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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

January 24th, 2020: McStas 2.6 release!

Dear all,

A new release of McStas, v. 2.6 has been built and is ready for download!

Download and installation instructions are available via our GitHub download pages.

Selected highligts from the release are listed below. The full list of changes is also available at

Changes in McStas v.2.6, January 24th, 2020

  • McStas 2.6 is the eight release in the 2.x series and fixes various issues with McStas 2.5, plus new developments.
  • Thanks to all contributors of components, instruments etc.! This is what Open Source and McStas is all about!
  • Installation:
  • Fixes of issues from last release:
  • Plus lots of work in general, see the relevant GitHub issues
  • Tools
    • Contribution from Tobias Weber ILL: Python-version of mcresplot.
  • Libraries:
    • Updated version 1.0.0 NCrystal library from T. Kittelmann (ESS) and X.X. Cai (CSNS), distributed with McStas on Unix platforms only. See the CHANGES document for full detail.
    • MCPL library from the same authors now included at v. 1.3.0. See the CHANGES document for full detail.
    • Updated version of the NXS lib from Mirko Boin HZB.
  • Components:
    • Updated Union library from Mads Bertelsen, ESS DMSC including
      • New geometries, mesh (for stl file input in Union setups) and cone (e.g. relevant for describing anvils in pressure cells.
      • New AF_HB_1D_process for modelling 1D antiferromagnetic Heisenberg chains and PhononSimple_process for modelling single-branchg acoustic phonons ala Phonon_simple
    • New SINE2020-developed Union physics processes from Victor Laliena, Uni Zaragoza: Texture_process.comp and IncoherentPhonon_process.comp. See DOI:10.3233/JNR-190117.
    • Shieldinglogger-components from Rodion Kolevatov, IFE for estimating gamma-production in guides:
      • Contributions Dose_calculator and Shielding_calculator
      • Patched versions of optics-components: Elliptic_guide_gravity_shieldinglogger, Guide_channeled_shieldinglogger, Guide_curved_shieldinglogger, Guide_gravity_shieldinglogger, Guide_shieldinglogger
      • Components patched / derived from the "scatterlogger" framework to model Ni and Ti layers seperately: Shielding_log_iterator_Ni_new, Shielding_log_iterator_Ti_new, Shielding_log_iterator_stop, Shielding_log_iterator_total, Shielding_logger.comp, Shielding_logger_stop.comp.
      • See DOI:10.3233/JNR-190123, DOI:10.1016/j.nima.2018.12.069 and DOI:10.3233/JNR-180088.
      • Please note that the included Shielding- and Dose- calculators will only give sensible for guides with borosilicate glass substrate. If the substrate is, e.g. copper, the dose rates from neutrons transmitted through the coating and captured in the substrate will overshoot the coating contribution significantly, so that shielding has to be enforced by few tens of centimeters of concrete.
    • Guide_anyshape_r additions from Peter Link MLZ. Allows describing geometry in OFF format with reflectivity "per" face. Test instrument is Test_guides which has been updated to include this modified component.
    • Vertical_Bender from Andrew Jackson ESS and Richard Heenan STFC. Allows modelling a multi-channel bender that curves vertically down.
    • SANS_spheres2 by Peter Willendrup, derived from Henrich Frilinghaus' SANS_benchmark2. More realistic cross-section calculations than from e.g. Sans_spheres. templateSANS2.instr is the related test instrument.
    • Updated version of Sample_nxs from Mirko Boin HZB.
    • Single_magnetic_crystal.comp is an experimental magnetic csingle crystal model. Its operational model is based on that of Single_crystal.comp but supports SF and NSF magnetic scattering. The present model only supports the SF-NSF paradigm along a given reference vector.
    • PSD_monitor_4PI_spin.comp is a version of PSD_monitor_4PI but with separate SF- and NSF-channels
  • Instruments:
    • Union_test_texture.instr demonstrates use of Texture_process.comp by Victor Laliena. To be used with datafile "coef_Four_L2.txt" found in the installation data-folder. This datafile contains texture information on Zr alloys derived from DOI:10.1016/j.jnucmat.2018.08.003.
    • Union_IncoherentPhonon_test.instr demonstrates use of IncoherentPhonon_process.comp by Victor Laliena. To be used with datafile "dos_meV.txt" found in the installation data-folder.
    • Union_test_mesh.instr demonstrates use of mesh geometry in Union
    • ESS_BIFROST_shielding.instr and PSI_Focus_shielding.instr, demonstration of Shielding_logger concept from Rodion Kolevatov
    • TasResoTest, triple-axis resolution test instrument from Tobias Weber ILL. Can be used with his new tool development
    • Tools_ONION, instrument to investigate q-resolution via Mantid, by Thomas Huegle, ORNL. See also DOI:10.1016/j.nima.2019.162711 and the related python code available at our new "snippet" repository that should eventually replace the old "share" part of this webpage.
    • templateSANS_MCPL, behaves like the normal templateSANS but dumps all events in an MCPL file.
    • MCPL-oriented tool-instruments by Peter Willendrup. See the CHANGES document for full detail.
    • SINE2020-developed McStas_Isotropic_Sqw, McStas_PowderN, McStas_Single_crystal by Erik Knudsen. They have MCPL input/output and are intended for easy use of McStas samples within SIMRES.
    • Test_guides has been modified to include Guide_anyshape_r from Peter Link MLZ.
    • templateSANS2 serves as test instrument for SANS_spheres2.
    • Test_single_magnetic_crystal.instr is a skeleton Laue camera which exemplfies use of Single_magnetic_crystal.comp
  • Datafiles:
    • Klaus Lieutenant from FZJ/Vitess has collected reflectitivy-data from SwissNeutronics, Mirrotron and S-DH, analysed these and fitted the "classical" McStas mirror-reflectivity profile to these. The resulting data have been placed in the data directory under the filenames of
      • SwissNeutronics_mirors_2020.txt
      • Mirrotron_mirors_2020.txt
      • S-DH_mirors_2020.txt.
    • The files are not to be used directly with reflecting components, but can instead be used as lookup-tables for relevant parameters in each case. I.e. for a mirror of nominal m-value m_nom, use m_real, R_0, W and alpha from the relevant table.
- Most other new datafiles are directly related to component- or instrument-additions and have been mentioned above.

We hope you will enjoy this new release!!!

Previous news items: 2019, 2018, 2017, 2016, 2015, 2014, 2013, 2012, 2011, 2010, 2009, 2008, 2007, 2006, 2005, 2004, 2003, 2002, 2001, 2000, 1999, 1998.

Last Modified: Friday, 24-Jan-2020 22:03:02 CET
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