October 22nd, 2014: Mac OS X Yosemite and McStas: Installation bundle put together

A tested download bundle for Mac OS X 10.10 Yosemite has been uploaded to


The enclosed McStas has a limited set of differences/bugfixes wrt. the official McStas 2.1 released in september, but should generally behave the same.

A few details are pointed out in the README.TXT of the tar.gz archive, please make sure to read that before installation.

October 18th, 2014: Mac OS X Yosemite and McStas: Hold your horses!

Upgrading to Mac OS X Yosemite 10.10 removes Perl 5.12, which the Perl tools in McStas 2.1 distributed for Maverics rely on...

In conclusion: If you need a fully functional McStas, please do not upgrade to Yosemite just yet... :-)

September 12th, 2014: McStas 2.1 finally released!!

Sorry for the wait - but here it is: McStas 2.1 is released and ready for download via http://downloads.mcstas.org/mcstas-2.1

Selected, important highligts from the release are:

We have also received a nice, long list of contributions and have also developed and improved both components, instruments and core package functionalty. For the full list of changes, please consult the CHANGES document.

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:

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 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.