How can I use the NIST XCOM online tool to calculate X and Gamma shielding?

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Discussion Overview

The discussion revolves around the use of the NIST XCOM online tool for calculating X and Gamma radiation shielding, specifically focusing on the mathematical modeling of scattering and attenuation in materials like lead. Participants explore the application of the tool in a practical example involving gamma rays and lead thickness.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant describes using the NIST XCOM tool to obtain scattering data for lead and calculates the scattering length based on the mass attenuation coefficient and density.
  • Another participant suggests a straightforward multiplication to derive scattering per length, indicating a potential simplification in the calculations.
  • A participant requests verification of their edited equation, indicating a collaborative effort to ensure accuracy in the calculations.
  • One participant points out that the term "scattering length" is misleading and clarifies that the value obtained is actually a total mass attenuation coefficient, which includes various interaction processes.
  • A later reply provides a LaTeX representation of the equation for clarity, emphasizing the importance of proper notation in scientific communication.
  • Participants discuss the use of different units in the equations, noting the preference for cgs units in the context of the XCOM tool.

Areas of Agreement / Disagreement

Participants generally agree on the mathematical approach to calculating shielding but express differing views on terminology and the representation of the equations. The discussion remains unresolved regarding the best practices for notation and the implications of using specific terms.

Contextual Notes

There are limitations regarding the clarity of terms used in the equations, as well as the dependence on specific units (cgs vs SI) which may affect the interpretation of results.

Javier Lopez
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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
 
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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?
 
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)
 

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Javier Lopez said:
the equation should be less strange in latex (I do not know how if possible here)
Just surround it by ##[/color] for inline formulas and $[/color]$ for full-size formulas.
$$\frac{1}{4.2\cdot 10^{-2} \frac{cm^2}{g}}$$
 
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Done, we are doing good job