Počet nalezených dokumentů: 424
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Preparation of ppHMDSO Thin Films in Capacitively Coupled RF Glow Discharges under Dusty Plasma Conditions
Homola, V.; Buršíková, V.; Kelar, L.; Kelarová, Š.; Stupavska, M.; Peřina, Vratislav
2018 - anglický
The deposition of organosilicone thin films from mixture of hexamethyldisiloxane (HMDSO) and oxygen by using capacitively coupled R.F. glow discharges under dusty plasma conditions was investigated. High resolution topography and mechanical property maps of the prepared films were acquired by using atomic force microscopy techniques. The chemical bond and composition of the deposited films were analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The mechanical properties of the films were studied using quasistatic as well as dynamic nanoindentation tests and their surface free energies were evaluated by means of contact angle measuring technique using several testing liquids exhibiting various surface tensions. The thermal stability of the films was studied using thermal desorption spectroscopy. Neural network modelling was used to study the effect of plasma parameters on the hardness of ppHMDSO films Klíčová slova: Hexamethyldisiloxane; mechanical properties; oxygen; PECVD Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Preparation of ppHMDSO Thin Films in Capacitively Coupled RF Glow Discharges under Dusty Plasma Conditions

The deposition of organosilicone thin films from mixture of hexamethyldisiloxane (HMDSO) and oxygen by using capacitively coupled R.F. glow discharges under dusty plasma conditions was investigated. ...

Homola, V.; Buršíková, V.; Kelar, L.; Kelarová, Š.; Stupavska, M.; Peřina, Vratislav
Ústav jaderné fyziky, 2018

Role of activation analysis in the preparation of reference materials
Kučera, Jan
2018 - anglický
The fundamentals of neutron activation analysis (NAA) and prompt gamma activation analysis (PGAA) and practices of both methods are briefly review, together with enlightening their specific role in the preparation of reference materials. The importance of homogeneity testing for the certification and use of reference materials (RMs) using NAA is appraised. Examples of the use of NAA and PGAA for the certification of element contents in environmental, biological, and material science RMs produced by world-leading institutions, such as U.S. NIST, IRMM, IAEA and by national institutions, as well, at the Nuclear Physics Institute within last almost 30 years are presented. Klíčová slova: analytical methods; INAA; RNAA Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Role of activation analysis in the preparation of reference materials

The fundamentals of neutron activation analysis (NAA) and prompt gamma activation analysis (PGAA) and practices of both methods are briefly review, together with enlightening their specific role in ...

Kučera, Jan
Ústav jaderné fyziky, 2018

Stability of the sodium content in selected botanical reference materials
Kameník, Jan; Kučera, Jan; Borovička, Jan; Havránek, Vladimír
2018 - anglický
Sodium mass fractions in NIST standard reference materials (SRM) SRM 1547 Peach Leaves and SRM 1515 Apple leaves determined by INAA in our laboratory in recent years has been higher than the certified values. Similarly, increased values were published for SRM 1547 by several other laboratories. The increased Na mass fractions was found also for freshly opened SRM 1547 bottle and for material originating from a different lab. Increased Na mass fractions were confirmed by ICP-MS analysis of both materials. Analysis of archived samples revealed that sodium mass fraction in materials stored in polyethylene capsules is in agreement with the certified values. The sodium content in the glass of SRM 1547 bottle was roughly 10 %. Direct measurement of the Na depth profile by micro-PIXE was not indicative whether Na is released, i.g., by a glass corrosion due to residual humidity in the botanical material. However, a model experiment with freshly prepared and pulverized peach leaves demonstrated that such a scenario is possible for leaf-based materials. Although the study was focused on two NIST materials, the process is possible for any material with rather low Na content. Klíčová slova: standard reference materials; analysis; methods Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Stability of the sodium content in selected botanical reference materials

Sodium mass fractions in NIST standard reference materials (SRM) SRM 1547 Peach Leaves and SRM 1515 Apple leaves determined by INAA in our laboratory in recent years has been higher than the certified ...

