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

October 6th, 2026: McStas and McXtrace 3.9.2 bugfix released

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.

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.
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.
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 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.
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.
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 and @willend.
McXtrace data files found again on Debian/Ubuntu package installs when instruments are run directly, without mxrun. By @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.

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

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.
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 and @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 and @g5t). Also new: Union_abs_logger_nD_scintillator (@MilanKlausz, with @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.
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) 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, with related fixes by @tkittel.
Much faster mcdisplay-webgl: the 3D instrument viewer no longer depends on Vite/npm and now starts up much faster. By @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 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, 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, 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.

New Contributors

@NoeB made their first contribution in #2697
@lomholy-agentic made their first contribution in #2694
@mccode-registrar[bot] made its first contribution in #2695

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

September 11th, 2026: McStas and McXtrace 3.8.4 released

Installation

For McStas proceed to the McStas install docs (GitHub)
For McXtrace proceed to the McXtrace install docs (GitHub)

Changes in McStas/McXtrace 3.8.4

Covers everything since the last full release, 3.7.9 (July 2, 2026), including all changes already shipped quietly via the intermediate conda-forge releases 3.7.10–3.8.3, and a ground-up rewrite of the McStas/McXtrace manuals.

Sorry for any incovenience caused if you installed any of 3.8.1-3... Some doc-details were still not in place!

What's Changed

Common to McStas and McXtrace

Manuals

First full manual makeover since the McStas 2.x / McXtrace 1.x series. Tool-usage chapters (mcrun/mxrun, mcplot, mcdisplay, mcgui, mcdoc, ...) rewritten against the actual CLI code; component reference/parameter tables now generated directly from the current .comp sources (closing a long-standing manual/code drift); mcdoc itself reworked to support it. By @willend in #2592
Numerous long-standing inaccuracies fixed along the way: RNG engine description (KISS default / MT optional), obsolete components now explicitly labelled as such, stale legacy sections removed, http->https, and a batch of LaTeX build-pipeline fixes; McXtrace manual also had McStas copy-paste leftovers removed and its "running"/RNG sections aligned with McStas's — all by @willend in #2592
AI-assisted: reference material and source code (usage articles, grammar/cogen.c, example instruments, component sources, tool CLIs) were given to an AI coding agent to draft the updated text, reviewed and merged by @willend. Given the scale of the rewrite, minor errors/omissions in the manuals are expected — please flag anything you spot via a GitHub issue
mcdoc's browser-based overview page now also links to per-tool cheat-sheets (mcrun, mcgui, mcplot, mcdisplay, mctest, mcdoc, code generators) and to new standalone Instrument/Component grammar reference pages, all a click away from the component browser by @willend

New links in mcdoc. Also visible on this website: Documentation overview page
Tool documentation overview
INSTRUMENT grammar
COMPONENT grammar

New tooling

New tools mcplotdiff-html/mcplotdiff-pyqtgraph/mcplotdiff-matplotlib: plot the difference between two simulation results, monitor by monitor (diff.monN = a.monN - b.monN), with a diverging blue/white/red colour scale for 2D monitors and diff datasets written out as normal, reopenable McCode .dat files by @willend in #2560, #2562, #2564 — later reworked to show %-difference in #2599 and to always write diff datasets in #2585
- mcviewtest now spawns mcplotdiff-html automatically by @willend in #2568
New tools mccoplot-html/mccoplot-pyqtgraph/mccoplot-matplotlib: companion to mcplotdiff, overlaying two (or more) datasets' 1D monitors on the same axes for direct curve comparison by @willend in #2587, with n-way overlay support in #2594 and a McXtrace-side fix in #2589
- mcviewtest also spawns mccoplot generation by @willend in #2588, #2595
mctest: added -s/--seed option and an option to emulate McCode's classic "Unix epoch" default seed, for reproducible test runs by @willend in #2575, #2576
mctest: new --strict mode fails a test if an instrument is missing its %Example: header line(s) by @willend in #2602 (spillover-bug fix in #2604), plus general robustness improvements in #2603 and a GPU-box-specific fix in #2613
mctest: fixed TypeError on re-runs caused by displaytime never being restored from the saved JSON state by @mads-bertelsen-agentic in #2624
mcplot-html: added a slider to control plot iframe size, and geometry/scaling adjustments, by @willend in #2547, #2548, #2549, #2550
Fix issue #2561 — make 2D-plot colourbars visible in more cases by @willend in #2563
Speed up execution of mcplot-matplotlib (especially for large 2D matrices) by @willend in #2570
Matplotlib-plotters: fix for non-draggable legends by @willend in #2614
mcrun/mxrun: allow multiscan -M with list-scan -L and new scan/list syntax par=a:delta:b for both -N and L modes by @willend in #2618
Plottable mccode.dat in the NeXus-scan case by @willend in #2619
mcgui/mxgui: non-numeric entries in nsteps are now deferred to mcrun for interpretation instead of rejected up front by @willend in #2625
mcdoc: list %Example: lines in bold by @willend in #2636
Minor tweak on mcviewtest — tolerate a trailing / in ref path by @willend in #2593

