McStas - A neutron ray-trace simulation package

Download and installation instructions are available via our GitHub INSTALL-doc pages.

Selected highlights from the releass are listed below. The full list changes is also available at https://mcstas.org/CHANGES_McStas.

If you didn't start already, please start your migration to 3.x:

• The Wiki has a dedicated section on McStas 2.x -> McStas 3.x conversion that includes:
  • An overview of differences
  • A nomenclature list containing short descriptions of new concepts and important keywords in McStas 3.x and OpenACC / CUDA code in general.
  • A document outlining the most importand differences between 2.x and 3.x.
  • A guide for 2.x -> 3.x instrument conversion.
  • A guide for 2.x -> 3.x component conversion.

Fixes of issues from last 3.x release:
A number of issues from 3.2 were addressed, see the relevant GitHub issues for details:
3.2 issue list

Release highlights

• Installation and core packaging:
  • McStas 3.3 comes with embedded NeXus support on macOS and on Debian/Ubuntu NeXus is pulled as a package dependency. On Windows, please install NeXus from the extras/ folder alongside your McStas bundle.
  • The build process for macOS has been overhauled and is now performed with the embedded conda environment. Further, the macOS builds should be more robust wrt. added, surrounding non-standard Python environments on the target machine.
• GPU support:
  • McStas 3.3 enables most components and instruments on GPU. A very limited instruments using the "scatter logger" mechanism are still only available on 2.x and key components (e.g. Union and NCrystal) compute only on CPU.
  Tools:
  • mcrun now automatically adds NeXus support to your binary if --format=NeXus is given on the commandline (or if DEPENDENCY " @NEXUSFLAGS@ " is included in your instrument or component file).
  • The new input flag --IDF will run an IDF generator (i.e. mcdisplay-mantid) prior to performing a NeXus-based simulation, i.e. for "one-click" support of output in Mantid-compatible NeXus format with an embedded IDF. Please consult the naming-conventions for sourceMantid, sampleMantid and nD_Mantid_xx found in https://github.com/McStasMcXtrace/McCode/wiki/McStas-and-Mantid#mcstas-mantid-workflow to succesfully generate your IDF. Please also inspire from the example instruments in the Mantid category, see mcgui -> File -> New from template -> Mantid .
  • mcrun now forwards the -I input to the code-generator, which allows you to add a chosen folder with extra components etc. to your search path. Setting the -I flag implies recompilation (-c). (Please also note the related SEARCH grammar below which allows working on the component search path directly via the instrument or component grammar.)
  • The mcgui run dialogue now allows to directly specify --format=NeXus and --format=NeXus --IDF when starting a simulation.
  • mcdisplay-mantid has been given a good overhaul and now works properly with all of the supported mantid-event-detector geometries of Monitor_nD: rectangular, cylindrical/banana and OFF-file based. Thanks to Torben R. Nielsen and Celine Durniak (ESS) for repeated testing.
  • mcplot (-pyqtgraph) and numpy related bug was quickly spotted and ironed out with the help of by Rose Robledo FZJ.
• Components and Instruments:
  • FZP_simple model.comp of Fresnel Zone-Plate (phenomenologic/closed-form thin-plate approximation) added along with test instrument Test_FZP_simple.instr, work by Anders Komar Ravn (NBI), and Erik B Knudsen (previously DTU, now Copenhagen Atomics)
  • Test_Monochromators.instr has been updated to include NCrystal_sample as a monochromator, plus includes multiple ways of parametrizing Single_crystal lattice orientation. (Please note that NCrystal support is still not complete on Windows.)
  • The 3 example ConicTracer interface-component codes Conics_EH.comp, Conics_PH.comp, Conics_PP.comp have been updated to allow specifying non-equidistant radii of the nested optical shells. Please use vector radii={a,b,c,d,e} or initialization via an instrument-based array and use a compatible setting of nshells.
  • The Elliptical_guide_gravity.comp will now complain if you are using arrays for specifying varied coating without setting the nSegments input.
  • The multi-v-cavity support from the McStas 2.x version of Pol_guide_vmirror.comp has been ported to 3.3. Thanks to Damian Rodriguez and Hal Lee (ESS) for interactions on this component.
  • By popular demand, certain characteristics of the ESS_butterfly component may be modified using compile-time re-definition. Defaults are ESS_SOURCE_DURATION0=2.857e-3 s, ESS_SOURCE_FREQUENCY 14 Hz, ESS_SOURCE_POWER 5 MW. (Use e.g. mcrun --D1=ESS_SOURCE_DURATION=1.0e-3 to simulate a 1 ms pulse.)
  • Similarly, the precession-algorithm constants of pol-lib may also be redefined at compile-time, defaults are: MCMAGNET_STACKSIZE=12, mc_pol_angular_accuracy=(1.0*DEG2RAD) deg, mc_pol_initial_timestep=1e-5 s.
• Core simulation framework / code-generator:
  • A new syntax called SEARCH has been added to the grammar, allowing users to run append a directory to the mcstas search path when looking for components. The syntax may be given in the instrument- or component-header directly after a SHELL token and before the DEPENDENCY, DECLARE tokens, available in two variants:
    • SEARCH "/the/path/to/add/"
    • SEARCH SHELL "the_executable --and --some --options"
    But you may also apply the same two SEARCH forms in connection with a component instance in TRACE, e.g.:
    TRACE
...
SEARCH SHELL "readout-config --show compdir"
COMPONENT readout = Readout(ring="RING", fen="FEN", tube="TUBE", a="left", b="right", ...)
AT (0, 0, 0) ABSOLUTE
...
    
  • Thanks to Gregory S. Tucker (ESS) for contributing this grammar enhancement!
• Libraries and other runtime code:
  • The (r-)interoff-lib.c family of codes have again received a couple of updates, thanks to McStas user Richard Wagner (ILL).
  • NCrystal library version 3.5.1 from T. Kittelmann (ESS) and X.X. Cai (CSNS), distributed with McStas on Unix platforms only. (Cross-compiles for Windows, but still needs work for "production" availability.)
  • MCPL library from the same authors included at v. 1.6.1
• Platforms:
  • We still support 64bit Windows 10/11 on Intel, three most recent 64bit macOS (11 Big Sur -> 13 Ventura) on both Intel and Apple Silicon/M-series processors. Debian-based distros on Intel and Arm, Fedora on Intel.
  • On macOS and Windows we bundle a Mambaforge Python with the installation.

Our Docker and binder containers will be updated within the following weeks.

We hope you will enjoy this new release!!!

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