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Artículos de revistas sobre el tema "Neutron absorption"

Autor: Grafiati

Publicado: 30 de noviembre de 2024

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1

Wang, Haoran, Shuo Zhao, Junqing Han, Yuying Wu, Xiangfa Liu y Zuoshan Wei. "Neutron-Absorption Properties of B/Cu Composites". Materials 16, n.º 4 (8 de febrero de 2023): 1443. http://dx.doi.org/10.3390/ma16041443.

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Copper has high electrical and thermal conductivity, which is frequently employed in structural and functional materials. In this research, powder metallurgy was used to incorporate boron nanosheets into metal matrix composites to create boron dispersion-enhanced copper matrix composites. The neutron-absorption characteristics of composite materials were investigated, as well as the link between neutron-absorption cross-section and neutron energy. The results told us that the morphology of the second phase on the particle surface is closely related to the size of Cu-B particles, copper and boron correspond atomically to each other on the interface without dislocation or lattice distortion, forming a completely coherent interface, and that the neutron absorption cross-section decreases exponentially as neutron energy increases. In low-energy neutrons with energies less than 0.1 eV, the increase of boron content and 10B abundance in Cu-B alloy will enhance the neutron-absorption capacity of the alloy. Boron dispersion-strengthened copper matrix composites have good neutron-absorption capacity, and the microstructure and size of boron do not affect the neutron-absorption performance of composites with the same content of boron. The hardness of the B-dispersion-strengthened Cu matrix composite obtained by nanoindentation test is about 3.04 GPa. Copper matrix composites with boron dispersion reinforcement exhibit high hardness and neutron-absorption characteristics.

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2

Selke, David L. "Physics Essay: Repulsionless Fusion by Neutron Absorption". Applied Physics Research 8, n.º 6 (17 de noviembre de 2016): 30. http://dx.doi.org/10.5539/apr.v8n6p30.

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<p class="1Body">It is possible to build Helium-4 from Hydrogen-1 by adding only neutrons. The key step is that Tritium decays to Helium-3; thus, a particle that entered the nucleus as a neutron becomes a proton. The need to overcome the mutual repulsion of positively charged nuclei is thus avoided. Given a cheap enough neutron source, this method promises fusion without Sun-like conditions.</p>

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3

Mahdavi, Mohammad y Maryam Shahbahrami. "Multiplication of Fast Neutrons Source Flux by Using Deuterium-Helium-3 Plasma". ISRN High Energy Physics 2013 (30 de mayo de 2013): 1–4. http://dx.doi.org/10.1155/2013/689739.

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The production of fast neutrons source is examined by using a thermal neutron flux inside plasma. In order to reach a favorable yield of fast neutrons flux, the parameters such as energy loss rate, reaction probability, and neutron absorption length are calculated. The nuclear conversion efficiency, , of thermal neutron to fast neutrons is obtained to be by calculating the physical parameters for the plasma designed.

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4

Volz, Heather M., Sven C. Vogel, J. A. Roberts, A. C. Lawson, D. J. Williams y L. L. Daemen. "Effect of Strong Neutron Absorption on Texture and Diffraction Data Analysis". Materials Science Forum 495-497 (septiembre de 2005): 119–24. http://dx.doi.org/10.4028/www.scientific.net/msf.495-497.119.

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The impact of strong neutron absorption on data analysis and the comparison of two different absorption corrections for neutron diffraction data implemented in the GSAS Rietveld code are the foci of this work. We investigated the effect of absorption on the texture and the thermal motion parameter for rolled elemental foils. The orientation distribution functions (ODF) of rolled foils of dysprosium and erbium metals were determined from neutron time-of-flight data patterns collected on HIPPO at LANSCE. Both Dy and Er are strong absorbers for thermal neutrons with absorption cross-sections of 994 barns for Dy and 159 barns for Er at l = 1.8 Å. Various stacks of foils of each material, along with combinations of absorbing and less-absorbing foils, were measured. The patterns were analyzed using the GSAS options for Debye-Scherrer and linear absorption models, as well as without an absorption correction. Discrepancies between refined and expected “true” values of crystallographic parameters if absorption is not taken into consideration are discussed.

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5

Mildner, D. F. R., H. Chen, R. G. Downing y V. A. Sharov. "Developing a focused neutron probe for materials analysis". Proceedings, annual meeting, Electron Microscopy Society of America 50, n.º 2 (agosto de 1992): 1728–29. http://dx.doi.org/10.1017/s0424820100133278.

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Long wavelength neutrons have optical properties analogous to those of photons, and may be focused to produce significantly higher fluxes using the principle of multiple mirror reflection from smooth surfaces at small grazing incident angles. Narrowly focused beams of cold neutrons (with wavelengths greater than 0.4 nm) allow greater spatial resolution for analytical applications than previously available, and will improve the detection limits of neutron absorption measurements (which are dependent on the neutron capture reaction rate) for quantitative analysis. Since the absorption cross section increases linearly with neutron wavelength, the reaction rate for a given isotope increases with the use of cold neutrons. This suggests microprobe capabilities which complement other radiation techniques for multidimensional microanalysis of trace elements in materials science. Among the techniques which will benefit by the development of focused neutrons are prompt gamma activation analysis and neutron depth profiling, by increasing the elemental sensitivity, lowering the detection limits, enhancing multi elemental as well as spatial analysis.

