Number of found documents: 507
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Investigation of nanosecond pulsed corona-like discharge generated in deionized water.
Pongrác, Branislav; Šimek, Milan; Babický, Václav; Člupek, Martin; Lukeš, Petr
2017 - English
We employed techniques of time–resolved ICCD microscopy and spectroscopy to register basic morphologic and emission fingerprints of micro-discharges produced in deionized water. Keywords: Underwater discharge; nanosecond pulsed discharge; time-resolved emission spectroscopy; time-resolved ICCD imaging Available at various institutes of the ASCR
Investigation of nanosecond pulsed corona-like discharge generated in deionized water.

We employed techniques of time–resolved ICCD microscopy and spectroscopy to register basic morphologic and emission fingerprints of micro-discharges produced in deionized water.

Pongrác, Branislav; Šimek, Milan; Babický, Václav; Člupek, Martin; Lukeš, Petr
Ústav fyziky plazmatu, 2017

FÁZOVÁ STABILITA Y2O3 A W-Y2O3 ZPRACOVANÝCH METODOU MECHANICKÉHO LEGOVÁNÍ.
Illková, Ksenia; Vilémová, Monika; Lukáč, František
2017 - Czech
Kinetika fázových transformací B -> C jak v samotném Y2O3 tak i ve slitině W-xY2O3 je velmi důležitá vzhledem k použití těchto materiálů ve vysokoteplotních aplikacích. Chování vysokotlaké fáze B práškového Y2O3 indukované mletím a vlastnosti kompozitu W-Y2O3 byly studovány pomocí diferenční termální analýzy a rentgenové difrakce. Bylo zjištěno, že fázová stabilita je výrazně závislá na rychlosti ohřevu a na době setrvání na dané teplotě. Properties of milling-induced high-pressure B phase in Y2O3 and W-Y2O3 powders were studied by differential thermal analysis and X-Ray diffraction. It was found that phase stability strongly depends on the heating rate and holding time. Keywords: yttrium oxide; tungsten; milling; differential thermal analysis Available at various institutes of the ASCR
FÁZOVÁ STABILITA Y2O3 A W-Y2O3 ZPRACOVANÝCH METODOU MECHANICKÉHO LEGOVÁNÍ.

Kinetika fázových transformací B -> C jak v samotném Y2O3 tak i ve slitině W-xY2O3 je velmi důležitá vzhledem k použití těchto materiálů ve vysokoteplotních aplikacích. Chování vysokotlaké fáze B ...

Illková, Ksenia; Vilémová, Monika; Lukáč, František
Ústav fyziky plazmatu, 2017

Measuring of Mean Plasma Electrical Conductivity in Anode Area of Plasma Torches with an External Anode
Ondáč, Peter; Mašláni, Alan; Hrabovský, Milan
2017 - English
We developed a non-intrusive direct procedure of measuring an average electrical conductivity of a plasma volume in hot anode areas of those plasma torches. For our measurements, we used a high-speed camera, a high-voltage probe, and a hybrid water–argon plasma torch. The measurements were made for various values of ambient pressure, arc electric current, and argon flow rate. The measured plasma conductivity is in agreement with a model, camera observations and indirectly also with spectroscopy measurements. The procedure provides missing experimental data on the average plasma electrical conductivity and estimates average plasma temperature in the anode areas. The procedure can be theoretically used in every plasma torch where the anode arc attachment movement can be observed during a restrike process\n Keywords: DC arc plasma torch; Plasma electrical conductivity; Anode area Available at various institutes of the ASCR
Measuring of Mean Plasma Electrical Conductivity in Anode Area of Plasma Torches with an External Anode

We developed a non-intrusive direct procedure of measuring an average electrical conductivity of a plasma volume in hot anode areas of those plasma torches. For our measurements, we used a high-speed ...

Ondáč, Peter; Mašláni, Alan; Hrabovský, Milan
Ústav fyziky plazmatu, 2017

The role of microstructure on wettability of plasma sprayed yttria stabilized zirconia coatings
Komarov, P.; Čelko, L.; Remešová, M.; Skorokhod, K.; Jech, D.; Klakurková, L.; Slámečka, K.; Mušálek, Radek
2017 - English
Atmospheric plasma spraying utilizing initial powder materials in micrometric size has been successfully used for various applications in different fields of the industry over the past several decades. Nowadays, the new trend in plasma spraying is to use sub-micron or nano-sized powder feedstocks in the form of colloidal suspension. This relatively new technology enables to obtain specific types of dense vertically cracked, fully dense or columnar microstructure. The aim of this work is to investigate the influence of coatings microstructure and topography on its water wetting properties. Two different microstructures, i.e. lamellar and columnar, were sprayed from chemically the same yttria-stabillized zirconia (YSZ) ceramics powders by the means of conventional atmospheric plasma spray and suspension hybrid water stabilized plasma spray techniques, respectively. Microstructural and phase composition of the initial powders and as-sprayed coatings were investigated using optical microscopy, scanning electron microscopy and X-ray diffraction techniques. Topography of coatings surface was measured by means of non-contact optical profilometry. The YSZ coatings wettability was evaluated based on water droplet contact angle using Sessile droplet method. The coatings microstructure reveals the important role in the change of droplet contact angle, where lamellar microstructure was found close to hydrophilic-hydrophobic transition and columnar microstructure was found superhydrophobic Keywords: Contact angle; Plasma spraying; Sessile drop method; Water; Yttria stabilized zirconia Available at various institutes of the ASCR
The role of microstructure on wettability of plasma sprayed yttria stabilized zirconia coatings

Atmospheric plasma spraying utilizing initial powder materials in micrometric size has been successfully used for various applications in different fields of the industry over the past several ...

