You are also affected by US financial shut down (NIST XCOM is off);

so please see also:

https://www.researchgate.net/post/X_ray_mass_attenuation_coefficients

For energies up to 30keV you may use the link given by Mohammad Nazmabadi there.

You may also have a look at the old tables at the following links:

https://apps.dtic.mil/dtic/tr/fulltext/u2/a278139.pdf

https://www.govinfo.gov/content/pkg/GOVPUB-C13-d79ab365252ddc7cff96dd333b3e2277/pdf/GOVPUB-C13-d79ab365252ddc7cff96dd333b3e2277.pdf

Good luck

Hi Gerhard

I am most grateful for your help. Thank you so much.

Please take a look at the http://henke.lbl.gov/optical_constants/

Thank you Mohammad

Hi Gilnaz.

I think it may be useful for you. :)

https://archive.org/details/tablesofxraymass5632hubb/page/30