Modeling a 30 GHz waveguide loaded detuned structure for the compact linear collider (CLIC)

One of the major challenges in designing a multi bunch structure for the Compact Linear Collider Study CLIC are the long range transverse wake fields, which couple the transverse motion of adjacent bu nches and lead to instabilities. To the most part, possible solutions, which suppress the long range wake, require a mechanical precision, which is difficult to achieve for the high fundamental freque ncy of 30 GHz. A possible way out of this dilemma consists of combining a loose detuning with the strong damping provided by radial waveguide loads. For this type of structure, an equivalent circuit m odel has been developed, which simulates the behavior of the total structure for the lower two dipole bands. The circuit parameters are derived from the results of numerical field calculations. Mismat ch of the waveguide loads is incorporated in the circuit model via a table of scattering parameters. Using this model, a first 'skeleton' design has been done. Requiring only a limited performance of the waveguide loads, this design shows a sufficient suppression of the transverse long range wakes.