New optimized fully loaded CLIC drive beam accelerating structure design

The CLIC drive beam accelerator (DBA) provides a very high current beam to supply the RF power to the main accelerator; therefore, its efficiency is the most important figure of merit. The travelling wave SICA (Slotted Iris – Constant Aperture) structures of CLIC DBAs accelerate the drive beam to 2.37 GeV. Recent updates of the CLIC parameters made a revision of the original design necessary. We optimized and redesigned the structure to match the new input power of 18.00 MW, keeping the RF to beam efficiency over 95 % and a filling time of 245.00 ns. Higher-Order Modes (HOMs) can be excited by the beam due to the large beam current of 4.21 A, despite the heavy damping by the slotted irises. We studied in detail the HOM to prove their damping accomplished by the SiC loads. Finally, we illustrate a design of the couplers. RF-kicks from the couplers have been studied using the beam dynamics code PLACET.