Test of two Nb superstructure prototypes

J. Sekutowicz, P. Castro, A. Gössel, G. Kreps, R. Lange, A. Matheisen, W.-D. Möller, H.-B. Peters, D. Proch, H. Schlarb, S. Schreiber, S. Simrock, M. Wendt DESY, Notkestrasse 85, 22603 Hamburg, Germany N. Baboi SLAC, 2575 Sand Hill Road, Menlo Park, CA 94025, USA M. Ferrario INFN, Via E. Fermi 40, 00044 Frascati, Italy M. Huening FNAL, MS 306, Batavia, IL 60510, USA M. Liepe Cornell University, Ithaca, NY 14853, USA C. Pagani INFN-Milano, Via Fratelli Cervi 201, 20090 Segrate, Italy S. Zheng Tsinghua University, 100084 Beijing, China ( Recieved ......................) An alternative layout of the TESLA linear collider [1], based on weakly coupled multi-cell superconducting structures (superstructures), significantly reduces investment cost due to a simplification in the RF system of the main accelerator. In January 1999, preparation of the beam test of the superstructure began in order to prove the feasibility of this layout. Progress in the preparation was reported frequently in Proceedings of TESLA Collaboration Meetings. Last year, two superstructures were installed in the TESLA Test Facility (TTF) linac at DESY to experimentally verify: methods to balance the accelerating gradient in a weakly coupled system, the stability of the energy gain for the entire train of bunches in macro-pulses and the damping of Higher Order Modes (HOMs). We present results of the first cold and beam test of these two Nb prototypes.