Fusion

Fusion reactions are inhibited by the electrical repulsive force that acts between two positively charged nuclei. For fusion to occur, the two nuclei must approach each other at high speed to overcome the electrical repulsion and attain a sufficiently small separation (less than one-trillionth of a centimeter) that the short-range strong nuclear force dominates. For the production of useful amounts of energy, a large number of nuclei must under go fusion: that is to say, …

…by its own gravity. It is not possible to assemble on Earth a plasma sufficiently massive to be gravitationally confined. The hydrogen bomb is an example of fusion reactions produced in an uncontrolled, unconfined manner in which the energy density is so high that the energy release is explosive. By contrast, the use of fusion for peaceful energy generating requires control and confinement of a plasma at high temperature and is often called controlled thermonucl