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# Fusion

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In physics, fusion is a process where two small nuclei join together to form a larger nucleus. This process occurs because the [binding energy]? per nucleon? of small nuclei such as 1H, 2H? and 3He is small compared to the binding energy per nucleon of the nuclei that they make when they fuse.

Because [nuclear energy levels]? are many orders of magnitude larger than [atomic energy levels]?the energy released is much larger than that for [chemical reactions]?. For example, the ionization energy of hydrogen is 13.6 eV, compare that number with the figures given later for hydrogen fussion.

Fusion powers the Sun and other stars?. The process is called the proton-proton cycle, [often shortened to p-p cycle] The first step involves the fusion of two hydrogen into Deuterium?

1H + 1H --> 2H + e+? + ν

This process releases 0.42MeV per event

The e+ immediately annihilates with one of the hydrogen's electrons and their mass energy is carried off by two gamma ray photons.

e+ +e- --> 2γ

This process releases 1.02 MeV? per event.

After this the deuterium produced in the first stage can fuse with another hydrogen to produce 3He

2H +1H --> 3He +γ

This stage produces 5.49 MeV? per event

Finally the 3He produced can fuse together to make 4He

3He +3He -->4He +1H +1H

This stage produces 12.86 MeV? per event

The whole cycle releases a net energy of 26.7 MeV? per cycle, and the sun processes { someone put the right number in here please} cycles every second.

Another way this happens is the CNO cycle in heavier stars.

The enormous power of fusion means that if were to succeed in creating a controlled fusion reactor? our energy problems would be solved. Unfortunately, success so far has been elusive.

/Talk

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Last edited August 15, 2001 5:40 pm (diff)
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