The plasma hits the wall, cools rapidly and you have to deal with hydrogen gas and a slightly warmed wall. The thing about fusion reactors is, that the energy d

The plasma hits the wall, cools rapidly and you have to deal with hydrogen gas and a slightly warmed wall. The thing about fusion reactors is, that the energy densities at any given moment are actually not that high at any given moment, it is just that the fuel cycles are quite rapid and consequently you can get a lot of energy out.