Monte Carlo simulations of the S-shaped neutron guide

TL;DR

This paper uses Monte Carlo simulations to analyze neutron transport in an S-shaped guide for SANS instruments, revealing wavelength cutoffs and flux behaviors influenced by guide geometry.

Contribution

It introduces Monte Carlo simulation results for S-shaped neutron guides, highlighting the impact of geometry on wavelength cutoff and neutron flux, validated against the Acceptance Diagram method.

Findings

Wavelength cutoff depends on guide geometry.

Flux at sample position varies with guide curvature.

Beam divergence behavior analyzed along the guide.

Abstract

Neutron transport along guides is governed by the Liouville theorem and the technology involved has advanced in recent decades. Computer simulations have proven to be useful tools in the design and conception of neutron guide systems in facilities. In this study, we use a Monte Carlo method to perform simulations for an S-shaped neutron guide with different dimensions for a Small-Angle Neutron Scattering (SANS) instrument, through the MCSTAS software. A wavelength cutoff is observed and shown to be dependent on the geometrical parameters of the guide. Results for the neutron flux at sample position are presented and a greater sensitivity of cutoffs concerning the curvatures of the guides than to their lengths is noticed. Our results are in agreement with those obtained from the Acceptance Diagram method and we analyze the beam divergence behavior along the S-shaped guide.