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6

Piscitelli, F., A. Khaplanov, A. Devishvili, S. Schmidt, C. Höglund, J. Birch, A. J. C. Dennison, P. Gutfreund, R. Hall-Wilton y P. Van Esch. "Neutron reflectometry on highly absorbing films and its application to 10 B 4 C-based neutron detectors". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, n.º 2185 (enero de 2016): 20150711. http://dx.doi.org/10.1098/rspa.2015.0711.

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Neutron reflectometry is a powerful tool used for studies of surfaces and interfaces. The absorption in the typical studied materials is neglected and this technique is limited only to the reflectivity measurement. For strongly absorbing nuclei, the absorption can be directly measured by using the neutron-induced fluorescence technique which exploits the prompt particle emission of absorbing isotopes. This technique is emerging from soft matter and biology where highly absorbing nuclei, in very small quantities, are used as a label for buried layers. Nowadays, the importance of absorbing layers is rapidly increasing, partially because of their application in neutron detection; a field that has become more active also due to the 3 He -shortage. We extend the neutron-induced fluorescence technique to the study of layers of highly absorbing materials, in particular 10 B 4 C. The theory of neutron reflectometry is a commonly studied topic; however, when a strong absorption is present the subtle relationship between the reflection and the absorption of neutrons is not widely known. The theory for a general stack of absorbing layers has been developed and compared to measurements. We also report on the requirements that a 10 B 4 C layer must fulfil in order to be employed as a converter in neutron detection.

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7

Chen, Junyang, Ulrich Rücker, Jörg Voigt, Paul Zakalek, Egor Vezhlev, Jingjing Li, Thomas Gutberlet y Thomas Brückel. "Thermal moderator-reflector design of the 24 Hz target station for the High Brilliance Neutron Source". EPJ Web of Conferences 286 (2023): 02005. http://dx.doi.org/10.1051/epjconf/202328602005.

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The High Brilliance Neutron Source (HBS) project develops a high current accelerator driven neutron source (HiCANS), aiming to substitute existing neutron research reactors, that reach the end of life. This study focuses on the thermal neutron moderator design for a low frequency, long pulse target station of HBS. We investigate the neutronic characteristics of the D2O+H2O mixture moderator material using the Monte Carlo particle transport code PHITS. Our findings show that, compared to D2O with lower neutron absorption, confinement of H2O is the dominant factor in achieving a high neutron flux within the moderator and thus a high neutron brightness. We find that surrounding the central thermal water moderator with a D2O+H2O mixture can achieve a better balance between confinement and absorption. However, because of multiple angles of reflecting neutron, this design will also increase the divergence of the neutron beam.

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8

Shishido, Hiroaki, The Dang Vu, Kazuya Aizawa, Kenji M. Kojima, Tomio Koyama, Kenichi Oikawa, Masahide Harada et al. "Crystalline Orientation of CaF₂ window determined by Neutron Transmission Imaging using a Delay Line Current-Biased Kinetic-Inductance Detector". Journal of Physics: Conference Series 2545, n.º 1 (1 de julio de 2023): 012020. http://dx.doi.org/10.1088/1742-6596/2545/1/012020.

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Abstract The combination of a high speed two-dimensional neutron detector and an intensive pulsed neutron source provides not only neutron transmission imaging but also information on crystal structures, orientations and constituent elements by analyzing neutron transmission spectra. The delay-line current-biased kinetic-inductance detector (CB-KID) is a two-dimensional superconducting neutron detector with high spatial and temporal resolutions, and multi-hit tolerance. We demonstrated that the delay-line CB-KID with a 10B neutron conversion layer can be applied for neutron transmission measurements up to 100 keV. We observed two-different dip structures in the transmission spectra in a CaF2 single crystal, i.e., one is from the Bragg diffraction and the other is from nuclear resonance absorption. We consider that some duplicated structures in resonance absorption dips are originating from a double-bunch structure of proton pulses for producing pulsed neutrons in the accelerator.

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9

Ekhwan Razali, Mohd, Roszilah Hamid y Yusof Abdullah. "Mechanical Properties and Thermal Neutron Absorption of Heavyweight Hematite Aggregate Concrete for Radiation Shielding". International Journal of Engineering & Technology 8, n.º 1.2 (30 de enero de 2019): 123–30. http://dx.doi.org/10.14419/ijet.v8i1.2.24883.

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Heavyweight aggregate concrete (HWAC) is the most widely used material as radiation shielding for nuclear reactors. The density of HWAC is increased through the use of heavy natural aggregates such as barites, hematite and magnetite. This study determines the density of HWAC with hematite aggregate replacing granite at 0%, 10%, 20%, 30%, 40% and 50%, its compressive strength and thermal neutron absorption of 1 MeV fast neutrons. The physical properties of hematite which include gradation, specific gravity, water absorption and loose unit weight are determined. The chemical composition of hematite is also determined using X-ray fluorescent (XRF) analysis. The slump, density, compressive strength and thermal neutron absorption of the heavyweight concrete containing different proportion of hematite as aggregate are also determined. Results show that the slumps of HWAC are between 77 mm â€“ 84 mm, the density of HWAC increases between 0.3% - 1.18% by increasing the hematite content. HWAC with 10% hematite exhibits highest strength at 52.5 MPa and the highest thermal neutron absorption at 2085 count per second. The optimum amount of hematite to replace granite for best strength and neutron absorption is 10%.Â

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10

Laureau, Axel, Max Begue, Vincent Lamirand, Elsa Merle y Oskari Pakari. "Fast simulation of neutron noise using the Transient Fission Matrix approach and validation on the CROCUS reactor". EPJ Web of Conferences 302 (2024): 08002. http://dx.doi.org/10.1051/epjconf/202430208002.

