Characterization of the BIFROST spectrometer through virtual experiments

TL;DR

This paper uses Monte Carlo ray tracing to create virtual experiments of the BIFROST neutron spectrometer, benchmarking its performance and exploring resolution effects and magnetic excitations, highlighting the importance of simulations in experimental planning.

Contribution

It introduces a detailed virtual model of BIFROST, enabling benchmarking and analysis of resolution effects and magnetic excitations beyond analytical methods.

Findings

Reproduces expected resolution behavior

Quantifies wavelength-dependent edge enhancement

Simulates realistic magnetic excitations

Abstract

Using the Monte Carlo ray tracing package McStas, we illustrate the possibilities of creating virtual experiments of the neutron spectrometer BIFROST at the European Spallation Source, ESS. With this model, we are able to benchmark BIFROST with respect to expected intensity, $Q$- and energy-resolution. The simulations reproduce the expected resolution behavior and quantify effects that are difficult to capture analytically, including a wavelength-dependent edge enhancement arising from a combination of the long-pulsed source and the pulse-shaping chopper. Furthermore, we present an antiferromagnetic (AF) spin wave simulation, which we use to create realistic datasets at different instrument operation settings. Our virtual experiments focus on realistic dispersive dynamics and illustrate how the virtual experiment approach reveal resolution effects, not easily calculable via analytical models. This demonstrates the crucial role of numerical simulations in the planning of challenging experiments.