Investigation of propagation algorithms for ray-tracing simulation of polarized neutrons

Ray-tracing of polarized neutrons faces a challenge when the neutron propagates through an inhomogeneous magnetic field. This affects simulations of novel instruments using encoding of energy or angle into the neutron spin. We here present a new implementation of propagation of polarized neutrons within the McStas simulation package and show that it outperforms the de-facto standard method implemented in the NISP package by Seeger and Daemen. We include simulation of a simplified model of a spin-echo instrument, including a simple virtual experiment.