Code generator & grammar

RNG correctness fix: the KISS generator's 7-word per-particle random state was only partially backed up/restored across a SPLIT loop (silently corrupting RNG state), and the Mersenne-Twister seed was never actually applied at start-up due to a stale RNG_ALG check — both fixed by @mads-bertelsen-agentic in #2620
Cogen: simplify COPY(instance) to no longer transfer EXTEND et al. by @willend in #2627 (two affected instruments updated in #2640)
Enable mcstas-antlr in McCode GitHub CI by @willend in #2610
Edits for increased compatibility with mcstas-antlr by @willend in #2612
Consequence-edits from antlr-compatibility: add missing pragmas by @willend in #2616
Add input parameters to base .py instrument generated by mccode-pygen by @willend in #2601
Implement pygen-suggestion from @MilanKlausz (#2554) by @willend in #2555
Fix for collision between stdlib:: syntax and mcrun min:delta:max scan syntax by @willend in #2626
Fix issue #2606 + other unneeded use of GETPATH() by @willend in #2609
[Ref] move static comparison out of the hot TRACE path by @g5t in #2591 — a good general reminder that a WHEN(...) clause runs once per particle, so precomputing a flag in INITIALIZE beats a strcmp() in TRACE

Infrastructure / build system / CI

New CMake FetchContent integration for Greg Tucker's mcstas-chopper-lib by @willend in #2631, with a test instrument added in #2632
Consolidate conda/non-conda 'basictest' workflows and use with new mcviewtest by @willend in #2577
Minor bugfixes for testsuite-workflows/nightlies by @willend in #2578, #2581
Back to 1e6, testsuite workers are killed by time-limit by @willend in #2582
Let testsuite run with 2 cores on macOS, auto elsewhere by @willend in #2583
Use mpi=2 on macOS also in basictests by @willend in #2586
Include GitHub worker id as unique identifier for datasets by @willend in #2598
Trigger 'RUNALL' if > 4 comps were changed by @willend in #2641
Suppress use of cif2hkl in Test_Powders by @willend in #2634
Repair 'autobuild' download of 'innosetup' installer by @willend in #2573
Release doc updates 3.7.9 by @willend in #2545
Update pullrequesttemplate.md by @willend in #2559
Update notebook template to reflect McStasScript 0.0.89 properties by @willend in #2580
CI: various workflow fixes by @willend in #2615
Minor instrument header fixes + plug missing README.md's by @willend in #2639
Rectification of Windows batch-wrappers by @willend in #2566, #2567

