Scientists have known for approximately seven decades that nuclear fusion reactions are a potentially important source of energy. A fusion reaction is one in which two small nuclei, such as protons or deuterons, combine with each other to form one large nucleus. In the fusion process, large amounts of energy are released.

The primary obstacle to achieving fusion is the fact that nuclei are all positively charged and, therefore, repel each other strongly. In order to overcome this force of repulsion, the nuclei must be given very large amounts of kinetic energy. In practical terms, that means heating the nuclei to temperatures in excess of 20,000,000K. Such conditions exist within stars, where fusion is the primary source of energy, but are unknown in any natural condition on the earth.

The first instance in which scientists were able to initiate fusion reactions artificially was the hydrogen (fusion) bomb. The...