Attenuation of 5.9-keV Photons by Helium and Hydrogen

Abstract
The narrow‐beam mass‐attenuation coefficients of helium and hydrogen were measured at 5.895 keV. A Kβ‐filtered 55Fe source of Mn x rays, a set of collimators, and a low‐energy sodium iodide counter were used with a high‐pressure gas chamber. Photon intensities were measured with and without gas in the chamber. The measured coefficients are 0.416±0.017 cm2/g for He and 0.400±0.016 cm2/g for H2. These numbers are compared with theoretical predictions of this parameter.