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This article presents the development of a neutron noise calculation technique with a reduced calculation time based on the TFM (Transient Fission Matrix) approach. The latter contains different information such as the system transfer function (fission and absorption probability density functions and corresponding neutron multiplicity) of prompt and delayed neutrons, and the corresponding propagation time. This information is used to reconstruct neutron showers based on precursor decays up to the shower disappearance by absorption, leakage or delayed neutron precursor creation. Then pseudo-detectors such as fission chamber count rate histograms are reconstructed from these neutron showers and the αprompt is calculated from the cross-correlation function. A very good agreement has been obtained on the uranium-fueled light water reactor CROCUS between the model developed and the reference value.

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11

Volz, H. M., S. C. Vogel, C. T. Necker, J. A. Roberts, A. C. Lawson, D. J. Williams, L. L. Daemen, L. Lutterotti y J. Pehl. "Rietveld texture analysis by neutron diffraction of highly absorbing materials". Powder Diffraction 21, n.º 2 (junio de 2006): 114–17. http://dx.doi.org/10.1154/1.2204058.

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We discuss the impact of strong absorption for thermal neutrons on data analysis and compare absorption corrections in the GSAS and MAUD Rietveld codes for texture and structural parameter refinement. Diffraction data were collected on the neutron powder diffractometer HIPPO at LANSCE from dysprosium and erbium, which are moderate-to-strong absorbers for thermal neutrons with absorption cross sections of 159 barns for Er and 994 barns for Dy at λ=1.8 Å. Both elements have hexagonal-close-packed (hcp) crystal structures, and the samples were various thicknesses of rolled foils. The orientation distribution functions (ODF) were fit to the same neutron time-of-flight data sets using two very different full pattern Rietveld analysis procedures. Spherical harmonics functions were fit to the textured data using GSAS. These data were also analyzed by the modified direct method E-WIMV using MAUD. The resulting pole figures from the ODFs determined by both Rietveld analysis packages are qualitatively similar, and the textures were confirmed by X-ray diffraction. Additionally, data from orthorhombic dysprosium and erbium fluoride powders show that atomic positions are not sensitive to absorption. We address inconsistencies and methodologies in data analysis when strong absorption is present.

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12

Kolevatov, Rodion, Christian Schanzer y Peter Böni. "Neutron absorption in supermirror coatings". Journal of Neutron Research 20, n.º 4 (23 de enero de 2019): 127–29. http://dx.doi.org/10.3233/jnr-180088.

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13

Løvhøiden, G. y E. Andersen. "Neutron Absorption in Geological Material". Physica Scripta T32 (1 de enero de 1990): 228–30. http://dx.doi.org/10.1088/0031-8949/1990/t32/038.

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14

Steinhauser, Georg, Stefan Merz y Johannes H. Sterba. "Instrumental neutron absorption activation analysis". Journal of Radioanalytical and Nuclear Chemistry 296, n.º 1 (11 de julio de 2012): 165–68. http://dx.doi.org/10.1007/s10967-012-1925-5.

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15

Macklin, R. L. y C. W. Alexander. "Neutron Absorption Cross Section of236U". Nuclear Science and Engineering 104, n.º 3 (marzo de 1990): 258–70. http://dx.doi.org/10.13182/nse90-a23724.

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16

Kamiyama, Takashi, Hirotaka Sato, Naoki Miyamoto, Hirokatsu Iwasa, Yoshiaki Kiyanagi y Susumu Ikeda. "Energy sliced neutron tomography using neutron resonance absorption spectrometer". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 600, n.º 1 (febrero de 2009): 107–10. http://dx.doi.org/10.1016/j.nima.2008.11.053.

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17

Lan, Zechen, Yasunobu Arikawa, Yuki Abe, Seyed Reza Mirfayzi, Alessio Morace, Takehito Hayakawa, Tianyun Wei y Akifumi Yogo. "Development of a Time-Gated Epithermal Neutron Spectrometer for Resonance Absorption Measurements Driven by a High-Intensity Laser". Quantum Beam Science 8, n.º 1 (29 de febrero de 2024): 9. http://dx.doi.org/10.3390/qubs8010009.

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The advance of laser-driven neutron sources (LDNSs) has enabled neutron resonance spectroscopy to be performed with a single shot of a laser. In this study, we describe a detection system of epithermal (∼eV) neutrons especially designed for neutron resonance spectroscopy. A time-gated photomultiplier tube (PMT) with a high cut-off ratio was introduced for epithermal neutron detection in a high-power laser experiment at the Institute of Laser Engineering, Osaka University. We successfully reduced the PMT response to the intense hard X-ray generated as a result of the interaction between laser light and the target material. A time-gated circuit was designed to turn off the response of the PMT during the laser pulse and resume recording the signal when neutrons arrive. The time-gated PMT was coupled with a 6Li glass scintillator, serving as a time-of-flight (TOF) detector to measure the neutron resonance absorption values of 182W and 109Ag in a laser-driven epithermal neutron generation experiment. The neutron resonance peaks at 4.15 eV of 182W and 5.19 eV of 109Ag were detected after a single pulse of laser at a distance of 1.07 m.

