Vibrating-wire measurement method for centering and alignment of solenoids

A method is proposed to center and align solenoids by means of a vibrating wire. The magnetic axis of a solenoid is defined as the path where the integral over the transversal field components takes its minimum. The wire, fed by an alternating current, oscillates in a plane that is perpendicular to the transversal magnetic field. When the wire position coincides with the magnetic axis, the transversal field components cancel out and therefore no motion is induced. To center and align the solenoid two wire resonance frequencies are excited for co- and counter-directional movements of the wire stages. The procedure to find the minimum oscillation amplitudes is sensitive to misalignment in the micrometer range. The experimental validation was carried out on a solenoid for the linear accelerator Linac4 at CERN