Effects of temperature and mechanical strain on Ni-Fe alloy CRYOPHY for magnetic shields

The twofold goals of this work are (i) to reduce the lack of experimental data in literature concerning the effectsof temperature and mechanical strain on magnetic properties of the Ni-Fe alloy Cryophy, and (ii) to validate itsuse as magnetic shield material for last-generation cryomodule prototypes of crab cavities used in particle ac-celerators for transverse deflection. The relative magnetic permeability was measured at room and cryogenictemperature, and its lowest value at 4 Kfits the minimum design criteria of 100,000 for the crab cavities ex-periment at CERN. Permeability after uniaxial plastic deformation between 0% and 3% was also measured bymeans of an Epstein frame. Results show that deformation induces a significant decrease in the magnetic per-formances, underlining that particular care must be taken during all stages of handling and operation. Finally,the attenuation inside the magnetic shields was tested for the prototype Super Proton Synchrotron at CERN.Results highlight that at 150 mm from the opening, the magneticfield is shielded as required.