Non-Iridium X-Ray Coatings for Lynx and other Future Missions

The proposed research is directed at the development of new optical interference coatings having low film stress and high reflectance in the X-ray band from 0.1 to 10 keV, which are critically needed for the construction of lightweight, nested X-ray telescopes having high collecting area and sub-arcsecond resolution for Lynx, the high-energy flagship mission under consideration for the 2020 Astrophysics Decadal Survey, as well as for other future NASA X-ray missions. Iridium-based coatings provide high reflectance over the Lynx energy band, however such films also have exceedingly high stress, and film stress deforms thin-shell mirror substrates, thereby degrading telescope angular resolution. The proposed effort aims to develop low-stress, high-X-ray-reflectance optical interference coatings for Lynx, using in place of iridium (Ir) either platinum or tungsten layers, in combination with layers of various light elements. These non-Ir interference coatings have the potential for lower stress and higher reflectance than Ir coatings, thus enabling the realization of lightweight X-ray telescopes having high collecting area and sub-arcsecond angular resolution.