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18

Alvarez-Estrada, Ramon F. y Maria L. Calvo. "Neutron Fibres: Confined Propagation and Focusing of Neutrons in the Micron Range and Residual Stress Analysis". Materials Science Forum 772 (noviembre de 2013): 51–56. http://dx.doi.org/10.4028/www.scientific.net/msf.772.51.

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We summarize the confined propagation of thermal neutrons along waveguides with small transverse cross section (neutron fibres). We outline proposals for neutron fibres with transverse sizes from microns (μm) down to tens of nanometers (nm). We summarize experimental implementations by means of polycapillary glass fibres, in the μm scale. Some diffraction experiments on small samples by means of thermal neutron capillary optics are summarized. Such developments (together with absorption techniques) could have possible interest for residual stress analysis, below the mm scale.

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19

Salamatov, Yu A. y E. A. Kravtsov. "Theoretical Study of Neutron Reflection from Thin Films and Layered Nanostructures Containing Highly Absorbing Gadolinium and Boron Isotopes". Поверхность. Рентгеновские, синхротронные и нейтронные исследования, n.º 8 (1 de agosto de 2023): 32–39. http://dx.doi.org/10.31857/s1028096023080125.

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The application of the method of phase-amplitude functions to the calculation of neutron propagation processes in layered media containing highly absorbing elements is described. This method allows us to simultaneously calculate the reflection, transmission and absorption coefficients of neutrons. It requires less computing resources than the other algorithms. A generalization of the method to matrix equations used in polarized neutron reflectometry is also presented. Examples of calculations of various characteristics of neutron propagation for layered resonator-type systems with a potential well are given.

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20

Aleksenskii, Aleksander, Markus Bleuel, Alexei Bosak, Alexandra Chumakova, Artur Dideikin, Marc Dubois, Ekaterina Korobkina et al. "Clustering of Diamond Nanoparticles, Fluorination and Efficiency of Slow Neutron Reflectors". Nanomaterials 11, n.º 8 (28 de julio de 2021): 1945. http://dx.doi.org/10.3390/nano11081945.

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Neutrons can be an instrument or an object in many fields of research. Major efforts all over the world are devoted to improving the intensity of neutron sources and the efficiency of neutron delivery for experimental installations. In this context, neutron reflectors play a key role because they allow significant improvement of both economy and efficiency. For slow neutrons, Detonation NanoDiamond (DND) powders provide exceptionally good reflecting performance due to the combination of enhanced coherent scattering and low neutron absorption. The enhancement is at maximum when the nanoparticle diameter is close to the neutron wavelength. Therefore, the mean nanoparticle diameter and the diameter distribution are important. In addition, DNDs show clustering, which increases their effective diameters. Here, we report on how breaking agglomerates affects clustering of DNDs and the overall reflector performance. We characterize DNDs using small-angle neutron scattering, X-ray diffraction, scanning and transmission electron microscopy, neutron activation analysis, dynamical light scattering, infra-red light spectroscopy, and others. Based on the results of these tests, we discuss the calculated size distribution of DNDs, the absolute cross-section of neutron scattering, the neutron albedo, and the neutron intensity gain for neutron traps with DND walls.

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21

Thiyagarajan, P., R. K. Crawford y D. F. R. Mildner. "Neutron Transmission of a Single-Crystal MgO Filter". Journal of Applied Crystallography 31, n.º 6 (1 de diciembre de 1998): 841–44. http://dx.doi.org/10.1107/s0021889898005858.

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The neutron transmission probability through a single-crystal MgO filter has been measured at both liquid-nitrogen (77 K) and room (300 K) temperatures, as a function of wavelength, using a pulsed neutron source. The data show that a cooled MgO filter is superior to room-temperature sapphire for both thermal and cold neutrons, principally because the absorption probability is reduced by a factor of three at long wavelengths.

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22

Brokmeier, H. G. "Neutron Diffraction Texture Analysis of Multi-Phase Systems". Textures and Microstructures 10, n.º 4 (1 de enero de 1989): 325–46. http://dx.doi.org/10.1155/tsm.10.325.

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Neutron diffraction methods for texture analysis are closely parallel to well-known X-ray diffraction techniques. The chief advantage of neutron diffraction over X-ray diffraction, however, arises from the fact that the interaction of neutrons with matter is relatively weak, and consequently the penetration depth of neutrons is 102–103 times larger than that of X-rays. Hence neutron diffraction is an efficient tool for measuring textures in multi-phase systems. Based on the high transmission of a neutron beam the effect of anisotropic absorption in multi-phase materials can be neglected in most cases. Moreover, the analysis of bulk textures becomes possible, such that textures in a wide variety of multi-phase systems can be studied which are of special interest in engineering and science (metals, alloys, composites, ceramics and geological specimens).

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23

Cousin, Fabrice y Alexis Chennevière. "Neutron reflectivity for soft matter". EPJ Web of Conferences 188 (2018): 04001. http://dx.doi.org/10.1051/epjconf/201818804001.

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Specular neutron reflectivity is a technique enabling the measurement of coherent neutron scattering length density profile perpendicular to the plane of a surface or interface, and thereby the profile of chemical composition. The characteristic sizes that are probed range from around 5Å up 5000 Å. It is a scattering technique that averages information over the entire surface and it is therefore not possible to obtain information on correlations in the plane of the interface. The specific properties of neutrons (possibility of tuning the contrast by isotopic substitution, negligible absorption, low energy of the incident neutrons) makes it particularly interesting in the fields of soft matter and biophysics. This course is composed of three parts describing respectively its principle, the experimental aspects (diffractometers, samples), and some scientific examples of neutron reflectometry focusing on the use of contrast variation to probe polymeric systems.

