controlled fusion not possible ?

[Widdekind]

Positively-charged nucleons resist fusion, according to the EM force. Logically, to compress plasma, with EM force-fields, seems impossible -- the charged particles repel each other, at nanoscopic range; but they would be compressed, with EM force-field-generating equipment, at macroscopic distances away. Since EM force-fields decay with distance, a fusion reactor would have to generate enormous fields, macroscopically, to over-come the particles' repulsion, at "point-blank" nanoscopic ranges.

 

Gravity in stars can over-come EM, b/c gravity is cumulative -- w/ enough mass, even the Strong Nuclear Force can be over-come, in relativistically compact objects.

 

But, fighting EM (at nanoscopic range), with EM (at macroscopic distances away, w/ some experimental apparatus), seems futile.

 

Perhaps EM-controlled "tokamak" fusion reactors, are intrinsically impossible (and tax-payers will never see return, on any investment) ?

[mathematic]

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

 

If you look at the above link, you will see that fusion has been accomplished in these reactors. The main question is to get to the point where they can get more energy out than they put in.

[Enthalpy]

In any tokamak, laser, magnetized target, striction fusion, it's heat that supplies the energy to overcome electrostatic repulsion, and not the macroscopic EM field. Heat is reasonable, because nuclei hit or near-hit an other many times, so the energy invested in their speed has some chances to make a fusion and be useful. In contrast, accelerating nuclei to collide them once or a few times by bombardment would give a probability of fusion far too low.

 

The macroscopic magnetic field in a Tokamak only serves to keep the plasma together so the invested heat really serves. To do so, the macroscopic field can act on the nuclei over a macroscopic distance: it's the energy that counts, not the force, giving the advantage to the bigger scale.

 

Widdekind, you underestimate other people once again. Sakharov was not a moron, you know. Tokamaks may have other drawbacks, like the radioactive pollution resulting from neutron multiplication needed to breed tritium, but they do fuse nuclei. And by the way, so does any fusor, built by amateurs using easy fields

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

 

What do you mean by "overcome strong nuclear force"? The strong force uses to be attractive, at least at the time scale of a thermal collision. And what is a "relativistically compact object"?

[Widdekind]

fusor's seem potentially amazing. Perhaps you could inject a certain quantity of fuel, quickly, and then ramp up the voltage, on the outer grid, to "wall off" the positively-charged plasma within the "fusion kettle" of the fusor? And, perhaps the inner grid could be built, intended to absorb all of that fuel. So, you'd inject a known quantity of fuel, which would translate into a known energy, which would be absorbed into the inner grid. After several minutes, when the fusions finished, the inner grid could be removed, and similar to a hot "cooking rock" plunged into some water to make steam. Or, perhaps the inner grid could be made of hollow fibers, carrying water through them, to whisk away the heat absorbed by bombarding ions.

 

 

otherwise, i only meant, that gravity can ultimately become stronger (in magnitude) than even the strong force, in BHs & NSs. Even in NSs, gravity crunches matter down into nuclear densities, showing that the magnitude of the force of gravity is comparable to the SF, in such objects.

 

In any tokamak, laser, magnetized target, striction fusion, it's heat that supplies the energy to overcome electrostatic repulsion, and not the macroscopic EM field. Heat is reasonable, because nuclei hit or near-hit an other many times, so the energy invested in their speed has some chances to make a fusion and be useful. In contrast, accelerating nuclei to collide them once or a few times by bombardment would give a probability of fusion far too low.

 

The macroscopic magnetic field in a Tokamak only serves to keep the plasma together so the invested heat really serves. To do so, the macroscopic field can act on the nuclei over a macroscopic distance: it's the energy that counts, not the force, giving the advantage to the bigger scale.

 

Widdekind, you underestimate other people once again. Sakharov was not a moron, you know. Tokamaks may have other drawbacks, like the radioactive pollution resulting from neutron multiplication needed to breed tritium, but they do fuse nuclei. And by the way, so does any fusor, built by amateurs using easy fields

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

 

What do you mean by "overcome strong nuclear force"? The strong force uses to be attractive, at least at the time scale of a thermal collision. And what is a "relativistically compact object"?

Edited June 28, 2013 by Widdekind

[Enthalpy]

It's the weak interaction that transforms electrons and protons into neutrons to make a neutron star, whose density results from the density of neutrons. Gravitation doesn't achieve this density; it only makes the electron absorption more probable than the electron emission.

[Widdekind]

??

 

Gravity compacts matter, to nuclear densities, in NS; and to some next-more-exotic state, in BH. Thus, the "cumulative" nature of gravity => that enough mass can exert forces, comparable to forces exerted in Strong (& Weak) nuclear interactions. That's all i was saying. (Yes, i understand, the Weak force converts electrons into neutrinos, and protons into neutrons (u quark -> d quark), during "neutronization" of matter. That is correct. And, "neutronization" only naturally occurs, in compact objects, because gravity supplies the forces / energies to "incentivize" the reaction. Gravity is cumulative; given enough matter, gravity can in principle be the strongest force of all.)

 

EM forces decrease with distance, away from what-so-ever generates those forces. So, even if you generate a "strong" EM field, from some apparatus "here"; then that field will be weak "there". So, trying to generate magnetic fields, from the walls of a tokamak, to squeeze plasma well away from those walls, seems impossible in principle. Even if you could generate some EM field, which was strong enough, within the generating apparatus, to overcome ion-ion repulsion, and induce fusion within the material of the apparatus itself; the field would be too weak to do so, outside of & far from the same.

 

But, the "fusor" could perhaps benefit, from what i'm (trying to) say. Why couldn't you not only charge the central grid, to -80KV (say); but also run current thru the wires, to generate magnetic fields, which would repel the plasma, keeping the plasma away from the grid material?

