The need for long-term energy sources, in particular for our highly
technological society, has become increasingly apparent during the last
decade. One of these sources, of tremendous poten- tial importance, is
controlled thermonuclear fusion. The goal of controlled thermonuclear
fusion research is to produce a high-temperature, completely ionized
plasma in which the nuclei of two hydrogen isotopes, deuterium and
tritium, undergo enough fusion reactions so that the nuclear energy
released by these fusion reactions can be transformed into heat and
electricity with an overall gain in energy. This requires average
kinetic energies for the nuclei of the order of 10 keV, corresponding to
temperatures of about 100 million degrees. Moreover, the plasma must
remain confined for a certain time interval, during which sufficient
energy must be produced to heat the plasma, overcome the energy losses
and supply heat to the power station. At present, two main approaches
are being investigated to achieve these objectives: magnetic confinement
and inertial con- finement. In magnetic confinement research, a
low-density plasma is heated by electric currents, assisted by
additional heating methods such as radio-frequency heating or neutral
beam injection, and the confinement is achieved by using various
magnetic field configurations. Examples of these are the plasmas
produced in stellarator and tokamak devices.