[Neutron] December 12th, 2025: McStas and McXtrace 3.6.1 released

Peter Kjær Willendrup pkwi at dtu.dk
Fri Dec 12 13:12:57 CET 2025 

Dear all,

The McStas and McXtrace release 3.6.1 is now available.
McStas installation instructions are found on GitHub <https://github.com/mccode-dev/McCode/tree/main/INSTALL-McStas> .
McXtrace installation instructions are found on GitHub <https://github.com/mccode-dev/McCode/tree/main/INSTALL-McXtrace> .
What's Changed - Main Highlights:
Overall release focus:

  *   Code quality improvements: Suppression of warnings from c-compilers and our static code analysis tool cppcheck
  *   Continuous integration improvement: Any change in instrument/component code is tested via GitHub CI features

New tool features / capabilities:

  *   mcrun/mxrun simulation launch tool: (@willend<https://github.com/willend>)
     *   Scans can be parallelised at the "step number" level, use --scan_split. Contribution from @Lomholy<https://github.com/Lomholy>.
     *   If installed, cppcheck can be used to perform static code analysis on the generated code, use -C/--c-lint?
     *   Improved string-handling in input parameters, e.g. in use with NCrystal config strings. Contribution from @tkittel<https://github.com/tkittel>.
  *   mcplot/mxplot simulation plot tools: (@willend<https://github.com/willend>)
     *   Better support for 'intermediate saves' done via kill -USR2 or  Progress_bar, and plots should work on an unfinished simulation.
     *   Plotting a completed simulation with 'intermediate saves' will give you latest plot version in the 2D case and multiple, overplotted curves in the 1D case
     *   The mcplot-matlab/mxplot-matlab tool is back. You need to manually install either Matlab or Octave to make use of this
  *   mcdisplay/mxdisplay instrument visualisation tools: (@willend<https://github.com/willend>)
     *   On conda-based installations, the mcdisplay-cad/mxdisplay-cad tool includes the cadquery dependency. On completion of building the model, the OS is asked to handle the resulting CAD model.
     *   The mcdisplay-matlab/mxdisplay-matlab tool is back. You need to manually install either Matlab or Octave to make use of this
     *   For better integration with McStasScript, the mcdisplay-webgl-classic/mxdisplay-webgl-classic is used in such scenarios
     *   The 'newer/fancy' mcdisplay-webgl/mxdisplay-webgl based on THREE.js, react and other javascript requires a slightly time-consuming installation process on 1st launch. The user now gets an info box about this.
     *   The McStas-specific mcdisplay-mantid IDF generator tool received a bug fix for OFF geometry detectors.
  *   mcdoc/mxdoc documentation tool: (@willend<https://github.com/willend>)
     *   Higher quality / more complete comp/instr doc pages
  *   mctest/mxtest test tool: (@willend<https://github.com/willend>)
     *   Easier to use locally for component/instrument developers

Components and instruments:
McXtrace:

  *   The Fluorescence components have a new flag to enhance statistics/signal from low concentration materials. Work by @farhi<https://github.com/farhi>.

McStas:

  *   The Union subsystem now handles 'surface physics' with the introduction of a system of refraction/reflection processes on geometry surfaces. Work by @mads-bertelsen<https://github.com/mads-bertelsen>.
  *   The Union subsystem now has a functional 3D-mesh system (Union_mesh) that supports CAD style geometries. (Ascii/binary STL files and OFF files are supported. - For now only those with triangular meshing.) Work by @Lomholy<https://github.com/Lomholy>.
  *   As part of the overall code-quality improvement process, various aspects of the Union subsystem have been tested / improved / revised. Contributions by @tkittel<https://github.com/tkittel> and @willend<https://github.com/willend> in close collaboration with @mads-bertelsen<https://github.com/mads-bertelsen>.
  *   New ISIS-related instrument files, components and data:
     *   ISIS_LET by Ross Stewart and Rob Bewley, serves as test-instrument for Commodus_I3 (ISIS source model - corresponds to ViewModISIS with a different parameter interface)
     *   Updated / larger set of input files for the ISIS moderator components
     *   Multilayer_sample from Rob Dalgliesh was updated with nrepeats which allows to repeat an SLD material stack. ISIS_CRISP was updated to include this feature.
     *   TOF_PSDmonitor_toQ is a new component with built-in data reduction from Rob Dalgliesh. Uses ToF to calculate Q. Test_TOF_PSDmonitor_toQ is a basic instrument to showcase the component.
  *   Several of the basic McStas sample components received a systematic validation against analytical methods, thanks to @Lomholy<https://github.com/Lomholy> with help from KU/NBI students.
  *   As part of the overall code-quality improvement process, the whole component / instrument base got a BIG overhaul as such (@willend<https://github.com/willend>)

Platform support:

  *   The Windows/conda platform which uses the MSVC compiler is now fully functional for all McStas code and a good part of the McXtrace code. As part of this process a new header-file mccode-complex-lib.h should be used by all code requiring complex numbers. (Implements functions for e.g. +-*/ operations across platforms - MSVC does not self implement these operations...) @willend<https://github.com/willend>

For all release details, please refer to the github release page for version 3.6.1<https://github.com/mccode-dev/McCode/releases/tag/v3.6.1>


Seasons greetings from all of McStas/McXtrace - and hope you will enjoy this new release!


Peter Willendrup


Peter Kjær Willendrup
Forskningsingeniør, Specialkonsulent

DTU Physics

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Technical University of Denmark


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Department of Physics
Fysikvej
Building 307
DK-2800 Kongens Lyngby

Main office at
ESS DMSC
Building 305
DK-2800 Kongens Lyngby

Direct +45 2125 4612
Mobil +45 2125 4612
Fax +45 4593 2399
pkwi at fysik.dtu.dk

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