Intro to Fusion

Fusion is the energy that powers the Sun and other stars.  It has been a goal of scientists around the world to harness this process by which the stars “burn” hydrogen into helium (i.e. nuclear fusion) for energy production on Earth since it was discovered in the 1940′s.

Though this has been challenging, significant progress has been made.  Many people feel the potential reward is well worth the time and effort to develop the science and technology.

Nuclear fusion is the process by which light nuclei fuse together to create a single, heavier nucleus and release energy.  Given the correct conditions (such as those found in plasma), nuclei of light elements can smash into each other with enough energy to undergo fusion.  When this occurs, the products of the fusion reaction have a smaller total mass than the total mass of the reactants.  The mass difference is converted to energy as determined by Einstein’s famous formula, E=mc2.  Here, m is the mass difference and c is the speed of light.  Even though the mass difference is very small, the speed of light is extremely large (about 670,000,000 miles per hour), so the amount of energy released is also very large.

The “easiest” (most energetically favorable) fusion reaction occurs between the hydrogen isotopes deuterium and tritium.  Hydrogen, deuterium, and tritium all have one electron and one proton, they only differ in the number of neutrons present in the nucleus.  These differences are demonstrated in the figure to the left.

When the nucleus of a deuterium atom crashes into the nucleus of a tritium atom with sufficient energy, a fusion reaction occurs and a huge amount of energy is released, 17.6 million electron volts to be exact.  To put this in terms of energy that we all experience, a single nuclear fusion reaction releases about 10,000,000 times as much energy as the combustion of gasoline.   The fusion reaction products are a neutron and a helium nucleus.  The huge amount of energy released during every fusion reaction makes it so attractive and is one of the reasons it has earned the nickname of the “holy grail” of energy sources.

When a deuterium and a tritium nucleus collide with enough energy they fuse together into a helium nucleus and release a neutron. A small amount of mass is converted into energy in this reaction.

Next: What is Plasma?

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