Wakefield induced Losses in the Manual Valves of the TESLA Cryomodule

The beam pipe of the TESLA cryomodule is closed off by manual valves on both sides of the string of 12 cavities. Compared to the manual valves with spring type rf-shield which are presently used in the linac of the TESLA Test Facility a simplified version will be needed by cost reasons for the TESLA linear collider. Therefore wakefield induced losses for two simplified valve geometries have been studied in detail. Three types of losses are distinguished: transient and resonant losses due to wake fields induced by the valves themselves and losses due to wakes induced in the cavities. The calculations have been done for two different operation modes linac operation and FEL operation. In addition the transverse kick has been calculated and compared with the strongest kick from a nine cell cavity. The results show, that the losses from a valve with simplified rf-shield are acceptable.