A Superconducting Permeameter for Characterizing Soft Magnetic Materials at High Fields

A superconducting permeameter is proposed to characterize the magnetic properties of high-energy superconducting magnet yokes at their operating temperature and saturation level. The main problem of superconducting coils, an undesired quench, was faced by specific protection simulations, which has led to a self-protected system. The superconducting permeameter was used to perform the magnetic characterization of ARMCO Pure Iron, the material for the new High-Luminosity Large Hadron Collider (HL-LHC) superconducting magnet yokes, which was performed at the cryogenic temperature of 4.2 K and a saturation level of nearly 3 T. Two case studies based on the new HL-LHC superconducting quadrupole and dipole magnets highlight the impact of the magnetic properties of the yoke on the performance of the superconducting magnets, showing that the common assumption that heavily saturated steels with similar chemical composition behave precisely the same way has been proven wrong.