3D magnetic analysis of the CMS magnet

The CMS magnetic system consists of a superconducting solenoid coil, 12.5 m long and 6 m free bore diameter, and of an iron flux-return yoke, which in cludes the central barrel, two end-caps and the ferromagnetic parts of the hadronic forward calorimeter. The magnetic flux density in the center of th e solenoid is 4 T, To carry out the magnetic analysis of the CMS magnetic s ystem, several 3D models were developed to perform magnetic field and force calculations using the Vector Fields code TOSCA, The analysis includes a s tudy of the general field behavior, the calculation of the forces on the co il generated by small axial, radial displacements and angular tilts, the ca lculation of the forces on the ferromagnetic parts, the calculation of the fringe field outside the magnetic system, and a study of the field level in the chimneys for the current leads and the cryogenic lines. A procedure to reconstruct the field inside a cylindrical volume starting from the values of the magnetic flu density on the cylinder surface is considered. Special TOSCA-GEANT interface tools have being developed to input the calculated m agnetic field into the detector simulation package.