Investigation of the temperature rise due to eddy currents in large chopper disks operated at polarized neutron beamlines

The detrimental temperature rise due to eddy currents in large chopper disks from aluminium alloy operated at high rotation frequencies was investigated experimentally and compared to calculations obtained with finite element analyses. We found that for magnetic field strengths which are commonly used for polarized neutron beam guidance, the temperature rise is only about 20 K, a value which does not compromise the use of these aluminium choppers. Furthermore, the induced magnetic field due to the eddy currents does not significantly affect the polarizing field. These findings will form the basis of our chopper development from this material.