Mo-overcoated grating-based beam intensity monitor for 13.9 nm x-ray laser

For the purpose of developing a high-efficiency beam intensity monitor with a diffraction grating for a 13.9 nm Ni-like Ag X-ray laser (XRL), a molybdenum thin film was overcoated on a gold-coated holographic grating. The performance was examined by measurements of absolute diffraction efficiencies with synchrotron radiation, and the improvement effect by Mo-overcoating was confirmed. In addition, it became clear that a high correlation was obtained between the intensities of the zeroth and first order diffracted lights of the Mo grating measured with the XRL. To validate the practicality of this beam intensity monitor, the polarization state of the XRL beam of the zeroth order diffracted light delivered from the Mo grating was determined quantitatively by using rotating-analyzer ellipsometry with a Mo/Si multilayer polarizer.