HOM DAMPING REQUIREMENTS FOR THE TESLA SUPERSTRUCTURES

A chain of four non-resonantly coupled 7-cell cavities is thought to replace the 9-cell cavities considered in the standard design of the accelerating structures for the TESLA main linac. The main advantages of these so called superstructures are the reduced number of power couplers and the increased fill factor in the linac. This paper deals with the damping of the higher order modes (HOM) to a level where they cause no harm on the beam. Calculations have been performed in order to set a safety limit to the quality factors. The measurements done on a copper model of the superstructure show that the required damping level can be achieved.