Engineers at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory are using the process shown here to create a super-strong weld for the upgrade of a key component of the Lab’s experimental nuclear fusion reactor. The whirling steel tool in this demonstration joins two copper plates by heating them through friction to the consistency of wax. The roughened surface will be smoothed out in the finished product. Called “friction stir welding,” the process is critical to the upgrade of the test reactor that will enable Laboratory scientists to address major questions on the road to developing nuclear fusion as a safe, clean and virtually limitless source of energy for generating electricity. (Video by Edison Welding, Columbus, Ohio)