The magnetic shielding for the neutron decay spectrometer aSPECT

In order to determine the most suitable geometry for the magnetic shielding for aSPECT, we simulated a variety of possible geometries and combinations of shielding materials of non-linear permeability. The results of our simulations were checked through magnetic field measurements both with Hall and nuclear magnetic resonance probes. The experimental data are in good agreement with the simulated values: the mean deviation from the simulated exterior magnetic field is (−1.7±4.8)%. However, in the two critical regions, the internal magnetic field deviates by 0.2% (decay volume) and <1×10−4 (analyzing plane) from the simulated values.