In a fusion reaction, nuclei of low atomic weight, such as hydrogen, fuse and thereby form nuclei of higher atomic weight, such as helium. When this occurs, some of the mass of the original nuclei are lost and transformed to energy in the form of high-energy particles. To begin the process, thermonuclear fuel (deuterium and tritium) must be heated to temperatures in excess of tens of millions of degrees centigrade. This heating causes the nuclei to fuse on impact. At such temperatures, it is difficult to contain the fuel long enough to allow efficient thermonuclear burning. Owing to their large masses, stars can contain their high-temperature fusion reactions by tremendous gravitational fields. Unfortunately, that effect cannot be created in the laboratory.
But researchers are getting closer. Progress in the field has come about through two general approaches to confine the fuel and thereby demonstrate controlled fusion reactions: magnetic confinement and ...
