Upgrade and recent performance of 24-m SGM at the Photon Factory

Performance of a 24-m spherical grating monochromator is described. This beamline is composed of a prefocusing toroidal mirror, a spherical grating monochromator with a movable exit slit and refocusing mirrors. With a 600-ℓ/mm grating and 50-μm slit openings, the resolving power of 5700 was achieved at 45 eV in good agreement with the theoretical prediction. The second-order contribution was estimated from Ne 2p photoelectron yield to be less than 40% of the first order for the spectral range of 30–90 eV and less than 11% for that of 90–160 eV with the grating of 600 ℓ/mm. As to the grating of 1800 ℓ/mm, it was estimated to be less than 31% for the spectral range of 80–90 eV and less than 11% for that of 90–150 eV. A photon flux of ≂5×1012 photons/s is obtainable at 70 eV for the grating of 600 ℓ/mm and that of ≂1012 photons/s is obtainable at 150 eV for the grating of 1800 ℓ/mm.