Monte Carlo simulations and data fitting for neutron three-axis spectrometers
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1. Introduction
RESTRAX is a tool for simulating TAS resolution functions and data fitting. The program includes both a high-speed analytical (Gaussian) convolution algorithm and a Monte Carlo ray-tracing code providing enhanced accuracy in description of most of the spectrometer components. The non-linear least-squares fitting routine is available with several scattering function models, which may be used either directly or as templates for other models created by users and called by Restrax as a dynamically linked run-time module. Graphical output permits visualisation of resolution functions in an arbitrary projection in the (Q,ω) space, plotting both simulated and experimental data and mapping S(Q,ω) as 2-dimensional sections in reciprocal space.
Typical tasks where RESTRAX may help:
- Planning an experiment
- RESTRAX permits to find optimum instrument configuration with respect to required size and orientation of the resolution function.
- Simulating data for a given scattering model
- Smearing due to instrumental resolution and relative intensities of diverse signal components can be assessed by simulation of experimental data with an expected scattering law.
- Analysis of experimental data
- The data fitting with RESTRAX is particularly useful in two cases: (1) when the Gaussian approximation of the resolution function is not sufficient and/or (2) when a complex scattering model is needed, which cannot be expressed as a simple analytical formula. With RESTRAX, you can also simultaneously fit multiple datasets with a single set of model parameters.
Note: This page does not refer to another modification of RESTRAX called SIMRES - an enhanced ray-tracing code useful for simulation of newly designed or upgraded instruments and optimisation of their configuration. Please consult the home page for more information and downloads.