Dynamic Nuclear Polarization; Neutron Optics; Neutron Physics; Photo-excited triplet states; Spin Filters; Polarized Targets
Perigo E. A., Mettus D., Gilbert E. P., Hautle P., Niketic N., van den Brandt B., Kohlbrecher J., McGuiness P., Fu Z., Michels A. (2016), Magnetic microstructure of a textured Nd-Fe-B sintered magnet characterized by small-angle neutron scattering, in JOURNAL OF ALLOYS AND COMPOUNDS
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N. Niketic, B. van den Brandt, W. TH. Wenckebach, J. Kohlbrecher, P. Hautle (2015), Polarization analysis in neutron small-angle scattering with a novel triplet dynamic nuclear polarization spin filter, in Journal of Applied Crystallography
, 48(5), 1514-1521.
Eichhorn T. R., Niketic N., van den Brandt B., Hautle P., Wenckebach W. Th. (2014), Neutron spin filtering with dynamically polarized protons using photo-excited triplet states, in International Workshop on Neutron Optics and Detectors (NOP&D 2013)
, IsmaingIOP Publishing, Bristol, UK.
Eichhorn T. R., Niketic N., van den Brandt B., Filges U., Panzner T., Rantsiou E., Wenckebach W. Th., Hautle P. (2014), Proton polarization above 70% by DNP using photo-excited triplet states, a first step towards a broadband neutron spin filter, in NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND
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The use of spin-polarized neutrons is a powerful tool to study a wide range of scientific phenomena with neutron scattering and in fundamental physics. It provides indispensible information for many current areas of research as magnetism, superconductivity, correlated electron systems, and also particle physics and cosmology.The most common techniques to polarize and analyze neutron beams are based on neutron optical mirror reflection. They are systematically restricted in angular acceptance and to neutron energies of the cold region only. Alternatively, polarized nuclei provide a way to build broad-band spin filters with a large acceptance. Optically polarized 3He is often considered the best choice; however its energy-dependent neutron absorption cross-section makes it difficult to optimise the filter thickness in a large range. With the advent of megawatt-class pulsed spallation sources (SNS, JSNS, ESS), alternatives to the well established neutron polarization techniques used at steady sources have to be found and the use of polarized protons as spin filter is recalled, as the large spin dependent neutron scattering cross section for protons is useful up to the sub-MeV region.Proton polarization is normally created employing the classical scheme of dynamic nuclear polarization (DNP). One polarizes electron spins by cooling them down to low temperature (~ 1K) and applying a strong magnetic field (2.5 - 5 T) and then transfers their high polarization to the nuclear spins by means of a microwave field. These stringent conditions can be relieved with a more recent and very promising DNP method that uses optically excited triplet states. Here the triplet electron spin is polarized as a result of the optical selection rules. Then the requirements for the cryogenic equipment and the magnetic field are significantly relaxed making technically simpler systems with open geometries possible. We have recently proved that the triplet DNP method can be used to build a reliably working neutron spin filter . Besides the pioneering work of Uesaka et al , this is the only time that an instrument based on this technique has been employed in a long term experiment on a particle beam. Interesting possibilities for a triplet spin filter are opened by the recent trend in neutron optics to adapt with focusing guides to the sample which is often only available in very small size . It is the goal of the present proposal to assess the potential of the triplet spin filter technique for polarized neutron scattering experiments. A key point will be the investigation of the filter integration with neutron optical devices. We intend to perform numerical simulations of neutron optics concepts for standard scattering schemes and to experimentally prove their feasibility for selected cases.