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, 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

February 1st: Various bugs and workarounds

A couple of annoyances have been reported, here they are plus relevant workarounds:

1.12c version of SNS_source.comp crashes on Windows systems. A functional version has been uploaded to the share. Thanks to Ruep Lechner for reporting the bug and to Garrett Granroth for providing a fixed component.
The previously released updated dmg image for Mac OS X should really only be used on Lion, not Snow Leopard, that is use this image on Lion and this image on older releases.
On (at least some) Mac systems, it seems Virtual_output.comp should not be used with type="double" or "float". The workaround for the time being is to use the default "text" format instead. The issue seems to become more severe if large ncounts are used.

January 6th: New affiliation for Erik Knudsen and Peter Willendrup

A reorganisation at DTU and RISØ DTU has resulted in a new home for the DTU effort on McStas, namely DTU Physics.

Hence, Erik Knudsen and Peter Willendrup have a new affiliation, see the Contact page.

At our new home we will be part of a dedicated neutron- and X-ray scattering group, which we think will become a very good home!

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