Controversies exist over whether the ions and electrons will thermalise and whether bremsstrahlung losses will emit more energy in an unrecoverable form than can be produced by the fusion reaction.[citation needed] Todd Rider calculates that bremsstrahlung losses with this fuel relative to the fusion production will be 1.20:1.00.[12] Bussard said that his calculation of the losses are about 5% of this, and therefore, greater gains than unity are possible.[13] According to Bussard the high speed and therefore low cross section for Coulomb collisions of the ions in the core makes thermalizing collisions very unlikely, while the low speed at the rim means that thermalization there has almost no impact on ion velocity in the core.[11]

Rick Nebel, the current lead scientist, has talked in more detail about how this could be avoided. There are various strategies, such as fuel mix and manipulating virtual anode height.

It’s really more of a concern for second-generation Polywells that would fuse hydrogen with boron-11 (this is highly desirable because it produces no neutrons, just alphas that can be converted directly to electricity), because the energies involved are much higher. First-gen Polywells would burn D-D or D-T, and brem should be a minor issue there.

Actually, no, the stakes are much lower because food and water are so plentiful now. That’s one reason wars have declined so much. There are fewer war deaths now as a percentage of population than at any time in history.

Also, Acksiom is correct: there will still be a huge market for dense liquid energy like gasoline, because it has obvious utility. Everything would just get cheaper, at the expense of current electric power plants.

i think that the radiation losses i mentionmed above might be one of tose negative outcome factors. who knows whether they can model it (the mag fields are pretty hairy in there, arent they?) but as you scale up, the problem will get worse. We call it brehmstrahlung radiation in imaging physics and its always a problem.

Basically, a tokamak is a heated plasma confined by magnetic fields. The really difficult thing is to keep the plasma hot enough for fusion (10-100KeV). In IEC fusion (fusors and Polywells), you don’t heat particles, you accelerate them with a cathode (temp=velocity), but it’s very difficult to get a high density because in a fusor that would melt your grid, but on the plus side it’s trivially easy to accelerate particles to tens of KeV.

So in a tokamak, density is easy and temperature is hard. In IEC, temperature is easy but density is hard.

Don’t be ashamed, I humiliated myself more than a few times learning about Polywells. Still do, actually.

Polywell is more or less synonymous with Bussard reactor; there were some polyhedral magnetic well machines proposed before Bussard but he greatly refined them and trademarked the term Polywell. What you’re describing in graf 1 is actually the main difference between a fusor and a Polywell. A fusor has a physical cathode, a Polywell confines electrons magnetically to create a virtual cathode.

http://en.wikipedia.org/wiki/Fusor
http://en.wikipedia.org/wiki/Polywell

Hrm, well, its a bit difficult because the arguments are extremely technical. The closest thing would be Art Carlson’s arguments on Talk Polywell in the theory forum. His arguments are probably wrong (the WB-7 results appear to rule out much of what he claims) but he does argue reasonably.

The reasonable argument you will hear the most often is the Rider paper that claims to establish limits on IEC fusion power well short of net power. However, studies done since then tend to argue Rider was probably incorrect in several of his assumptions (for instance, Rider assumes square wells, but it is now established experimentally that parabolic wells are more realistic and give large Q values).

The best argument against Polywell is that something we don’t know yet will cause losses to scale much faster than the r^2 Bussard proposed, or other unforeseen effects will doom a larger machine (electron maxwellianization perhaps, which isn’t an issue in smaller machines). Don’t let enthusiasts kid you, given the poor record of fusion device predictions in general these negative outcomes are still susbtantially likely.

and that the fundamental difference between a polywell and a tokamak is that the tokamak uses no physical electrodes, only magnetic fields? I had assumed that tokamaks dont use electrostatic acceleration, but i could be/probably am wrong about this.

yes i guess i could google but i think you’ll give me a more integrated answer.

my imaging physics background makes me wonder if there aren’t any xray byproducts from having the electrons zooming around in proximity to the hydrogen ions. its a serious problem in CT imaging because its junk energy wavelengths that interfere with the image and increase radiation dose. I guess dose isnt an issue in energy, but you are going to probably sacrifice a lot of efficiency that way, which is going to eat into your output/input ratio.

frankly between Polywell in the long term and pebble bed reactors in teh shortterm, I dont see how we cant win the energy game. I am pessimistic about Obama’s support for nuclear power, but I figure if he doesnt step up we can buy energon cubes from the Chinese.