Advances in stretched and oscillating-wire methods for magnetic measurement

A versatile measurement system has been designed and commissioned at CERN, which is based on a wire sensor in different modes of operation: the classical single-stretched wire mode, the oscillating wire mode employing frequencies well below the first natural resonance, as well as the vibrating wire mode where the wire is excited in the first or higher-order resonance conditions. In this paper, the main technical challenges and constraints of the wire methods are presented, together with the applications to locate the magnetic axis of a string of magnets on a common girder and to the measurement of multipole errors. Sources of uncertainty, stemming from the wire motion unsuitability, are discussed, different wire motion transducers are compared, and the effect of background fields and environmental effects is studied.