Monte Carlo simulations and data analysis for three-axis neutron spectrometers
Authors:3rd party code used in RESTRAX
Written in Fortran 77/90. Binaries are available for Windows and Linux/i686.
The software package RESTRAX has been developed in the last decade into an efficient tool for neutron ray-tracing simulations of neutron scattering instruments, useful for instrument design, optimization of experimental conditions and analysis of experimental data. The ray-tracing code has proved to be very fast thanks to the application of several sampling optimization techniques. It yields typical count rates of 103 - 104 successful events (source to detector trajectories) per second on a standard PC even for complex configurations including crystal monochromators/analyzers, narrow apertures, reflecting optics etc.
At the same time, physically realistic models for neutron transport through key neutron optical components like sources, guides, benders and crystals (both mosaic an elastically deformed), permit to predict correctly neutron flux distributions and instrument resolution functions. Reliability of the code has been successfully tested in several intercomparison projects with other established ray-tracing packages
The package actually includes two standalone programs
RESTRAX – the vesion specially designed for three-axis spectrometers (TAS) is equiped with simplified (but faster) ray-tracing code for simulation of TAS resolution functions and additional tools for data analysis. It provides graphical representation of resolution functions as well as both simulated and experimental scattering functions. The non-linear least-squares fitting routine is available with variety of scattering models and a possibility to add other models created by users as a library linked dynamically to the main program. The program has been equiped with intuitive graphical user interface written in Java (portabe across platforms)
SIMRES – provides instrument scientists with more flexible (and more realistic) ray-tracing code useful for simulation of newly designed or upgraded instruments and optimisation of their configuration. This version permits to simulate neutron flux and its distribution in both real and momentum subspaces as well as resolution functions. In contrast to previous versions, SIMRES can now simulate any user-defined instrument layout, which can be built from available neutron optical components. This newly designed code still includes highly efficient sampling strategy, so that the high speed of simulations carried out with SIMRES is preserved. Flexibility of the code is further enhanced by Java based graphical user interface, which includes instrument layout editor, 3D visualization of the instrument model, graphs representing various types of results, as well as a number of commands useful for optimisation of instrument parameters.