A New Twist in Fusion; July 1998; Scientific American Magazine; by Gibbs; 1 Page(s)
For the past 30 years, fusion energy researchers have been forecasting that commercially viable reactors are just a decade away. One reason that great day keeps receding into the distant future is that holding a gas of charged deuterium or tritium (isotopes of hydrogen) steady while its atoms fuse into helium is harder than almost anyone expected. The most popular reactor designs, called tokamaks, try to confine the hydrogen plasma inside shifting magnetic fields generated both by currents inside the plasma itself and by giant external magnets. If there are leaks in this magnetic bottle, the plasma hits the reactor¿s inner walls and loses its energy.
Physicists have known for many years that another kind of magnetic fusion device, called a stellarator, might get around this problem. In a stellarator, intertwined spiral magnets (photograph) and several ring magnets do all the work of confining the plasma inside its doughnut-shaped chamber. Because, unlike tokamaks, there is no need to pass electric current through the plasma, the arrangement is inherently stable. But this design has never been tested at large scales.