Multi-beam-energy control unit based on triple bend achromats

Abstract: X-ray free electron lasers (XFELs) are the new generation of particle accelerator-based light sources, capable of producing tunable, high-power X-ray pulses that are increasingly vital across various scientific disciplines. Recently, continuous-wave (CW) XFELs driven by superconducting linear accelerators have garnered significant attention due to their ability to enhance availability by supporting multiple undulator lines simultaneously. However, different undulator lines typically require distinct electron beam qualities, particularly varying electron beam energy to achieve a wide range of photon energy tunability. Consequently, precise bunch-to-bunch control of electron beam energy is essential. A double-bend achromat based electron beam delay system has been proposed to enable multi-beam energy operations in CW-XFELs. In this paper, we introduce a novel delay system comprising four triple-bend achromats (TBAs). Based on parameters of the Shanghai High-Repetition-Rate XFEL and Extreme Light Facility, start-to-end simulations demonstrate that the TBA-based delay system achieves better electron beam qualities while providing a wide beam energy tuning range.