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O Uca
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6 records found
1
Journal article
(2002)
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M. T. Rekveldt, W. G. Bouwman, W. H. Kraan, S. V. Grigoriev, O. Uca, T. Keller
Larmor precession has been used in the past in neutron spin-echo and neutron depolarisation. In the last decade, interest has been revived in the inclined front and end faces of the precession regions combined with the neutron-resonance spin-echo (NRSE) technique. Various techniques based on these inclined faces have been developed, such as spin-echo, small-angle neutron scattering (SESANS), off-specular neutron reflectometry using SESANS and high-resolution diffraction using Larmor precession. An overview will be given of the various state-of-the-art techniques.
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Larmor precession has been used in the past in neutron spin-echo and neutron depolarisation. In the last decade, interest has been revived in the inclined front and end faces of the precession regions combined with the neutron-resonance spin-echo (NRSE) technique. Various techniques based on these inclined faces have been developed, such as spin-echo, small-angle neutron scattering (SESANS), off-specular neutron reflectometry using SESANS and high-resolution diffraction using Larmor precession. An overview will be given of the various state-of-the-art techniques.
The use of π-flippers for correction of line integrals in Larmor-precession devices is described. The π-flippersconsist of magnetised foils of the proper thickness, magnetised by the field of the precession device itself. Application of such π-flippers in a spin-echo small angle neutron scattering set-up with fields perpendicular and parallel to the beam direction is discussed. It appears that such flippers avoid corrections for the inhomogeneity of the field-line integrals, for the main part, in both options.
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The use of π-flippers for correction of line integrals in Larmor-precession devices is described. The π-flippersconsist of magnetised foils of the proper thickness, magnetised by the field of the precession device itself. Application of such π-flippers in a spin-echo small angle neutron scattering set-up with fields perpendicular and parallel to the beam direction is discussed. It appears that such flippers avoid corrections for the inhomogeneity of the field-line integrals, for the main part, in both options.
Larmor-precession devices need homogeneous line integrals of the magnetic field along the neutron trajectories over the beam cross section. Line-integral inhomogeneities must be homogenized or corrected in order not to spoil the initial polarization. They can be corrected by two sets of coils. The first set of coils generates a vertical field gradient opposite to the precession-field gradient. Actually, these coils transform a gradient of the line integral in the field direction to a direction perpendicular to it. This last gradient is corrected by the second set of coils, which has a homogenous field in the vertical direction and a parabolic shape in the perpendicular direction. The corrected beam has a polarization of 0.82 for a beam cross section of 10×15 mm2 whereas, for the uncorrected beam, the polarization is 0.20.
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Larmor-precession devices need homogeneous line integrals of the magnetic field along the neutron trajectories over the beam cross section. Line-integral inhomogeneities must be homogenized or corrected in order not to spoil the initial polarization. They can be corrected by two sets of coils. The first set of coils generates a vertical field gradient opposite to the precession-field gradient. Actually, these coils transform a gradient of the line integral in the field direction to a direction perpendicular to it. This last gradient is corrected by the second set of coils, which has a homogenous field in the vertical direction and a parabolic shape in the perpendicular direction. The corrected beam has a polarization of 0.82 for a beam cross section of 10×15 mm2 whereas, for the uncorrected beam, the polarization is 0.20.
Journal article
(2002)
-
W. G. Bouwman, O. Uca, S. V. Grigoriev, W. H. Kraan, J. Plomp, M. T. Rekveldt
Spin-echo small-angle neutron scattering of dilute dispersions of mono-disperse polystyrene spheres is measured. The spheres have radii of 60 and 100 nm. The measurements agree well in shape and absolute intensity with calculations. Multiple scattering is significant in these experiments and is easily taken into account. This is the first time that quantitative analysis of real-space small-angle neutron scattering is possible. The calculations show that this technique will have most applications in systems with strong scattering, which usually implies larger length scales.
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Spin-echo small-angle neutron scattering of dilute dispersions of mono-disperse polystyrene spheres is measured. The spheres have radii of 60 and 100 nm. The measurements agree well in shape and absolute intensity with calculations. Multiple scattering is significant in these experiments and is easily taken into account. This is the first time that quantitative analysis of real-space small-angle neutron scattering is possible. The calculations show that this technique will have most applications in systems with strong scattering, which usually implies larger length scales.