Measurement of the x-ray mass attenuation coefficient of copper using 8.85-20 keV synchrotron radiation - art. no. 062506

This work presents the x-ray extended range technique for measuring x-ray m ass attenuation coefficients. This technique includes the use of multiple f oil attenuators at each energy investigated, allowing independent tests of detector linearity and of the harmonic contributions to the monochromated s ynchrotron beam. Measurements over a wide energy range allow the uncertaint y of local foil thickness to be minimized by the calibration of thin sample measurements to those of thick samples. The use of an extended criterion f or sample thickness selection allows direct determination of dominant syste matics, with an improvement of accuracies compared to previous measurements by up to factors of 20. Resulting accuracies for attenuation coefficients of copper (8.84 to 20 keV) are 0.27-0.5%, with reproducibility of 0.02%. We also extract the imaginary component of the form factor from the data with the same accuracy. Results are compared to theoretical calculations near a nd away from the absorption edge. The accuracy challenges available theoret ical calculations, and observed discrepanicies of 10% between current theor y and experiments can now be addressed.