DANTE (Diagnostica Avanzata di Neutroni e Tecnologia per l'ESS) - POLARIZZAZIONE

Polarized neutron scattering provide a powerful tool in important areas of current research such as magnetism, nanoscience, soft matter, and fundamental neutron physics, which include measurements of fundamental constants in particle physics, astrophysics and cosmology. In magnetic scattering studies the discrimination of the neutron polarization state allow one to separate the magnetic signal from the nuclear one, in particular when the magnetic signal is weak. The neutron polarization analysis gives also a means to separate the coherent and incoherent contributions to the total scattering cross-section, an important advantage in studies of polymeric and soft matter. In general, polarized neutrons have relevant applications in all scientific domains where it is useful to analyse in details the anisotropy of the magnetic response, as in thin films or multilayers. The design of polarized neutron devices in one of the main challenges for the instrumental program addressed to the future ESS, in particular for those spectrometers for the first phase of the construction (cold and thermal chopper spectrometers, cold triple-axis diffractometers, horizontal reflectometers, SANS for small samples Imaging and tomography). The availability of polarized neutron sources together with the improvement of focusing condition could be one of the major challenges for the future neutron spallation source ESS, because the Long Pulse Spallation Source (LPSS) configuration is well suited for neutron polarimetry (cold neutrons and narrow band). The development of neutron polarimetry could open new avenues not only in the fundamental and applied scientific program focused on the study of magnetic materials, but also in other research domain in which a high brillance cold neutron polarized source is necessary. Among the different propositions for polarizing neutrons, which include Stern-Gerlach and dynamical polarization devices, particular attention was addressed to a new device which consists in a periodic magnetic field assembly (a "neutron undulator"), which produces a spatially periodic gradient magnetic field, and provides a neutrons selection by wavelength and by the spin state. This method could have potential applications in polarizing guides, monochromators and polarization analysis of neutron beam. Synergy between these efforts will contribute to other goals such as the development of a robust programme of instrument innovation that will be required at new pulsed neutron sources to maintain their vitality in future decades.