Komarov, P.; Čelko, L.; Remešová, M.; Skorokhod, K.; Jech, D.; Klakurková, L.; Slámečka, K.; Mušálek, Radek
Ústav fyziky plazmatu, 2017

Nanosecond discharge in deionized water: morphology, propagation velocity and optical emission during initial phase.
Šimek, Milan; Pongrác, Branislav; Babický, Václav; Člupek, Martin; Lukeš, Petr
2017 - English
In this work, we have explored micro-discharges produced in deionized liquid water by applying fast-rising positive HV pulses of nanosecond duration (pulses of ~80 kV in amplitude and of 5 ns in duration, either with the repetition rate of 1 Hz or in a single-shot regime) in a point-to-plane electrode geometry. Keywords: Underwater discharge; nanosecond pulsed discharge; time-resolved emission spectroscopy; time-resolved ICCD imaging Available at various institutes of the ASCR
Nanosecond discharge in deionized water: morphology, propagation velocity and optical emission during initial phase.

In this work, we have explored micro-discharges produced in deionized liquid water by applying fast-rising positive HV pulses of nanosecond duration (pulses of ~80 kV in amplitude and of 5 ns in ...

Šimek, Milan; Pongrác, Branislav; Babický, Václav; Člupek, Martin; Lukeš, Petr
Ústav fyziky plazmatu, 2017

Reflectivity of a mirror in XUV spectral region (46.9 nm).
Schmidt, Jiří; Koláček, Karel; Štraus, Jaroslav; Frolov, Oleksandr; Prukner, Václav; Melich, Radek; Psota, Pavel; Sobota, Jaroslav; Fořt, Tomáš
2017 - English
A focusing mirror as an optical element is used in our applications that require light collection (e.g. for laser ablation studies). A knowledge of the mirror reflectivity is important for determination of focused laser pulse energy, or for determination of local fluencies near the laser focus. The reflectivity of our spherical focusing mirror with(/without) multi-layer coating was measured. Reflection coefficients of this mirror in a long period of time are also reported. Further, the incidence-angle dependence of the XUV reflectivity of flat mirrors is presented as well. Keywords: Reflectivity of multilayer mirror in XUV range; aging of multilayer mirrors Available at various institutes of the ASCR
Reflectivity of a mirror in XUV spectral region (46.9 nm).

A focusing mirror as an optical element is used in our applications that require light collection (e.g. for laser ablation studies). A knowledge of the mirror reflectivity is important for ...

Schmidt, Jiří; Koláček, Karel; Štraus, Jaroslav; Frolov, Oleksandr; Prukner, Václav; Melich, Radek; Psota, Pavel; Sobota, Jaroslav; Fořt, Tomáš
Ústav fyziky plazmatu, 2017

Double pulse capillary discharge assessment for nitrogen soft X-ray laser.
Hübner, Jakub; Nevrkla, M.
2017 - English
The work examines possibilities of capillary discharge pinching plasma driven by combination of two electric current pulses ("pedestal" slow exponentially damped sinus t1/4 > 200 ns, peak current Ipeak < 50 kA and fast triangular pulse with a rise time about 38 ns, Ipeak > 60 kA) to obtain the maximum possible gain at wavelength l = 13.4 nm (hydrogen-like nitrogen recombination scheme). The optimal initial density ρ0 (or pressure) and start time tstart of second triangular pulse (second pulse start at peak current Ipeak of the first pulse) were determined for two capillary radii (0.5 and 1 cm) and four current peaks of the first pulse (20, 30, 40 and 50 kA).\n Keywords: capillary discharge; XUV laser; pinch dynamics; nitrogen recombination schema; ablation Available at various institutes of the ASCR
Double pulse capillary discharge assessment for nitrogen soft X-ray laser.

The work examines possibilities of capillary discharge pinching plasma driven by combination of two electric current pulses ("pedestal" slow exponentially damped sinus t1/4 > 200 ns, peak current ...

