The Simulation Code VITESS

The program VITESS (Virtual Instrumentation Tool for the ESS)  which simulates neutron scattering instruments has been developed at HZB since 1999.  Although the development of the program was originally motivated by the ESS planning phase (http://ess-scandinavia.eu), all kinds of  instruments and most instrument components at any source can be simulated by VITESS.  Thus the program is used world wide at many research institutes. At HZB all newly built instruments have at least partially been simulated with VITESS. Users may contact the team of  developers at vitess@helmholtz-berlin.de.

The development of VITESS and competing programs McStas (http://www.mcstas.org) and Restrax (http://neutron.ujf.cas.cz/restrax) have been supported by the European Commission for many years. At the moment further development of VITESS is funded in the framework of the German in-kind contribution to ESS. It is the aim of this project to complete and improve some modules, to visualise instruments and neutron trajectories, to simplify the use of numerical optimisation programs and to prepare a complete documentation.  Simultaneously, many instruments and components of the ESS are being simulated, partially in comparison with McStas and/or Restrax simulations.

The simulation of the instrument EXED is a good example of the application of VITESS. The entire instrument from the source to the detector was simulated and an optimal solution was found for a number of components, either by comparison of different simulations (extraction system, chopper system, coating, kink) or by numerical optimisation (converging guide.)