What is “hot” fusion (conventional, plasma fusion)?
Hot fusion is the kind of nuclear reaction that powers the Sun and the stars—it is also the reaction used in thermonuclear weapons (hydrogen bombs). At temperatures of tens to hundreds of millions of degrees Celsius (or Kelvin), the nuclei of hydrogen atoms can get close enough together, frequently enough, such that the nuclear force between some of the close-approaching nuclei has a chance to overcome the natural tendency of the positively charged nuclei to repel one another. The nuclei then join or fuse to form helium nuclei. This releases enormous energy. Fusion of light elements to form heavier elements (e.g. hydrogen fusing to helium) is the opposite of fission, which is the release of energy by splitting heavy uranium or plutonium nuclei.
