This was the last day of scientific presentations, and it ended on a high note with a banquet, about which more later. L. J. Perkins did an excellent overview of fusion physics, and mentioned a couple of things in passing that caught my attention. The most significant is that p-B11 is viable as a fuel in fast ignition ICF. In ICF a fuel pellet is compressed by depositing energy symmetrically on a spherical capsule, blowing off the outer layer. The resulting reaction force collapses the pellet to fusion relevant densities, heating in the process. Fast ignition is a scheme where you hit the compressed pellet at or just before the moment of maximum compression with an additional energy source (ion beam or laser) focused on a small spot. Ignition of the fusion fuel is initiated at the spot, and this serves as a spark plug which sends a shock front through the high density fuel, triggering fusion throughout the volume. The nice thing about ICF is that the fuel density is really high, so the mean free path for photons is really short, smaller than the size of the pellet. This means that bremstrahlung, the traditional enemy of p-B11, is less of a problem, since bremstrahlung photons are captured within the pellet, rather than escaping as they do with the lower density plasmas used in magnetic confinement.

There was a talk on Deuterium-Helium 3 fusion, coming out in favor of it as a power production scheme. I remain skeptical, but I’d love to be proved wrong. There was the usual invocation of lunar He3 production, and a mention of the possibility of obtaining He3 from the gas giants. It’d be interesting to see if the energy cost of extracting the He3 from the gravity well is worth it.

In comments to my previous post Phil Fraering asked about electrostatic confinement. I had a chat with Greg Piefer, who is working on the UW IEC device. The upshot is that inertial electrostatic confinement cannot scale to a commercial reactor, even in theory, unless there are major breakthroughs in grid materials or a way to get rid of the grid altogether. The problem is that the grid simply erodes iunder ion bombardment. There are people working on dealing with these issues, but limited success so far. The major item of good news from IEC is that there is commercial interest in it as a neutron source or a proton source (using Deuterium-Helium3).

The highlight of the conference for me was the banquet, where I got to hang out with some people who’ve forgotten more than I’ll ever know about fusion. One of my tablemates is a senior scientist at a national lab, and he was able to name $750 million worth of fusion experiments where significant hardware was built but zero data produced before the plug was pulled. I’m not sure he’d want his name widely associated with this number, which is why I’m leaving it out. Anyway, the experiments in question weren’t over budget, just killed because DOE decided to change the direction of the program, often as a result of lobbying by people hoping to switch the funding over to their pet projects. This sort of crap is why large scale government funded research has to be approached very carefully. Without hawk-like oversight politics ends up beating both good science and good sense. The analogies in the space program are left as an excercise for the reader.