Kameník, Jan; Kučera, Jan; Borovička, Jan; Havránek, Vladimír
Ústav jaderné fyziky, 2018

Ultra-low intensity proton beams for radiation response related experiments at the U-120M cyclotron
Matlocha, Tomáš; Křížek, Filip
2018 - anglický
The U-120M cyclotron at the Nuclear Physics Institute (NPI) of the Czech Academy of Sciences in Rez is used for radiation hardness tests of electronics for high-energy physics experiments. These tests are usually carried out with proton fluxes of the order of 105–109 proton cm-2 s -1. Some tests done for the upgrade of the Inner Tracking System of the ALICE experiment at CERN, however, required proton beam intensities several orders of magnitude lower. This paper presents a method which has been developed to achieve the proton beam flux of the order of 1 proton cm-2 s -1. The method is mainly based on reduction of the discharge current in the cyclotron internal Penning type ion source. Influence of this new operation mode on the lifetime of ion source cathodes is discussed. Klíčová slova: ultra-low intensity proton flux; penning ion source; negative hydrogen yield resonance; cyclotron irraditation facility; radiation hardness tests Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Ultra-low intensity proton beams for radiation response related experiments at the U-120M cyclotron

The U-120M cyclotron at the Nuclear Physics Institute (NPI) of the Czech Academy of Sciences in Rez is used for radiation hardness tests of electronics for high-energy physics experiments. These tests ...

Matlocha, Tomáš; Křížek, Filip
Ústav jaderné fyziky, 2018

Stanovení prvkového složení drog neutronovou aktivační analýzou pro zjišťování jejich původu - studie proveditelnosti
Kučera, Jan; Kameník, Jan; Sabol, J.; Šesták, B.; Kolář, P.; Roman, M.
2018 - český
Analyzovali jsme pět vzorků heroinu a pět vzorků kokainu zachycených na území České republiky metodou instrumentální neutronové aktivační analýzy (INAA). Alespoň v jednom z analyzovaných vzorků heroinu jsme stanovili 16 stopových prvků, ve vzorcích kokainu se jednalo o 9 stopových prvků. Pozoruhodné rozdíly až v rozmezí několika řádů, jsme zjistili v obsazích prvků Na, Cl, Cr, Zn a Br, zejména ve vzorcích heroinu. Přesnost výsledků INAA jsme prokázali simultánní analýzou certifikovaného referenčního materiálu NIST SRM 1547 Peach Leaves. Výsledky stanovení stopových prvků v heroinu jsme porovnali s výsledky zahraničních autorů. Dosažené výsledky ukazují na vysoký potenciál metody INAA pro prvkovou charakterizaci drog za účelem zjištění jejich původu, způsobu výroby a čištění či způsobu ředění pro konečné uživatele. Pokládáme za účelné pokračovat v analýzách většího množství vzorků s konečným cílem vytvoření databáze prvkového složení vzorků zkonfiskovaných na území ČR, která by později mohla být rozšířena ve spolupráci se zahraničními protidrogovými a policejními orgány v mezinárodním měřítku. We analyzed five samples of heroine and five samples of cocaine seized in the Czech Repulic using instrumental neutron activation analysis (INAA). In the heroine speciments, we determined 16 trace elements in at least one of the samples analyzed, in the cocaine speciment, 9 trace elements could be determined. We have found remarkable differences, up to several orders of magnitude, in contents of the elements Na, Cl, Zna and Br, especially in the heroine samples. The accuracy of INAA results was proved by simultaneous analysis of a certified reference material NIST SRM 1547 Peach Leaves. The results of trace element determination in heroine samples are compard with those published by autors from abroad. The results obtained show a high potential of INAA for the drug elemental characteriaztion aimed at determination of their provenance, procedures used for their manufacturing and purification and cutting for the end users. The results achieved also suggest that it is desirable to analyze more samples with the final aim of establishing a database of elemental composition of drugs seized in the Czech Republic, which could possibly be extended later, in cooperation with foreign drug abuse and police bodies, at the international level. Klíčová slova: heroine; cocain; INAA Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
Stanovení prvkového složení drog neutronovou aktivační analýzou pro zjišťování jejich původu - studie proveditelnosti

Analyzovali jsme pět vzorků heroinu a pět vzorků kokainu zachycených na území České republiky metodou instrumentální neutronové aktivační analýzy (INAA). Alespoň v jednom z analyzovaných vzorků ...

