Nuclear Fusion

A second method for creating controlled nuclear fusion makes use of a laser beam or a beam of electrons or atoms. In this approach, hydrogen isotopes are suspended at the middle of the machine in tiny hollow glass spheres known as microballoons. The microballoons are then bombarded by the laser, electron, or atomic beam and caused to implode. During implosion, enough energy is produced to initiate fusion among the hydrogen isotopes within the pellet. The plasma thus produced is then confined and controlled by means of the external beam.

The production of useful nuclear fusion energy by either of these methods depends on three factors: temperature, containment time, and energy release. That is, it is first necessary to raise the temperature of the fuel (the hydrogen isotopes) to a temperature of about 100 million degrees. Then, it is necessary to keep the fuel suspended at that temperature long enough for fusion to begin. Finally, some method must be found for tapping off the energy produced by fusion.

A measure of the success of a machine in producing useful fusion energy is known as the Lawson confinement parameter, the product of the density of particles in the plasma and the time the particles are confined. That is, in order for controlled fusion to occur, particles in the plasma must be brought close together and they must be kept together for some critical period of time. All of this must take place, of course, at a temperature at which fusion can occur.