INGENIA
Index/Radiation physics/RAD-13

RAD-13

Rayleigh scatter sketch

σ_R ∝ Z² / E². Coherent scatter, no energy loss.

Reading speed
AttenuationRayleigh

Governing equation

σR∝Z2/E2\sigma_R\propto Z^2/E^2

E∈[1,150]E \in \left[1, 150\right]

where

Z
Atomic number (—)
E
Photon energy (keV)
\sigma_0
Prefactor (b)
\sigma_R
Rayleigh (b)

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.

RAD-13 · spectrum
00:0 / 00:08
①

Governing law — red

σR∝Z2/E2\sigma_R\propto Z^2/E^2

E∈[1,150]E \in \left[1, 150\right]

E=1E = 1σR=8\sigma_R = 8

②

Domain of the variable — blue

Emin⁡=1,Emax⁡=150E_{\min} = 1,\quad E_{\max} = 150

E∈[1,150]E \in \left[1, 150\right]

E=1E = 1E=1E = 1

③

Response curve — green

σR∝Z2/E2\sigma_R\propto Z^2/E^2

E∈[1,150]E \in \left[1, 150\right]

E=1E = 1σR=8\sigma_R = 8

④

Rate of change — amber

dσRdE\frac{\mathrm{d}\sigma_R}{\mathrm{d}E}

E∈[1,150]E \in \left[1, 150\right]

E=1.937E = 1.937σR′=−3.752\sigma_R^{\prime} = -3.752

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-13 — Rayleigh scatter sketch) is the form associated with Rayleigh. Working symbols: ZZ, EE, σ0\sigma_0 →\rightarrow σR\sigma_R. Forward-peaked. Important at low energy and high Z, never a dose channel of its own.

Purpose

Purpose: compute σR\sigma_R from ZZ, EE, σ0\sigma_0 in Radiation physics via σR∝Z2/E2\sigma_R\propto Z^2/E^2 σ_R ∝ Z² / E². Coherent scatter, no energy loss. 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 Z=20.000 —Z = 20.000\,\mathrm{—}, E=20.000 keVE = 20.000\,\mathrm{keV}, σ0=0.020 b\sigma_0 = 0.020\,\mathrm{b}, the governing relation σR∝Z2/E2\sigma_R\propto Z^2/E^2 yields σR=0.0200 b\sigma_R = 0.0200\,\mathrm{b}. A cloud of bound electrons, a gentle scatter. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Outputs

  • Rayleigh \sigma_R0.0200 b
Reading speed

Watch on YouTube

Free library

Full library

Free PDF / open book

YouTube channels

RAD-13 · spectrum
00:0 / 00:08

Narration of this film

A cloud of bound electrons, a gentle scatter.

Forward-peaked. Important at low energy and high Z, never a dose channel of its own.

Reading speed

Watch on YouTube