Hübner, Jakub; Nevrkla, M.
Ústav fyziky plazmatu, 2017

Maksutovovy soustavy z Turnova
Rail, Zdeněk; Melich, Zbyněk; Jareš, Daniel; Pintr, Pavel; Vápenka, David
2017 - Czech
Tento referát popisuje vývoj a výrobu optických soustav, u kterých byl použit meniskový korektor Maksutova jako vstupní člen. Řada těchto vysoce kvalitních systémů byla v Turnově vyráběna od sedmdesátých let na několika pracovištích. V naší práci presentujeme zkušenosti s optickým designem, výrobou a konstrukcí meniskových dalekohledů a komor. This paper deals of a design and a manufacture of optical systems with the entrance meniscus corrector of Maksutov. Many of these high performance systems have been manufactured in several workshops in Turnov since Seventies. We present our experience with the optical design, manufacture and construction of the meniscus telescopes and cameras in this article. Keywords: Catadioptric system; meniscus corrector; spherochromatic aberration; spherical aberration; coma; astigmatism; Petzval´s curvature; MTF curve; glass dispersion curve Available at various institutes of the ASCR
Maksutovovy soustavy z Turnova

Tento referát popisuje vývoj a výrobu optických soustav, u kterých byl použit meniskový korektor Maksutova jako vstupní člen. Řada těchto vysoce kvalitních systémů byla v Turnově vyráběna od ...

Rail, Zdeněk; Melich, Zbyněk; Jareš, Daniel; Pintr, Pavel; Vápenka, David
Ústav fyziky plazmatu, 2017

Preparation of spheroidized and nano-structural spinels by the SPPS method
Brožek, Vlastimil; Lukáč, František; Medřický, Jan; Mušálek, Radek; Mašláni, Alan; Mastný, L.; Brodil, R.
2017 - English
Solution Precursor Plasma Spraying (SPPS) method, using hybrid water-stabilised plasma torch (WSP®-H), is presented in this study. Precursor, in a form of a solution of inorganic salts, is injected into the plasma jet, where the temperature can reach up to 25 000 K and a series of reactions lead to the formation of spherical sub-micrometric sized particles. The complete process of evaporating the liquid, crystallization, thermic decomposition, melting and recrystallization takes place in few milliseconds before the particles solidify. Melted nanoparticles can be either directly collected in order to obtain ultrafine powders or deposited onto a substrate to form micro-splats and continuous polycrystalline, and often partially amorphous, coatings. The possibility of continuous and discontinuous changes of stoichiometric composition in tetrahedral and octahedral configurations were analysed for the deposits of MgAl2O4, CoAl2O4 and CoFe2O4 spinels. Furthermore, thin colourful coatings of ruby and modified cobalt oxides were deposited onto ceramic and metallic substrates. Keywords: Solution plasma spraying; suspension plasma spraying; spinels; ferrites; ruby; nanoparticles Available at various institutes of the ASCR
Preparation of spheroidized and nano-structural spinels by the SPPS method

Solution Precursor Plasma Spraying (SPPS) method, using hybrid water-stabilised plasma torch (WSP®-H), is presented in this study. Precursor, in a form of a solution of inorganic salts, is injected ...

Brožek, Vlastimil; Lukáč, František; Medřický, Jan; Mušálek, Radek; Mašláni, Alan; Mastný, L.; Brodil, R.
Ústav fyziky plazmatu, 2017

On tungsten spraying using inductively coupled plasma system - First results
Klečka, Jakub; Mušálek, Radek; Vilémová, Monika; Lukáč, František
2017 - English
Thanks to its unique properties such as high melting point and density, tungsten and tungsten-based alloys are commonly used in a wide range of applications. Among others, these materials are promising candidates for the plasma facing components in the future fusion reactors. One of considered ways of production of these parts is plasma spraying. There are however several limitations for conventional gas stabilized torches, mainly in plasma enthalpy (i.e. the ability to efficiently melt tungsten particles in considerable feed rates) and susceptibility of tungsten to oxidation (which complicates spraying in oxidizing open-air atmosphere). The radio frequency inductively coupled plasma torch (RF-ICP) is a unique system which can potentially overcome both these problems and can be used for efficient tungsten spraying. The tungsten powder, which can be finer than the one used for the conventional systems, is fed axially into the hot plasma core, both factors lead to a more efficient melting of the particles. The deposition is performed in a chamber with controlled atmosphere of inert gas or decreased pressure, the oxidation is therefore suppressed. In this first study carried out with the newly commissioned RF-ICP system TekSpray 15 (Tekna), samples of tungsten coatings on graphite substrates were prepared. The X-ray diffraction and SEM images of the free surfaces and cross-sections were obtained, documenting high purity of the deposits and appropriate flattening of the splats leading to a dense coating microstructure. The effect of substrate preheating on the microstructure, porosity and hardness was also studied. Keywords: Radio frequency inductively coupled plasma torch; tungsten; plasma facing components; plasma spraying Available at various institutes of the ASCR
On tungsten spraying using inductively coupled plasma system - First results

Thanks to its unique properties such as high melting point and density, tungsten and tungsten-based alloys are commonly used in a wide range of applications. Among others, these materials are ...

Klečka, Jakub; Mušálek, Radek; Vilémová, Monika; Lukáč, František
Ústav fyziky plazmatu, 2017

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