Kučera, Jan; Kameník, Jan; Sabol, J.; Šesták, B.; Kolář, P.; Roman, M.
Ústav jaderné fyziky, 2018

Trojan horse method with neutrons induced reactions: The 17O(n,alpha)14C reaction
Guardo, G. L.; Spitaleri, C.; Lamia, L.; Gulino, M.; Tang, X.; Bucher, B.; Burjan, Václav; Couder, M.; Davies, P.; deBoer, R.; Fang, X.; Kroha, Václav; La Cognata, M.; Ma, C.; Mrázek, Jaromír; Mukhamedzhanov, A.; Notani, M.; O'Brien, S.; Pizzone, R. G.; Rapisarda, G. G.; Roberson, D.; Sergi, M. L.; Tan, W.; Wiescher, M.
2017 - anglický
The experimental study of the 17O(n,alpha)14C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) nucleosynthesis in various astrophysical scenario. To over-come the practical problems arising from the neutrons production, a new application of the Trojan Horse Method has been recently suggested. Klíčová slova: reaction study; nucleosynthesis; Trojan Horse Method Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Trojan horse method with neutrons induced reactions: The 17O(n,alpha)14C reaction

The experimental study of the 17O(n,alpha)14C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) ...

Guardo, G. L.; Spitaleri, C.; Lamia, L.; Gulino, M.; Tang, X.; Bucher, B.; Burjan, Václav; Couder, M.; Davies, P.; deBoer, R.; Fang, X.; Kroha, Václav; La Cognata, M.; Ma, C.; Mrázek, Jaromír; Mukhamedzhanov, A.; Notani, M.; O'Brien, S.; Pizzone, R. G.; Rapisarda, G. G.; Roberson, D.; Sergi, M. L.; Tan, W.; Wiescher, M.
Ústav jaderné fyziky, 2017

Theranostic Mercury Part 1: A New Hg/Au Separation by a Resin Based Method
Walther, M.; Lebeda, Ondřej; Preusche, S.; Pietzsch, H.-J.; Steinbach, J.
2017 - anglický
The development of a fast and efficient method for Mercury/Gold separation is described as a necessary precondition for large scale production of theranostic mercury Hg-197(m). To achieve this, the application of so called LN resin (LaNthanides) was studied. The results confirm the applicability of this resin for Au/Hg separation by high efficiency, high separation factor and reproducibility. Klíčová slova: cyclotron; Hg-197(m); LaNthanides Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Theranostic Mercury Part 1: A New Hg/Au Separation by a Resin Based Method

The development of a fast and efficient method for Mercury/Gold separation is described as a necessary precondition for large scale production of theranostic mercury Hg-197(m). To achieve this, the ...

Walther, M.; Lebeda, Ondřej; Preusche, S.; Pietzsch, H.-J.; Steinbach, J.
Ústav jaderné fyziky, 2017

On the scientific utilisation of low power research reactors
Mikula, Pavol; Strunz, Pavel
2017 - anglický
In our contribution we focus our attention on the scientific utilisation of the beam tubes at the low power research reactor LVR-15. Namely, it will be reported about the neutron scattering instrumentation development and the educational possibilities at the low power neutron sources. The feasibility of carrying out the methodology and instrumental development research at the low power neutron sources will be demonstrated on designs of several high resolution and good luminosity neutron scattering instruments exploiting Bragg diffraction optics. Some of them have been already realized e.g. for small angle neutron scattering studies or residual strain/stress measurements. As the mentioned instrumental development and testing can be carried out at the low power neutron sources, due to the much lower safety requirements in comparison with the medium and high flux sources, they offer excellent educational and training programmes in neutron scattering or imaging for students. Klíčová slova: low power reactor; research with thermal neutrons; LVR-15 Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
On the scientific utilisation of low power research reactors

In our contribution we focus our attention on the scientific utilisation of the beam tubes at the low power research reactor LVR-15. Namely, it will be reported about the neutron scattering ...

