Comparison of lithium divertor options for the DEMO-FNS tokamak

The choice of an idea for a divertor with evaporating liquid lithium that meets the requirements for removing the thermal load from the edge plasma and provides an acceptable level of change in the ionic composition of the main plasma for the DEMO-FNS tokamak being developed in Russia has been discussed. The results of numerical simulation and optimization of the design of divertors with multiple volumes sectioned by slotted diaphragms have been presented. The parameters of lithium streams flowing into the edge layer have been estimated for the temperature range of divertor chambers from 500 to 1000 K under the conditions of the gas-kinetic and free-molecular modes of lithium vapor outflow from the divertor. Analysis of the processes that reduce the outflux of lithium from the chambers and its penetration into the main volume of the plasma inside the separatrix showed that sectioning effectively reduces the outflow streams to acceptable levels of $\approx$ 10$^{20}$ atom/s.