Optical design of the NSRL undulator beamline

Abstract

The optical design of the NSRL undulator beamline is presented. The NSRL undulator has 29 periods of 9.2 cm that produce a photon energy of 7.7–124 eV with the fundamental and third harmonics at a ring energy of 800 MeV. The beamline consists of a typical Kirkpatrick–Baez prefocusing mirror system, a modified spherical-grating monochromator (SGM) and a refocusing toroidal mirror. The monochromator has two including angles of 148 and 157° with two plane mirrors inserted into the entrance arm in order to cover the wide energy range with high grating diffraction efficiency. Calculation shows that the resolving power of the monochromator can be greater than 5000 with the slits fully opened and 20000 with a 20 µm opening of the slits. The spot at the sample is about 1.5 (H) mm × 0.5 (V) mm.