Improvement study on heat resistance of multilayer-coated replica gratings

We have been developing aperiodic W/B₄C multilayer-coated replica gratings for use in the tender X-ray range 2 to 4 keV. It has become apparent that surface degradation was caused by heating multilayer gratings at around 60°C; the multilayer structure has been well maintained, whereas the grating grooves formed in epoxy resin of the replica grating were significantly deformed. Such degradation has not been observed in conventional gold-coated replica gratings as far as we know. In this study, replica gratings made with a high glass transition temperature resin were prototyped to improve the heat resistance of multilayer-coated replica gratings. Diffraction efficiencies of multilayer gratings with and without heat treatment at approximately 95°C for 60 hours were measured and compared. The fact that the change rate between the peak values is slight, being less than 3%, indicates that the heat resistance has been improved.