McStas only

New instrument: import of FRMII_SPODI / FRMII_SPODI_MULTI, a powder diffractometer at MLZ Garching (contributed by V. Kochetov, C. Hauf, M. Hoelzel and A. Senyshyn) by @kinetik161 in #2608 — enabled to run on GPU/OpenACC by @willend in #2623
New instruments: import of 3 x imaging instruments from various sources (PSI_ICON, Radiography_Lithium_Battery, Radiography_Sword) by @willend in #2569
New components (via mcstas-chopper-lib, see FetchContent integration above): Masked_ESS_butterfly and NXdisk_chopper, with their test/example instruments Masked_ESS_butterfly_image, NXdisk_chopper_display and NXdisk_chopper_image, courtesy of @g5t's mcstas-chopper-lib — installed directly into the normal mcstas-comps/contrib and examples/Tests_optics locations, so they appear in mcdoc/mcgui like any other McStas component
PowderN: remove erroneous order parameter by @Lomholy in #2622
Sans spheres intensity fix by @Lomholy in #2600
ILL_SALSA: fix linter and add n reflections to parameters by @Lomholy in #2572
Patch issue #2637 — Vertical_Bender gravity always disabled by @MilanKlausz in #2638
Union: add nowritefile parameter to all Union loggers and abs_loggers by @mads-bertelsen-agentic in #2607
Work on ESS source description / comparison with MCPL inputs by @willend in #2596
Fix for compilation failure of ESS/MCPL instrument under openacc by @willend in #2597
Use filenames in MCPL instrument Monitor_nD instances to get rid of timestamps by @willend in #2574
Add another MCPL_output -> producing neutrons in instrument coordinate frame by @willend in #2629
MCPL file was moved - update instrument file by @willend in #2630

McXtrace only

McXtrace: work toward fixing #2514 (GPU) by @willend in #2556
Likely fix for McXtrace / Abs_objects test on GPU by @willend in #2557
WORKAROUNDS: disable key tests in McXtrace (#2514) by @willend in #2558
Filter.comp: better handling of non-standard input files by @willend in #2552
Fix for mxcoplot-html McXtrace by @willend in #2589

New Contributors

@kinetik161 made their first contribution in #2608
@mads-bertelsen-agentic made their first contribution in #2624
@MilanKlausz made their first contribution in #2638

Full Changelog: https://github.com/mccode-dev/McCode/compare/v3.7.9...v3.8.4

July 2nd, 2026: McStas and McXtrace 3.7.9 released

Changes in McStas/McXtrace 3.7.9, July 2nd, 2026

Release 3.7.9 marks a milestone for McXtrace that finally gets full support for complex number calculations using MSVC on Windows. We further improve the installation experience on Windows by addition of a new install script for downloading and setting up the MSVC compiler tool chain.

Install instructions

For McStas 3.7.9
For McXtrace 3.7.9

What's Changed

Common to McStas and McXtrace

Platform suppport

Windows
- mctest / windows output improvement by @willend in #2505
- batch-script to help install msvc on Windows by @willend in #2505
- Add micromamba clean --all -y in install batches by @willend in #2507
- Improved wording for README and add non-admin option to msvc-install script by @willend in #2508
- Add git when setting up dev-env on Windows by @willend in #2510
Tools
- mctest:
  - Improvements to mctest tool by @willend in #2511
  - More fixes to mctest logic by @willend in #2512
  - Add simple infrastructure to mctest for generating plots (when possible) by @willend in #2539
- mcplot-html
  - Minor tweaks on html plotter and mctest by @willend in #2540
  - More minor tweaks mcplot-html by @willend in #2541
  - Add mcplot-html batch wrapper for Windows support by @willend in #2542
  - Flat / pixellated 2D plots for mcplot-html by @willend in #2544
- mcdisplay:
  - Pass at key points in mcdisplay particleparser instead of raising exceptions. by @willend in #2516
- mcrun
  - New --dirsuffix/--dirprefix switches for mcrun/mxrun by @willend in #2533
Shared lib-codes
- Provide SCATTER_func for libraries to replicate SCATTER functionality by @mads-bertelsen in #2535

McStas only

Minor comp / instrument improvements
- Exit minus 1 harmonization by @willend in #2503
- Fix for Incoherent component limited order + hollow geometry by @mads-bertelsen in #2506
- Various fixes for FZJ_BenchmarkSfin2/SANS_benchmark2 by @willend in #2517
- ILL_H15_SAM.instr: Common SPLIT=100 at sample(s) ensure ncount >=1e7 by @willend in #2518
- Ensure 1e7 for non-display runs of ILL_H22_D1B by @willend in #2519
- Various fixes for McXtrace and McStas instruments by @willend in #2520
- Various fixes for McXtrace instruments by @willend in #2520
- Added mcdisplay section to FlatEllipse_finite_mirror component by @mads-bertelsen in #2521
- Fix ascii reallocation in Union_mesh by @mads-bertelsen in #2532
- H frielinghaus SANS_benchmark2 input files by @willend in #2536
- Fix #2537: Bug in PSD_monitor_4PI found by BSc. student Christian Thyssen NBI. by @willend in #2538

