Vertical Shape determination of a stretched wire from oscillation measurements

The Geodetic Metrology group at CERN uses stretched wires as a reference for the position monitoring and alignment of accelerator components. Until now, stretched wires find in particular use as horizontal offset measure- ment references, since their vertical projection is a line. However, the wire positioning system is able to measure not only the horizontal but also the vertical wire position. In order to use this data as vertical reference of the alignment system, a framework to describe the vertical wire shape is required. This work re-conceptualises a previously proposed optimization based algorithm, that calculates the vertical wire shape via its fundamental frequency from oscillation measurements. As a result, the determination of the vertical shape with respect to a static parabola fitting model was improved one order of magnitude compared to the previously available oscillation-based algorithm. Now, it is possible to determine the wire position with respect to static wire measurements with a precision of the same order of magnitude as the static parabolic fitting model for wires of up to 140 m length. Furthermore, the study of wire oscillations revealed methods to localize restrictions of the wire. With these means, an alternative evaluation method to the static parabolic fitting model is provided that adds information to already existing alignment systems and offers new sensor configuration possibilities for future alignment systems.