**Mass Attenuation Coefficient **

Tables and graphs of the mass attenuation coefficients at photon energies from 1 keV to 20 MeV for all of the elements *Z* = 1 to 92, and for compounds and mixtures of radiological interest are available at the National Institute for Standards and Technology website.

**Converting a Mass Attenuation Coefficient to a Linear Attenuation Coefficient**

Since a linear attenuation coefficient (m) is dependent on the density of a material, the mass attenuation coefficient is often reported for convenience. The mass attenuation coefficient is simply the linear attenuation coefficient divided by the material density. This action will produce a value that is constant for a particular element or compound.

To convert a mass attenuation coefficient (m/r) to a linear attenuation coefficient (m), simply multiply it by the density (r) of the material.

For more information on mass and linear attenuation coefficients see the material in the NDT on-line section.