MuPAD is used on the triple axis spectrometer TASP to allow the arbitrary orientation of a polarized neutron beam so spherical neutron polarimetry (SNP) and xyz polarization experiments can be performed.
MuPAD is constructed from Mu-Metal to reduce the magnetic field within the sample chamber and hence prevent the depolarization of the neutron beam. Any external fields will be reduced by a factor of approximately 1000 within the chamber and the minimum field is approximately 0.3 mG.
The incident beam is polarized with super-mirror benders. The polarization is maintained by conduction coils until the beam is within the sheilded region. The orientation of the neutron polarization is then changed by two precession coils. The first coil has a horizontal field to control the elevation of the polarization from the scattering plane. The second coil has a field in the vertical direction to control the rotation of the polarization about the azimuth.
The oriented polarized beam then enters the sample chamber and is scattered by the sample. At this point the polarization is again rotated, by the field present within the sample. The direction of polarization after the scattering event is found by measuring the vector components of the final polarization orientation.
Residual Field: ~0.3 mG
Flipping Ratio: >10