McXtrace only

General
- Support for MSVC (and complex numebers via mccode-complex-lib) on Windows
Comp / instrument improvements
- McXtrace: Fix of #1579 for most (if not all) comps/instrs by @willend in #2504
- McXtrace test target updates by @willend in #2515
- Various fixes for McXtrace instruments by @willend in #2520
- Filter.comp is in fact incomplete for refraction and shape != cube. by @willend in #2522
- Temporary hack to avoid McXtrace cif2hkl fct. in Single_crystal on Windows by @willend in #2524
- Windows/cif2hkl issue workaround for Test_PowderN by @willend in #2525
- Various changes to stabilise McXtrace SOLEIL_PX2a tests by @willend in #2526
- More McXtrace tweaks, SOLEIL_PX2a and SOLEIL_PSICHE by @willend in #2527
- Beef up required stats for SOLEIL_PSICHE + adjust target val by @willend in #2528
- McXtrace Enable all tests in Test_Mirrors by @willend in #2529
- Fix header by @willend in #2530
- Fix of McXtrace/mxdisplay of specific instr by @willend in #2533
- Fix filter geometry by @ebknudsen in #2534
- Improve on flexibility of McXtrace Filter.comp input types by @willend in #2543

Full Changelog: v3.7.6...v3.7.9

June 16th, 2026: McStas and McXtrace 3.7.6 released

Installation:

See McStas install pages on GitHub for details

What's Changed

Common to McStas and McXtrace:

Tools

mcgui/mxgui list mode scanning:
- Support mcrun -L scan mode via mcgui 'Scan steps' entry by @willend in #2493
Small but important improvements to mcdisplay/mxdisplay:
- pyqtgraph variant:
  - Restore various click/keyboard control across PyQt5/PyQt6
  - Improvements to mcdisplay(-pyqtgraph) component list (do not underflow main window) by @willend in #2489
  - Fix missing PyQt5->PyQt6 correction for mcdisplay-pyqtgraph by @willend in #2481
  - Fix of another mcdisplay-pyqtgraph PyQt6 vs PyQt5 bug by @willend in #2485
- matplotlib variant:
  - Silence mcdisplay-matplotlib noise when pressing 'q' by @willend in #2483
- Common, parsing-system:
  - Fix for rare bug: Add fflush(stdout) protection of DEBUG_COMPONENT (fix #2486) by @willend in #2487

Libraries

KDSource functional in mingw builds (+other minor improvements) by @willend in #2497 (comes with both McStas and McXtrace even though KDSource.comp is McStas-only for now
Get rid of 'dirent' dependency on Windows systems
- Dirent windows fixup by @willend in #2496

Installers

New MSVC-based installer-bundle for both McStas and McXtrace, will eventually fully replace the MinGW installer-bundle
- See McStas windows install page for details
- See McXtrace windows install page for details

McStas only:

Components

Update NMO.comp by @willend in #2474

McXtrace only:

No McXtrace-specific comp/instr changes

Infrastructure, common to McStas/McXtrace:

Fixes to installdocs by @willend in #2476
Various work on GitHub actions by @willend in #2488
Give mctest a --displaymax handle by @willend in #2495
Prepare for 3.7.6 release by @willend in #2498

Full Changelog: v3.7.1...v3.7.6

May 22nd, 2026: McStas and McXtrace 3.7.1 released

Installation instructions

For McStas go to The McStas install page on GitHub
For McXtrace go to The McXtrace install page on GitHub

What's Changed

Main new developments:

Common McStas and McXtrace developments:

Up to 10 USERVARS supported with Monitor_nD (named user0,...,user9)
Qt5 -> Qt6 across the package and dependencies
Bugfix: Fix of rare visualisation bug in mcdisplay/mxdisplay (e.g. box was not allowed as a comp name)
Doc improvements:
- mcdoc/mxdoc can render .tex and .md in addition to .html
- Example instruments come with an in-repo README.md generated via this mechanism
- See e.g. McStas BNL_H8 or McXtrace ESRF ID01
CI/test improvements:
- mcdisplay/mxdisplay visualisation is performed as part of mctest/mxtest runs (-> CI)
- See top html files in McStas and McXtrace nightly test runs

