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Energy deposition is the transfer of energy from incident particles or radiation to a specified material region during a specified time. In a detector, it can produce ionization, excitation, scintillation or heat. The measured signal depends on how those channels are collected and calibrated.

An energetic charged particle may deposit only part of its energy while crossing a thin sensor. Secondary photons or particles can carry energy out of the sensitive volume, so incident energy and deposited energy need not coincide. Conversely, a sufficiently containing calorimeter aims to collect the full shower response. Separating energy deposition from readout response prevents an uncalibrated pulse height from being mistaken for a direct energy measurement.

Robert R. Wilson proposed using fast protons for radiation therapy by exploiting their depth-dependent energy deposition. A proton loses kinetic energy along its path and has enhanced stopping near the end of its range, producing a Bragg peak. His 1946 paper connected this measured interaction with a way to concentrate irradiation at a chosen depth. The physical idea links particle accelerator design, stopping power and spatial control of deposited energy.^[ref]

Physicist who proposed the use of fast protons for radiation therapy in 1946.^[ref]