Development and testing of RF double window input couplers for TESLA

More and more accelerators are built with superconducting cavities operating at cryogenic temperatures. A possible window failure might result in contamination of the cavity surface and degrade the accelerating performance. A cost effective design and fabrication method for a new coupler has been developed by AMAC. This new design is an alternative to the present TESLA cylindrical ceramic windows layout. The new design includes two planar disc windows separated by a vacuum space. An alternative design option proposes filling dry nitrogen gas in between the two ceramic windows. Furthermore the new design is optimized for RF input power, taking into consideration the possible requirements of the TESLA superstructure layout. Two prototype couplers with this design have been fabricated. The couplers are being tested on the high power test stand at DESY, Germany. This paper describes the new coupler design and discusses the first measured results.