[mcstas-users] McStas and McXtrace 3.9.2 released

[Peter Kjær Willendrup]

Dear all,

Due to a minor issue with McXtrace on the Debian platform, a new release from the 3.9 series has now replaced it:

Changes in McStas/McXtrace 3.9.2

A bug-fix release covering everything since the previous "announced" release, 3.9.0, including the changes already shipped quietly in 3.9.1. For the main new features of the 3.9 series, see the 3.9.0 release notes<https://github.com/mccode-dev/McCode/releases/tag/v3.9.0>.

Highlights

  *   OFF/PLY geometry library overhauled: polygons can now have any number of corners, and several geometry bugs are fixed: gravity with OFF samples, double hits on shared edges, and McXtrace Mirror in OFF mode, which did not reflect. Faces in the geometry file can now also carry their own properties. By @willend<https://github.com/willend>.
  *   Guide_anyshape now reads per-face coatings (m, alpha, W, ...) directly from the OFF/PLY file with the new file_coatings=1 option. This replaces Guide_anyshape_r, which moves to the obsolete components. By @willend<https://github.com/willend>.
  *   ESS Test Beamline (TBL) in ESS_butterfly: selecting sector W, beamline 11 automatically switches to a TBL mode that views both cold wings of the moderator. Consolidated by @willend<https://github.com/willend> with Claude from the TBL team's local version.
  *   Correct neutron ID and user variables in Union absorption loggers: the Monitor_nD-based Union loggers now record the real neutron ID and user0–user9 values instead of random numbers. By @tkittel<https://github.com/tkittel>.
  *   SasView samples combine with Union and more: instruments using a SasView sample together with Union_master, Refractor or the Bispectral mirrors now compile. By @tkittel<https://github.com/tkittel>.
  *   mcstas-chopper-lib updated to v4.2.3: the external chopper components NXdisk_chopper, Masked_ESS_butterfly and Polygon_ESS_butterfly now show up properly in mcdoc. By @g5t<https://github.com/g5t> and @willend<https://github.com/willend>.
  *   McXtrace data files found again on Debian/Ubuntu package installs when instruments are run directly, without mxrun. By @willend<https://github.com/willend>.

The full, categorised list of changes, common to McStas and McXtrace as well as specific to each, is in the McCode v3.9.2 release notes on GitHub<https://github.com/mccode-dev/McCode/releases/tag/v3.9.2>.

Full Changelog: https://github.com/mccode-dev/McCode/compare/v3.9.0...v3.9.2


Best and sorry for any inconvenience caused,

Peter Willendrup

On 5 Oct 2026, at 10.52, Peter Kjær Willendrup <pkwi at fysik.dtu.dk> wrote:

October 5th, 2026: McStas and McXtrace 3.9.0 released
Changes in McStas/McXtrace 3.9.0

Covers everything since the previous "announced" release, 3.8.4.

Highlights

  *   MPI is now enabled by default when compiling instruments. Multi-core runs work out of the box, and a long-standing hang in MPI runs with empty event lists is fixed. By @willend<https://github.com/willend>.
  *   NCrystal everywhere: NCrystal materials can now be used in Union, and PowderN / Single_crystal accept multiphase and single-crystal NCrystal materials. New components: Union_NCrystal_material and NCrystal_filter. By @tkittel<https://github.com/tkittel> and @mads-bertelsen-agentic<https://github.com/mads-bertelsen-agentic>.
  *   Union framework simplified: Union_init and Union_stop are no longer needed in your instruments, the framework is now self-contained (@mads-bertelsen-agentic<https://github.com/mads-bertelsen-agentic> and @g5t<https://github.com/g5t>). Also new: Union_abs_logger_nD_scintillator (@MilanKlausz<https://github.com/MilanKlausz>, with @tkittel<https://github.com/tkittel>).
  *   MCViNE sample kernels in McStas: 16 sample kernels from MCViNE (S(Q), S(Q,E), phonon, SANS and more), each available both as a standalone sample component and as a Union process. Contributed by @Fahima-Islam<https://github.com/Fahima-Islam>.
  *   New Dispersion_relation sample component for phonon or magnon scattering from tabulated (numerical) dispersion relations, tested against Phonon_simple and SpinWave_BCO. By Daniel Lomholt Christensen (@lomholy-agentic<https://github.com/lomholy-agentic>) and Kim Lefmann.
  *   Full component settings in NeXus output: in NeXus output mode, every component variable is now embedded in the output file with its actual runtime setting, so each simulation fully documents how its components were configured. By @willend<https://github.com/willend>, with related fixes by @tkittel<https://github.com/tkittel>.
  *   Much faster mcdisplay-webgl: the 3D instrument viewer no longer depends on Vite/npm and now starts up much faster. By @willend<https://github.com/willend>.
  *   Models of NeXT, the ILL neutron + X-ray imaging instrument, in both packages: ILL_H521_NeXT (neutron branch) in McStas and ILL_NeXT_Xray (X-ray branch) in McXtrace. Both were "vibe-coded" by @willend<https://github.com/willend> with Claude, starting from the instrument's webpage and the existing ILL information in McStas.
  *   New SOLEIL beamlines for McXtrace: SIRIUS, SAMBA and PUMA, plus fixes to CRISTAL. By @farhi<https://github.com/farhi>, with PUMA written by Uxue Saez Fernandez.
  *   Another big documentation round: refreshed manuals, new Union chapters, web versions of the manuals, and updated documentation for every component and instrument. By @willend<https://github.com/willend>, AI-assisted.

What's Changed

The full, categorised list of changes, common to McStas and McXtrace as well as specific to each, is in the McCode v3.9.0 release notes on GitHub<https://github.com/mccode-dev/McCode/releases/tag/v3.9.0>.

New Contributors

  *   @NoeB<https://github.com/NoeB> made their first contribution in #2697<https://github.com/mccode-dev/McCode/pull/2697>
  *   @lomholy-agentic<https://github.com/lomholy-agentic> made their first contribution in #2694<https://github.com/mccode-dev/McCode/pull/2694>
  *   @mccode-registrar[bot]<https://github.com/apps/mccode-registrar> made its first contribution in #2695<https://github.com/mccode-dev/McCode/pull/2695>

Full Changelog: https://github.com/mccode-dev/McCode/compare/v3.8.4...v3.9.0

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
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Direct +45 2125 4612
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pkwi at fysik.dtu.dk


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