Editing Fusor (section)

===Underlying physics===
Fusion takes place when [[Atomic nucleus|nuclei]] approach to a distance where the [[nuclear force]] can pull them together into a single larger nucleus. Opposing this close approach are the positive charges in the nuclei, which force them apart due to the [[electrostatic force]]. In order to produce fusion events, the nuclei must have initial energy great enough to allow them to overcome this [[Coulomb barrier]]. As the nuclear force is increased with the number of nucleons, protons and neutrons, and the electromagnetic force is increased with the number of protons only, the easiest atoms to fuse are [[isotope]]s of hydrogen, [[deuterium]] with one neutron, and [[tritium]] with two. With hydrogen fuels, about 3 to 10&nbsp;keV is needed to allow the reaction to take place.<ref name=overcome>{{cite web | url = http://hyperphysics.phy-astr.gsu.edu/hbase/NucEne/coubar.html |title= Coulomb Barrier for Fusion |website=Hyperphysics}}</ref>

Traditional approaches to [[fusion power]] have generally attempted to heat the fuel to temperatures where the [[Maxwell-Boltzmann distribution]] of their resulting energies is high enough that some of the particles in the long tail have the required energy.<ref name=overcome/> High enough in this case is such that the rate of the fusion reactions produces enough energy to offset energy losses to the environment and thus heat the surrounding fuel to the same temperatures and produce a self-sustaining reaction known as ''ignition''. Calculations show this takes place at about 50&nbsp;million&nbsp;[[kelvin]] (K), although higher numbers on the order of 100&nbsp;million&nbsp;K are desirable in practical machines. Due to the extremely high temperatures, fusion reactions are also referred to as ''thermo''nuclear.

When atoms are heated to temperatures corresponding to thousands of degrees, the electrons become increasingly free of their nucleus. This leads to a gas-like state of matter known as a [[plasma (physics)|plasma]], consisting of free nuclei known as ions, and their former electrons. As a plasma consists of free-moving charges, it can be controlled using magnetic and electrical fields. Fusion devices use this capability to retain the fuel at millions of degrees.