An optical design for spherical-grating monochromators for application to synchrotron radiation is presented. High spectral and spatial performance is obtained with a spherical variable-line-spaced grating coupled to a spherical mirror with its tangential plane coincident with the grating’s equatorial plane. The monochromator works without an entrance slit in an off-Rowland configuration with a fixed entrance arm and demagnification on the exit slit. The law for groove-space variation of the grating compensates for the main spectral aberrations; spectral focusing in an extended energy range is ensured by a slight change in the exit arm with translations of the order of a few tens of millimeters. The inclusion of a spherical mirror ensures focusing on a plane perpendicular to the plane of spectral dispersion. The ultimate resolution is limited by the slope errors of a single spherical surface. The layout is applied to the design of a high-resolution monochromator for the 1000–250-eV region.
© 2000 Optical Society of America
(050.1950) Diffraction and gratings : Diffraction gratings
(120.4570) Instrumentation, measurement, and metrology : Optical design of instruments
(120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
(340.6720) X-ray optics : Synchrotron radiation
Luca Poletto and Giuseppe Tondello, "Spherical-Grating Monochromator with a Variable-Line-Spaced Grating for Synchrotron Radiation," Appl. Opt. 39, 5671-5678 (2000)