Can you combine protium and tritium to produce Helium-4? I think they're a perfect match like a piece of puzzle since tritium just need another proton and electron to make a stable helium-4 atom. Also, protium is much more abundant than deuterium so wouldn't it make sense to use protium-tritium than deuterium-tritium for fusion?
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1The standard proton-tritium reaction is T(p,n)3He, which turns on above proton energies of about 1MeV. – Jon Custer Apr 30 '18 at 14:21
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Hi, I'm talking about Protium (1H), not proton – booger king Apr 30 '18 at 17:13
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1@boogerking, at nuclear energies, you really only need to worry about the nucleons like the proton. You can ignore the electrons, so there's no difference between protium and a lone proton. It would be ionized at the required temperatures. – BowlOfRed Apr 30 '18 at 17:30
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1The capture would be to an excited state in He-4, which would relax by emitting a proton or neutron. – rob Apr 30 '18 at 17:58
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The problem is that the proton and tritium nucleus have to be given a lot of kinetic energy to get them past their mutual electrostatic repulsion and into the region where the strong nuclear force can bind them together. But this energy has nowhere to go, so the newly formed helium nucleus has a energy in excess of its binding energy and it immediately falls apart again. The only way the newly formed helium nucleus can survive is if it manages to collide with another object in the few femtoseconds before it falls apart and shed its excess energy in the collision. Since this is wildly improbable, the proton-tritium fusion is hopelessly inefficient.
Fusion reactors use deuteron-tritium fusion because it forms a helium nucleus plus a free neutron, and the free neutron carries away the excess energy that would otherwise cause the helium nucleus to fall apart again.
John Rennie
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"The problem is that the proton and tritium..." It's Protium (1H) and Tritium (3H). – booger king Apr 30 '18 at 17:09
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3@boogerking if you want to make helium you have to fuse the protium nucleus with the tritium nucleus to create a helium nucleus. The protium nucleus is of course just a proton, which is why everyone is mentioning protons. – John Rennie Apr 30 '18 at 17:30
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Expanding on rob's comment in answer 1: the excited He4 would either decay immediately to He3 or back to the original constituents. In the latter case (the more likely of the two) the result would not yield any additional energy to the system. It would essentially be an elastic scatter between the P and the T thus a push, which is the main point in the second answer. In the former case you would get the He3 and a neutron to carry away the kinetic energy, but because the separation energy required to take the neutron from the He4 is greater than the energy produced from the fusion (Sn = 20.6 MeV and Qf = 19.8 MeV respectively), a loss of energy in the system would result.
hapstone
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