Design considerations for a CBXFEL facility driven by the LCLS-II HE linac at SLAC

The addition of a laser cavity at the x-ray wavelengths to the linac-driven free electron lasers promise to delivery true laser-like x-ray source properties. This so-called cavity based X-ray FEL (CBXFEL) approach can produce stable full-3D coherence and yet another 2-3 orders of magnitude improvement in brightness compared to various single-pass schemes under development. The LCLS-II HE project will extend the LCLS-II linac to an 8GeV continuous-wave accelerator capable of continuous delivery of MHz high peak current electron bunches. This paper discuss practical design considerations for a CBXFEL user facility at SLAC, driven by the 8GeV superconducting linac. Challenges and potential solutions surrounding cavity schematics, tunability, alignment, stabilization, thermal management, beamline and endstation layouts, and facility operation modes will be discussed.