| 1. |
- Hilger, A., et al.
(författare)
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Neutron guide optimisation for a time-of-flight neutron imaging instrument at the European Spallation Source
- 2015
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Ingår i: Optics Express. - 1094-4087. ; 23:1, s. 301-311
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Tidskriftsartikel (refereegranskat)abstract
- A neutron transport system for the planned imaging instrument ODIN at the future European Spallation Source (ESS) based on neutron optical components was designed and optimized. Different ways of prompt pulse suppression were studied. The spectral performance of the optimal neutron guide configuration is presented. In addition, the influence of the gaps in the guide system needed for the required chopper configuration was investigated. Given that the requirements for an imaging instrument located on a long guide system and hosting a complex chopper system are extremely demanding in terms of spectral and divergence needs, this study can be beneficial for a wide range of instruments in various ways. (C) 2015 Optical Society of America
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| 2. |
- Lehmann, E. H., et al.
(författare)
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The energy-selective option in neutron imaging
- 2009
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 603:3, s. 429-438
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Tidskriftsartikel (refereegranskat)abstract
- In the past, neutron imaging investigations have been mostly performed in "integrating mode", which averages over the full applied neutron energy spectrum. This article describes four different methods and devices of obtaining energy selectivity in the thermal to cold energy range, which allow a new approach in neutron imaging. Two principles have been used and tested: (a) selection of neutrons by suppression of contribution of other spectral parts; (b) using the flight-time information in distance from the source. For the (a) option, three different devices have been exploited practically. Information about material properties can be revealed that cannot be obtained in integrating mode. The energy-dependent transmission measurements make use of the Bragg edges in the total cross-sections of materials. Energy-selective radiography has vast potential for contrast variation, and for mapping structural properties such as crystallographic texture and residual strains with high spatial resolution. The obtained images highlight new opportunities in materials and engineering research, in comparison and complementary to what can be obtained by neutron scattering. There is likely to be an increasing need for implementing time-of-flight neutron imaging at present and future pulsed spallation sources, where the energy range can be selected almost without limitations. In this paper we attempt to give an overview over the current state of the art of energy-selective imaging and the experimental configurations required. (C) 2009 Elsevier B.V. All rights reserved.
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| 3. |
- Oji, U.K., et al.
(författare)
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Implementation of time of flight polarized neutron imaging at IMAT-ISIS
- 2023
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 235
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we report the first case of design and implementation of a polarized neutron imaging option on the Imaging and Materials Science & Engineering Station (IMAT). This is a significant addition to the capabilities of the station that allows the characterization of advanced magnetic materials for different engineering applications. Combining its time-of-flight feature with a polarized beam yields data that facilitate both quantitative and qualitative analysis of magnetic materials. Using the simple field of an aluminium solenoid, we perform a characterization of the new setup. In addition, we present polarized measurements of additively manufactured (AM) MnAl samples where the magnetic anisotropy due to the fabrication process has been investigated as a first scientific application of the setup. The results indicate that the anisotropy of the material can be engineered through variation of the AM fabrication parameters.
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| 4. |
- Strobl, Markus, et al.
(författare)
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Using a grating analyser for SEMSANS investigations in the very small angle range
- 2012
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Ingår i: Physica B: Condensed Matter. - : Elsevier BV. - 0921-4526. ; 407:21, s. 4132-4135
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Tidskriftsartikel (refereegranskat)abstract
- Spin-echo modulation small-angle neutron scattering (SEMSANS) is based on the detection of spatial beam modulation, which is induced by triangular spin echo precession regions and subsequent spin analyses. In order to detect such signal and exploit it for small angle scattering investigations neutron detection with sub-millimeter spatial resolution is required. Here an approach is reported where instead of a position sensitive detector an absorption grating is used to analyze the beam modulation stepwise. The spin-echo length scan in this case is performed by varying the sample-to-detector distance. The real space correlation functions of reference sample structures in the range 10(2) nm, i.e. giving rise to small-angle scattering in the very small-angle range, are recorded and analyzed successfully. (C) 2012 Elsevier B.V. All rights reserved.
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| 5. |
- Tremsin, A. S., et al.
(författare)
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Imaging of dynamic magnetic fields with spin-polarized neutron beams
- 2015
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- Precession of neutron spin in a magnetic field can be used for mapping of a magnetic field distribution, as demonstrated previously for static magnetic fields at neutron beamline facilities. The fringing in the observed neutron images depends on both the magnetic field strength and the neutron energy. In this paper we demonstrate the feasibility of imaging periodic dynamic magnetic fields using a spin-polarized cold neutron beam. Our position-sensitive neutron counting detector, providing with high precision both the arrival time and position for each detected neutron, enables simultaneous imaging of multiple phases of a periodic dynamic process with microsecond timing resolution. The magnetic fields produced by 5- and 15-loop solenoid coils of 1 cm diameter, are imaged in our experiments with similar to 100 mu m resolution for both dc and 3 kHz ac currents. Our measurements agree well with theoretical predictions of fringe patterns formed by neutron spin precession. We also discuss the wavelength dependence and magnetic field quantification options using a pulsed neutron beamline. The ability to remotely map dynamic magnetic fields combined with the unique capability of neutrons to penetrate various materials (e.g., metals), enables studies of fast periodically changing magnetic processes, such as formation of magnetic domains within metals due to the presence of ac magnetic fields.
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| 6. |
- Ţuţueanu, A. E., et al.
(författare)
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Non-destructive characterisation of dopant spatial distribution in cuprate superconductors
- 2020
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Ingår i: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534 .- 1873-2143. ; 575
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Tidskriftsartikel (refereegranskat)abstract
- Proper characterisation of investigated samples is vital when studying superconductivity as impurities and doping inhomogeneities can affect the physical properties of the measured system. We present a method where a polarised neutron imaging setup utilises the precession of spin-polarised neutrons in the presence of a trapped field in the superconducting sample to spatially map out the critical temperature for the phase transition between superconducting and non-superconducting states. We demonstrate this method on a superconducting crystal of the prototypical high-temperature superconductor (La,Sr)2CuO4. The results, which are backed up by complementary magnetic susceptibility measurements, show that the method is able to resolve minor variations in the transition temperature across the length of the LSCO crystal, caused by inhomogeneities in strontium doping.
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