FACET-II facility for advanced accelerator experimental tests

The National User Facility for Advanced Accelerator Experimental Tests II (FACET-II) at SLAC National Accelerator Laboratory expands upon the experiments conducted at FACET. Its purpose is to build upon the decades-long experience developed conducting accelerator R&D at SLAC in the areas of advanced acceleration and coherent radiation techniques with high-energy electron and positron beams. This paper summarizes the motivations for the design and resulting capabilities of the FACET-II facility.