McStas specific developments:

Integrated support for KDSource
- New component KDSource
- For usage details, see example instrument Test_KDSource and the KDSource documentation website
- Available as automatic dependency on conda-forge based installations (including macOS and Windows 'installers'
- Not available as .deb package on Debian systems but may function by installing via pip.
  Recommendation: Just use conda-forge.
Pulse-length adjustment available for ESS_butterfly
- Handled via specifically named instrument input parameter and DEPENDENCY line
- See example instrument ESS_butterfly_Adjustable_Pulse
PowderN now supports NCrystal cfg-strings.
- Forwards request to NCrystal that populates datastructures without intermediate .laz/.lau files
- See example instrument Test_Powders - comp=0 mode
Bugfixes:
- Fix to Union, orientation of loggers wrt. master comp
- Bugfixes to recently added improved Union mesh
Contributions from NBI/KU:
- Inhomogenous_incoherent_process in Union from @Lomholy, (via ‘tinyexpr' string-expression inputs) - see rel. test instrument
- New spinwave comp SpinWave_BCO from @SSBNS - see rel. test instrument
- ESS KVASIR instrument proposal - backend instrument with MCPL input from BIFROST optic. @AmalieFalkenberg. Includes Jupyter notebook in McStasScript syntax.
McStas component manual uses .tex snippets from generated via components mcdoc

McXtrace specific developments:

Much improved Union subsystem for McXtrace by @ebknudsen. Makes use of Xraylib for Compton and Rayleigh scattering models.
Test instruments for the new Union processes, both from @ebknudsen
- PowderCompton_union - Compton scattering and powder diffraction
- Test_KN_Comp_Rayl_union - test instrument using Klein-Nishina, Rayleigh, or Compton
  scattering processes.

New Contributors

@SSBNS made their first contribution in #2373
@AmalieFalkenberg made their first contribution in #2345

Full Changelog: v3.6.14...v3.7.1

April 13th, 2026: McStas and McXtrace 3.6.14 released

Installation instructions

For McStas go to The McStas install page on GitHub
For McXtrace go to The McXtrace install page on GitHub

What's Changed
(Selected items, please consult the GitHub changelog for full set)

New comps/instruments

Adding the ILL SANS instrument 'SAM' by @nmgm in #2388

New tool feature: NeXus scans become entries in one common HDF file

Prototype solution to allow 'append' mode for datasets by @willend in #2376

Various updates to instruments/components/data files

Fix Union mcdisplay bugs by @Lomholy in #2294
Fix to MPI-mode use of Brilliance Transfer calculation. by @willend in #2300
Minor instrument and comp updates, McStas by @willend in #2332
More %Example tests for McStas instruments by @willend in #2333
More additions of McStas %Example lines by @willend in #2337
Update of McXtrace Incoherent_process comp from EBK branch by @willend in #2338
Add more %Example lines to McStas instruments by @willend in #2341
Add Test instrument for Be-filter models by @willend in #2349
Re-enable a few tests on the nightlies by @willend in #2364
ESS_butterfly: Wrap all printf / fprintf in MPI_MASTER( ); by @willend in #2372
Updated Rubredoxin lau file from @aaronfinke by @willend in #2384
Updated Example values following updated Rubredoxin.lau by @willend in #2386
Adapt Guide_m interface -> style of Guide_gravity parameters by @willend in #2389
McStas Monitor_nD “nexusbins” only in listmode by @willend in #2387
Mono bent complex string parsing by @Lomholy in #2395

Various tool improvements

mctest / timeout system - ensure to kill underlying processes by @willend in #2363
Add timers for maximal compile / runtime in mctest by @willend in #2356
Add hints for alternative mcdisplay visualisation in Jupyter... by @willend in #2353
mcrun -L list was broken, fixed here by (re-)calculating number of elements … by @willend in #2377
Changed (hard-coded) mcgui 3D visualiser to be webgl-classic by @willend in #2381
On Windows use psutil for probing number of available cores in MPI by @willend in #2367

