McStas logo McStas - A neutron ray-trace simulation package ILL; PSI; ESS Niels Bohr Institute DTU Physics NEXMAP


About McStas
 Conditions of use
 Project funding

 Linux Install (deb/rpm)
 Mac OS X Install
 Unix Install (src code)
 Windows Install
 Other Downloads (share)

Mailing list

Search web/mailinglist

 McStas manual
 Known problems
 C Compilers




Report bugs


McStas Ubuntu live-dvd

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

July 17th, 2014: Updated ESS moderator component available

Unfortunately we are still hunting a few bugs in the development tree, and are (still!!) not ready to release the official McStas 2.1.

In the meantime, those of you simulating ESS instruments can try out our new ESS moderator component, available through the download share for use with both McStas 2.x and 1.12c.

The component comes with a library of ESS source brilliances, including:

  • 2001, legacy "Mezei moderators" from the original F. Mezei documents, rescaled to ESS TDR frequency, pulselength and power.
  • TDR, Mezei moderators, with a wavelength-dependent correction term to the cold flux, derived from 2012 MCNPX calculations by ESS neutronics group. Corrections calculated by K Lieutenant (Vitess) NOTE: uses the 2001 brilliance for the thermal moderator!
  • 2013, post-TDR update with non-Maxwellian cold spectrum, Troels Schoenfeldt, BEFORE the ESS pancake geometry was introduced.
  • 2014 updated brilliance using formulation by Troels Schoenfeldt, including support for the "pancacke", i.e. flat geometry and geometrical brilliance over the moderator surface.

An important detail about the 2014-pancake moderator is that the component origin is NOT at the centre of the cylindrical cold source, but instead at the middle of the front face of the cylinder. For technical reasons, neutrons are in this case propagated from a tangential plane through that point.

  • We further provide a set of example instruments for producing curves corresponding to each of the brilliance settings.
  • ... as well as an updated version of the Brilliance_monitor.comp, allowing multiple instances within an instrument file

We hope you will find this useful even though the official McStas 2.1 is still pending...

Vacation greetings on behalf of the McStas team
Peter Willendrup

July 2014: ESS formally joins the McStas project

DTU and ESS have signed a collaboration contract, formally making the ESS a partner in the McStas project and Peter Willendrup affiliated with both institutions in the coming years.

Welcome on board European Spallation Source

March 10th, 2014: Public beta McStas 2.1rc1 available

A public beta-release of the forthcoming McStas 2.1 is now available.

As this is a beta-release that will be replaced by the official McStas 2.1, it is available via a special download page:

The public beta includes an updated model for the ESS moderator (ESS_moderator.comp), including the "pancake" brilliance model and vertical assymetry of the cold moderator brilliance. (Special thanks to Troels Schoenfeldt and Esben Klinkby!) The final McStas 2.1 may still include further improvements of this new source component.

Please also consult the new platform-oriented installation pages:

If you are on Unix (Linux/Mac) and want to keep your McStas 1.x or 2.0 alongside McStas 2.1rc or the forthcoming 2.1, please use our migration scripts

March 10th, 2014: Preparing for McStas 2.1

We are busy preparing for the release of McStas 2.1 within a couple of days and are reorganizing parts of the website for that reason. The updated list of changes for McStas can be found on our trac

Please bear with us if you have difficulties finding information or if the found information feels inconsistent. :-)

Looking forward to releasing McStas 2.1 in a couple of days!

Previous news items: 2013 2012, 2011, 2010, 2009, 2008, 2007, 2006, 2005, 2004, 2003,2002, 2001, 2000, 1999, 1998.

Last Modified: Thursday, 17-Jul-2014 16:29:01 CEST
Search website McStas site RSS feed mailinglist archive SVN repos McCode Trac