Phonons calculations, triple-axes spectrometers, and more

We present a new tool, miFit, dedicated to data analysis. One of the features allows fitting inelastic scattering data, taking into account the full 4D resolution of the instrument. The software is based upon iFit [1] as the computational infrastructure, ASE [2] for the phonon S(q,w) evaluation, and ResLibCal for the TAS resolution calculation. The instrument model may use, at will, analytical estimates, as well as a full Monte-Carlo simulation using McStas [3]. Other instrument models (e.g. TOF) may be implemented in the future. The methodology can also be extended to QENS and diffraction. In this presentation, I will present these tools, and demonstrate their application to a fit of phonon TAS data using a 4D S(q,w) model with full instrumental convolution.

[1] E. Farhi et al, J. Neut. Res., 17 (2013) 5.

[2] S. R. Bahn and K. W. Jacobsen, Comput. Sci. Eng., Vol. 4, 56-66, 2002.

[3] K. Lefmann and K. Nielsen, Neutron News 10, 20, (1999).