Design and Implementation of an Automated Polarity Checker for Superconducting Magnets

In this paper a new measurement system for the polarity check of all the superconducting magnets that will compose the Large Hadron Collider (LHC) is described. The polarity checker is a scanning probe that, thanks to a rotating Hall plate, performs a complete local analysis of the magnet under test. By Fourier analysis of the radial component of the magnetic field picked up by the Hall sensor, the instrument identifies the magnet order and type, the field polarity, and provides the transfer function of the main harmonic and an estimation of the magnetic field angle. After the description of the measurement principle, the hardware and the software of the instrument are detailed. Particular attention is devoted to the metrological characterization and the correction of deterministic errors in order to ensure a polarity measurement practically error free on all the magnet types