Higher-order modes and Beam-Loading compensation in CLIC Main Linac

Compensation of transient beam loading is one of the major performance issues of the future compact linear collider (CLIC). Recent calculations, which consider the most important fundamental mode, have shown that the 0.03% limit on the rms relative bunch-to-bunch energy spread in the main beam can be reached by optimizing the RF power pulse shape for the TD26, the CLIC baseline accelerating structure. Here we perform an additional dedicated study of the influence of higher-order modes on the energy spread compensation scheme. It is demonstrated that taking these modes into account in the accelerating structure does not increase the rms energy spread in the main beam above the CLIC specification level.