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

Issue title: Workshop on the Monte Carlo Simulation of Neutron Scattering Instruments MCNSI7

Article type: Research Article

Authors: Knudsen, E.B.^; | Tranum-Rømer, A. | Willendrup, P.K.^; | Christiansen, P. | Lefmann, K.^;

Affiliations: Department of Physics, Technical University of Denmark, Lyngby, Denmark | Nanoscience Center, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark | Department of Physics, Lund University, Lund, Sweden | ESS Design Update Programme, Denmark

Note: [] Corresponding author: E.B. Knudsen, Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark. Tel.: +45 21326655; Fax: +45 45932399; E-mail: erkn@fysik.dtu.dk

Abstract: 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.

Keywords: Ray-tracing, neutron spin-echo, Larmor precession, McStas, algorithms

DOI: 10.3233/JNR-130003

Journal: Journal of Neutron Research, vol. 17, no. 1, pp. 27-34, 2014