2D coupled structural/magnetic analysis of SSC CQM

The deformation of a collider quadrupole magnet (CQM) coil under pre-compression, cool down and Lorentz forces may cause some significant changes in magnetic multipoles. The magnetic measurements of the CQM short model magnets at 4.2 K showed an average b/sub 5/ of -2.866 units compared to a numerical prediction of -0.162 units. Out of these -2.866 units, -1.5 units are due to a shim placed at the mid-plane to increase coil precompression. We also suspect that the permeability of the stainless steel collar may contribute some of the missing b/sub 5/. For example, a permeability of 1.004 for the collar adds -0.5 units of b/sub 5/. Including the collar, we are still missing -0.8 to -1.0 units. We believe that the mechanical deformation due to pre-compression of the coil is responsible for the remaining units. This study builds a 2D magneto-structural coupled model, calculates the magnetic multipoles under different loading conditions and establishes a correlation between multipole changes and coil pre-compression and Lorentz force stresses.<>