LOW ENERGY X-RAY MASS ATTENUATION COEFFICIENTS FOR RADIATION 850 TO 3000 eV IN SELECTED ELEMENTS WITH Z=6 TO Z=l8 By

The attenuation of X-rays with energies from 853 to 2991 ev by an Aluminum film, and C_H., N, 0«, Ne, and A gases has been measured using a beryl crystal monochromator..Experiment has led to the determination of mass attenuation coefficients with less than two percent probable error obtained by low kilovoltage operation of the X-ray tube and by flow propor-tional counter detection with pulse height discrimination. Some features of flow proportional counting using He-A-CH, gas are discussed. Also a comparison of this work with previous determinations of a few experimental values i