Calibration of waveguide beam position monitors

To ensure overlap between the photon beam and electron beam at the SASE-FEL at the TESLA Test Facility [1], several position-sensitive diagnostics components are installed along the beamline of the FEL. For the undulator part, a new type of waveguide beam position monitors (BPMs) is designed, tested, and installed inside the beam pipe of one undulator module. This paper proposes a method to calibrate these monitors with beam-based measurements