Czech Republic: A new interface for SIMRES

Effective simulations of neutron scattering instruments and experiments are invaluable tools in the world of neutron research. Optimised and user-friendly simulations performed prior to experiments can save time, money and energy and lead to more efficient use of beam time. If simulations take into account shielding and signal-to-noise ratios too, they could also evaluate prospective designs for future instruments.

Unfortunately, many existing simulation software packages were created, and have subsequently evolved, independently. This causes a problem in interoperability – many of them cannot talk to each other. Yet, some packages contain ingenious tools that would be extremely useful if they were accessible to the whole community.

One of these is RESTRAX: a software package for neutron ray-tracing simulations. It was developed at NPI in the Czech Republic. It includes a standalone neutron ray-tracing program SIMRES, which has a unique ability to simulate neutrons along the reverse direction (from sample to source) as well as the standard forward direction (from source to sample). The reverse direction is statistically more efficient to simulate and thus quicker to obtain.

In order to extend these useful techniques to the wider community, Jan Šaroun from NPI has been working on a Monte Carlo Particle List (MCPL) interface for SIMRES. The interface will export/import neutrons to/from an MCPL data format, which is recognized by many other simulation software packages like McStas. It allows for interoperability between SIMRES and other simulation tools during simulation.

This compatibility will then permit combined SIMRES-McStas reverse direction simulations, for example. Initial tests run by Jan have demonstrated a speed gain factor of about 200 in a virtual experiment simulation for the ESS BEER instrument when going from forward to reverse tracing direction.

This interface will also benefit NPI in other ways. By enabling SIMRES to interact with MCPL code, they will now have access to the unique capabilities of other simulation packages that can talk this common language.

The latest update for RESTRAX is available from here.

Acknowledgements: Jan Šaroun, NPI