Numerical Investigations of Waveguide Input Couplers for the TESLA Superstructure

A superstructure of cavities has been proposed for the superconducting TESLA Linear Accelerator which will reduce the number of components (Input and HOM couplers) and also improve the average gradient. Thus the input power per input coupler has been drasticallyincreased: 700 kW ($T_{hf}$ =1.4 ms, $f_{rep}$=5 Hz) for the design operation and 1.4 MW for the possible upgrade version. In this paper two types of waveguide couplers were examined, including windows and bellows, taking the geometrical limitations of the cryomodule into account with respect to: maximum fields, cryogenic losses and the kick experienced by the beam