Microscopic calculations of heavy-ion fusion reactions

Article By:

Umar, A. Sait Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee.

Oberacker, Volker E. Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee.

Last reviewed:2012

DOI:https://doi.org/10.1036/1097-8542.YB120405

Nuclear fusion refers to the process in which two atomic nuclei combine to form a single larger nucleus. The two fundamental forces that determine the probability of nuclear fusion are the electrostatic Coulomb force and the strong nuclear force. The Coulomb force acts only between protons; it has a long range and is repulsive. On the other hand, the strong nuclear force acts between any combination of protons and neutrons; it has a short range (about 1.4 × 10⁻¹⁵ m) and is attractive. The fusion process is hindered by the Coulomb repulsion between the protons of the two colliding nuclei. To overcome this repulsive force, one must supply kinetic energy to bring the nuclei into close contact. Only when the nuclear surfaces are almost touching does the attractive strong nuclear force set in and cause the nuclei to “snap together,” that is, to fuse. Thermonuclear fusion occurs naturally in the interior of stars. As explained by Hans Bethe in 1938, the Sun produces the energy it radiates by burning hydrogen into helium nuclei. In this case, the kinetic energy of the hydrogen nuclei is supplied by a conversion of gravitational stellar energy into thermal energy. The source of the energy released in the fusion of light nuclei is the difference between the nuclear binding energies of the reaction partners. Significant progress has been made in recent years to achieve controlled thermonuclear fusion in a fusion reactor. In the magnetic confinement method, a plasma confined in a magnetic “bottle” is heated to very high temperature, and in the inertial confinement approach the initial kinetic energy is supplied by powerful laser beams. Another frontier is the production of new superheavy elements in heavy-ion fusion reactions, in particular around the predicted “island of stability” with proton numbers Z = 114, 120, and 126, and neutron number N = 184.

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