RAD-05

KERMA

K = Ψ (μ_tr / ρ). Kinetic energy released per unit mass.

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DosimetryKERMA

Governing equation

K=\Psi(\mu_{tr}/\rho)

where

\Psi: Energy fluence (J/m²)
\mu_{tr}/\rho: Mass energy transfer (cm²/g)
K: KERMA (mGy)

Lecture brief

Historical brief

Beer attenuation, Compton (1923), Klein–Nishina, Bragg–Gray cavity and KERMA are the transport of photons and charged particles in matter. The sheets compute fluence, kerma and stopping. This sheet (RAD-05 — KERMA) is the form associated with KERMA. Working symbols: $\Psi$ , $\mu_{tr}/\rho$ $\rightarrow$ $K$ . Under charged-particle equilibrium D ≈ K (1−g). Air kerma is the calibration quantity.

Purpose

Purpose: compute

K

from

\Psi

\mu_{tr}/\rho

in Radiation physics via

K=\Psi(\mu_{tr}/\rho)

K = Ψ (μ_tr / ρ). Kinetic energy released per unit mass. Use it when a real radiation physics question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

\Psi = 0.050\,\mathrm{J/m^{2}}

\mu_{tr}/\rho = 0.030\,\mathrm{cm^{2}/g}

, the governing relation

K=\Psi(\mu_{tr}/\rho)

yields

K = 0.150\,\mathrm{mGy}

. A fluence, a transfer coefficient, a kerma. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Energy fluence \Psi0.05 J/m²Mass energy transfer \mu_{tr}/\rho0.03 cm²/g

Outputs

KERMA K0.150 mGy

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Narration of this film

A fluence, a transfer coefficient, a kerma.

Under charged-particle equilibrium D ≈ K (1−g). Air kerma is the calibration quantity.

Reading speed

Watch on YouTube