Design and performance of a spherical grating monochromator used at MAX I

We report on the performance of a grazing incidence spherical grating monochromator installed at MAX I and designed to cover the photon energy range from about 15–200 eV with high resolving power. It is intended mainly for angle-resolved photoemission work. Therefore, both refocusing optics, to obtain a small spot size at the sample, and a higher order light suppressor, to reduce the content of higher orders, have been incorporated in the design. The theoretically calculated energy resolution is presented and compared to the resolution obtained in photoabsorption measurements of gas-phase He, Ne, Kr, Xe, and N2. The possibility to reduce the influence of higher orders is illustrated by photoemission data collected on Si (1 0 0). The experimental results show that the monochromator fulfills the expected design goals.