Building a Gigantic Machine

Abstract

The ITER tokamak will be a perfectly formed jewel of technology. Probably the most complex (and most expansive) machine ever built by humankind. With the largest magnets in the world, the most powerful cryogenic plant, and endless banks of high-powered computers ITER’s ambition and scale are unprecedented. In principle, a tokamak is a relatively simple machine: it is a toroidal vacuum chamber (shaped like a doughnut or tire, to use a more down-to-earth analogy) surrounded by magnets that confine the plasma and keep charged particles from touching the walls. Hydrogen gas is injected into the chamber and heated reaching temperatures of tens or even hundreds of millions of degrees. Energy is generated by the fusion of hydrogen nuclei and released as kinetic energy of the neutrons produced. Since neutrons are not electrically charged they are not affected by the magnets surrounding the chamber, so they hit the walls and their kinetic energy is absorbed as heat. As with conventional power generators an operational fusion reactor uses this heat to convert water into steam and produce electricity through turbines and alternators. In this chapter we will visit the interior of the machine. We will look at its main components: the vacuum vessel, the magnets, the inner walls, the divertor, the cryostat, and the heating techniques. Then we will look at how all these parts interconnect in assembly. This is another logistics challenge as a result of the thousands of annual deliveries and millions of coded products stored in facilities both on-site and off-site, something that couldn’t be done without a sophisticated materials management system.