International developments in controlled thermonuclear fusion

Basic processes and fundamental technological requirements of controlled thermonuclear fusion have been widely discussed. Briefly, they include: heating an ultrapure, low-density deuterium and tritium plasma to superhigh temperatures; stably containing the extreme temperature plasma by magnetic fields for a duration adequate to fuse the nuclei; diminishing particle losses occurring through diffusion and instabilities to acceptable levels; gaining useful fusion products conveying energy sufficiently in excess of thermal and radiant energy losses; and, finally, converting the energy released to useful electric power. Recent progress has been encouraging. Numerous and diverse plasmas have been produced and improved understanding and experimental confirmation of stable magnetic containment have been obtained. Also, increased plasma density, temperature, and containment times in a few experimental systems have been achieved. However, complex difficulties, such as new types of instabilities, raise formidable barriers to a workable reactor concept.