Two color experiments combining Free Electron Laser and Synchrotron Radiation

We present the results of the first two color experiment coupling FEL and Synchrotron Radiation, where the SuperACO FEL was used to photoexcite carriers at semiconductor surfaces and the consequently induced surface photovoltage was studied with soft X-ray photoemission spectroscopy. Thanks to the subnanosecond temporal resolution and high surface sensitivity of our experimental setup, we were able to measure for the first time the effect of surface states on band bending dynamics. Based on our direct experience during these experiments, and on the future developments related to other two color experiments proposed on SuperACO, we will discuss the advantages and the technical aspects of this mode of operating the storage ring and the FEL.