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24

Nikitenko, Yu V. "Neutron Absorption in a Layered Structure". Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques 16, n.º 4 (agosto de 2022): 533–36. http://dx.doi.org/10.1134/s1027451022040139.

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25

Smith, Alan B. "The Neutron Spherical Optical Model Absorption". Annals of Nuclear Energy 35, n.º 5 (mayo de 2008): 890–903. http://dx.doi.org/10.1016/j.anucene.2007.09.004.

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26

Kaloyerou, P. N. y H. R. Brown. "On neutron interferometer partial absorption experiments". Physica B: Condensed Matter 176, n.º 1-2 (enero de 1992): 78–92. http://dx.doi.org/10.1016/0921-4526(92)90600-w.

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27

Johnson, Elijah y Larry Robinson. "Neutron multiple scattering and absorption factors". Review of Scientific Instruments 60, n.º 11 (noviembre de 1989): 3447–51. http://dx.doi.org/10.1063/1.1141076.

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28

Skobelev, V. V. "Absorption of neutrinos in neutron stars". Astrophysics 31, n.º 1 (1990): 502–5. http://dx.doi.org/10.1007/bf01004398.

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29

Kulikov, Gennady G., Anatoly N. Shmelev, Vladimir A. Apse y Evgeny G. Kulikov. "On a significant slowing-down of the kinetics of fast transient processes in a fast reactor". Nuclear Energy and Technology 6, n.º 4 (20 de noviembre de 2020): 295–98. http://dx.doi.org/10.3897/nucet.6.60379.

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The kinetics of nuclear reactors is determined by the average neutron lifetime. When the inserted reactivity is more than the effective delayed neutron fraction, the reactor kinetics becomes very rapid. It is possible to slow down the fast reactor kinetics by increasing the neutron lifetime. The authors consider the possibility of using the lead isotope, 208Pb, as a neutron reflector with specific properties in a lead-cooled fast reactor. To analyze the emerging effects in a reactor of this type, a point kinetics model was selected, which takes into account neutrons returning from the 208Pb reflector to the reactor core. Such specific properties of 208Pb as the high atomic weight and weak neutron absorption allow neutrons from the reactor core to penetrate deeply into the 208Pb reflector, slow down in it, and have a noticeable probability to return to the reactor core and affect the chain fission reaction. The neutrons coming back from the 208Pb reflector have a long ‘dead-time’, i.e., the sum of times when neutrons leave the reactor core, entering the 208Pb reflector, and then diffuse back into the reactor core. During the ‘dead-time’, these neutrons cannot affect the chain fission reaction. In terms of the delay time, the neutrons returning from the deep layers of the 208Pb reflector are close to the delayed neutrons. Moreover, the number of the neutrons coming back from the 208Pb reflector considerably exceeds the number of the delayed neutrons. As a result, the neutron lifetime formed by the prompt neutron lifetime and the ‘dead-time’ of the neutrons from the 208Pb reflector can be substantially increased. This will lead to a longer reactor acceleration period, which will mitigate the effects of prompt supercriticality. Thus, the use of 208Pb as a neutron reflector can significantly improve the fast reactor nuclear safety.

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30

Yanchukovsky, Valery y Vasiliy Kuz'menko. "Method of automatic correction of neutron monitor data for precipitation in the form of snow in real time". Solnechno-Zemnaya Fizika 7, n.º 3 (28 de septiembre de 2021): 120–26. http://dx.doi.org/10.12737/szf-73202108.

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We have carried out an experimental study of the influence of precipitation in the form of snow on measurements of the neutron flux intensity near Earth's surface. We have examined the state of the snow cover and its density, and found out that the density depends on the depth of the snow cover. Using the experimental results, we estimate the neutron absorption path in the snow. Changes in snow cover by 10–12 cm at a depth of 80 cm are shown to cause variations in the monitor count rate with an amplitude of 0.9 %. At the snow depth of 80 cm, the neutron monitor count rate decreases by about 8 %. The observed variations should be attributed to the meteorological effects of cosmic rays. The absorption coefficient of neutrons in the snow was also found from the correlation between the count rate of the neutron monitor and the amount of snow above the detector. We propose a real-time correction of the neutron monitor data for precipitation in the form of snow. For this purpose, we implement continuous monitoring of the amount of snow cover. The monitoring is provided by a snow meter made using a laser rangefinder module. We discuss the results obtained.

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31

Yanchukovsky, Valery y Vasiliy Kuz'menko. "Method of automatic correction of neutron monitor data for precipitation in the form of snow in real time". Solar-Terrestrial Physics 7, n.º 3 (28 de septiembre de 2021): 114–20. http://dx.doi.org/10.12737/stp-73202108.

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We have carried out an experimental study of the influence of precipitation in the form of snow on measurements of the neutron flux intensity near Earth's surface. We have examined the state of the snow cover and its density, and found out that the density depends on the depth of the snow cover. Using the experimental results, we estimate the neutron absorption path in the snow. Changes in snow cover by 10–12 cm at a depth of 80 cm are shown to cause variations in the monitor count rate with an amplitude of 0.9 %. At the snow depth of 80 cm, the neutron monitor count rate decreases by about 8 %. The observed variations should be attributed to the meteorological effects of cosmic rays. The absorption coefficient of neutrons in the snow was also found from the correlation between the count rate of the neutron monitor and the amount of snow above the detector. We propose a real-time correction of the neutron monitor data for precipitation in the form of snow. For this purpose, we implement continuous monitoring of the amount of snow cover. The monitoring is provided by a snow meter made using a laser rangefinder module. We discuss the results obtained.

