McStas logo McStas - A neutron ray-trace simulation package ILL; PSI; ESS Niels Bohr Institute DTU Physics

McStas

About McStas
 Conditions of use
 Authors/Contacts
 Project funding

Download
 Components
 Other Downloads (share)

Mailing list

Search web/mailinglist

Documentation
 Wiki (GitHub)
 McStas manual
 Publications

Links

Report bugs (GitHub)

Code-repository (GitHub)

McStas - A neutron ray-trace simulation package

McStas is a general tool for simulating neutron scattering instruments and experiments. It is actively supported by DTU Physics, NBI KU, ESS, PSI and ILL. 

Simulated scattering from a hollow-cylinder vanadium sample.

The plot shows the intensity of scattered neutrons (red is highest intensity). The sample is at the center of the sphere with the neutron beam coming from the left. Clearly seen is the shadowing effect of the sample causing a lower intensity opposite the beam. Also seen is the effect of the non-symmetric geometry of the sample, causing lower intensity directly above and to the side of the sample.


Recent news

Migrating from McStas 2.x to 3.x? - Use the wiki-based guides

April 29th, 2025: McStas and McXtrace 3.5.27 released

Dear all,
McStas and McXtrace release 3.5.27 is now available.
McStas installation instructions are found on GitHub .

What's Changed - common McStas/McXtrace highlights:

  • [Feature] McStas and McXtrace are now fully on conda-forge also for Windows, since MCPL 2.0 arrived.
    This means that we now recommend to install via this mechanism on Windows. See the instructions for details.
  • [Feature] mcrun/mxrun have a new -y switch which runs a given instrument using its default parameters.
  • [BUGFIX] mcplot/mxplot should now deal better with negative / very small numbers in 'log' mode plotting.
  • [Feature] mcgui/mxgui improved tooltips on the run dialogue.
  • [Feature] rootmccode works with newer versions of ROOT
  • [BUGFIX] The KISS random number generator was earlier running with systematically different random numbers (and a shorter period) on Windows.
    Identical instruments now run with identical random numbers across platforms, when using identical seed.
  • [CI, packaging, platform support] Lots of work behind the scenes for portability, packaging, and improved CI of the code on GitHub.
    Better standard solutions and easier possibility of spotting when/if we make errors!

What's Changed - McStas specific highlights:

  • [BUGFIX] As reported on mcstas-users, reflective/transmissive polarisers/analysers could sometimes lead to |P|>1.
    This is now fixed by ellimination of "non-up-down" polarisation components when measuring an "up-down" polarisation.
  • [Feature] Contributed component Source_custom by @pablogila, useful features for simulatiung e.g. CANS and other pulsed sources.
    Comes with corresponding new test instrument.

What's Changed - McXtrace specific highlights:

  • [Feature] New components for Fluorescence + Single_crystal and Fluoresence + Powder.
    Come with corresponding new test instruments.
For a full list of changes, please consult the CHANGES or GitHub release notes

April 6th, 2025: Component doc pages back online

We are now in the air with new server hardware.

Among other things this means that component mcdoc pages are back online - by popular demand!

April 5th, 2025: Ongoing webserver upgrade

We are in the process of upgrading the webserver for McStas, McXtrace and other sites. Please bear with us if you experience service interruptions. :-)

February 19th, 2025: McStas and McXtrace 3.5.24 released

Dear all,
McStas and McXtrace release 3.5.24 is now available - McStas installation instructons on GitHub .

What's Changed

Important note

  • McStas and McXtrace will soon change organisation-name on GitHub - from McStasMcXtrace -> mccode-dev

User interfaces and tools

Components and instruments

Core simulation toolkit

Interfaces and interoperability with other codes

NCrystal

mccode-antlr

  • Thanks to @g5t for ping-pong on this :)
  • [Feature] mccode-antlr is an alternative code-generator for McStas and McXtrace - a new development by @g5t and based on ANTLR instead of lex/yacc. The new tool is mainly written in python and thus has a lower barrier for changes in language syntax and code generation. The tool implementations mcstas-antlr and mcxtrace-antlr are thus a candidate implementations to potentially replace the classic mcstas and mcxtrace code generators in the future. Current status is that
    • McStas: mcstas-antlr is fully feature complete wrt. mcstas for CPU simulations and close to complete for GPU simulations
    • McXtrace: Not all instruments will compile using mcxtrace-antlr but basic functionality is in place
    • To try:
      1. Install mccode-antlr from conda-forge or via pip
      2. Adapt your configuration to use e.g. mcstas-antlr by
        • Setting the new --cogen=mcstas-antlr option in mcrun
        • Enable or edit the MCCOGEN field of mccode_config.json using the new Save/Edit configuration in mcgui
        • (The antlr tools default to download comps etc. to an internal cache: Add e.g. -I${MCSTAS} to prefer ingredients fromyour local library)
      3. Use the mcrun-antlr/mxrun-antlr tools provided directly by mccode-antlr

Platform support

  • Debian/Ubuntu
  • Windows
    • [Feature] NCrystal is now available with McStas on Windows
    • [Info] Windows via cross-compiled .exeinstaller from mccode.org: Please place the MCPL-related .bat files from the extras folder in e.g. c:\mcstas-3.5.24\bin to enable MCPL (May require giving your user 'full access' permissions to the bin folder)
    • [Info] Windows via conda-forge: MCPL is not yet available but expected during the spring

Full Changelog: https://github.com/mccode-dev/McCode/compare/v3.5.16...v3.5.24

January 8th, 2025: Monte Carlo Satellite to ICNS2025

Dear all,

The ICNS2025 conference is taking place in Copenhagen and Lund this summer, and the abstract submission is closing January 15th - in one week.

Of special interest to McStas users:
A satellite event is being planned for July 11th, arranged by Mads Bertelsen, ESS and Peter Willendrup DTU/ESS. We envision a one-day event with contributed talks on instrument simulation and its use, abstract submission will open soon:

Advanced computer simulations methods for neutron scattering instruments

Abstract:
Neutron scattering relies heavily on computer simulations of neutron scattering instrumentation to optimize their performance. These simulation tools are also evolving to be more relevant for a running facility, aiding in both preparation and analysis for individual experiments. It is even becoming possible to make better decisions during experiments by running simulations in parallel.

All the best and hope to see you this summer in Copenhagen,
Peter Willendrup

Previous news items: 2024, 2023, 2022, 2021,2020,2019, 2018, 2017, 2016, 2015, 2014, 2013, 2012, 2011, 2010, 2009, 2008, 2007, 2006, 2005, 2004, 2003, 2002, 2001, 2000, 1999, 1998.

Last Modified: Tuesday, 29-Apr-2025 16:45:02 CEST
Search website mailinglist archive GitHub repos