NuMagSANS: a GPU-accelerated open-source software package for the generic computation of nuclear and magnetic small-angle neutron scattering observables of complex systems

Adams, M.P.; Michels, A.

doi:10.1107/S160057672600258X

Journal of Applied Crystallography Journal of Applied
Crystallography

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Figure 1
Sketch of the neutron scattering geometry that is implemented in NuMagSANS. The neutron optical elements (polarizer, spin flipper, analyzer) that are required to measure the spin-resolved SANS cross sections are not drawn. The external magnetic field $[{\bf B}_{0}\parallel{\bf e}_{z}]$ is here applied perpendicular to the wavevector $[{\bf k}_{0}\parallel{\bf e}_{x}]$ of the incident neutron beam ( $[{\bf B}_{0}\perp{\bf k}_{0}]$ ). The momentum transfer or scattering vector $[{\bf q}]$ is defined as the difference between $[{\bf k}_{0}]$ and $[{\bf k}_{1}]$ , i.e. $[{\bf q} = {\bf k}_{0}-{\bf k}_{1}]$ . Its magnitude for elastic scattering, $[q = ({{4\pi}/ {\lambda}})\sin\psi]$ , depends on the average neutron wavelength λ and on the scattering angle $[2\psi]$ . The angle $[\theta = \angle({\bf q},{\bf e}_{z})]$ is used to describe the angular anisotropy of the scattering pattern on the two-dimensional detector. In the small-angle approximation the component of $[{\bf q}]$ along $[{\bf k}_{0}]$ is small compared with the other two components, so that $[{\bf q}\cong\{0,q_{y},q_{z}\}]$ .

JOURNAL OF
APPLIED
CRYSTALLOGRAPHY

ISSN: 1600-5767

Volume 59| Part 3| June 2026| Pages 943-959

https://doi.org/10.1107/S160057672600258X

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