How does one confine a 100-million-degree plasma in the laboratory? Because charged particles tend to follow magnetic field lines, one can use a well-constructed magnetic field to isolate and insulate the plasma from its surroundings. If the constituent ions of a plasma are sufficiently reactive (for example, a mixture of deuterium and tritium), and if the isolated plasma is sufficiently hot and dense, nuclear fusion will occur. Should the plasma touch the wall of the containment vessel, it would instantly cool and pollute the bulk plasma with material from the wall.
The magnetic approach to fusion has already produced megawatts of fusion energy—an amount roughly comparable to the external heating supplied to the plasma. The international fusion research community is confident enough about the future of magnetic fusion to be planning experiments in which the fusion yields will exceed the external heating energy by factors of 10 or more. Such...
