Lattice Matching with a Quadrupole Missing
  The lattice for the present design of the TESLA Linear Collider with integrated X-Ray Laser Facility is basically a FODO structure with constant beta-function. There are more than 800 individually powered superconducting quadrupoles to focus the beam in the two main linear accelerators (each with a length of 15 km). For the availability of the beams it is important that a power supply failure or even a magnet failure does not cause a significant down time of the linac. It is demonstrated that the beta-function can be matched with a quadrupole "missing". One part of the main linac (up-to 50 GeV) will be used to accelerate the High Energy Physics beam and the Free Electron Laser drive beam with different accelerating gradients. Therefore the betatron phase advance will be 60 deg. or 90 deg. depending on the beam energy. It is shown that even in that case it is possible to match the lattice simultaneously for both beams with a quadrupole missing. 
Rainer Wanzenberg