Design of the Magnetic Shielding for PERC

Full text: The new facility PERC (Proton Electron Radiation Channel) is a novel source of neutron decay products. PERC is currently under development by an international collaboration and will be installed at the FRM II in Garching, Germany. The main component of PERC is a more than 11 m long superconducting magnet system, with a strong longitudinal magnetic eld of 0.5 T up to 6 T. In order not to disturb other experiments in the vicinity of PERC, we have designed a magnetic field return yoke for the magnet system. The following aspects must be taken into consideration: The magnetic stray eld must be suppressed to the cardiac pacemaker level. The internal magnetic eld and its homogeneity should not be disturbed. The additional forces onto the coils must not be destructive. The magnetic shielding must deal with the limited space conditions. We will show that for experimental reasons, the magnet geometry is non-axisymmetric and therefore has to be simulated in three dimensions. In order to reduce the computing time and, at the same time, increase the numerical accuracy, we simulated only one half of the geometry by taking advantage of the symmetry of the magnet and its shielding. The design of the magnetic shielding for PERC will be presented in this poster: The nite element method (COMSOL Multiphysics) has been used to determine the most suited geometry for the magnetic shielding. Various geometries and combinations of shielding materials of non-linear permeability have been simulated. (author)