Production of the soft magnetic steel laminations for the LEP dipole magnets

The methods used to produce soft-magnetic-steel sheets for the steel-concrete cores of the Large Electron Positron colliding-beam accelerator at CERN are described. Statistical data are presented along with measured characteristics such as impurity analyses, carbon contents, coercivities, permeabilities, aging behavior and geometry for the steel sheets and laminations. In total, 20280 batches of 172+or-4 laminations were punched, stacked, and conditioned for equal density, weight, and length. The average number of laminations per batch was 171.75 with a standard deviation of one. The average mass per batch was 362.85 kg; the average mass per lamination was 2.113 kg. From these data, the relative variation of the average sheet thickness of the batches was determined to be 0.5% for one standard deviation.