Speakers
Description
Monte Carlo simulations are a key tool for the design and optimisation of neutron scattering instruments at modern reactor and spallation neutron sources.
VITESS (Virtual Instrumentation Tool for ESS) is a modular simulation framework widely used for modelling neutron transport through complex instrument layouts and evaluating instrument performance during the design phase.
Beyond instrument design, such simulations are increasingly important for enabling virtual experiments and digital twins of neutron instruments, allowing realistic modelling of experiments and supporting the development of future data analysis and instrument operation workflows.
The recently released VITESS 3.7 introduces several developments aimed at improving the coupling between moderator simulations and instrument modelling, as well as extending the physical modelling capabilities of the software. Two new source modules facilitate the use of neutron distributions obtained from detailed target–moderator simulations. The new module KDSource enables statistically enhanced sampling of neutron phase space based on kernel density estimation. In addition, the new source_AI module uses machine-learning techniques to construct compact parametric representations of neutron flux distributions as functions of time, wavelength and other parameters derived from moderator simulations.
Further additions include a prism module for simulating arrays of triangular prisms for beam deflection and a sample_ncrystal module enabling the integration of the NCrystal library for realistic crystal scattering models. Existing modules have also been extended, including support for spin-dependent scattering in inelastic simulations and extended motion capabilities for monochromator systems.
In addition to these developments, ongoing work towards VITESS 3.8 focuses on further improving simulation workflows, expanding physics modelling capabilities, and preparing the transition toward the next-generation architecture of the VITESS framework.