New Superconductor Found "Immune To Magnetism"

[vernes]

http://science.slashdot.org/article.pl? ... 03/1841253

[MSimon]

This has already been covered here.

Here is a better report:

http://www.eurekalert.org/pub_releases/ ... 052808.php

So far the hype is already running ahead of the facts. We only know that it super conducts in a 45 T field. That is not immune to magnetism. At least not yet.

If it could be used to generate fields in the 100 T range then the MaGrids might be able to deflect 2.7 MeV alphas. That would be a huge gain in terms of engineering. Heat load on the grids is one of the limiting factors in scaling up a BFR. Even a 90% deflection rate would allow immediate scaling to 1 GWth plant size.

CuO superconductors discussed:

http://www.physik.uni-augsburg.de/exp6/ ... ations.pdf

LHe LN2 prices:

http://hypertextbook.com/facts/2007/NadyaDillon.shtml

[jmc]

If you could generate fields of 100T with a super conductor you could generate fusion with any old magnetic confinement device, (mirrors, tokamaks spindle cusps etc., etc.)

[drmike]

I don't have my books with me, but I would think 100T field would be powerful enough to blow apart just about any physical structure. Pulsed fields in that range usually destroy the magnets - but maybe it is the pulsing that is the problem. You might be able to build up to that level slowly.

But the stresses would be huge.

[MSimon]

I think the Polywell at .3T generates about a ton of force per magnet.

X 300 = 100 Tons. Using 65,000 psi steel that is about 3 sq in. Not a big deal by itself. Bending moments are where the real forces come in.

[OneWayTraffic]

I think the Polywell at .3T generates about a ton of force per magnet.

X 300 = 100 Tons. Using 65,000 psi steel that is about 3 sq in. Not a big deal by itself. Bending moments are where the real forces come in.

Don't you mean 300 tons?

[MSimon]

I think the Polywell at .3T generates about a ton of force per magnet.

X 300 = 100 Tons. Using 65,000 psi steel that is about 3 sq in. Not a big deal by itself. Bending moments are where the real forces come in.

Don't you mean 300 tons?

Yeah. Still 10 sq in of steel is not a lot. Divide it among 4 supports with a safety factor and you are probably only at 5 sq in per support. The vacuum vessel will have to be seriously engineered with FEMA. Stiffeners where the vessel meets the supports. Doable.

[charliem]

I thought that, because the goal is to confine electrons, rather than ions or fusion products, the B-fields in the WB reactors wouldn't have to be as powerful as in magnetic confinement machines (WB-6 coils only gave 0.1-0.13 teslas, although it was only for experiment).

Am I wrong?

Is there any estimation about how strong will have to be the B-field in the 100MW prototype?

Isn't aiming to magnets in the tenths of tesla overkill?

[energyfan]

hmm..this be good news me thinks ...generating fusion with any magnatic confinement device

[tonybarry]

Hello Carlos,
Yes the magnetic field is there to contain electrons rather than ionic species (at least in the prototypes).

In general, the higher the field strength, the further away the MaGrid can be from the confinement region while still generating a wiffleball.

If the field gets up to a certain level, then it will begin to protect the MaGrid from alpha impacts as well.

I do not know the field strength required to obtain confinement, because we haven't actually gotten confinement yet (I class Dr. Bussard's work with WB-6 to be promising but far short of publishable data = and that is *not* a criticism of Dr. Bussard). Dr. Nebel may have this information ... or he may not. I think I can speak for everyone here when I say I am finding it difficult to wait.

Regards,
Tony Barry

[Keegan]

I don't have my books with me, but I would think 100T field would be powerful enough to blow apart just about any physical structure.

Im kinda thinking the same thing

I thought that, because the goal is to confine electrons, rather than ions or fusion products, the B-fields in the WB reactors wouldn't have to be as powerful as in magnetic confinement machines ......

..... Isn't aiming to magnets in the tenths of tesla overkill?

Yeah charliem you've got the right idea.

While its good news to hear that some species of super conductors are surprisingly immune to high magnetic fields, it really isn't going to help us too much

At the heart of the polywell is a virtual cathode, aka a potential well. The stability of which is dependant upon it being near the "Beta = 1" condition.

Beta = 1 is where magnetic pressure equals electron kinetic pressure. If you plan on increasing the strength of your magnetic field, it must be accompanied by in increase in electron kinetic pressure or else the potential well will become unstable.

So talking about high B fields, especially ones that could theoretically deflect alphas is nice, the electron hardware required to maintain Beta = 1 in B fields of 10-100 Tesla would seem to me, to be fantastically exotic, perhaps Unobtanium for some time yet.

[charliem]

Hello Carlos,
I do not know the field strength required to obtain confinement, because we haven't actually gotten confinement yet

There is one thing I dont get. No magnetic field can guarantee a 100% keep to loss ratio so, how is confinement defined?

Beta = 1 is where magnetic pressure equals electron kinetic pressure. If you plan on increasing the strength of your magnetic field, it must be accompanied by in increase in electron kinetic pressure or else the potential well will become unstable.

... the electron hardware required to maintain Beta = 1 in B fields of 10-100 Tesla would seem to me, to be fantastically exotic ...

Thank you Keegan. At first I thought that very high B-fields would be a waste, but now I see that it is not only that, but that has to be proportionated to the other components of the machine, or it simply wont work.

Again, any idea of the B-fields necessary for WB100?

[MSimon]

Keegan says:

Beta = 1 is where magnetic pressure equals electron kinetic pressure. If you plan on increasing the strength of your magnetic field, it must be accompanied by in increase in electron kinetic pressure or else the potential well will become unstable.

You just raise the density to raise the electron pressure. The reactor gets smaller.

You deflect the alphas the cooling load gets smaller.

[charliem]

Yep Simon, wouldnt it be nice to reduce the minimum size of a net energy producer Polywell?

But I still see a problem (although I'm most probably mistaken).

As you said, if you augment B you have to raise the electron density too, ok, but that means increasing the E field also, so we'd end up with higher energy electrons and higher energy ions.

Higher energy electrons is "just" a question of engineering , but higher energy ions could be a problem if the E-field well gets over 226 kV deep, where the maximum cross-section for the p-11B reaction is (about 550 keV according to my data), isn't it?

And how about more exotic reactions at energies that high?

So the B-field cannot be raised at will without some adverse side effects.

P.D. If I'm making a fool of myself dont be too hard on me please, I'm learning.

[MSimon]

Yep Simon, wouldnt it be nice to reduce the minimum size of a net energy producer Polywell? :D

But I still see a problem (although I'm most probably mistaken).

As you said, if you augment B you have to raise the electron density too, ok, but that means increasing the E field also, so we'd end up with higher energy electrons and higher energy ions.

What actually happens is the density gets higher in the core. The e-field can stay the same.

In fact that was one of the things that Dr. Nebel got excited about around here. A calculated 62,000 times increase in density vs ITER with 10 T magnets. ITER is using 20 T magnets. Potentially a properly magnetized reactor could be 40X smaller for the same power out. Dr. Nebel said that POPS would be like an afterburner once we got up into that range. Also 10 T coils will deflect some ions that are close to the edge of the grids. That will reduce the heat load some. It will also deflect some ions to the edge of the grids where the cooling is better.