Science Initially and for the first couple of months, the reactor will be filled with helium—an unreactive gas—so that operators can make sure that they can control and heat the gas effectively. By Daniel Clery
'At the end of January, experiments will begin with hydrogen in an effort to show that fusing hydrogen isotopes can be a viable source of clean and virtually limitless energy.
'The real test will come once W7-X is full of plasma and researchers finally see how it holds on to heat. The key measure is energy confinement time, the rate at which the plasma loses energy to the environment. “The world’s waiting to see if we get the confinement time and then hold it for a long pulse,” PPPL’s Gates says.
'Success could mean a course change for fusion. The next step after ITER is a yet-to-be-designed prototype power plant called DEMO. Most experts have assumed it would be some sort of tokamak, but now some are starting to speculate about a stellarator. “People are already talking about it,” Gates says. “It depends how good the results are. If the results are positive, there’ll be a lot of excitement.”'