 

If magnetic fields can serve as shielding, for space stations / space craft vs. plasma in solar wind / CRs / ISM / IGM, then they could do so, for the fusor's central grid, which is immersed in plasma. in my swift scanning of the wikipedia article, the same seemed to differentiate the "fusor" from magnetic-confinement methods, implying magnetic fields are not used, although not explicitly saying so. You could create a spherical grid, composed of (say) triangular sections of wire -- 'twould look like a geodesic dome -- each section of which was a current loop, producing a solenoidal field, funneling plasma thru the middle, away from the wires. By alternating the sense of circulation of current, in adjacent loops -- like a checkerboard in pattern -- you could create a geodesic-dome-ish grid, of a checkerboard-like patchwork of "left-handed" & "right-handed" current loops, producing magnetic fields alternately going "in" & "out" of the sphere, such that all the currents w/in the wires would add, and none would wind up canceling out the currents of adjacent sections.

[Enthalpy]

Gravity compacts matter, to nuclear densities, in NS.

No. The weak interaction does.

[Widdekind]

No. The weak interaction does.

not w/o gravity

 

the Strong interaction fuses He in stars... not w/o gravity (ultimately) providing the pressure / temperature

 

 

-------------------

 

how would a fusion furnace "catch" the energy released? Our's sun's central temperature ~1KeV; the gamma-ray photons released are ~MeV, x1000 greater. The ratio of protons to helium-nuclei in the sun's center is (a little less than) 14:1. So, after a gamma-ray photon is generated, probabilities imply, that the photon will "rattle around through, amongst, off" of numerous other protons, dispersing its energy amongst them, until they all equilibrate to ~1KeV. Of course, if the first thing the gamma-ray photon collided into, was another helium-nucleus, then the latter would be un-fused by the former, absorbing the gamma-ray and splitting back into pieces / parts. Since, however, the sun's center is only "tainted / doped" with helium, such inverse-fusions are surely rather rare.

 

In an artificial energy-by-fusion-generator, what would diffuse & disperse the gamma-ray photons, from fusions, into lower frequencies / longer wavelengths? All the sun's plasma, surrounding its center, acts as a natural frequency converter, reducing photon energies, down to more manageable levels. In a lab version, what would absorb the energy? Would some sort of lead-like lining have nuclei, with tightly-bound electrons, with ~MeV binding energies / resonances ? The binding-energy, of the lowest-lying 1S orbitals, scales as Z squared; so for elements near A=100 (e.g. Pb, U), that would be about 1MeV.

[Enthalpy]

Why shouldn't you read a bit about tokamaks? ITER's site for instance provides much explanations, Wiki as well.

 

Fusion creates little gamma, certainly nothing capable of splitting a helium nucleus.

Absorbing them by technological means is no big worry. It's done every day.

Heavy elements have their 1s shells 100keV deep, not 1MeV.

[...] So, trying to generate magnetic fields, from the walls of a tokamak, to squeeze plasma well away from those walls, seems impossible in principle.

Or maybe the old Andrei had on this occasion a reasoning even more accurate than yours? Who knows?

Edited July 4, 2013 by Enthalpy

[Widdekind]

Why shouldn't you read a bit about tokamaks? ITER's site for instance provides much explanations, Wiki as well.

 

Fusion creates little gamma, certainly nothing capable of splitting a helium nucleus.

Absorbing them by technological means is no big worry. It's done every day.

Heavy elements have their 1s shells 100keV deep, not 1MeV.

Or maybe the old Andrei had on this occasion a reasoning even more accurate than yours? Who knows?

1) has any tokamak worked ?

 

2) fusion is reversible... if protons fuse into helium, emitting gamma-rays... then those gamma-rays could split apart helium, into constituent proton pieces parts... yes ?

[Enthalpy]

1) has any tokamak worked ?

Yes. They fuse D-T to helium for years. Why shouldn't you read before posting?

2) fusion is reversible... if protons fuse into helium, emitting gamma-rays...

No. Humans fuse D and T to ⁴He and n in tokamaks. The energy leaves as neutron speed mainly.

 

Again, why not read a little minimum? Wiki, you know.

[Widdekind]

Yes. They fuse D-T to helium for years. Why shouldn't you read before posting?

No. Humans fuse D and T to ⁴He and n in tokamaks. The energy leaves as neutron speed mainly.

 

Again, why not read a little minimum? Wiki, you know.

 

what tokamak has broken even ?

 

so, D-T reactions do not emit gamma rays, all the energy is released, as KE, of the He-4 and of the free space neutron ?

 

i guess only astrophysical "natural" fusion often generates gamma-rays

 

how do you capture that kinetic energy ?

[howlingmadpanda]

If you are trying to imply that controlled fusion is not possible you might want to have a chat with Taylor Wilson (A kid who built a fusion reactor), heat is used to overcome EM repulsion. To get energy out of a fusion reactor one would need an area (Possibly a lithium blanket) to absorb the heat energy from the neutron radiation being produced.

[Widdekind]

so, if the number of massive particles is conserved, e.g. D+T ----> n + He, then no other particles (photons, neutrinos) need be emitted ?

[Enthalpy]

No photon emitted by some radioactive decays for instance.

Electron neutrinos appear each time a protons and neutrons transform in an other. None at alpha emission for instance.

 

Lithium blankets are necessary (but not enough!) to recreate the tritium used by the reactor and unavailable on Earth. For other purposes, and material would fit.

 

Breeding tritium is a huge weak point of tokamaks. Maybe this will be possible, maybe not (adios tokamaks then), and I claim this step would be as polluting as a uranium reactor (hence abandon fusion, I say).