If I was going to build a fusion device for energy production I would build a cylinder filled with fusion fuel and the fusion would happened in the center. First it would be hard to start the fusion with relatively cold fuel. After a while of heating, the surrounding fuel would be hotter even if the fuel in the center wouldn't fuse. With rising temperature and focusing the plasma in the center, fusion would happen. Removing reactant from the center and adding fuel from the outside, the fuel just outside the center would fall in to the center and react and so on. After a while the fuel just outside the center would be very hot to. Almost reaction hot, sort of speaking. The further away from the center the cooler it gets. The heat waste from the fusion is not waste then. It's preheating the fuel, making fusion lot easier. Is it possible? To confine the plasma in a cylinder is possible and quite easy. To concentrate plasma in a string or thread is possible. But what I don't know is: Does the heat transfer from the hot plasma to the not so hot plasma. I suppose it's most radiation and that works well between two bodies with different temperatures, but does it work between layers of plasma. Plasma is a funny thing sometimes and I don't know what to think. Is it totally transparent? Gas can absorb radiation, maybe not so much, but plasma is't just a gas, so I don't know, do you?