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Author Topic: Is proton-proton fusion feasible?  (Read 2339 times)

Offline jaiii

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Is proton-proton fusion feasible?
« on: 18/08/2015 10:12:41 »
Hi.

It is possible in proton proton fusion
replace the temperature of a magnetic field frequency of about 1 GHz plasmi and increases the density of an increasing voltage from 1kV voltage of 1 GV?

Thank.
« Last Edit: 24/08/2015 11:51:19 by chris »


 

Offline evan_au

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Re: Temperature of fuzion instead microwave.
« Reply #1 on: 19/08/2015 16:09:01 »
Proton-proton fusion is not an expected route to hydrogen fusion on Earth (it does occur to a useful extent in stars larger than the Sun). On Earth, mixtures of Deuterium and Tritium are thought to be most useful in commercial fusion.

The Lawson criterion identifies the conditions under  which hydrogen fusion could reach the "break-even point: exceed a threshold value of the "triple product" of density, confinement time, and plasma temperature.

The Lawson criterion does not identify how to reach this threshold, and many techniques have been tried in the lab; one active direction of research is being studied in the JET project: magnetic confinement.

If the magnetic field can be made significantly stronger, this allows higher pressures, favouring fusion.

If the magnetic field can induce high currents in the plasma, that can increase the temperature. Other techniques like microwave radiation and neutral atom injection can also help increase the temperature.

Quote from: jaii
increasing voltage from 1kV voltage of 1 GV?
I assume that the reference to kV & GV refer to plasma heating?
- Note that 1 GV is extremely high voltage that is very hard to manage - it will cause breakdown in air for distances of 1 km, which is why we can't produce steady voltages in this range.
- If nuclear physicists want to reach energies of GeV, they tend to let charged particles "surf" on more manageable, lower-amplitude electromagnetic waves, which accelerates the particles more slowly, but with a more manageable field strength.
- Plasma is very conductive, and even a 1kV voltage induced in the plasma can produce high currents in the plasma.
- So I don't really understand how you were proposing to apply the kV or GV.
 

Offline jaiii

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Re: Temperature of fuzion instead microwave.
« Reply #2 on: 20/08/2015 19:37:53 »
But if the Lorentz force added for about 1E20 N.
A frequency magnetcikého field 1E10 Hz would help to further reduce the requirements for fusion PP or CNO?

I would need it as a source of energy for spacecraft.
« Last Edit: 20/08/2015 19:41:00 by jaiii »
 

Offline PmbPhy

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Re: Temperature of fuzion instead microwave.
« Reply #3 on: 24/08/2015 18:37:00 »
Quote from: jaiii
It is possible in proton proton fusion
replace the temperature of a magnetic field frequency of about 1 GHz plasmi and increases the density of an increasing voltage from 1kV voltage of 1 GV?
If you're asking whether its possible to fuse two hydrogen atoms together to form one helium atom then the answer is yes. But you writing style is confusing. You left out the period so its hard to tell if "replace the temperature..." is the start of a new sentence or part of the old one. If its the start of a new sentence then you should put a period at the end of the last sentence and capitalize the first letter of the first word in the new sentence. Otherwise it can be confusing.

In any case there's no such thing as the temperature of a magnetic field nor is it meaningful to speak of the density of voltage.

Quote from: evan_au
Proton-proton fusion is not an expected route to hydrogen fusion on Earth...
While true its not what the OP asked. Unsolicited advice: I recommend answering the OPs question first and then post the useful tidbits after that's been done. Just my humble opinion.

In this case it appears to me that the OP wants to know if two protons can be fused together, presumably creating a stable nuclei in the process.
 

Offline evan_au

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Re: Is proton-proton fusion feasible?
« Reply #4 on: 28/08/2015 15:04:18 »
Quote from: PmbPhy
the OP wants to know if two protons can be fused together, presumably creating a stable nuclei in the process
The answer to this question is "yes" - but it doesn't create the Helium with which we are familiar on Earth.

Fusion of 2 protons to produce a Helium nucleus with 2 protons (2He) takes a very high temperature. This nucleus is fairly stable (comparable to Uranium), but its formation releases a relatively small amount of energy.

To release a larger amount of energy (such as for a space rocket engine), you need to fuse 4 protons into 2 protons & 2 neutrons (4He=an Alpha particle), which is the nucleus of the familiar Helium atom. This occurs through the decay of 2He into 2H=Deuterium, which is the rate-limiting step, with a half-life of a billion years or so.

This is why the most feasible route to fusion starts with Deuterium, and avoids this rate-limiting step.

See https://en.wikipedia.org/wiki/Proton%E2%80%93proton_chain_reaction#The_pp_chain_reaction
 

Offline UltimateTheory

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Re: Is proton-proton fusion feasible?
« Reply #5 on: 28/08/2015 15:42:54 »
Fusion of 2 protons to produce a Helium nucleus with 2 protons (2He) takes a very high temperature. This nucleus is fairly stable (comparable to Uranium), but its formation releases a relatively small amount of energy.

What?! Where did you get such idea?
Helium-2 is extremely unstable
https://en.wikipedia.org/wiki/Isotopes_of_helium
(some source said half-life 3×10−27 s)

To release a larger amount of energy (such as for a space rocket engine), you need to fuse 4 protons into 2 protons & 2 neutrons (4He=an Alpha particle), which is the nucleus of the familiar Helium atom. This occurs through the decay of 2He into 2H=Deuterium, which is the rate-limiting step, with a half-life of a billion years or so.

Proper reaction is:
p+ + p+ -> D+ + e+ + Ve + 0.42 MeV
then
p+ + D+ -> He-3 + y + 5.494 MeV
we need to repeat it once again to have two.
then
He-3 + He-3 -> He-4 + p+ + p+ + 12.856 MeV

Half-life of He-2 has nothing to do with rate.

Probability of hitting two He-3 together to form one He-4 in cloud of protons is very small.
Star has initial content ~75% of H-1, and ~25% of He-4, by mass. Which is 12:1 ratio per mole.
Once concentration of Helium-3 increases with time, probability is growing.

Additionally fusion energies 5.49 MeV and 12.856 MeV are way too high for some other Deuterium around, and it can be disintegrated:
D+ + 2.22 MeV -> p+ + n0
 

Offline evan_au

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Re: Is proton-proton fusion feasible?
« Reply #6 on: 30/08/2015 03:55:00 »
Oops! I was rather surprised that 2He would be stable, as I thought at least 1 neutron would be needed to overcome the strong electrostatic repulsion of the two protons. (...and if it were as stable as Uranium, you would expect to find some of it on Earth...)

I misread the following statement:
Quote from: Wikipedia
the beta-plus decay of the diproton to deuterium is extremely rare (the vast majority of the time, the diproton decays back into hydrogen-1 through proton emission). The half-life of a proton in the core of the Sun before it is involved in a successful p-p fusion is estimated to be a billion years, even at the extreme density and temperatures found there.

« Last Edit: 30/08/2015 03:57:02 by evan_au »
 

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Re: Is proton-proton fusion feasible?
« Reply #6 on: 30/08/2015 03:55:00 »

 

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