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

April 2nd, 2019: Announcing ISTSI2019

The workshop Innovative Simulation Tools, Shielding and Instrumentation 2019 (ISTSI2019) will be held at Holiday Inn St. Petersburg, Russia, on Saturday June 29th 2019, as a satellite of the ECNS conference.

The workshop brings together the partners of the SINE2020 WP8 that have contributed work in the areas of

For more information and registration, please consult the website at

This workshop / project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 654000.

March 25th-20th, 2019: McStas School at CSNS

Dear all,

In collaboration with the China Spallation Neutron Source, the McStas team participated in the first ever McStas school in China in the last week of March.

All lecture material and exercises are available through our new McStas school site, hosted on GitHub

Further, our hosts suggested we recorded videos of the lectures which are slowly becoming available on the new McStas youtube channel.

January 18th, 2019: McStas survey results

Dear all,

The results from the 2018 McStas user survey are now online at

The main conclusions are that

Thank you very much for the (generally) very positive review - also, you are more than welcome to participate in continuing debate on user suggestions that will take place in the individual GitHub survey issues.

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