Talk-Polywell.org

Mmm...

FuFu as an electron injector for a Polywell. It seems strange on first thought, but if DPF "FuFu" can produce a high intensity collimated electron beam frequently enough for for a pulsed Polywell, and do so while near breakeven even from X-ray direct conversion and ion beam direct conversion, the energy balance picture changes. Even with poor electron injection efficiency into the Polywell the energy cost of injecting electrons is minimal, or even slightly profitable. A strange hybrid might actually make physics sense. The engineering would be daunting, but the concept may not be that much different from using a FRC for plasma injection. The FuFu electron beam injector may not even be much bigger than the e-gun already on WB 8, especially as they would have to be beefed up a lot to reach required output. The electron beam from a FuFu might be too energetic, but it could be partially direct converted- slowed to desired KeV with the benefit of harvesting more of FuFu output for electricity generation.

Lets see. If a DPF manages to produce ~ 4 MJ per pulse, and if ~ 500KJ of that is in the electron beam, and it pulses ~ 100 times per second/ per FuFu gun, then 50 MW (Mega Joules per second) or more of electron input power could be available.

The DPF might be a failure at producing net profitable power, but an overall Q of 0.5 would still make it an excellent and energy cheap electron injector for a Polywell (assuming the Polywell is a profitable machine). The essentially two stage fusion approach might make the two marginal machines a cooperative success.

Mmm....

PS: Polywell , FRC, and DPF are the three primary alternate fusion approaches. Of course General Fusion, and Laser fusion is ignored in this speculation. It would be ironic if major componets of all three systems end up providing a solution that dethrones the tokamak.

Dan Tibbets

You could have 6 spheromaks for the cube faces and 8 Fofu's for the corners, alternate firing the 6 spheromaks at once then the Fofu's, the idea being to squeeze each virtual polywell in an equally but oppositely polarized magnetic layer. Depending on how quickly you can trigger and how long the plasmoids last you get an onion of repelling layers,(high beta). Takes a huge cap bank, but maybe smaller smaller plasmoid generators. Fun to model, lots of pinched off cusps, you even could have a POPs effect.

You've reversed the polarity

The ion beam is what is expelled away from a DPF. The electron beam heads in the opposite direction and strikes the DPF anode.

And at plasma densities approaching breakeven the corresponding electron beam is not expected to make it out of the plasmoid... it will just expend itself further heating the plasma.

So no DPF electron guns.

We have to stick with Spheromaks or FRC's instead, at least we don't have to worry about superconducting magrid coils with built in cooling issues, neutron shielding, or the risk they go normal.

'Virtual' magrids and, more generally, synergistic blends of promising, low-cost fusion concepts are intriguing.

We should start a new thread in Design or Theory to keep this going.

I'm now thinking 14 spheromaks generators and 14 e guns, one per corner and cube face. When the corner e guns fire the face spheromaks are generated, and then the machine switches to corner spheromaks and face e guns. The spheromaks deliver the ions to the machine core.

So... something like this?

http://www.researchgate.net/publication ... amaterials

It's "better", but not quite a "laser" like system. But still, shows that you can use two systems (one "generator", one "receiver") to concentrate a magnetic field at a distance. Still not like an infinite system, but shows that things can be manipulated in a way.

zapkitty wrote:You've reversed the polarity

The ion beam is what is expelled away from a DPF. The electron beam heads in the opposite direction and strikes the DPF anode.

And at plasma densities approaching breakeven the corresponding electron beam is not expected to make it out of the plasmoid... it will just expend itself further heating the plasma.

So no DPF electron guns.

The anode might be made hollow on the bottom. But the electrons being absorbed,or rather cooled from heating the dense pinched plasma puts a damper on extracting a hot dense electron beam. I wonder though, how much are the electrons cooled? Presumably they are not cooled not much below the average plasma temperature near the end of the pinch-it is a thermalized machine, I think. Then the more important question is what happens to the electrons, is there any direction beam component remaining? Could it be refocused to a tight beam? Assuming good burn up of the fuel plasma, the fusion ion beam exits the system, so the electrons have to go somewhere to prevent charge build up. Of course they could hit the anode walls, once the magnetic field containment has collapsed, but this may be a late occurrence. Is there a manipulation that could be performed to make the DPF a good, energy cheap electron gun? At first, reading the above quote seemed to dash that hope, but further speculation and hand waving might modify that.

Dan Tibbets

My thinking with using both Spheromaks and Fofu was you launch six plasmoids of the same magnetic polarity at the center then trap them inside of eight plasmoids from the corners with the opposite magnetic polarity. Gives you a FRC effect and a POPs effect combined with a torturous path for any electrons trying to escape the system. Keep the face and corner guns firing alternately and it keeps getting squeezed in the middle. The other way, with only Spheromaks maybe you get an additive effect to the magnetic fields. The other thing is the cooling is all on the plasmoid generators and wall doubling as heat exchanger, the generators get cooling time between firing with alternation. All the heat and pressure at R=0 has to go somewhere.