Energygain

Energygain is a term used in physics and engineering to describe the ratio of the energy delivered by a system to the energy supplied to it. Defined as G_E = E_out / E_in, it provides a simple measure of how much energy is obtained at the output for a given input. The definition depends on what counts as input energy and what counts as output energy, and is commonly used in energy conversion devices, amplifiers, and particle accelerators.

In electronics and photonics, energy gain describes amplification: an optical amplifier may produce output energy higher than input optical energy because electrical energy from a power supply is converted into optical energy. Passive components typically have a gain ≤ 1; active devices can exceed 1.

In particle accelerators, energy gain refers to the increase in beam energy due to RF cavities and magnets; measured as the difference in energy before and after a stage, often expressed in MeV per pass or per structure.

Relation to other metrics: Energy gain is distinct from efficiency, which is the fraction of input energy converted to desired useful work. It is closely related to power gain in the sense that energy gain over a time interval corresponds to the ratio of output energy to input energy during that interval. It is sometimes reported in decibels as 10 log10(G_E).

Notes: The term is general and may be used differently across fields; for precise communication, it is important to specify the energy definitions and conditions under which the gain is evaluated.