The Stellarator - Fusion Power with a Twist

Getting sustained fusion to work has been fraught with frustration, expense and failure, something that maybe finally coming to an end thanks to a bizarre design that just may work. 

Stellarators face the same challenge as all fusion devices: They must heat and hold on to a gas at more than 100 million degrees Celsius—seven times the temperature of the sun’s core. Such heat strips electrons from atoms, leaving a plasma of electrons and ions, and it makes the ions travel fast enough to overcome their mutual repulsion and fuse. But it also makes the gas impossible to contain in a normal vessel.

Instead, it is held in a magnetic cage. A current-carrying wire wound around a tube creates a straight magnetic field down the center of the tube that draws the plasma away from the walls. To keep particles from escaping at the ends, many early fusion researchers bent the tube into a doughnut-shaped ring, or torus, creating an endless track.

But tokamaks have serious drawbacks. A transformer can drive a current in the plasma only in short pulses that would not suit a commercial fusion reactor. Current in the plasma can also falter unexpectedly, resulting in “disruptions”: sudden losses of plasma confinement that can unleash magnetic forces powerful enough to damage the reactor. Such problems plague even up-and-coming designs such as the spherical tokamak (Science, 22 May, p. 854).

Stellarators, however, are immune. Their fields come entirely from external coils, which don’t need to be pulsed, and there is no plasma current to suffer disruptions. Those two factors have kept some teams pursuing the concept.

Seen below is the stellarator. Gotta love the insane design set made possible only by visionary use of supercomputers and manufacturing of precision hardware that borders on the supernatural. :)

Addendum: It works.

But the team reported earlier today that using just 2 megawatts of microwave radiation, they were able to heat hydrogen gas to 80 million degrees for a quarter of a second. This might not sound like much, but again, it’s a proof of concept, and the team says they’re conceivably able to scale things up to heat the hydrogen gas to that 100 million degree benchmark, and also sustain the resulting plasma for much longer.