Upgrade of the Beamline 10.0.1 at the Advanced Light Source

Beamline 10.0.1 delivers the photons from a 4.5 m long 10 cm periodicity undulator (U100) to various endstations in its three branchlines. The beamline uses a spherical grating monochromator (SGM) to produce high energy resolution photon beam, with three gratings to cover the photon energy range from 17 to 340 eV. Typically, angle-resolved photoemission (ARPES) measurements use 30-70 eV photons. The beam size at the High Energy Resolution Spectroscopy (HERS) endstation, designed for ARPES, is measured to be 250 mu m (H) by 100 mu m (V). Due to grazing incidence geometry in the HERS endstation, the photon beam will have a large projection on the sample surface which could lead to degradation of experimental resolutions. We are in the process of designing and replacing some of the existing mirrors to improve the focus spot at HERS endstation. The detailed design parameters and possible upgrade paths will be presented with verifications using SHADOW ray-tracing program.