MIRACLES, the backscattering spectrometer of the European Spallation Source: Meeting scientific requirements with design.

MIRACLES, the neutron time-of-flight backscattering instrument of the European Spallation Source (ESS), will be the spectrometer with the highest energy resolution at the start of the ESS user program. The long pulse provided by the ESS source allows tuning the energy resolution of the instrument, with the concomitant capability of probing a wide range of molecular and atomic timescales, unfolding new opportunities in neutron spectroscopy to disentangle complex dynamics faster in a single experiment and allowing the use of smaller and more diluted samples. This work will report on a detailed description of the design efforts to bring MIRACLES from the scientific requirements to the construction and commissioning phases. This includes the provision of high and tailored energy resolution, optimization of the signal-to-background ratio, and the ability for integration of new equipment and scientific capabilities that will make MIRACLES a paramount asset for the ESS neutron scientific instrument suite.