Soft x-ray monochromator configurations for the ELETTRA undulators: A stigmatic SX700 (invited)

This report presents a modification of an SX700 plane grating monochromator, which can be made to work stigmatically by introducing an entrance slit. It will then provide the highest possible photon density in the exit slit with resolving powers that can be very high because it is not any longer source-size limited. Instead it can be adjusted according to the slit settings. The deterioration of the resolving power because of slope errors in the ellipsoid can be avoided by orienting this mirror for sagittal focusing in the grating dispersion plane. In this configuration the instrument can be matched almost ideally to undulator sources.