Editing Fusion power (section)

=== Lawson criterion ===
The [[Lawson criterion]] considers the energy balance between the energy produced in fusion reactions to the energy being lost to the environment. In order to generate usable energy, a system would have to produce more energy than it loses. Lawson assumed an [[First law of thermodynamics|energy balance]], shown below.<ref name="Lawson"/>

:<math>P_\text{out} = \eta_\text{capture}\left(P_\text{fusion} - P_\text{conduction} - P_\text{radiation}\right)</math>
where:
* <math>P_\text{out}</math> is the net power from fusion
* <math>\eta_\text{capture}</math> is the efficiency of capturing the output of the fusion
* <math>P_\text{fusion}</math> is the rate of energy generated by the fusion reactions
* <math>P_\text{conduction}</math> is the conduction losses as energetic mass leaves the plasma
* <math>P_\text{radiation}</math> is the radiation losses as energy leaves as light and neutron flux.

The rate of fusion, and thus P<sub>fusion</sub>, depends on the temperature and density of the plasma. The plasma loses energy through [[Thermal conduction|conduction]] and [[radiation]].<ref name="Lawson"/> Conduction occurs when [[ion]]s, [[electron]]s, or [[neutral particle|neutrals]] impact other substances, typically a surface of the device, and transfer a portion of their kinetic energy to the other atoms. The rate of conduction is also based on the temperature and density. Radiation is energy that leaves the cloud as light. Radiation also increases with temperature as well as the mass of the ions. Fusion power systems must operate in a region where the rate of fusion is higher than the losses.