Thursday, February 24, 2005

Laserbrains: Direct-Drive Fusion

One thing I find as a constant in my discussions of fusion (here, here, here, and here): I keep forgetting one subspecies of fusion or another, and this time it's inertial fusion. The idea is that a phalanx of lasers, equispaced, hit a deuterium-tritium target simultaneously with a big pulse of energy. This should be sufficient to make the whole thing compress mighty hard, hard enough to spark a fusion reaction and make everyone go home happy. (General Atomics has a pretty nice explanation on their website.) The boys working the big lasers are getting smarter about it; the University of Rochester is harboring one group working on ICF, and according to this Popular Mechanics article, they've learned a thing or two about the confinement process. In particular, the problem with ICF is not unlike that with conventional fusion: convincing the plasma to stay in one place long enough to fuse a large percentage of the fuel is really hard. But, say the UR folks, they claim to have developed a laser "polarization smoothing" technique that should allow them to get to actual ignition. This "bodes well" for further experiments both at UR and at the National Ignition Facility at Lawrence Livermore Labs. The full paper from the UR team can be found in PDF form.