Nuclear Physics Institute

Latest additions:
2019-05-16
18:17
Instrumentation for study of nanomaterials in NPI REZ (New laboratory for material study in Nuclear Physics Institute in REZ)
Bejšovec, Václav ; Cannavó, Antonino ; Ceccio, Giovanni ; Hnatowicz, Vladimír ; Horák, Pavel ; Lavrentiev, Vasyl ; Macková, Anna ; Tomandl, Ivo ; Torrisi, Alfio ; Vacík, Jiří
Nano-sized materials become irreplaceable component of a number of devices for every aspect of human life. The development of new materials and deepening of the current knowledge require a set of specialized techniques-deposition methods for preparation/modification of the materials and analytical tools for proper understanding of their properties. A thoroughly equipped research centers become the requirement for the advance and development not only in nano-sized field. The Center of Accelerators and Nuclear Analytical Methods (CANAM) in the Nuclear Physics Institute (NPI) comprises a unique set of techniques for the synthesis or modification of nanostructured materials and systems, and their characterization using ion beam, neutron beam and microscopy imaging techniques. The methods are used for investigation of a broad range of nano-sized materials and structures based on metal oxides, nitrides, carbides, carbon-based materials (polymers, fullerenes, graphenes, etc.) and nano-laminate composites (MAX phases). These materials can be prepared at NPI using ion beam sputtering, physical vapor deposition and molecular beam epitaxy. Based on the deposition method and parameters, the samples can be tuned to possess specific properties, e.g., composition, thickness (nm-μm), surface roughness, optical and electrical properties, etc. Various nuclear analytical methods are applied for the sample characterization. RBS, RBS-channeling, PIXE, PIGE, micro-beam analyses and Transmission Spectroscopy are accomplished at the Tandetron 4130MC accelerator, and additionally the Neutron Depth Profiling (NDP) and Prompt Gamma Neutron Activation (PGNA) analyses are performed at an external neutron beam from the LVR-15 research reactor. The multimode AFM facility provides further surface related information, magnetic/electrical properties with nano-metric precision, nano-indentation, etc.

Detailed record
2019-04-29
09:26
Study of lithium encapsulation in porous membrane using ion and neutron beams
Ceccio, Giovanni ; Cannavó, Antonino ; Horák, Pavel ; Torrisi, Alfio ; Tomandl, Ivo ; Hnatowicz, Vladimír ; Vacík, Jiří
Ion track-etched membranes are porous systems obtained by etching of the latent ion tracks using a suitable etchant solution. In this work, control of the pores' spatial profiles and dimensions in PET polymers was achieved by varying etching temperature and etching time. For determination of the pores' shape, Ion Transmission Spectroscopy technique was employed. In this method, alterations of the energy loss spectra of the transmitted ions reflect alterations in the material density of the porous foils, as well as alterations of their thickness. Simulation code, developed by the team, allowed the tomographic study of the ion track 3D geometry and its evolution during chemical etching. From the doping of porous membranes with lithium-based solution and its analysis by Thermal Neutron Depth Profiling method, the ability of porous PET membranes to encapsulate nano-sized material was also inspected. The study is important for various applications, e.g., for catalysis, active agents, biosensors, etc.

Detailed record
2019-04-29
09:26
Production and characterization of micro-size pores for ion track etching applications
Cannavó, Antonino ; Havránek, Vladimír ; Lavrentiev, Vasyl ; Torrisi, L. ; Cutroneo, Mariapompea ; Ceccio, Giovanni ; Torrisi, Alfio ; Horák, Pavel ; Vacík, Jiří
For many years the applications of ion track etch materials have increased considerably, like charged particles detection, molecular identification with nanopores, ion track filters, magnetic studies with nanowires and so on. Over the materials generally used as track detector, the Poly-Allyl-Diglycol Carbonate (PADC), offers many advantages, like its nearly 100 % detection efficiency for charged particle, a high resistance to harsh environment, the lowest detection threshold, a high abrasion resistance and a low production costs. All of these properties have made it particularly attractive material, even if due to its brittleness, obtaining a thin film (less than 500 μm) is still a challenge. In this work, PADC foils have been exposed to a-particles emitted by a thin radioactive source of 241Am and to C ions from the Tandetron 4130 MC accelerator. The latent tracks generated in the polymer have been developed using a standard etching procedure in 6.25 NaOH solution. The dependence of the ion tracks' geometry on the ion beam energy and fluence has been evaluated combining the information obtained through a semiautomatic computer script that selects the etched ion tracks according to their diameter and mean grey value and nanometric resolution images by atomic force microscopy.

Detailed record
2019-04-29
09:26
Laser-generated nanoparticles to change physical properties of solids, liquids and gases
Torrisi, Alfio ; Cutroneo, Mariapompea ; Ceccio, Giovanni ; Cannavó, Antonino ; Horák, Pavel ; Torrisi, L. ; Vacík, Jiří
Synthesis of nanoparticles was possible employing a Nd: YAG pulsed laser at fundamental harmonic. The production of nanoparticles in water depends mainly on the laser parameters (pulse duration, energy, wavelength), the irradiation conditions (focal spot, repetition rate, irradiation time) and the medium where the ablation occurs (solid target, water, solution concentration). The nanoparticles can be introduced in solids, liquids or gases to change many physical characteristics. The optical properties of polymers and solutions, the wetting ability of liquids, the electron density of laser-generated plasma, represent some examples that can be controlled by the concentration of metallic nanoparticles (Au, Ag, Ti, Cu). Some bio-medical applications will be presented and discussed.

Detailed record
2019-02-13
17:44
Stability of the sodium content in selected botanical reference materials
Kameník, Jan ; Kučera, Jan ; Borovička, Jan ; Havránek, Vladimír
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.

Detailed record
2019-02-13
17:44
Role of activation analysis in the preparation of reference materials
Kučera, Jan
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.

Detailed record
2019-02-13
17:44
Ultra-low intensity proton beams for radiation response related experiments at the U-120M cyclotron
Matlocha, Tomáš ; Křížek, Filip
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.

Detailed record
2018-12-07
17:59
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.
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.

Detailed record
2018-11-15
12:43
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
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

Detailed record
2018-03-09
13:20
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
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.

Detailed record