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32

Tremsin, A. S., J. B. McPhate, J. V. Vallerga, O. H. W. Siegmund, W. Kockelmann, E. M. Schooneveld, N. J. Rhodes y W. B. Feller. "High Resolution Neutron Resonance Absorption Imaging at a Pulsed Neutron Beamline". IEEE Transactions on Nuclear Science 59, n.º 6 (diciembre de 2012): 3272–77. http://dx.doi.org/10.1109/tns.2012.2215627.

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33

Takano, Hidekazu, Yanlin Wu, Tetsuo Samoto, Atsushi Taketani, Takaoki Takanashi, Chihiro Iwamoto, Yoshie Otake y Atsushi Momose. "Demonstration of Neutron Phase Imaging Based on Talbot–Lau Interferometer at Compact Neutron Source RANS". Quantum Beam Science 6, n.º 2 (1 de junio de 2022): 22. http://dx.doi.org/10.3390/qubs6020022.

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Neutron imaging based on a compact Talbot–Lau interferometer was demonstrated using the RIKEN accelerator-driven compact neutron source (RANS). A compact Talbot–Lau interferometer consisting of gadolinium absorption gratings and a silicon phase grating was constructed and connected to the RANS. Because of pulsed thermal neutrons from the RANS and a position-sensitive detector equipped with time-of-flight (TOF) analysis, moiré interference patterns generated using the interferometer were extracted at a TOF range around the design wavelength (2.37 Å) optimal for the interferometer. Differential phase and scattering images of the metal rod samples were obtained through phase-stepping measurements with the interferometer. This demonstrates the feasibility of neutron phase imaging using a compact neutron facility and the potential for flexible and unique applications for nondestructive evaluation.

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34

Feldmann, K. "Texture Investigations by Neutron Time-of-Flight Diffraction". Textures and Microstructures 10, n.º 4 (1 de enero de 1989): 309–23. http://dx.doi.org/10.1155/tsm.10.309.

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For the majority of isotopes the thermal neutron absorption cross section is two or more orders lower than that for X-rays. This makes neutron diffraction well-suited for bulk texture investigations. Some characteristics of neutron diffraction are discussed. The principles of neutron time-of-flight diffraction are described. The pole figure determination by means of TOF technique is considered. The main parameters of the present Dubna texture facility are given. Further developments of the experimental technique are considered. The application of the TOF technique for inverse pole figure measurement is discussed as an approach to direct observation of the texture forming process. The magnetic moments of neutrons can be used to study magnetic textures. Two different techniques are discussed.

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35

Singh, Vishvanath, Nagappa Badiger y Rene Vega-Carrillo. "Studies on neutron and photon kerma parameters for human body organs". Nuclear Technology and Radiation Protection 31, n.º 2 (2016): 128–34. http://dx.doi.org/10.2298/ntrp1602128s.

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A study on neutron kerma factors and photon air-kerma for human organs is presented for neutron energy range 2.53?10-8 MeV to 29 MeV and photon energy range 1 keV to 20 MeV. The human organs water equivalence for photon and neutron, is also presented. The ratio of the mass-energy absorption coefficients of human organs to water was found constant and unity above 100 keV, whereas there was a large difference for energies below 100 keV. The neutron kerma factors of human organs and water are found of same order of magnitude whereas differs for air. The neutron kerma factors of human organs and tissue substitutes were found to be equal to water for neutron energies between 63 eV and 200 keV. The skeleton-cortical bone was found to be away from water equivalence for low-energy photons and high-energy neutrons.

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36

Pape, Sebastian, Marcos Fernández García, Michael Moll y Moritz Wiehe. "Study of Neutron-, Proton-, and Gamma-Irradiated Silicon Detectors Using the Two-Photon Absorption–Transient Current Technique". Sensors 24, n.º 16 (22 de agosto de 2024): 5443. http://dx.doi.org/10.3390/s24165443.

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The Two-Photon Absorption–Transient Current Technique (TPA-TCT) is a device characterisation technique that enables three-dimensional spatial resolution. Laser light in the quadratic absorption regime is employed to generate excess charge carriers only in a small volume around the focal spot. The drift of the excess charge carriers is studied to obtain information about the device under test. Neutron-, proton-, and gamma-irradiated p-type pad silicon detectors up to equivalent fluences of about 7 × 1015 neq/cm2 and a dose of 186 Mrad are investigated to study irradiation-induced effects on the TPA-TCT. Neutron and proton irradiation lead to additional linear absorption, which does not occur in gamma-irradiated detectors. The additional absorption is related to cluster damage, and the absorption scales according to the non-ionising energy loss. The influence of irradiation on the two-photon absorption coefficient is investigated, as well as potential laser beam depletion by the irradiation-induced linear absorption. Further, the electric field in neutron- and proton-irradiated pad detectors at an equivalent fluence of about 7 × 1015 neq/cm2 is investigated, where the space charge of the proton-irradiated devices appears inverted compared to the neutron-irradiated device.

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37

Kosarev, V. F., S. V. Klinkov, V. S. Shikalov y A. E. Chesnokov. "A Study of the Neutron Absorbing Properties of Al + B4C and Al + B Coatings Formed by Cold Gas-Dynamic Spraying". Физика металлов и металловедение 124, n.º 3 (1 de marzo de 2023): 323–29. http://dx.doi.org/10.31857/s0015323022600629.

