Two Important Fusion Reactions
D + T => He4 + n
For first generation fusion reactors
The "D-T" reaction has the highest reaction rate at the plasma temperatures
which are currently achievable; it also has a very high energy release.
These properties make it the easiest reaction to use in a man-made fusion reactor.
As the figure shows, the products of this reaction include an alpha particle
(Helium4 nucleus) with 3.5 MeV energy, and a neutron with 14.1 MeV energy.
The neutron escapes from the plasma (it has no charge and is not confined)
and can be trapped in a surrounding "blanket" structure, where the
n + Li6 => He4 + T reaction can be used to "convert" the neutrons back
into tritium fuel.
Notes:
- 1 eV = 1.6022x10-19 joules;
- Average particle thermal kinetic energy is 1 eV per 11,600 K.
"P-P": Solar Fusion Chain
Known as the proton-proton chain, the reaction process depicted above is
the dominant fusion mechanism in light stars, including our sun.
(In heavier stars, a more complicated process known as the carbon cycle
predominates.)
In the P-P chain, two pairs of protons fuse, forming two deuterons.
Each deuteron fuses with an additional proton to form helium3.
The two helium3 nuclei which
then fuse to create beryllium6, which is unstable and disintegrates into
two protons plus a helium4 (alpha particle). In addition, the process
releases two neutrinos, two positrons, and gamma rays. The positrons
annihilate quickly with electrons in the plasma, releasing additional energy
in the form of gamma rays. The neutrinos interact so weakly that they
fly right out of the sun immediately.
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Robert F. Heeter.
Page originally assembled by Jason Edson and Hannah Cohen.
Last Revised 10-Oct-97 by Robert
F. Heeter
Fusion in the Sun
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