Modeling with Scattering (2D)

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ID:(1155, 0)



Compton Scattering

Definition

Compton scattering occurs when a photon interacts with a charged particle, in particular with an electron. In the process the photon loses energy and deviates by putting the electron in motion:

ID:(9176, 0)



Scattering

Image

Scattering that contributes (in) or describes the abandonment of particles (out) can be plotted as follows:

It should be noted that the term collision:

- integrates on all external speeds to those of volume

- includes the likelihood of both speeds leading to scattering simultaneously

- the relative velocity multiplied by the total effective section represents the flow of particles towards the target

The latter can be shown in a simple way through

\Delta v\sigma\sim\displaystyle\frac{dX}{dt}S\sim \displaystyle\frac{dV}{dt}\sim J

ID:(9177, 0)



Simulador random walk with Compton scattering

Note

The Klein-Nishina model can be studied in numerical form. This is shown

- the total effective section as a function of photon energy

- the differential section as a function of the angle for the minimum, medium and maximum energies defined

- what would be the total effective section in a one-dimensional system that gives according to the energy transmission or reflection

ID:(9114, 0)



Modeling with Scattering (2D)

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Examples

Compton scattering occurs when a photon interacts with an electron by transferring the first energy to the second (inelastic interaction). The wavelength of the photon after the scattering can be calculated by

$\lambda_2=\lambda+\lambda_c(1-\cos\theta)$



where

$\lambda_c=\displaystyle\frac{h}{m_ec}$

Compton wave length and \theta the angle of deviation of the photon is.

(ID 9145)

Compton scattering occurs when a photon interacts with a charged particle, in particular with an electron. In the process the photon loses energy and deviates by putting the electron in motion:

(ID 9176)

In the case of Compton scattering, the differential effective section is according to Klein-Nishina

$\displaystyle\frac{d\sigma_{KN}}{d\Omega}=\displaystyle\frac{3}{16\pi}\displaystyle\frac{\sigma_T}{(1+\epsilon(1-\cos\theta))^2}\left(\epsilon(1-cos\theta)+\displaystyle\frac{1}{1+\epsilon(1-\cos\theta)}-\cos^2\theta\right)$



where

$\sigma_T=\displaystyle\frac{8\pi}{3}r_0^2$



is the Thomson total effective section and the

$\epsilon=\displaystyle\frac{E}{m_ec^2}$

is the normalized energy.

(ID 9144)

The Compton wavelength is defined by

$\lambda_c=\displaystyle\frac{h}{m_ec}$

where h is the Planck constant, m_e mass of the electron and c the speed of light.

(ID 9146)

Scattering that contributes (in) or describes the abandonment of particles (out) can be plotted as follows:

It should be noted that the term collision:

- integrates on all external speeds to those of volume

- includes the likelihood of both speeds leading to scattering simultaneously

- the relative velocity multiplied by the total effective section represents the flow of particles towards the target

The latter can be shown in a simple way through

\Delta v\sigma\sim\displaystyle\frac{dX}{dt}S\sim \displaystyle\frac{dV}{dt}\sim J

(ID 9177)

The solid angle is defined by

$d\Omega=2\pi \sin\theta d\theta$

(ID 9147)

If the differential effective section is taken according to Klein-Nishina

$\displaystyle\frac{d\sigma_{KN}}{d\Omega}=\displaystyle\frac{3}{16\pi}\displaystyle\frac{\sigma_T}{(1+\epsilon(1-\cos\theta))^2}\left(\epsilon(1-cos\theta)+\displaystyle\frac{1}{1+\epsilon(1-\cos\theta)}-\cos^2\theta\right)$



and integrates in the solid angle

$d\Omega=2\pi \sin\theta d\theta$



the total effective section is obtained

$\sigma_{KN}=\displaystyle\frac{3}{4}\sigma_T\left(\displaystyle\frac{(1+\epsilon)}{\epsilon^3}\left(\displaystyle\frac{2\epsilon(1+\epsilon)}{1+2\epsilon}-\log(1+2\epsilon)\right)+\displaystyle\frac{\log(1+2\epsilon)}{2\epsilon}-\displaystyle\frac{(1+3\epsilon)}{(1+2\epsilon)^2}\right)$



where

$\sigma_T=\displaystyle\frac{8\pi}{3}r_0^2$



is the effective section of Thomson and the

$\epsilon=\displaystyle\frac{E}{m_ec^2}$

is the normalized energy.

At the limit of small \epsilon\ll1 we have that the total section is

\sigma_{KN}\sim\sigma_T\left(1-2\epsilon+\displaystyle\frac{26}{5}\epsilon^2\ldots\right)

and in the limit \epsilon\gg 1 the total effective section is

\sigma_{KN}\sim\displaystyle\frac{3}{8}\displaystyle\frac{\sigma_T}{\epsilon}\left(\log(2\epsilon)+\displaystyle\frac{1}{2}\right)

(ID 9111)

The total effective section of Thomson is equal to 2/3 of the surface of a sphere of radius r_0

$\sigma_T=\displaystyle\frac{8\pi}{3}r_0^2$

The radius r_0 corresponds to the classical radius of the electron which is defined as e^2/m_ec ^ 2.

(ID 9112)

To simplify we introduce the initial energy of the photon E, normalized by m_ec^2

$\epsilon=\displaystyle\frac{E}{m_ec^2}$

where m_e is the mass of the electron and c the speed of light.

(ID 9113)

The Klein-Nishina model can be studied in numerical form. This is shown

- the total effective section as a function of photon energy

- the differential section as a function of the angle for the minimum, medium and maximum energies defined

- what would be the total effective section in a one-dimensional system that gives according to the energy transmission or reflection

(ID 9114)


ID:(1155, 0)