A strategy for handling aberration in Spherical Neutron Polarimetry

Abstract

We present a strategy for identifying and correcting for aberration effects in Spherical Neutron Polarimetry. The transformation of the neutron beam polarization vector due to scattering from a material is determined with Spherical Neutron Polarimetry. This neutron scattering technique measures the three cardinal components of the scattered polarization for any chosen cardinal direction of the incident polarization for a given Bragg reflection. As a consequence, the instrumentation required for this technique is desired to be capable of measuring the three-dimensional polarization vector over the sphere. As with all instrumentation, the field of measurement is subject to aberration which must be characterized.

Small-angle neutron polarimetry apparatus (SANPA): Development at the NIST Center for Neutron Research

“…6, a strategy we address elsewhere. 37 However, the type of calibration described above is at least sufficient for small-angle neutron scattering where the coordinate system does not change with the sample orientation, i.e., the coordinate system used for measuring Fig. 6 is fixed to the lab frame, as is implied in Fig.…”

A Polarization Tensor for Neutron Optics

“…The tensor T is a composition of cross-sectional measurements that includes in it effects due to both crystal structure [3,4] and experimental aberration [5,6]. In such 3D scattering applications it would be desirable to represent T as a product of matrices, e.g., T = ( n P n )M( m P m ), such that M again describes the scattering, and a P i (for i = n or m) might describe the transport of either a neutron-optical component or aberration imposed by some sample environment fixture [6]. To facilitate this product as a matrix multiplication, the P i need to have the same rank and dimension as the Blume-Maleev tensor.…”