MEASUREMENT OF MASS ATTENUATION COEFFICIENTS OF MODERATE-TO-HIGH ATOMIC-NUMBER ELEMENTS AT LOW PHOTON ENERGIES

Mass attenuation coefficients for 12 selected moderate-to-high atomic- number elements have been obtained from good-geometry measurements mad e at five Am-241 photon energies of significant emission intensity. Pa rticular interest focuses on measured values for photon energies close to absorption edges. Comparisons with renormalized cross-section pred ictions indicate agreement to within stated error limits for the major ity of cases. Significant discrepancies (> 10%) are noted for Ta at 17 .8 and 26.3 keV and W at 59.5 keV. Some support for a discrepancy betw een measurement and theory for W in the region of 60 keV is found in t he reported measurements of others.