3D Magnetic Analysis of the CMS Magnet

TL;DR

This paper presents a comprehensive 3D magnetic analysis of the CMS magnet system, including field behavior, force calculations, fringe field estimation, and a method for reconstructing the magnetic field inside a volume, using TOSCA models.

Contribution

It introduces detailed 3D models and a reconstruction procedure for the CMS magnetic system, enhancing simulation accuracy and understanding of magnetic forces and fields.

Findings

Magnetic field behavior characterized in detail.

Force calculations for displacements and tilts performed.

Fringe field and field in chimneys analyzed.

Abstract

The CMS magnetic system consists of a super-conducting solenoid coil, 12.5 m long and 6 m free bore diameter, and of an iron flux-return yoke, which includes the central barrel, two end-caps and the ferromagnetic parts of the hadronic forward calorimeter. The magnetic flux density in the center of the solenoid is 4 T. To carry out the magnetic analysis of the CMS magnetic system, several 3D models were developed to perform magnetic field and force calculations using the Vector Fields code TOSCA. The analysis includes a study of the general field behavior, the calculation of the forces on the coil generated by small axial, radial displacements and angular tilts, the calculation 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 flux density on the cylinder surface is considered. Special TOSCA-GEANT interface tools have being developed to input the calculated magnetic field into the detector simulation package.