Automatic online optimization on transverse emittance at SXFEL-UF injector

During the online tuning of a large-scale accelerator, the improvement of beam properties is usually conducted by operators manually, which is time-consuming and is highly dependent on their personal experience of it. In this work, we try to introduce the extremum seeking algorithm into the online beam transverse emittance optimization project in Shanghai soft X-ray Free-Electron Laser facility (SXFEL) Injector. The transverse emittance is essential to be well-controlled in the injector section, which facilitates the FEL lasing performance in the undulators. The experiment result demonstrates the efficiency of this automatic tuning approach and lays the foundation to further study and research on the achievement of automatic control in the free-electron laser facilities.