“…Fairly accurate tables of elemental mass attenuation coefficients have been available for some years now but unless the sample composition can be anticipated fully it is often more efficient to determine absorption data experimentally. One method is to measure the Compton scatter (83) which is usually linearly related to the mass attenuation coefficient. The same method has been employed by Van Dyck and Van Grieken (84) but with a little more sophistication, in that allowances have been made in the computer routine for differences between effects with high and low atomic number elements and for variations in thickness.…”