Dr. Bussard Passes Away, Polywell Fusion Continues

Vinz writes "Dr Bussard, the man behind the Bussard Collector and inventor of the Polywell fusion device, passed away last Sunday in the morning. He leaves behind him a legacy of EM fusion devices, and a team determined to continue his efforts. The news of funding extension for the construction of his WB-7 fusion devices made it to slashdot months ago (as well as his talk at google). They may be a serious candidate in the run to bring commercial fusion, and may work at lower scales than other projects. Let's hope the project continues in good shape despite his departure."

Read the Wiki Article

[NeverVotedBush]

It's referenced in the summary. I hadn't heard about Bussard or the polywell. It sounds promising. Navy-funded research too. I'm sorry this person died before he could see it through to demonstration. Hopefully this really works.

may work at lower scales?

[fluffy99]

"may work at lower scales than other projects"???? - One of the main reasons for pushing for the WB7 model was that they couldn't get positive net energy at small scales. The prediction was that they'd need something on the size of a standard fission reactor to see viable energy output. Plus, the design team originally modeled all the coils with as a zero thickness circle and couldn't understand that when they built the thing that the coil circle centers had to be spaced apart which caused field losses. After seeing stupid design errors like that, I don't have much faith in the research team, but still the concept is worth investigation.

Re:Electron losses

[BCGlorfindel]

The catch to these devises appears to be that if you have a strong enough electrostatic field to contain the ions then you will also lose A LOT of high energy electrons (Rider 1995)

And Bussard insisted that Rider's math model was flat out wrong. Recent experiments by Yoshikawa and MIT have both demonstrated that Rider's model is, in fact, wrong.
The Polywell design has tremendous merit to it and the experiments that Bussard managed at the end of his life were successful in measuring fusion scaling factors and electron loss factors. From those experimental results Bussard's team rushed together what was expected to be their last device in WB-6. On analyzing the data it generated, it achieved record breaking fusion rates. Now that the navy has re-funded his team to finish WB-7, expect to see some big announcements in a year or so.

For more on Polywell theory and background go here. [talk-polywell.org]

Re:may work at lower scales?

[BCGlorfindel]

Plus, the design team originally modeled all the coils with as a zero thickness circle and couldn't understand that when they built the thing that the coil circle centers had to be spaced apart which caused field losses. After seeing stupid design errors like that, I don't have much faith in the research team, but still the concept is worth investigation.

Actually, they initially designed it with permanent magnets and drove the electrons right into the magnets themselves. But the point was to prove electron densities in the center could get high enough for fusion. Regardless of the mistakes made along the way, the got the concept to work for their final tests and expect some big results from the new WB-7 some time next year.

Re:Electron losses

[mako1138]

I've read Rider's papers and thesis. He basically goes through the various ways of creating a non-Maxwellian electron/ion distribution, and shows that there are significant problems with those concepts. The Polywell is supposed to sidestep those issues rather than proving Rider wrong.

WB-6 ran for a short time and a few neutrons were caught in a detector. The estimated fusion rate is an extrapolation that I am not entirely comfortable with. The statistics simply are not there, nor do I agree with the claim that steady-state operation was reached.

While the Polywell is a fresh concept, it looks like nothing more than a three-dimensional arrangement of magnetic mirrors. I simply don't see how cusp losses can be overcome, nor the collisional dumping of energy from the ions to the electrons. There are lots of things that can go "wrong" in plasmas.

Looking around talk-polywell, the Yoshikawa paper doesn't seem to have much to do with the Polywell (though it's interesting that nobody's measured a double well before).

http://wwwsoc.nii.ac.jp/aesj/division/fusion/aesjfnt/Yoshikawa.pdf [nii.ac.jp]

Re:Makes perfect sense to me.

[Lonewolf666]

I agree...

Quote from GP:

In this case he believed he had the scaling laws down. With power proportional to the seventh power of the radius and energy gain proportional to the fifth power, you were only talking about building a device maybe 10 times the radius of the lab device. That's TINY as fusion experiments go, and also compared to fission plants. And the thing is basically a slightly gassy vacuum tube with some magnets in it, i.e. mostly empty space, very little material.

If there are any gotchas you'd have to scale it up about that much to find them. So why go halfway and then build a full-size one when, if it turns out there AREN'T any gotchas you've got an operating power plant on the next step?

His plan was to do two more small prototypes, to get some more solid data than his three-neutron final run ...

Three neutrons is indeed very thin, and from the WB-6 photos on Wikipedia, the coils look like they are about two feet in diameter. That leaves some room for scaling up without moving into a special building.
So I'd recommend to scale it up to something whose parts fit through the door of a normal room, then assemble it in place. Maybe twice the diameter of WB-6, that should leave enough room around the coils to build the vacuum chamber and still be quite affordable.
If Bussard was right about power proportional to the seventh power of the radius, that should give a few hundred (2^7*3 = 384) neutrons where WB-6 gave three. That is something you can derive useful statistics from.