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


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McStas Ubuntu live-dvd

Nov 28th: Monitor_nD: avoid using "per cm2" and "per steradian" options

A minor bug that affects Monitor_nD has been found recently. It results in spikes appearing randomly in the monitored distributions. To temporarily avoid it, do not use the options="... per cm2 ..." and "... per steradian ..." component arguments. To obtain the flux per cm2 or steradian, divide manually the result by the monitor area or the effective solid angle.

Nov 9th, 2011: Installation with MPI on Linux/Ubuntu 11.10

It has been reported that the mpich2 parallel processing library should be avoided under Ubuntu 11.10 ('mpd' clashes with an other executable). Please install instead openmpi with e.g.:

  # sudo apt-get install openmpi-bin libopenmpi-dev
or from Synaptic/Ubuntu Software Center.
In case Mcstas was installed before openmpi, you will need to re-configure it with e.g.:
  # cd /usr/local/lib/mcstas/tools/perl
  # sudo chmod a+x mcstas_reconfigure
  # sudo ./mcstas_reconfigure
or change your $HOME/.mcstas/mccode_config.perl, or re-install it (which should not affect your instrument definitions).

Oct 31st, 2011: LEGO (c) neutron scattering instruments controlled with McStas

We have set-up LEGO models of a TAS and crystal TOF instrument, using the NXT technology. This is a robotic model (it moves) to be used for teaching/training and in exhibitions. When a McStas simulation is launched on the PC, the model positions itself with the corresponding geometry.
The methodology to build and control the models is detailed at

ILL/Computing for Science/Virtual instruments/LEGO
were you will learn:
  • the LEGO parts required, and how to order them
  • the building of the LEGO models
  • the Ubuntu computer to be configured (using t2n and nbc)
  • the control programs to load in the NXT
  • the McStas components to use in order to communicate with the LEGO model.

July 26th, 2011: McStas 1.12c on Mac OS X Lion - new DMG added to download section.

A new DMG for Mac OS X 10.7 Lion has been put together and can be found in the download section.

Note that to enable multi-core / parallel simulations, you need to compile openmpi yourself before installing McStas, since it is not provided by Apple on Lion. Alternatively you can perhaps get it via MacPorts.

The DMG should also work on Snow Leopard - but all software on the DMG must be reinstalled if McStas was previously installed.

July 24th, 2011: McStas 1.12c on Mac OS X Lion - hold your horses!

The newly released Mac OS X 10.7 Lion includes a lot of nice upgrades from Apple - including some that break the tool-layer and mpi support for McStas:

mpi compile fails The system-provided mpi is not detected by the McStas configure script
mcgui does not start mcgui requires perl::Tk, and the version we ship with McStas 1.12c explicitly requires perl 5.8, which has been removed from Lion
mcplot does not plot For plotting, we rely on the SciKarl port of pgplot, perl::PDL and perl::PGPLOT. The SciKarl perl modules are built for perl 5.8 which has been removed from Lion

In conclusion: If you want to keep a functional McStas install, please do not upgrade to Lion yet!

June 15th, 2011: Teaching- and talk material from the NIDS school

The McStas and Vitess teams are currently in Lilla Vik for the NIDS school.

The material for the Monte-Carlo part the school is available here

June 11th, 2011: iFit, a new Matlab tool to run, scan and optimize McStas simulations

The new iFit tool is currently being developed. Among its general data analysis features (load, do math, save, plot, ...), it may import McStas data sets, perform simulations, including scans (even multidimensional), and optimize simulation parameters (maximize or minimize a criteria which can be defined by the user).
iFit can also be used for basically any data analysis and reduction. It supports a very large data format list (including any text based file), works with any dimensionality data, and provides powerful optimization and fitting methods.

You can learn more and get the iFit package at <> (requires Matlab to be installed). The iFit/McStas help page is also available.

June 3rd, 2011: McStas 1.12c re-released!

Unfortunately, the McStas 1.12c release from May 24th contained a series of bugs, primarily in source components, related to a type-change of the neutron counter.

We have decided that since only a limited number of people have downloaded the release, we will simply re-release McStas 1.12c with the above bugs fixed.

If you already downloaded and installed the packages released on May 24th, please re-download and reinstall the fresh 1.12c packages from our download page.

A complete liste of changes is available in the CHANGES document.

Sorry for the inconvenience and best regards from the McStas team.

May 24th, 2011: McStas 1.12c released!

A reasonably serious bug in our rectangular focusing routine was identified by several McStas users and has now been corrected. We felt that this warranted an update of the stable McStas release, meaning a new 1.12c release.

The 1.12c release is available now from our download page.

A complete liste of changes is available in the CHANGES document.

For those of you looking forward to the 2.0 release, all required new functionality has been implemented, but documentation is still lacking. The 2.0 release will become officially available once the documentation has been updated, hopefully fall 2011.

Tips and tricks for running McStas on Windows systems

Recently, a new McStas user has (rightfully) pointed out that some annoyances when running McStas on Windows have not been properly documentd. The list below is a first attempt to remedy that fact.

  • Ideally, your user should be a local admin of Windows.
  • On windows, to run a simulation, the "run" button in mcgui needs to be clicked twice - once for compilation and second for actually running.
  • The resulting "perl" windows should be closed - put an "enter" character in them and they will close once finished. (Otherwise they will drain resources from your machine). The same strategy should be applied when visualizing data, either using the "3d/trace" mode or when pressing 'plot'.
  • It can cause problems to run mcgui from directories containing spaces, e.g. c:\Documents and Settings\User. Our suggestion is to instead create a work dir e.g. c:\McStasWork for your work. Simply save your instrumentfile there and re-open using mcgui.

The hope is that a new set of tools will be available in the McStas 2.x series of releases - but likely there will be at least a McStas 1.12c before this.

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

Last Modified: Wednesday, 01-Feb-2012 11:37:30 CET
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