# X & G Photon scattering

• I
In order to calculate X and Gamma shielding of I should like use the NIST XCOM online at https://physics.nist.gov/PhysRefData/Xcom/html/xcom1.html
In the Xcom tool it is obtained a graph and table of scattering in cm2/g.

In order to calculate as example the shielding from 1e19 gamma rays of 4MeV using 10cm of lead.
Using the tool I obtained a scattering of 4.2e-2 cm2/g and the density of Pb solid is 11.34 g/cc
I suppose scattering length= 1/(4.2e-2 cm2/g * 11.34 g/cc)=21cm
Then the remainder rays should be: N=N0*exp(- lead thick/scattering length)=6.2e18 so 62% of generated radiation passes through lead

Last edited:

mfb
Mentor
Just multiply the two to get scattering per length.

sorry, I edited while you wrote :( , staff mentor, could you or somebody else check the equation as I edited?

mfb
Mentor
Looks good.

Javier,
your equation is good but the terms you used are Strange. 4.2e-2 cm2/g is not a "scattering length" but a total mass attenuation coefficient (due to Scattering, Photoelectric Absorption, Pair Production).

Hello PSR1919121, you are right, the equation should be less strange in latex (I do not know how if possible here):
$$\lambda =\frac{1}{4.2*10^{-2}*\frac{cm^2}{g}*11.34\frac{g}{cm^3}}=21cm$$

Then I write the formula here:
$$N=N_0*e^{-\frac{thick}{\lambda }}=N_0*e^{-thick*SC*\rho}$$
SC is the scattering parameter (cm2/g) and rho is the density (g/cm3), thick is in cm
(It could be used SI using kg and metres instead of g and cm but unfortunately SC is written in cgs)

#### Attachments

• e7nxoz.jpg
10.7 KB · Views: 380
3.7 KB · Views: 341
Last edited:
mfb
Mentor
the equation should be less strange in latex (I do not know how if possible here)
Just surround it by ## for inline formulas and $$for full-size formulas.$$\frac{1}{4.2\cdot 10^{-2} \frac{cm^2}{g}}

Javier Lopez
Done, we are doing good job