Fusion 2.0

20080424_fusion Over at Cosmos, Robin McKie looks at the International Thermonuclear Experimental Reactor:

Recreating the fusion process clearly offers great rewards, but it is not an easy task – to say the least. In particular, the business of containing a cloud of plasma that has been heated to around 100 million degrees Celsius has taxed the imaginations of a great many scientists. You can’t hold super-hot matter in an old bathtub, after all. In the end, it took the ingenuity of Russian scientists Igor Tamm and Andrei Sakharov, working at Moscow’s Kurchatov Institute in the late 1950s, to come up with the answer: the tokamak.

The key feature of a tokamak is its central chamber which is shaped like a giant, hollow doughnut or torus, and which gives the device its name. Abbreviating the Russian ‘TOroidalnaya KAmera v MAgnitnykh Katushkakh’ results in ‘tokamak’, or its similar English equivalent, TOroidal CHAmber in MAgnetic Coils (tochamac). Powerful electric currents are passed through coils that wind round the doughnut-shaped chamber and through the plasma inside it, creating a twisting magnetic field that holds the super-hot plasma in a tight, invisible grip.

However, massive amounts of electricity are needed to create this unseen container, and to date, far more energy has been spent powering-up tokamaks than has been released through the resulting fusion of atoms. For example, JET soaks up 25 megawatts of electrical power to generate only 16 megawatts of fusion power. However, ITER – which will be the biggest tokamak reactor ever built when completed – is scheduled to have an output of 500 megawatts for an input of only 50 megawatts of electricity.