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For the first time, the efficiency of thermal neutron absorption by composite coatings deposited by cold gas-dynamic spraying from mechanically activated mixtures of Al + B4C and Al + B powders on the surface of stainless steel samples has been compared with a reference standard. The comparison with the standard, which was boron steel plates, showed that the resulting coatings are somewhat inferior in terms of neutron absorption efficiency. To estimate the required thickness of the coatings, an approach based on the processing of the experimental data obtained is proposed that, in particular, takes into account the dependence of the absorption cross section on the distance traveled by the neutron flux. As well, the analysis has shownthat the existing undulation (periodic inconstancy of the thickness) of the coating has virtually no effect on its protective properties (namely, on its neutron absorption coefficient).

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38

Shmelev, A., V. Apse, G. Kulikov y E. Kulikov. "ADVANTAGES OF THE FAST REACTOR CORE SURROUNDED BY THE PHYSICALLY THICK NEUTRON REFLECTOR MADE OF LEAD-208". PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. SERIES: NUCLEAR AND REACTOR CONSTANTS 2020, n.º 4 (26 de diciembre de 2020): 46–59. http://dx.doi.org/10.55176/2414-1038-2020-4-46-59.

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The paper analyzes the effects produced by the use of lead isotope 208Pb instead of natural lead as a coolant and neutron reflector on neutron-physical parameters of fast reactor. A possibility is demonstrated to reach substantial (up to three orders of magnitude) elongation of mean prompt neutron lifetime in the fast reactor with physically thick 208Pb-reflector. So large elongation of prompt neutron lifetime opens an opportunity for remarkable enhancement of the reactor safety under conditions of reactivity-induced accidents. Numerical analyses have shown that it became possible to form high flux of slowed down and epithermal neutrons in 208Pb-reflector even at large distances from the reactor core. Spacious area of high neutron flux out of the reactor core may be used to transmute long-lived fission products and to produce significant quantities of necessary isotopes. Weak neutron absorption in 208Pb makes it possible to reach remarkable (up to 20 %) reduction of plutonium fraction in mixed uranium-plutonium fuel composition. It is proposed to place a layer with neutron absorber in 208Pb-reflector above the reactor core for the reactivity control with no variations in neutron-physical properties of the reactor core. If reactivity of the control rods in the reactor core is lower than effective fraction of delayed neutrons, then the reactor is obviously subcritical on prompt neutrons of the reactor core. In this case the danger of the reactivity-induced accident on prompt neutrons of the reactor core disappears. If the reactivity-induced accident is caused by joint action of the neutrons produced in the reactor core and in 208Pb-reflector, then the accident propagation will be substantially slowed down because of the longer lifetime of neutrons in 208Pb-reflector.

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39

Variale, Vincenzo y Boris Skarbo. "Neutron imager with micro channel plates (MCP) in electrostatic mirror configuration: Neutron beam test". International Journal of Modern Physics: Conference Series 50 (enero de 2020): 2060018. http://dx.doi.org/10.1142/s2010194520600186.

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A recent advancement in a new high transparency monitor device based on Micro Channel Plate (MCP) has been proposed for monitoring flux and beam spatial profiles of neutrons. It consisted of the assembly of a very thin aluminum (Al) foil with a 6Li deposit placed along the beam and a MCP equipped with a phosphor screen readout viewed by a CCD camera outside the beam line. The peculiar feature of this device is that it uses an electrostatic mirror to minimize the perturbation of the neutron beam, i.e. absorption and scattering. It can be used at existing time-of-flight facilities, in particular at the neutron Time-of-Flight (n_TOF) facility at CERN, for monitoring the flux and the spatial profile of neutron beams in the thermal and epithermal region. In this contribution, the device experimental test carried out on the n_TOF neutron beam at CERN will be presented and discussed.

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40

Mehrnejad, Rasoul, Abdulhalik Karabulut, Turgay Korkut y Bunyamin Aygun. "Improving Neutron Shielding Capacities of Galena and Barite Hybrid Fiber Heavyweight Aggregate Concrete for Nuclear Reactor". International Journal on Applied Physics and Engineering 2 (5 de octubre de 2023): 128–36. http://dx.doi.org/10.37394/232030.2023.2.12.

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Biological shielding of nuclear reactors is an important interest and diminishing the intricacy and cost of these installations is an important interest. In this paper, we used galena minerals and barite for the production of a hybrid fiber heavyweight aggregate concrete. Galena minerals that exist in many parts of Iran were used in the concrete mix design. Barite is an important chemical element for neutron absorption processes. The cross-section in matter and neutron capture is a utilizable cause to explain the neutron shielding characteristics of samples. Neutron cross-section measurements of samples were done by using a source of 4.5 MeV neutrons. Cross-section and neutron capture of each sample were calculated by using the Geant 4 Monte Carlo code. As a result, the use of appropriate galena concentration and barite and the use of monofilament polypropylene fiber with steel fiber can improve cross cross-section value of hybrid fiber heavyweight aggregate concrete and enhance the properties of neutron shielding.

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41

Platt, Simon P., Shaun August, Michael MacLeod, Michael J. Anderson, David Cheneler y Stephen D. Monk. "Thermal Neutron Absorption in Printed Circuit Boards". IEEE Transactions on Nuclear Science 68, n.º 4 (abril de 2021): 463–69. http://dx.doi.org/10.1109/tns.2021.3060864.

