates, for practical examples.