why not positrons

Discuss how polywell fusion works; share theoretical questions and answers.

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wacker.popeln
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Joined: Fri Apr 06, 2012 5:38 pm

why not positrons

Postby wacker.popeln » Tue Dec 18, 2012 1:11 am

Hey people

how would a positron confinement system work?

Magnetic fields grab them too
the forces would accelerate anything towards center even stronger
and kill anything in the center like that

so it would be an antimatter polywell grilling any proton you send in wiht a few positrons.

the only benefit of the confinement would be that in the center that attracts the protons would be nothing
it would be an xraying machine though if positrons fall apart.


is there any theoretical limit to this ?:

this would be a form of cold fusion through antimatter reactions. right?

in theory

GIThruster
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Joined: Tue May 25, 2010 8:17 pm

Postby GIThruster » Tue Dec 18, 2012 1:50 am

http://en.wikipedia.org/wiki/Penning_trap

IIRC, there is some cutting edge work happening with Penning Traps at Penn State. Search "ICAN II".
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

KitemanSA
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Joined: Sun Sep 28, 2008 3:05 pm
Location: OlyPen WA

Postby KitemanSA » Tue Dec 18, 2012 2:15 am

Can you give a positron enough energy to overcome Coulomb repulsion? With a proton, you can give enough that its momentum will get you close enough for the strong force to tunnel thru. But a positron without that much mass and no strong force attraction?

And by the way, the well would be a tower. Doesn't make sense to me.

GIThruster
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Joined: Tue May 25, 2010 8:17 pm

Postby GIThruster » Tue Dec 18, 2012 2:34 am

The trouble is making positrons is a very expensive endeavor. I htink you'd spend all your Q.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

happyjack27
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Postby happyjack27 » Tue Dec 18, 2012 2:55 pm

also electrons will probably annihilate all the positrons in short order, making high energy photons. there is absolutely no repulsive force between electrons and positrons and a very strong attractive force, and they'll have opposite orbits around the mag field. so how do you keep electrons out of the plasma? how do you keep them from bleeding off of the coils, or off of the vacumm chamber?

and the energy from the photons is not an efficient power source. it'd be more easy to convert if it stayed as electrons and positrons. and if all you're doing for energy is making photons, than what's the polywell for? electrons and positrons will do that on their own - no need for confinement. but even then you're still getting less energy out than you put in.

oh, and the positrons are _repelling_ the protons. only thing they'd attract are electrons (which care way more about the magnetic field, anyways) and anti-protons (which if you have, why use positrons instead of plain old protons to attract them? protons are much cheaper and have way more mass = way more energy released)

D Tibbets
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Postby D Tibbets » Wed Dec 19, 2012 5:49 pm

Several clarifications...

First, positrons (anti electrons) are the reverse of what is tried to promote fusion. The key is to decrease the Coulomb barrier by shielding the positively charged protons from each other till they approach close enough for the short range Strong Force to become dominate over the repulsive Electromagnetic Force. Positively charged positrons would only make the matter worse. You need something negatively charged to have a benefit. Electrons may help some(?) but due to quantum mechanical issues, Pauli exclusion principle, etc. the effect is minimal. Heavier particles with a negative charge helps because they can get closer to the protons before being Excluded from closer approach. Muons are better, and anti protons are even better yet (provided they do not annihilate to quickly). The following assumes you were thinking of anti protons, not positrons...

Electrons and anti protons repel each other, but that is pretty much insignificant for this discussion. Also, electrons and anti protons do not annihilate, that only occurs between protons and anti protons (or positrons and electrons). What is more important is that protons and anti protons attract each other since they have opposite charges. If they meet, they annihilate each other with the release of 100% of the bound energy. This is ~ 100 times more than the puny fusion reactions. As mentioned though, the cost of producing the anti proton is expensive. Considering the inefficiencies in an accelerator, it will always cost more energy to produce the positron - proton pair than is contained in the rest mass of the particles. Note that anti protons are always produced in a pair with a proton in an accelerator, so the energy balance at 100% accelerator efficiencies is zero, but accelerator efficiencies may be only 0.1% efficient. Also, note that this may not apply to some forms of radioactive decay that produces anti protons(?). This might serve as a useful store (battery) for anti protons, but remember that the parent isotope has to be mined/ produced at some energy cost. I've not seen any discussion about if such an anti proton source might be useful for a space ship application.

There have been proposals to use anti protons to promote a fusion reaction. Provided the anti proton promotes (essentially catalyzes) enough fusion reactions before it is consumed a net positive energy balance might be obtained. My understanding is that this is an extension of the Muon catalyzed fusion reaction idea. The negatively charged anti proton shields repelling protons till they get closer together, and thus the probabilities of a fusion reaction goes way up. The problems are producing anti protons in large numbers, and storing them . Penning traps can store a few anti protons for long times, but when the numbers increase the magnetic confinement goes to pot. It is the same problem of confining ions. Once the density increases enough, the plasma becomes collisional and then diffusion (ExB drift) through the magnetic field becomes significant. This is handled best (I believe) in Tokamaks, but they have to be huge in order for this drift to be relatively small enough that significant amounts of profitable fusion can occur. A Polywell type device that confines the ions/ anti protons electrostatically might store significantly higher densities of anti protons (once made), but for significantly shorter periods of time. Where the balance would work out is a question. It is conceptually easy to do anti proton catalyzed fusion with a few fusions per second. The problem comes when you try to scale this up to useful fusion rates of perhaps 10^15 fusions per second or more.

http://www.icarusinterstellar.org/wp-co ... ssions.pdf

http://proceedings.aip.org/resource/2/a ... horized=no

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


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