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42

Andersen, E. y G. Lovhoiden. "Measurement of neutron absorption in geological material". Journal of Physics D: Applied Physics 21, n.º 11 (14 de noviembre de 1988): 1550–55. http://dx.doi.org/10.1088/0022-3727/21/11/002.

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43

Cooke, D. W., B. L. Bennett y E. H. Farnum. "Optical absorption of neutron-irradiated silica fibers". Journal of Nuclear Materials 232, n.º 2-3 (septiembre de 1996): 214–18. http://dx.doi.org/10.1016/s0022-3115(96)00405-9.

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44

Nakaidze, Shota, Vazha Garibashvili, Marina Antadze y Otar Tsagareishvili. "Neutron-absorption deformable boron-rich ferrous alloys". Journal of Solid State Chemistry 177, n.º 2 (febrero de 2004): 592–95. http://dx.doi.org/10.1016/j.jssc.2003.07.007.

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45

Sato, Hirotaka, Takashi Kamiyama, Yoshiaki Kiyanagi y Susumu Ikeda. "Simulation for neutron resonance absorption spectroscopic tomography". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 600, n.º 1 (febrero de 2009): 135–38. http://dx.doi.org/10.1016/j.nima.2008.11.107.

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46

Szmidt, E. y Cz Bobrowski. "Reversible hydrogen absorption in neutron generating tubes". Journal of Radioanalytical and Nuclear Chemistry Articles 178, n.º 1 (febrero de 1994): 73–80. http://dx.doi.org/10.1007/bf02068658.

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47

Mook, H. A., J. A. Harvey y N. W. Hill. "Measurement ofTefffor Cu inYBa2Cu3O7by neutron resonance absorption". Physical Review B 41, n.º 1 (1 de enero de 1990): 764–65. http://dx.doi.org/10.1103/physrevb.41.764.

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48

Mikhnov, S. A. y V. �. Grinkevich. "Broad-band absorption in neutron-irradiated leucosapphire". Journal of Applied Spectroscopy 56, n.º 1 (enero de 1992): 77–81. http://dx.doi.org/10.1007/bf00658255.

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49

Just, O., S. Goriely, H.-Th Janka, S. Nagataki y A. Bauswein. "Neutrino absorption and other physics dependencies in neutrino-cooled black hole accretion discs". Monthly Notices of the Royal Astronomical Society 509, n.º 1 (8 de octubre de 2021): 1377–412. http://dx.doi.org/10.1093/mnras/stab2861.

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ABSTRACT Black hole (BH) accretion discs formed in compact-object mergers or collapsars may be major sites of the rapid-neutron-capture (r-)process, but the conditions determining the electron fraction (Ye) remain uncertain given the complexity of neutrino transfer and angular-momentum transport. After discussing relevant weak-interaction regimes, we study the role of neutrino absorption for shaping Ye using an extensive set of simulations performed with two-moment neutrino transport and again without neutrino absorption. We vary the torus mass, BH mass and spin, and examine the impact of rest-mass and weak-magnetism corrections in the neutrino rates. We also test the dependence on the angular-momentum transport treatment by comparing axisymmetric models using the standard α-viscosity with viscous models assuming constant viscous length-scales (lt) and 3D magnetohydrodynamic (MHD) simulations. Finally, we discuss the nucleosynthesis yields and basic kilonova properties. We find that absorption pushes Ye towards ∼0.5 outside the torus, while inside increasing the equilibrium value $Y_\mathrm{ e}^{\mathrm{eq}}$ by ∼0.05–0.2. Correspondingly, a substantial ejecta fraction is pushed above Ye = 0.25, leading to a reduced lanthanide fraction and a brighter, earlier, and bluer kilonova than without absorption. More compact tori with higher neutrino optical depth, τ, tend to have lower $Y_\mathrm{ e}^{\mathrm{eq}}$ up to τ ∼ 1–10, above which absorption becomes strong enough to reverse this trend. Disc ejecta are less (more) neutron rich when employing an lt = const. viscosity (MHD treatment). The solar-like abundance pattern found for our MHD model marginally supports collapsar discs as major r-process sites, although a strong r-process may be limited to phases of high mass-infall rates, $\dot{M}\, \, \raise0.14em\rm{\gt }\lower0.28em\rm{\sim }\, \, 2\times 10^{-2}$ M⊙ s−1.

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50

Désert, Sylvain, Tobias Panzner y Patrice Permingeat. "Focusing neutrons with a combination of parabolic and elliptical supermirrors". Journal of Applied Crystallography 46, n.º 1 (21 de diciembre de 2012): 35–42. http://dx.doi.org/10.1107/s0021889812047346.

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Cold-neutron focusing is a challenge with regard to improving the flux at the sample, decreasing measurement time and/or gaining statistical reliability. Several techniques are used for neutron focusing, such as simple or multi-beam collimation, refractive or magnetic lenses, and focusing mirrors. In this work, a new device for focusing neutrons using a combination of a parabolic supermirror, an asymmetric slit system and an elliptical supermirror is presented. The aim of this focusing system is to improve the neutron flux at the sample compared to other techniques without either achromatism or absorption. The performance of the device obtained by simulations and measurements with a prototype on a small-angle neutron scattering setup shows a flux gain of four at the sample position and an intensity gain higher than 100 when the sample size can be increased compared to classical setups. Finally the applications for neutron instruments are commented on.

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