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.

Continue reading ICC conference, day 3 →

Today had some fairly cool space related stuff, starting with the first talk of the day, by Alan Hoffman of RPPL. His topic was Field Reversed Configurations, and he mentioned space propulsion as one of the applications. The nice thing about FRCs is that they include open field lines, which means the field lines are not circling the plasma, but exit the fusion device – all magnetic field lines are topologically circles, but there is an important distinction between lines that enclose plasma and ones that do not. Open field lines allow plasma to be expelled, providing propulsion. Obviously this is utterly useless if you don’t have net power gain in the reactor, but hey… Anyway, FRCs are a good candidate for the fusion power core in fusion powered spacecraft, if they ever materialize.

Continue reading ICC highlights, day 2 →

The first day of the ICC conference was pretty much as expected. A bit of schmoozing, renewing contacts, that sort of thing. Today’s sessions were on Magnetic relaxation and confinement, and plasma flow and shear. The overall focus of the conference has shifted slightly since the last one I was at, in 2002. This year is much more science focused, and that’s a good thing. It’s always tempting to focus talks on your own machine and where you want to take it, but in order to move the whole enterprise down the road there has to be communication across groups working on different machines, and there has to be crossfertilization. This means that the focus needs to be on the underlying physics, not the engineering details.

Adil Hassam (one of our Principal Investigators) presented the results from MCX, and there was a fair amount of interest. It’s only been a year and a half since we started getting real results, but already we have enough under our belts to generate a fair amount of interest. It’s becoming increasingly clear that velocity shear stabilizes a wide range of instabilities, and there are now results from machines as diverse as Z-Pinches, Tokamaks, and Mirror Machines all of which show improved stability in the presence of velocity shear.

Eventually the PowerPoints from the talks and posters will be put up on the ICC2004 website, but I just checked and there’s nothing there yet. When they are put up I’ll try to remember to post a pointer – Paul Bellan of Caltech had a really cool movie in his presentation showing plasma current filaments merging, kinking, and pinching off to form a spheromak (essentially a plasma “smoke ring”).

Obviously I have net access here in Madison, though it’s excruciatingly slow.

Rand’s post below reminds me of an idea I had a while back, and which has a little bit of traction in the fusion community (though I think it’s had multiple independent inventors). The basic idea is to make a virtue of the neutrons produced in D-T or D-D fusion by using them to transmute nuclear waste into short lived (high radioactivity) isotopes. The isotopes could then be stored while they decay into something (relatively) stable. The benefits are many. First of all it deals with fission waste, helping to remove one of the obstacles to widespread deployment of fission power. Secondly, it doesn’t require break-even from the fusion reactor, which makes everything a heck of a lot easier. The net transmutation plant power balance is now the sum of the fusion power and the power produced by the decay of the transmuted isotopes. A transmutation plant might plausibly be fully self sustaining. Once fusion reactors are in the hands of capitalist captains of industry, they will get better, cheaper, and more reliable.

A more exciting option is a mature fission-fusion hybrid cycle in which there are multiple passes of fission fuel through the reactor wall, to generate power using a set of reactions which spits out very low activity waste, cutting the initial fission reactor part entirely out of the cycle. This, it seems to me, is the logical long-term consequence of getting the evolutionary driving force of the markeplace to bear on the problem of commercial fusion. In the very long term, of course, we will likely see pure fusion power plants, but the path there must be along a sequence of evolvable reactor designs, each of which is at least marginally profitable.

More tomorrow, when the conference proper starts.

Via SciTech Daily, a company called BioTime is making progress in freezing tissues and restoring them to life. They’ve taken tissue to below freezing and restored it to vitality for implantation, and revived whole animals after two hours of clinical death at 35 degrees Fahrenheit. I think that if cryosuspension ever becomes really practical it will emerge out of research like that conducted by BioTime. They are working on extending time under the knife for surgery, but the limiting case of that is days, and perhaps eventually weeks under the knife as the surgical team hunts down and fixes problems, perhaps maintaining different parts of the body at different temperatures so that some organs can heal after surgery while other areas are kept cryosuspended while being operated on. For pursuing really aggressive cancers this might be the way to ferret out the last little metastases.

I’m a little bit of a cryonics skeptic, but open minded to the possibility that revival of people from a natural death might be possible. Much more probable is that people near death can be cryosuspended while alive, and kept on ice until either a cure is found or some contractual criterion requires their revival. The obstacles to freezing a person while alive are currently regulatory (since the cryonicist would be charged with murder, even if it’s a whole-body thing as opposed to just the head). If it becomes clear that people can be frozen and then revived the legal obstacles to preemptive cryopreservation will be much lower. Sadly, there will always be busybodies who will try to interfere, but chances are good that they will be a minority once enough of the population are only a couple degrees of separation from someone who has had surgery while chilled to the point of (what we now call) clinical death. I just hope it happens before I catch anything really nasty 🙂