Spin enhanced fuels?

[evaitl]

Maybe I've missed it, but I haven't seen a discussion here of spin
enhanced fuels.

A reference: http://tinyurl.com/ykv4uw2

My reading of this is that there are two important points:

1) p-B11 fusion cross sections are enhanced by about 60% due to
spin and a bit more by the quadrupole moment of the B11 ion.

2) The spin of the ions randomizes slow enough that the ions will
retain the enhanced reaction rates throughout their lifetimes in
the plasma.

My question is how to add spin. It seems from
wiki ( http://en.wikipedia.org/wiki/Nuclear_magnetic_resonance )
that we would need to apply a new magnet and an RF emitter to the
end stage of the ion injectors.

Assuming Dr. Rider is wrong, I've read somewhere or other a
calculation showing a 150MW IEC reactor would require about 15MW for
the ion injectors and magnets. Can we actually improve overall efficiency
by close to 60% by doing the spin polarization? By that, I mean the
injector/magnet power would be reduced to around 8MW (3MW magnets
unchanged, 12MW injectors reduced to 5MW).

Anybody have an idea how much energy would be needed to set the spins
in the ion streams?

[chrismb]

I think this has come up before, as I seem to think I gave the following answer: The improvement to be gained if you can line up each and every proton into the most optimum 'position' relative to the boron-11 is about two. So if you find yourself in the position where you've got a reactor at Q=1.5 to Q=3 (and presuming you need a Q=3 minimum) then it might make a difference. Otherwise, it's just blah-dee-blah chin-wagging. I'd say, get to a 1.5<Q<3 reactor first and if that's the best you can do then maybe it's important. Otherwise, don't waste your time thinking about it.

[Aero]

So if you find yourself in the position where you've got a reactor at Q=1.5 to Q=3 (and presuming you need a Q=3 minimum) then it might make a difference. Otherwise, it's just blah-dee-blah chin-wagging.

I don't know that I'd agree with that. I think it really depends on where you find yourself when its time for the next contract. It really would be good if we had some sort of trustworthy computer model, but we don't. What would you propose if you were sitting at a Q < ~1.0 from the experiment but you knew of 4 things you could tweak from results of a model?

Tweak 1 indicated 10%, 2 indicated 25%, 3 > 50% and then the spin polarization tweak seems to be 100% improvement. (I have no idea what tweaks 1,2 and 3 are.) You see, any one of the 4 Tweaks will give you break even and you'd do all four if money was not an issue. But that is what evaitl's question is getting at. Does anyone know what it would take to "set the spins in the ion streams?"

You certainly wouldn't bid it without an estimate of it's cost and Rick might just go ahead and do it if it were really, really cheap and simple.

[DeltaV]

Anybody have an idea how much energy would be needed to set the spins
in the ion streams?

I haven't read this yet (it relates to FRCs, not Polywell), but maybe it might assist in answering your question:

http://depts.washington.edu/rppl/papers ... S_2002.pdf

[Art Carlson]

In low-beta confinement schemes, like the much-maligned tokamak, spins can be aligned either parallel to the magnetic field or perpendicular to it, and they tend to stay that way. I'm not sure you can maintain spin alignment in a device like the polywell that hardly has any magnetic field in the interior.

[evaitl]

In low-beta confinement schemes, like the much-maligned tokamak, spins can be aligned either parallel to the magnetic field or perpendicular to it, and they tend to stay that way. I'm not sure you can maintain spin alignment in a device like the polywell that hardly has any magnetic field in the interior.

I'm having trouble digesting that statement along with some statements in the article. The article seems to say that depolarization rates are faster in the tokamaks because of the magnetic fields:

One might think that the intense electromagnetic fields would cause rapid depolarization. This turns out to be invalid. ...This is particularly true for FRCs, unlike depolarization rates of triton nuclei in tokamaks which can be fast comparied to fusion rates.

Could you clarify?

[chrismb]

I rather think it is largely irrelevant. It applies to p 11B and even if you could globally hold 11B 'in prime attitude', the next question is how do you get the protons to go in the same direction in relation to that polarisation. A Polywell is clearly not the technology to do such a thing with, you need some sort of reactor scheme which is at most two, if not one, dimensional.

[evaitl]

I rather think it is largely irrelevant. It applies to p 11B and even if you could globally hold 11B 'in prime attitude', the next question is how do you get the protons to go in the same direction in relation to that polarisation. A Polywell is clearly not the technology to do such a thing with, you need some sort of reactor scheme which is at most two, if not one, dimensional.

I think I disagree with that. The internal spin of the ions is not the same as the external motion of the ions. If the spins are matched between p and 11B, it may enhance the fusion cross section regardless of the collision angle (relative to the spin axis).

Fusion cross section due to quadrapole moment will probably be preferentially enhanced depending on collision angle, but we are taking that as a side effect of the spin enhancement.

I don't think that the polywell is up to the point where it can wave off a potential 60% or more fusion reaction rate increase without somebody sitting down and doing the analysis.

[Betruger]

much-maligned tokamak

The what now?

[evaitl]

much-maligned tokamak

The what now?

Certainly a fair statement around here, isn't it?

http://www.askmar.com/ConferenceNotes/S ... uclear.pdf

Some people speculate that the Russians “gave” us tokamaks, to make sure that we never achieved practical fusion!
...
One of the top fusion researchers, Dr. Nicholas Krall said, “We have spent 15B studying tokamaks, and all we know about them is that they’re no darn good! How ever, while they may never be economical, they are really good science!” To date, the United States has spent 18B chasing tokamak designs with no end in sight. There are estimates that 30B will be spent on this research over the next 15 to 20 years.

From what I've seen, the ITER folks don't even claim to anymore to be shooting for aneutronic fusion. With just D-T, I'm not sure what the advantage is of fusion over a thorium reactor.

[Betruger]

I don't think you can seriously say that a project like the Tokamak is, overall, more maligned than pretty much any other fusion project. If only budget-wise.
It just struck me as very funny.

[Art Carlson]

much-maligned tokamak

The what now?

I take my pot-shots where I can get them. I don't get many chances.

But I'm already at the end of my knowledge, some of which may be wrong. It's interesting physics, but not interesting for fusion until a device gets in the right ball park, and even then a lot could go wrong. p-B11 is so bad, I just concede the factor of 1.6 and go on.

[Betruger]

[kunkmiester]

Lining up the spin in a BFR would be statistics, wouldn't it? You'd do some studies to see how the spin survives as it runs through, and you'd tweak your injector to give the spins most likely to get the most particles lined up properly. I can't imagine you'd mess with getting 100% spin rates, even if you had a way to control the spin well into the reactor.

Next thing is to split that 60% according to your statistics on spin line-up, and see if it's still worth it.