Mikula, Pavol; Strunz, Pavel
Ústav jaderné fyziky, 2017

Measurements and usage of cross sections of various (n,chi n) threshold reactions
Chudoba, Petr; Vrzalová, Jitka; Svoboda, Ondřej; Krása, Antonín; Kugler, Andrej; Majerle, Mitja; Suchopár, Martin; Wagner, Vladimír
2017 - anglický
Current trend in nuclear reactor physics is a transition from technologies using thermal neutrons to technologies utilizing fast neutrons. Unfortunately focus was put mainly on the thermal neutrons for a long time and lead to very good knowledge about this low energy region, but very scarce coverage of the high energy region. This means that there is a gap in the knowledge of excitation functions for higher energies. This gap spreads from 20 MeV up to 1 GeV and higher. This is exactly the energy region needed for description of advanced nuclear systems such as accelerator driven systems (ADS). Our group from Nuclear Physics Institute (NPI) of the CAS is a member of an international collaboration Energy & Transmutation of Radioactive Waste (E&T RAW). This collaboration focuses on ADS for many years. In order to measure neutron field within ADS models it is necessary to know excitation functions of reactions used to monitor the neutron field. In many cases there are almost no experimental data for suitable reactions. Worse and quite common case is that there are no data at all. Therefore we are also focusing on measurements of these data in order to fill the databases as well as to allow further improvements of codes for nuclear data calculations. Klíčová slova: cross section; NPI; E&T RAW Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Measurements and usage of cross sections of various (n,chi n) threshold reactions

Current trend in nuclear reactor physics is a transition from technologies using thermal neutrons to technologies utilizing fast neutrons. Unfortunately focus was put mainly on the thermal neutrons ...

Chudoba, Petr; Vrzalová, Jitka; Svoboda, Ondřej; Krása, Antonín; Kugler, Andrej; Majerle, Mitja; Suchopár, Martin; Wagner, Vladimír
Ústav jaderné fyziky, 2017

Ion beams provided by small accelerators for material synthesis and characterization
Macková, Anna; Havránek, Vladimír
2017 - anglický
The compact, multipurpose electrostatic tandem accelerators are extensively used for production of ion beams with energies in the range from 400 keV to 24 MeV of almost all elements of the periodic system for the trace element analysis by means of nuclear analytical methods. The ion beams produced by small accelerators have a broad application, mainly for material characterization (Rutherford Back-Scattering spectrometry, Particle Induced X ray Emission analysis, Nuclear Reaction Analysis and Ion-Microprobe with 1 um lateral resolution among others) and for high-energy implantation. Material research belongs to traditionally progressive fields of technology. Due to the continuous miniaturization, the underlying structures are far beyond the analytical limits of the most conventional methods. Ion Beam Analysis (IBA) techniques provide this possibility as they use probes of similar or much smaller dimensions (particles, radiation). Ion beams can be used for the synthesis of new progressive functional nanomaterials for optics, electronics and other applications. Ion beams are extensively used in studies of the fundamental energetic ion interaction with matter as well as in the novel nanostructure synthesis using ion beam irradiation in various amorphous and crystalline materials in order to get structures with extraordinary functional properties. IBA methods serve for investigation of materials coming from material research, industry, micro- and nano-technology, electronics, optics and laser technology, chemical, biological and environmental investigation in general. Main research directions in laboratories employing small accelerators are also the preparation and characterization of micro- and nano-structured materials which are of interest for basic and oriented research in material science, and various studies of biological, geological, environmental and cultural heritage artefacts are provided too. Klíčová slova: Ion beams; Electrostatic accelerators; Electronics; Nanostructures; Optics and optical physics Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Ion beams provided by small accelerators for material synthesis and characterization

The compact, multipurpose electrostatic tandem accelerators are extensively used for production of ion beams with energies in the range from 400 keV to 24 MeV of almost all elements of the periodic ...

Macková, Anna; Havránek, Vladimír
Ústav jaderné fyziky, 2017

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