Increased flexibility and efficiency of a double-scattering FLASH proton beamline configuration for in vivo SOBP radiotherapy treatments

. To commission a proton, double-scattering FLASH beamline by maximizing efficiency and field size, enabling higher-linear energy transfer FLASH radiotherapy to cells and small animals using a spread-out Bragg peak (SOBP) treatment configuration. We further aim to provide a configuration guide for the design of future FLASH proton double-scattering (DS) beamlines.