Fusion Reactions

Atomic nuclei have the potential for releasing huge amounts of energy. In the last 100 years, man has learned about this power and learned how to harness it. There are two types of nuclear reactions, fusion and fission. Fission was the first of the two discovered by man and involves large nuclei. Fission is the type of reaction that occurs in the core of the Sun and other stars and is also the nuclear reaction that man has not learned how to tame as yet. Even though these two reactions involve atomic nuclei, the fission and fusion could not be more different.

Since the late 1930's scientists, and then ultimately the world, discovered the power that the atom could unleash. Albert Einstein opened the floodgate for scientific research when he published his paper entitled "The General Theory of Relativity". In this paper, Einstein proved that matter could be converted into an enormous amount of energy. His formula E=mc², is among the world's most recognized mathematical formulas.

This process produces energy, mostly heat, when the nucleus is split. Others used Einstein's findings in a quest for the ultimate weapon. Fission is the principle behind the atomic bombs, which were dropped on Hiroshima and Nagasaki at the end of World War II. Fission is only possible with very large nuclei such as Uranium-235 and Plutonium-235. This is because the force that holds these nuclei together, the strong force, does not hold a nucleus together as strongly when a nucleus is large.

Fusion, which occurs in the core of the sun, is the opposite of fission. This process requires high temperature and density. This is quite true of the cores of stars where this process is commonly found. For example the theoretical temperature in the core of the sun is in the region of 18,000,000°F. At temperatures this high, the matter in the core of the sun is not matter as we know it. Matter in the core of the sun is composed of loose electrons and nuclei, known as plasma. With matter in plasma form, fusion is capable of occurring because the energy of collisions (due to heat) are above the minimum energy necessary to overcome the repulsion due to positive charge of the atomic nuclei. This minimum energy is called Coulomb's barrier.

Fusion requires two nuclei, of small size, and combines them into a nucleus of larger size. In the process, specifically with hydrogen conversion to helium, a small amount of the mass of one of the protons is converted to energy (~0.7%). The process looks like the following:

Yellow Ball	Proton
White Ball	Neutron
Green Ball	Electron
P	Proton
D	Deuterium, intermediate mass hydrogen with one proton and one neutron in the core
e ^-	Electron
e⁺	Positron, the mirror image of an electron, except with a positive charge
n	Neutrino, a chargeless particle that is nearly massless which is produced during fusion reactions. This particle can theoretically pass through hundreds of miles of lead without interacting with any of the nuclei
g	gamma ray, highly energetic photon on the far end of the electromagnetic spectrum beyond x-rays
³He	Helium deficient in one neutron. Also known as Helium-3. Means that the nucleus has one neutron and two protons
⁴He	Normal elemental Helium, two neutrons, two protons
⁶Be	Beryllium with atomic weight of 6 (4 protons and 2 Neutrons)

As a star ages other fusion reactions can take place to continue energy production. Fusion is a much more energetic process than fission due to the production of intense gamma radiation as well as heat. The gamma radiation given off from fusion is absorbed by the hydrogen, helium and other elements throughout the star and is converted to ultraviolet, x-rays and other forms of the electromagnetic spectrum.