SM-PGM monochromator design for large spectral range

The achievement of high resolving power from VUV to soft X-rays is a new challenge for synchrotron radiation beam-lines. When the X-UV range has to be privileged, we show that an optimized Plane grating monochromator (PGM), which can be corrected up to large aperture angles, offer a good compromise between resolution, flux and easiness of use. The design method and especially the determination of deviation angles and gratings parameters are outlined. The dependence of ultimate performances on the fabrication accuracy is evaluated; This design is compared to an alternative SGM design and their performances are found complementary.