ATLAS Cavern Magnetic Field Calculations

A new approach has been adopted in an attempt to produce a complete ATLAS cavern B-field map using a more precise methodological approach (variable magnetisation, depending on the external field) and the latest design taking into account of the structural elements. The basic idea was to produce a dedicated basic TOSCA model and then to insert a series of ferromagnetic structure elements to monitor the perturbative effect on the basic field map. Eventually, it was found: The bedplate field pertubation is an order of magnitude above the permissible level. Manufacturing of the bedplates from nonmagnetic material or careful evaluation of their field contribution in the event reconstruction codes is required. The field value at the rack positions is higher than the permissible one. The final position of racks should be chosen taking into account the detailed magnetic field distribution.