2025-03-02
00:01 |
High-resolution neutron diffraction for finer studies of powder diffraction lines
Mikula, Pavol ; Ryukhtin, Vasyl
Feasibility of focusing high-resolution three axis diffractometer with the polycrystalline sample between the monochromator and the analyzer for studies of finer effects of diffraction lines is routinely used at the medium-power reactor LVR-15 in Řež. The focusing three-axis set-up equipped with bent perfect crystal monochromator and analyzer exploits both focusing in real and momentum space and provides the intensity and resolution parameters for measurements within a reasonable measurement time.
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2025-03-02
00:01 |
Experimental equipments of Neutron physics laboratory for testing of metalic samples
Mikula, Pavol ; Strunz, Pavel
The use of neutron scattering for structural and property studies of technologically interesting materials as well as solution of industrial problems has been expanding in the last years. Correspondingly, demands for the beam time at neutron sources have been strongly increased. After using Bragg diffraction optics based on diffraction by curved perfect crystals some experiments of materials science - usually done with small sample volumes - can be effectively performed even at a medium power reactor, in our case at LVR-15 in Řež. Examples of unique experimental results obtained namely, by medium-resolution small-angle neutron scattering, residual strain/stress measurements and conventional powder diffraction at the reactor will be presented. An access to experiments for external users is also presented. \n
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2025-02-22
00:00 |
On a Possibility of High-Resolution Neutron Scattering Observations of TiAl Substructure
Mikula, Pavol ; Michalcová, A. ; Ryukhtin, Vasyl
In this contribution, we present the feasibility of using two unconventional neutron scattering methods, namely, high-resolution neutron diffraction and small-angle neutron scattering, for substructure studies of TiAl alloys. The first one permits the finer studies of the diffraction line profiles and the second one the size distribution of pores on a rather large scale. The feasibility experiments were carried out on the three TiAl samples of the f = 9 mm diameter which were made from the 3D printed material of gamma titanium aluminides (Ti48Al2Cr2Nb) loaded on the bulk Ti substrate.
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2023-12-06
00:37 |
Analýza obsahu prvků v automobilových sklech pomocí neutronové aktivační analýzy a rentgenové fluorescenční analýzy
Kameník, Jan ; Fikrle, Marek ; Kučera, Jan
Mikrofragmenty skel nesou cenné informace o některých druzích zločinů spojených s vozidly. Metodika popisuje využití Rentgenové fluorescenční analýzy (RFA) a neutronové aktivační analýzy (NAA) pro stanovení prvkových přímesí ve střepech automobilových skel. RFA umožňuje rychlé nedestruktivní testování vzorku, které umožní výběr analytických postupů pro další analýzu. Metoda NAA je časově náročnější, má potenciál poskytovat robustní výsledky pro orgány činné v trestním řízení. Metodika zahrnuje popis obou metod a jejich uplatnění při analýze fragmentů skel. Součástí metodiky jsou výsledky analýzy více než 80 vzorků automobilových skel.
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2023-12-06
00:37 |
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2023-03-12
00:04 |
Spectrometry of neutron field based on p(20)+Be source reaction
Kozic, Ján ; Štefánik, Milan
The research deals with a spectrometry of neutron field based on the p(20)+Be source reaction. The p(20)+Be interaction stands for a nuclear reaction where protons accelerated to energy of 20 MeV bombard Be target. Produced neutron field has broad energy distribution up to 18 MeV. The research was carried out at the Nuclear Physics Institute of the Czech Academy of Sciences and was motivated by extension of experimental possibilities of the NG-2 target station. To determine the neutron spectrum, the activation foil technique was used. During the experiment, ten activation foils were irradiated. Activated foils were measured using the HPGe detector to determine the reaction rates of observed reactions. The neutron field was simulated in the MCNPX code, and the simulation served as a priori information for the unfolding of the neutron spectrum in the SAND-II code. A determined neutron spectrum is essential for various experiments, e.g., material research, measurements of nuclear data, etc.
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2023-03-12
00:04 |
The characterization of the collimated beams of fast neutrons with the CLID detecion system
Ansorge, Martin ; Novák, Jan ; Majerle, Mitja ; Kozic, Ján
A new detection device for the measurements of light ions (p, d, t, α) emitted as the products of the nuclear reactions induced by fast neutrons (5-33 MeV) was recently developed at the Nuclear Physics Institute of the Czech Academy of Sciences. The main objective of the Chamber-for-Light-Ion-Detection (CLID) is to produce new differential nuclear data of high interest for the material applications related to fusion and aerospace technologies and to potentially test and validate models of nuclear reactions. Hereby the experimental set-up for the measurements with the CLID is described in detail. The experimental characterization of the collimated fast neutron beams produced by the cyclotron-driven converter (p(35 MeV)+Be(2.5 mm)) is presented. In particular, the implementation of the Proton-Recoil-Telescope technique used for neutron energy spectra determination with the CLID is described.
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2022-09-28
00:47 |
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2021-03-28
00:00 |
Effect of implantation of C, Si and Cu into ZrNb nanometric multilayers
Daghbouj, N. ; Karlík, M. ; Lorinčík, J. ; Polcar, T. ; Callisti, M. ; Havránek, Vladimír
Sputter-deposited Zr/Nb nanometric multilayer films with a periodicity (L) in the range from 6 to 167 nm were subjected to carbon, silicon and copper ion irradiation with low and high fluences at room temperature. The ion profiles, mechanical proprieties, and disordering behavior have been investigated by using a variety of experimental techniques (Secondary Ion Mass Spectrometry - SIMS, nanoindentation, X-ray diffraction - XRD, and scanning transmission electron microscopy - STEM). On the STEM bright field micrographs there is damage clearly visible on the surface side of the multilayer. Deeper, the most damaged and disordered zone, located close to the maximum ion concentration, was observed. The in-depth C and Si concentration profiles obtained from SIMS were not affected by the periodicity of the nanolayers. This is in accordance with SRIM simulations. XRD and electron diffraction analyses suggest a structural evolution in relation to L. After irradiation, Zr (0002) and Nb (110) reflexions overlap for L=6 nm. For the periodicity L > 6 nm the Zr (0002) peak is shifted to higher angles and Nb (110) peak is shifted to lower angles.
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2021-03-28
00:00 |
Investigation of deformation mechanisms in textured magnesium alloy
Dittrich, J. ; Čapek, J. ; Knapek, Michal ; Minárik, P.
Advanced in-situ and ex-situ methods were used to reveal active deformation mechanisms during deformation of magnesium alloy with a strong texture. Three sets of samples were prepared from the rolled sheet of commercial AZ31 alloy with respect to its strong basal texture - normal direction (ND), rolling direction (RD) and 45 degrees between RD and ND, and were deformed in both compression and tension. The signal of acoustic emission (AE) was measured concurrently during the deformation. Electron backscattered diffraction (EBSD) was used to study the microstructure after the selected stages of the deformation. It is shown that the extension twinning played an important role during the plastic deformation in the samples having favorably oriented basal texture component, whereas in the unfavorably oriented samples, the role of twinning was marginal. Pronounced activation of twinning only in some samples caused a considerable variation in the deformation behavior and AE response. A consistent link between the energy and amplitudes of the AE signal and the microstructure changes investigated by EBSD was established.
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