McStas - Monte Carlo simulation of neutron instruments
McStas is an ongoing project to create a general tool for simulating
scattering instruments. The project is a collaboration between DTU
Physics (formerly RISØ DTU and RISØ Natnl. Lab),
European Spallation Source, University of Copenhagen, Paul Scherrer Institute and Institut
The efforts have historically
been funded through multiple EU
The software is freely available and can be downloaded
from this site.
McStas is based on a compiler that reads a high-level specification
language defining the instrument to be simulated and produces C code
performs the Monte Carlo Simulation. The system is very fast in use,
when setting up the instrument definition and when doing calculations.
Typical figures are 500000 neutron histories per second on a fast
McStas supports triple-axis, time-of-flight instruments, and
neutrons. It comes with a comprehensive manual and a library of
components that include most standard elements of neutron scattering
including steady-state and pulsed sources, monochromators/analysers,
collimators, vanadium and powder samples, velocity selectors and
and a variety of detectors.
McStas runs on most of the popular computer systems
(Unix/Linux, Windows, macOS). Please refer to our GitHub
installation pages for installation requirements.
This software required a substantial effort to be brought to you. If
you enjoy this software, please use the folowing references in your
- K. Lefmann and K. Nielsen, Neutron News 10, 20, (1999).
- P. Willendrup, E. Farhi and K. Lefmann, Physica B, 350 (2004) 735.
- P. Willendrup, E. Farhi E. Knudsen, U. Filges and K. Lefmann, Journal
of Neutron Research, vol. 17, no. 1, pp. 35-43, 2014
- P. Willendrup, and K. Lefmann, Journal of Neutron Research, vol. 22, no. 1, pp. 1-16, 2020
- P. Willendrup, and K. Lefmann, Journal of Neutron Research, vol. 23, no. 1, pp. 7-27, 2021
If you are using the McStas Union framework, please also reference:
Conditions of use
Authors and contacts
McStas - Project funding
Last Modified: Tuesday, 20-Dec-2022 13:59:02 CET