McStas - A neutron ray-trace simulation package

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.

• Click here for a Desktop
• Click here for a Jupyter

mcgui

Note that the session is not persistent, so using this for actual work is a bad idea. :-)

Instead you may also use the corresponding Docker container, can be run with

podman run -p 8888:8888 -p 5173:5173 docker.io/mccode/mcstas-mcxtrace

September 16th, 2024: McStas and McXtrace 3.5.1 release!

Dear all,

It is finally time for a set of new McStas and McXtrace releases: v3.5.1!

Thanks:

• Thanks to all members of the joint McStas-McXtrace team and input from our users via emails and GitHub issues alike! Further a special thanks to Theodor Peter Guttesen (former DTU diploma student) who has helped modernise our 3D visualisation!

Most important changes going forward:

• From release 3.5.1 McStas and McXtrace are released simultaneously and with the same versioning (meaning that McXtrace takes a jump from 3.2 up to 3.5)
• With release 3.5.1 we are officially dropping support for the "legacy" McStas 2.7.2 release and the "legacy" McXtrace 1.7.1 release.
• To minimize work required for platform support and builds, we are now focusing on fewer platforms:
  • Debian packages at packages.mccode.org are provided for x86_64 and arm64 Linux (Thanks to the work of Emmanuel Farhi and his team at SOLEIL, official Debian packages are already available in Debian Testing and Unstable (see https://tracker.debian.org/pkg/mccode) and should become widely available with next Debian Stable, after which we might drop our "own channel").
  • conda-forge is to become our distribution channel for "everything else", meaning that:
    1. Our macOS "bundles" are effectively now self-extracting conda-installers and REQUIRE an active internet connection during installation
    2. From a later release in the 3.5 series the same will be the case for Windows
  • We are dropping builds for ALL rpm-oriented platforms. Please use conda-forge instead.
• We want to release more "early and often" going forward, see the linked CHANGES documents under conda-forge.

Both codes have received a number of bug fixes, new models and features - and to mention everything here would quickly become too long. But those interested in the details are recommended to read the respective CHANGELOGs for the two codes:

• CHANGES_McStas
• CHANGES_McXtrace

One little P.s:
The transition to the new releases require a little extra, unexpected work on the websites - so please expect a little website-documentation inconsistency for the next week or two.

All the best from the joint

McStas-McXtrace team

May 16th, 2024: (experimental) previews of the forthcoming 3.5-release

Dear all,

If you want a sneak preview at the forthcoming 3.5-release, we recommend you to try either

• Our conda-forge packages
  (NB: The Windows version of the package does not include MCPL and NCrystal yet)
• A new set of conda-based macOS app bundles
  (Based on conda-forge and should auto-download the newest conda-package plus dependencies)
• Corresponding Debian packages, Windows/MinGW package and macOS/Intel package are built on a nightly basis via GitHub action "mcstas-autobuild" see e.g. this latest one
  (The packages are available in the "artifacts", download may require being logged in on GitHub. Somewhat confusingly, the Windows build is enclosed in the "ubuntu" artifact.)

Among the hightlights are:

1. New default-CFLAGS
   (Gives improved simulation performance of ~ 30-40% when using gcc and/or clang on Unix platforms at the cost of 5-10% longer compile time. -
   Thanks to Thomas Kittelmann for help debugging a slowdown found when using the built-in compilers on conda :-) )
2. Tighter integration with McStasScript
   (mcstas-pygen-driven button in mcgui directly spawns JupyterLab with a generated notebook)
3. McStasScript is automatically included and configured on mac and Windows builds
4. We have started organising the instrument-examples in a folder-structure, allowing to distribute "more than just the instrument-file" as an example.
   (Case-specific datafiles or geometry-files, c-code snippets, python scripts or McStasScript notebooks welcome - we still want new comps to arrive in contrib)
5. New GISANS_sample.comp contribution from Henrich Frielinghaus, allows to simulate selected samples for Grazing Incidence SANS.
6. New File.comp contribution from Greg Tucker, allows to use metadata blocks to store input-files for components
   (e.g. for a small OFF file or other datafile - then visible alongside instr in your editor.)
7. ... and we are working on freshening up certain aspects of the 3D-visualisation... ;-)
   (New visualisation is not yet included in the above-mentioned packages...)

Do you have new component- or instrument-developments you would like included in next release?
- Then NOW is a good time to send them. :-) We prefer of you open a PR on GitHub but of course email-based contributions are also welcome. :-)

Finally, if you know anyone running McXtrace most of the above should also work for them. And going forward, releases of McStas and McXtrace should come in pairs with the same versioning.

Previous news items: 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.