IN1-LAGRANGE - the new ILL instrument to explore vibration dynamics of complex materials

We report on the first experimental results obtained with the recently commissioned IN1-Lagrange spectrometer, which has replaced the old IN1 Be-filter setup used for studies of lattice dynamics and molecular vibrations in an extended energy range, typically used for materials containing light chemical elements, in particular hydrogen. Unlike its predecessor, IN1-Lagrange uses, in addition to a cooled Be-filter, a large area crystal analyzer to collect the scattered neutrons and to define their final energy of 4.5 meV. Using the available set of double-focussing monochromators the incident neutron energy on IN1 can be scanned over the entire range of 4 - 600 meV provided by the ILL hot neutron source. Thanks to its large solid angle of 2.5 steradian and flexibly tuned energy resolution in the range of 1 - 5%, the IN1-Lagrange setup offers an unprecedented sensitivity permitting very rapid data acquisition and revealing fine spectral features in 'standard' samples as well as efficient measurements of hydrogen vibrations in samples containing equivalent masses of H-2 as low as 100 mu g.