The potential of controlled nuclear fusion

The potential of controlled nuclear fusion rests primarily on the nuclear energy in lithium and deuterium which can be exploited through the D.T. thermonuclear reaction. Potentially this is a very large source of energy, with indigenous resources in the U.K. and with environmental merits. Significant progress has been made in the achievement of the control of high temperature matter required to realize the potential. In toroidal pinches of the tokamak type, it is now routine to generate, sustain and control for times of up to a second, matter at temperatures of 10 MK. Temperatures - and particularly ion temperatures -can be raised by auxiliary heating, and have already approached 20 MK, less than a factor of three from ideal minimum ignition temperature. The energy confinement times tau have improved at near-reactor values of the number density n, so that values of ntau approaching 1013 cm-3s, a factor of ten from Lawson's criterion and already sufficient for energy production in special systems, have been obtained. These results have been achieved in apparatus of comparatively modest size - about 20 cm minor radius of the plasma ring. The studies of the engineering and technology needed to establish practical electricity generating systems based on magnetic confinement of a thermonuclear reacting plasma indicate formidable but not, apparently, insuperable problems which will require well-planned and large-scale technological developments. (author)