Paper 
Title 
Page 
MOPB043 
Detailed Analysis of the LongRange Wakefield in the Baseline Design of the CLIC Main Linac 
270 

 V.F. Khan, A. Grudiev
CERN, Geneva, Switzerland



The baseline design for the accelerating structure of the CLIC main linac relies on strong damping of transverse higher order modes (HOMs). Each accelerating cell is equipped with four damping waveguides that enables HOM energy to propagate to damping loads. Most of the HOMs decay exponentially with a Qfactor of about 10 however, there are modes with higher Qfactors. Though the amplitude of the high Q modes is nearly two orders of magnitude smaller than the dominating lowest dipole mode, their cumulative effect over the entire bunch train may be significant and dilute the beam emittance to unacceptable level. In this paper we report on an accurate calculation of the longrange wakefield and its overall effect on beam dynamics. We also discuss possible measures to minimise its effect in a tapered structure.


