RAD-25

Air kerma from exposure

K_air = X (W/e) / (1−g). Exposure converted with 33.97 J/C.

Reading speed

DosimetryAir kerma

Governing equation

K_{\mathrm{air}}=X\,(W/e)/(1-g)

$X \in \left[0.001, 50\right]$

where

X: Exposure (R)
W/e: W/e (J/C)
g: Radiative fraction (—)
K_{air}: Air kerma (mGy)

The figure, part by part

Each numbered marker wears the color of its card. Hover a card to light the marker. Tap a marker to jump to that card. The slider walks a red point along the curve; Animate drawing traces it like a pen.

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①

Governing law — red

K_{\mathrm{air}}=X\,(W/e)/(1-g)

$X \in \left[0.001, 50\right]$

$X = 0.001$ $K_{air} = 0.009$

Along the curve

②

Domain of the variable — blue

X_{\min} = 0.001,\quad X_{\max} = 50

$X \in \left[0.001, 50\right]$

$X = 0.001$ $X = 0.001$

Along the curve

③

Response curve — green

K_{\mathrm{air}}=X\,(W/e)/(1-g)

$X \in \left[0.001, 50\right]$

$X = 0.001$ $K_{air} = 0.009$

Along the curve

④

Rate of change — amber

\frac{\mathrm{d}K_{air}}{\mathrm{d}X}

$X \in \left[0.001, 50\right]$

$X = 0.315$ $K_{air}^{\prime} = 8.773$

Along the curve

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-25 — Air kerma from exposure) is the form associated with Air kerma. Working symbols: $X$ , $W/e$ , $g$ $\rightarrow$ $K_{air}$ . The modern calibration chain. 1 R corresponds to about 8.8 mGy of air kerma.

Purpose

Purpose: compute

K_{air}

from

X

W/e

g

in Radiation physics via

K_{\mathrm{air}}=X\,(W/e)/(1-g)

K_air = X (W/e) / (1−g). Exposure converted with 33.97 J/C. 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

X = 1.000\,\mathrm{R}

W/e = 33.970\,\mathrm{J/C}

g = 0.001\,\mathrm{—}

, the governing relation

K_{\mathrm{air}}=X\,(W/e)/(1-g)

yields

K_{air} = 8.773\,\mathrm{mGy}

. An ion chamber reading, an air-kerma value. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Exposure X1 RW/e W/e33.97 J/CRadiative fraction g0.001 —

Outputs

Air kerma K_{air}8.773 mGy

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Narration of this film

An ion chamber reading, an air-kerma value.

The modern calibration chain. 1 R corresponds to about 8.8 mGy of air kerma.

Reading speed

Watch on YouTube