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vIMPS is an instrument simulator for the multiplexed TAS instrument IN8-IMPS. It makes it possible to easily experiment various measurement strategies through free or predefined instrument configurations. vIMPS is part of the vTAS suite.

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vIMPS - Virtual IN8-IMPS instrument

by Martin Böhm, Alain Filhol and Yannick Raoul.


vIMPS is an instrument simulator for the multiplexed Three Axis Spectrometer IN8-IMPS of the ILL. It is part of the vTAS suite (see below) written in Java.

IMPS (Imaging MultiPlexed Spectrometer) is a multi-analyser (6 blades) and multidetector system for the thermal TAS IN8.

Multiplexed instruments make assessing a measurement strategy very difficult without any computer assistance, thus vIMPS was designed to address this problem. It implements a dual real space and reciprocal space graphical interactivity that much facilitates the understanding of the instrument behavior and limits. It makes it possible to easily experiment various measurement strategies through free or predefined instrument configurations. It proved to be a valuable tool for both instrument users and responsible, and also for teaching.

IMPS is still operated in test mode (Jan. 2011) and vIMPS helps experimenting new measurement strategies. These will be implemented as "predefined" once thoroughly tested. Thus the features of the application are a reflection of our current understanding of the capabilities of the instrument.

Ref.: "The vTAS suite: a simulator for classical and multiplexed three-axis neutron spectrometers"
       M. Boehm, A. Filhol, Y. Raoul, J. Kulda, W. Schmidt, K. Schmalzl,
       Nuclear Inst. and Methods in Physics Research, A (2013) 697, 40-44.

The vTAS suite is now a single application vTIU regrouping three TAS simulators:

  • vTAS: classical TAS geometry and multiplexed geometry of FLATCONE
  • vIMPS: multiplexed geometry of IN8-IMPS
  • vUFO: multiplexed geometry of IN12-UFO

An early version of vTAS was developped by Alain Bouvet in 1998.
The current vTAS project was funded by the ILL and NMI3.

Running the application

Warning: vIMPS is a prototype application since the instrument IMPS is not yet commissioned.

Requires Java 2 v1.6 or higher. Make sure that is installed and activated. On some computers you may also need to clear the Java cache.
The JNLP mechanism will give you the opportunity to install a standalone version of the application on your hard drive.
Prior installing a new version of vUFO it is recommended to delete the old preference files.
     E.g. for OS X users, delete folder ~/Library/Preferences/ILL/vIMPS.
Release date: 7 Nov 2013.

Click HERE to launch vIMPS v1.19

Caution: an initialization bug makes the current version difficult to use. We are working on a fix.
Report bugs to forge.epn-campus.eu

Mac users should read this : OS X 10.9 or higher, Safari 6 or higher !

Special keys and options

For both the instrument and scattering pane:

  • right click+drag: paning
  • [Mac OS X] cmd-key+click+drag: paning
  • mouse wheel: zoom in/out at mouse position


vIMPS is a free application. Use it at your own risks. Neither the authors nor the ILL endorse or accept any responsibility for problems or wrong results you may obtain with it. No support is provided but feedback is warmly welcome -> <filhol(at)ill.eu>.


Updates: 20 Jan 2011, 13 march 2013, A.Filhol, <filhol(at)ill.eu>