- Jiří Kulda: ThALES and the cold neutron spectroscopy at the ILL
- 11. 11. 2015, 14:50
- lecture room F2, first floor Ke Karlovu 5
- more information
Abstract:
Neutron inelastic scattering is the method of choice to study elementary excitations in systems with magnetic orbital and spin degrees of freedom. Although other experimental techniques like NMR, muon spin rotation or resonant X-ray scattering can provide valuable information on the same systems, neutrons provide the most complete picture of space and time correlations of local magnetic moments on atomic scale and of their interplay with the underlying chemical structure. Neutrons couple with comparable strength to both the structural and magnetic degrees of freedom, but the two scattering components can be cleanly separated using modern neutron polarization analysis techniques.
The new cold neutron spectrometer ThALES, replacing one of the most popular ILL instruments IN14, integrates the state-of-the-art in neutron optics and sample environment to achieve a significant step forward in terms of kinematical range, efficiency of neutron polarization analysis and data collection rate. The new completely non-magnetic spectrometer structure can host cryomagnets providing fields of 15 T (and more, once available) for measurements in its entire kinematic range. The new polarizing monochromator and analyzer (Heusler) - to be commissioned in summer 2016 - will provide neutron count rates comparable to the old IN14 in its unpolarized mode, opening access to a wide class of experiments with modest sample sizes and low signal levels. The unpolarized work with mm3-sized samples will be facilitated by the implementation of focusing optics using elastically bent perfect silicon crystals.
Since summer 2015 ThALES, in its baseline configuration, is being offered to the regular ILL users as well as to the Czech user community within its preferential access quota. In parallel the commissioning of its more advanced options (silicon optics, polarization analysis, FlatCone multi-analyzer) goes on to be completed progressively until autumn 2016.
The ThALES spectrometer has been designed at the ILL Grenoble and built in collaboration with the Charles University, Prague, using funds from the Ministry of Science and Education of the Czech Republic (project LM2010001).