photon attenuation experiment

[cxh]

Hi, I'm using a software program called Maestro for an experiment on photon attenuation. We observed that different region of interets (ROI) gives different mass attenuation coefficients. Is there a way to determine the best ROI besides choosing it so that it's closest to the accepted coefficient?

[mormonator_rm]

Wish I could help you, but my knowledge in the field of particles passing through barriers and such is limited. I looked at some graphs and noticed that the attenuation lengths do change a great deal with the energy of the photons used and the density of the material (afterall, the coefficient is related to the density of the target). Looks like all the absorption lengths become fairly constant beyond 10 MeV, though, for their respective elements. The PDG has a couple links that show the experimental behavior of attenuation lengths for data between 30 eV to 100 GeV for all of the elements. Check out http://www-cxro.lbl.gov/optical_constants (Courtesy of LBNL; this is data from 30 eV to 1 keV) and http://physics.nist.gov/PhysRefData (Courtesy of NIST; this is data from 1 keV to 100 GeV). I hope this is helpful, although you may already have it.