Other changes

Please consult the GitHub changelog

Fixes to various bugs
LaTeX in doc headers
Clang-format formatting of component syntax
Various updates to project infrastructure: PR template, CI etc.
Various GPU related fixes

New Contributors

@nmgm made their first contribution in #2388

Full Changelog: v3.6.5...v3.6.14

March 31st: First circular: PHOTONS AND NEUTRONS REALISTIC ARTIFICIAL INTELLIGENCE DATASETS (PaNRAID)

Dear Colleagues,

In collaboration with the French DIADEM Academy, we invite interested participants to attend the following course in September:

PHOTONS AND NEUTRONS REALISTIC ARTIFICIAL INTELLIGENCE DATASETS (PaNRAID)

Dates: 21-25 September
Location: Île d’Oléron, France

Objective

The course will develop an integrated approach for generating synthetic data for supervised learning. This approach combines multi-scale materials simulations (DFT, MD, XAS spectroscopy) with comprehensive digital twins of experimental X‑ray and neutron facilities, explicitly accounting for instrumental effects and experimental artefacts.

Intended audience

Doctoral students
Postdoctoral researchers
Faculty and teaching-research staff
Researchers and research engineers

Further information and pre-registration: https://formation.pepr-diadem.fr/formation-panraid

Attached are PDF flyers in French and English.

Best regards,
Peter Willendrup

March 28th, 2026: McStas 2.x and McXtrace 1.x formally out of support

Dear all,

We have decided to formally declare that we no longer support McStas 2.x and McXtrace 1.x, so user issues with these released will from now on always prompt us to request that you upgrade.

If you are still running such an old release, please upgrade and port your comps/instruments using the information in the use the wiki-based porting-guides

We are of course at your service if you have issues porting your existing code, please create a GitHub issue.

March 13th, 2026: "Best of McStas compilation"

Dear all,

In connection with a user request I realised that occasionally we may all benefit from easier access to old McStas variants.

I have therefore put together a "Best of McStas compilation" - a Linux image with McStas version 1.12c, 2.7.2 and the latest 3.6.8.

You can give the image a quick trial spin via binder:
https://mybinder.org/v2/gh/mccode-dev/jupyter-mcstas-mcxtrace-desktop/HEAD?urlpath=desktop
(will not in practice sustain much actual work / load)

Or alternatively pull docker.io/mccode/mcstas_v1.12c_v2.7.2_v3.6.8:latest via Docker / podman / etc., i.e. something like

podman run -p 8888:8888 docker.io/mccode/mcstas_v1.12c_v2.7.2_v3.6.8:latest

connect your browser to the listed URL

Best and hope this may be useful,
Peter

Screenshot of the running compilation:

January 7th, 2026: McStas and McXtrace 3.6.5 released

McStas and McXtrace release 3.6.5 is now available.
McStas installation instructions are found on GitHub .

What's Changed - Main Changes:

Bugfixes, new features, all common to McStas and McXtrace:

macOS bundles in 3.6.1 did not actually install that version but something earlier. Fixed by pinning in yml file, @willend in #2285
PDF manuals had wrong version numbers, @willend in #2285
Allow mcrun / mcdisplay to run / visualize without access to .c/.instr by @willend in #2281
mcgui/mxgui editable font colors, handle long filenames without extreme window resizing by @willend in #2275
Fix cross-platform sort-order issue in PowderN by @willend in #2272
Platform-independent reflection list sort in Single_crystal by @willend in #2273
mcrun/mxrun: feature addition - scan by seed by @willend in #2276
Add mcplot toggle to "plot 1D-curves from 0-value" in linear mode by @willend in #2278
Add commentstring to vim editor by @Lomholy in #2284

Other stuff

%Example adjustments, McXtrace by @willend in #2269
Test_SANS/Test_SAXS, supplement stats by x10 SPLIT by @willend in #2270
Use ${{ matrix.mpi }} to ensure different output dirs by @willend in #2271
Fix indentation bug - issue #2279 by @willend in #2280
Temporarily disable this instr from McXtrace tests by @willend in #2283

Full Changelog:https://github.com/mccode-dev/McCode/compare/v3.6.1...v3.6.5

Previous news items: 2025, 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.