Towards improving the PF1B beamline <i>McStas</i> model through simulations of a beam characterization experiment

The PF1B instrument at the Institut Laue–Langevin (ILL) delivers a high-flux cold neutron beam through the H113 neutron guide. In the years following the characterization published with the highest polarization in 2006, radiation-damaged sections of the guide have been replaced and the in-pile part has been upgraded. In 2024, a new experiment using time of flight was performed to characterize the instrument. Simulations intended to reproduce this experiment have been performed with McStas using an already existing model of H113. In this work, we present a first comparison of experimental and simulated time-of-flight spectra, showing overall good agreement but discrepancies which might be reduced by adjusting the existing McStas model. Parameter optimization is ongoing, aiming at a more accurate description that would serve for future experiments on PF1B.