The Achilles Heel of fusion is low volumetric power density. This is because all the energy has to go through the first wall, which has limited area compared to the surfaces of fuel pins in a fission reactor.
So, there's been effort to try to maximize the power/area at the first wall. One part of that is the power that directly strikes the surface (ions, electrons, photons). The capacity to carry away this heat is limited by the strength of the wall material and its thermal conductivity, a fact that was pointed out by Pfirsch and Schmitter in the 1980s.
One could raise this limit by doing away with a solid wall (with its limits on thermal conductivity and stress) and instead using a liquid wall. This would also address erosion of the wall by sputtering, and help reduce damage from plasma disruptions (which may well otherwise be a showstopper for tokamaks.)
So, there's been effort to try to maximize the power/area at the first wall. One part of that is the power that directly strikes the surface (ions, electrons, photons). The capacity to carry away this heat is limited by the strength of the wall material and its thermal conductivity, a fact that was pointed out by Pfirsch and Schmitter in the 1980s.
https://pure.mpg.de/rest/items/item_2131865_1/component/file... (see section 4.1.1)
One could raise this limit by doing away with a solid wall (with its limits on thermal conductivity and stress) and instead using a liquid wall. This would also address erosion of the wall by sputtering, and help reduce damage from plasma disruptions (which may well otherwise be a showstopper for tokamaks.)