Kerma (physics)

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In radiation physics, kerma is an acronym for "kinetic energy released per unit mass" (alternately, "kinetic energy released in matter",^[1] "kinetic energy released in material",^[2] or "kinetic energy released in materials"^[3]), defined as the sum of the initial kinetic energies of all the charged particles liberated by uncharged ionizing radiation (i.e., indirectly ionizing radiation such as photons and neutrons) in a sample of matter, divided by the mass of the sample. It is defined by the quotient ${\displaystyle K=\operatorname {d} \!E_{\text{tr}}/\operatorname {d} \!m}$.^[4]