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

Migrating from McStas 2.x to 3.x? - Use the wiki-based guides

May 14th, 2022: Neutron-optics and McStas/Union related Post Doc position at PSI:

Dear all,

An interesting Post Doc position is available within the Neutron Optics and Scientific Computing Group at PSI:

A central part of the position is expanding features of the McStas Union by adding support for reflectivity (and potentially refraction).

Main tasks are:

For more information please refer to the link below or contact Dr. Christine Klauser <>

Peter Willendrup

February 18th, 2022: New ready-to-run McStas box in a browser

We are happy to provide a ready-to-run system with McStas pre-installed. It typically pulls-out an 8-cores computer running at Binder, for free, with both McStas 2.x and 3.x (with MPI multi-core support but no GPU). Perfect for running McStas from anywhere, for training/schools/workshops.

Start it in a single click here:

(Please note that load-time can be a couple of minutes.)



The above docker image has been pushed to dockerhub and can also be run locally at your machine using docker:

Previous news items: 2021,2020,2019, 2018, 2017, 2016, 2015, 2014, 2013, 2012, 2011, 2010, 2009, 2008, 2007, 2006, 2005, 2004, 2003, 2002, 2001, 2000, 1999, 1998.