Multibunch instabilities at the SB-Linear-Collider damping ring

For the SB-Linear-Collider project (SBLC) at DESY a redesign of the damping ring has been performed, mainly in order to optimize the dynamic aperture. The damping ring is build up with 6 super periods. The straight sections between these periods are used for the injection, ejection and rf-cavities. Each super period consists of 6 DBA cells. The straight sections of these cells are used for the installation of over 150 m of wigglers, the normalized emittances are : εx,n = 3.8·10-6 m·rad and εy,0 = 7.6·10-8 m·rad. The damping time results in τy ≤ 3.4 ms. The dynamic acceptance including misalignment and magnet errors is in the range of Ax ≤ 72 mm·mrad and Ay ≤ 80 mm·mrad. Because of the required high luminosity of the collider, instabilities have to be avoid. The most severe instabilities are the single- and couple bunch ones determined by the rf.-system. In this paper we investigated the excitation of the couple bunch instability by chosen the rf.-system used at the Synchrotron Trieste (ELETTRA-cavity). The temperature of each cavity can be regulated in order to avoid any excitation of the coupled bunch instability. (author)