Low-voltage power from a p-B11 fusion alpha storage ring?

Discuss the technical details of an "open source" community-driven design of a polywell reactor.

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DeltaV
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Low-voltage power from a p-B11 fusion alpha storage ring?

Post by DeltaV »

Here's another dumb question from a non particle/plasma physicist.

Imagine a truncated-cube Polywell with sufficient B-field intensity that the p-B11 fusion product alphas exit mostly along the magrid coil axes. Further imagine curved, magnetic and/or electrostatic beam guiding tubes (design details ignored here) that channel the alphas into a toroidal alpha-storage ring surrounding the magrid (design details again ignored). For a first pass, let's assume the guide tubes have flared ends at the alpha inlets, as the alpha "beams" will want to expand after they pass the magrid coils. Four of the curved guide tubes would have the same arc length. The remaining two, originating from the magrid top and bottom coils, would be longer. The guide tubes are assumed to intersect the storage ring tangentially at six equally-spaced points. The travel time through the two longer guides would be greater, which hopefully doesn't matter after steady-state operation is reached.

Question --
Could the alphas circulating in the storage ring be used to produce low-voltage electrical power with a reasonable efficiency?

MSimon
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Post by MSimon »

The alpha beams are not going to be monoenergetic. The rage will be from about 100 KeV to 6,000 KeV. This is fundamental and can't be fixed except by an energy separator (design TBD).
Engineering is the art of making what you want from what you can get at a profit.

DeltaV
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Post by DeltaV »

Even dumber than I'd suspected. I'm batting 1000 today. BP and Horizon Deepwater Unified Command just rejected my cast-in-place concrete seabed compressor and valve mount idea.

DeltaV
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Post by DeltaV »

Since I'm on a roll, and have no professional standing to lose...

Could an intense, multi-energetic alpha particle plume be (mostly) constrained by closely-spaced bulk HTS tiles via diamagnetic exclusion of the B field arising from a moving charge?

viewtopic.php?t=2401

If so, make both the curved guides and the toroidal storage ring out of these tiles. Whatever power takeoff scheme is used would be embedded at one or more locations around the toroid.

Unless there's no advantage to lumping all the alphas together, in which case it would be one HTS "funnel" per magrid coil.

BenTC
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Post by BenTC »

DeltaV wrote:Could an intense, multi-energetic alpha particle plume be (mostly) constrained by closely-spaced bulk HTS tiles via diamagnetic exclusion of the B field arising from a moving charge?
Or just make a fusor grid out of HTS?
In theory there is no difference between theory and practice, but in practice there is.

D Tibbets
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Post by D Tibbets »

I sounds like what you want is a torus storage ring for the alphas. In that regard a Polywell could be serving as a source for alpha particle heating of a Tokamak. Something Tokamaks are susposed to do insitu, once they reach ignition. Then you need a diverter to extract the alphas, which will be a great challange from an engeenering standpoint if Tokamaks ever reach that stage. You are elimiating the direct conversion advantages in the Polywell for the difficult and lower efficiency thermal conversion of a Tokamak type system. You would be much better to just let the alphas hit and heat the wall, and worry about the vacuum pumping issues.

Of course the diverter in a Tokamak is suposed to remove the alphas while retaining the fuel ions. If the torus is just a temperary storage device that is then used to direct the alphas into a direct conversion port, it would make more sense. But the complexity would presumably be much more than just directly converting the beams coming out of the cusps.
There is mention of using electrostatic ports to aid vacuum pumping. It would seem that this would be attractive for the final stage of a direct conversion array.

Dan Tibbets
To error is human... and I'm very human.

DeltaV
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Post by DeltaV »

D Tibbets wrote:I sounds like what you want is a torus storage ring for the alphas.
Only if there is some advantage for direct + down conversion mass. I doubt there is.
D Tibbets wrote:If the torus is just a temperary storage device that is then used to direct the alphas into a direct conversion port, it would make more sense.
Yes, port or whatever. But it probably makes more sense to do things on a per-magrid-coil basis and skip the storage ring.

Per-coil or otherwise, seems like bulk HTS tiles/shapes might have some sort of utility in guiding alphas, but it depends on whether the diamagnetic repulsion can overcome the momentum of the alphas, sufficiently to deflect their path away from the HTS. The alpha particle's magnetic self-field goes up with v, so the trend is right, but the repulsion magnitude might not suffice.

More on bulk HTS:
viewtopic.php?t=2401

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