Mass attenuation Coefficients flat after 800 keV

[avagpingham]

I am interested in photon transport in the energy range from 20-3000 keV. I noticed that the mass attenuation coefficients cut off in accuracy around 800 keV. Is this a limitation of the https://www.nist.gov/pml/data/ffast/index.cfm database? Would it be possible to point to XCOM data?

[newville]

@avagpingham Yeah, the data included here is mostly "X-ray" data, and for that FFAST is approximately the best available data. That data goes up to 1 MeV. And it may lose reliability somewhere (not sure I know exactly where) above around 800 keV. For most folks working with X-rays as a probe (notably, synchrotron etc methods), going above 50 keV is helpful, but stopping at 500 keV seems pretty reasonable. The low-energy end is probably more problematic, with lots of different effects that make any tables like this (ie, that consider only "the element") less reliable.

All that said, supporting more datatsets, including XCOM (see also #31), and maybe others (EPDL?), could be useful.

I have not looked into any details of how to get the XCOM data or guidance for how to use/interpolate those datasets. Do you have any such information?