Efficiency measurements on gratings in the off-plane mount for ahigh-resolution grazing-incidence XUV monochromator

摘要

The design of a high-resolution monochromator for XUV radiation is presented. The configuration consists of an entrance slit, a paraboloidal mirror which collimates the XUV beam, a plane grating operated in the off-plane mount and illuminated by the parallel beam and a paraboloidal mirror which refocuses the beam on the exit slit. The off-plane geometry allows using the grating in grazing incidence and in high diffracted orders, resulting in broad-band XUV efficiency and high spectral resolution in a relatively compact environment. The wavelength selection is performed by rotating the grating around an axis passing through its center and parallel to the grooves, simplifying the mechanical movements. Spectral resolution as high as 100000 at 10 nm is expected in an instrument of <15 m length. The configuration will be discussed in details. To validate the concept, some efficiency measurements have been performed on two gratings operated in the off-plane geometry at high diffracted orders in the 50 to 140 nm region. Peak efficiencies in the 0.10-0.13 range have been measured. The configuration could be applied to realize a high-resolution monochromators for Free Electron Laser sources.