This paper describes an experimental arrangement utilized at SSRL for obtaining high‐quality Fraunhofer diffraction spectra from a group of specially‐fabricated gold transmission gratings prepared at IBM. The data taken will ultimately be utilized to estimate the optical constants of gold in the 120 eV‐640 eV range, but in the present paper our focus is on the new advances achieved in the attained spectral quality of our measurements in this range and on the improvements that are plausible in future utilizations of the same experimental scheme.