Performance Study of the Vibrating Wire Technique to Determine Longitudinal Magnetic Field Profile Using Scans to High Wire Harmonic

Particle accelerator laboratories, which enable world-class research across many scientific fields, depend on the magnets used to manipulate their particle beams for successful operation. The community employs various techniques, typically based on Hall probes and induction sensors/coils, to verify the performance of accelerator magnets. Conventional Hall probe systems cannot be deployed, or require significant modification, when the transverse access around a magnet is restricted; meanwhile, moving wire/coil systems tend to provide information only on the B field’s integral. This research builds upon a vibrating wire setup first commissioned to locate the magnetic center of quadrupole magnets. Scans up to the n=200 wire harmonic (∼10 kHz drive frequency) were measured to reconstruct the B field across a vibrating wire strung through a test magnet. New software was developed to systematically process the many wire harmonics needed for a detailed field reconstruction. This research investigated the speed and precision of the measurement, identifying limitations due to both instrumentation and nonlinear wire behaviour at very high harmonic. The vibrating wire data agreed with a reference Hall probe scan on the order of 6%; roughly 0.7% RMS error persisted after calibrating the vibrating wire data to the reference scan via scaling factor.