An ultra-high energy resolution and wide energy range soft X-ray beamline in SSRF

A new ultra-high energy resolution and wide energy range soft X-ray beamline is designed and is being constructed in Shanghai Synchrotron Radiation Facility (SSRF), which has two experimental stations: angle resolved photoemission spectroscopy (ARPES) and photoelectron emission microscopy (PEEM). The source is a pair of EPUs covering the evergy ranges 20 to 200 eV and 200 to 2000 eV with arbitrary polarized light. The beamline, based on a plane grating monochromator(PGM) and four variable line spacing gratings, will deliver flux higher than 1.0$\times10^{12}$ photons/s/0.01\%BW. A grating dedicated for high energies and very high resolution will provide more than 5$\times10^{10}$ photons/s at 1 keV with a resolution of 14 meV. The refocusing for both endstations is based on KB pairs with which the spot size will be 15$\times4.7 \mu m^{2}$ (hor.$\times$ver. FWHM) at ARPES and 9.9$\times4.8 \mu m^{2}$ (hor.$\times$ver. FWHM) at PEEM, respectively, with a 10 $\mu m$ exit slit. Owing to high thermal radiation from the source, a new method is used to eliminate the influence of the thermal deformation on mirrors in order to achieve ultra-high energy resolution.