Počet nalezených dokumentů: 582
Publikováno od do

Fluctuations in the scrape-off layer and edge plasma of the COMPASS tokamak
Seidl, Jakub; Jiráková, Kateřina; Adámek, Jiří; Grover, Ondřej; Horáček, Jan; Hron, Martin; Vondráček, Petr
2018 - anglický
We have identified two distinct types of turbulent fluctuations in COMPASS plasmas, the high-frequency edge oscillations and low-frequency SOL blobs. The transition region is localized in the near SOL, where both types spatially overlap and interact and the radial particle transport gradually transfers from high to low frequencies. Even though skewness of isat fluctuations is positive even inside LCFS, distinguishable Gamma-distributed PDF, formed by the low-frequency fluctuations, arises in the near SOL. This supports, together with turbulence spreading rate being positive in the near SOL but negative in the edge, the picture presented in [3] that most of the fluctuations that form a positive skewness in the edge region disappear around LCFS and new blobs are formed in the near SOL. Further, we cannot confirm the assumption that the blobs are generated randomly according to a Poisson process. Oscillations of all measured quantities, incl. radial particle flux, in the near SOL are peaked around ∼13 kHz. This seems to correspond to a poloidally rotating structure with a rather large poloidal wave-length ∼ 15 − 20 cm, that at least partly modulates blob generation. Nevertheless, we note that time separation of blobs becomes more random further in the SOL, possibly due to differences in their individual propagation. These observations hold for diverted plasmas, but the situation may be different in limited low-elongation plasmas where the radius of zero skewness was observed to be shifted significantly (several cm) inwards, compared to diverted configuration, and Gamma-like PDF is detected even inside the LCFS. Study of these plasmas is ongoing. Klíčová slova: plasma; tokamak; turbulence Dokument je dostupný na externích webových stránkách.
Fluctuations in the scrape-off layer and edge plasma of the COMPASS tokamak

We have identified two distinct types of turbulent fluctuations in COMPASS plasmas, the high-frequency edge oscillations and low-frequency SOL blobs. The transition region is localized in the near ...

Seidl, Jakub; Jiráková, Kateřina; Adámek, Jiří; Grover, Ondřej; Horáček, Jan; Hron, Martin; Vondráček, Petr
Ústav fyziky plazmatu, 2018

Effect of sintering temperature on microstructure and mechanical properties of AE42 magnesium alloy prepared by spark plasma sintering
Minárik, P.; Lukáč, František; Cinert, Jakub; Šašek, S.; Král, R.
2018 - anglický
Magnesium alloy AE42 was prepared by powder metallurgy technique of spark plasma sintering. The effect of sintering parameters, particularly sintering temperature, on the microstructure and mechanical strength was investigated. The gas-atomized powder was sintered at four temperatures in the temperature range of 400-550 °C. It was found that mechanical strength of the sintered samples was significantly affected by several microstructural features. Application of relatively high load during sintering caused deformation of the individual particles and consequent recrystallization depending on the processing temperature resulted in the release of internal strain and in grain growth. As a result, the evolution of the mechanical strength as a function of the sintering temperature was significantly affected by residual stress, grain size and coarsening of secondary phase particles. Klíčová slova: Magnesium; Mechanical properties; Microstructure; Spark plasma sintering Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Effect of sintering temperature on microstructure and mechanical properties of AE42 magnesium alloy prepared by spark plasma sintering

Magnesium alloy AE42 was prepared by powder metallurgy technique of spark plasma sintering. The effect of sintering parameters, particularly sintering temperature, on the microstructure and mechanical ...

Minárik, P.; Lukáč, František; Cinert, Jakub; Šašek, S.; Král, R.
Ústav fyziky plazmatu, 2018

Technical manual - collimator
Kredba, Jan; Steiger, Lukáš; Tomka, David; Václavík, Jan
2018 - anglický
The purpose of this document is to provide basic set of rules and instructions that allows using and maintaining of the NEOSTED collimator (COL).\nBe aware that it is not purpose of this document to provide detailed description of individual parts of the COL system. If necessary all the details and proper references can be found in [AD-2]. Klíčová slova: collimator; NEOSTED; TOPTEC; optical testing; interferometry Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Technical manual - collimator

The purpose of this document is to provide basic set of rules and instructions that allows using and maintaining of the NEOSTED collimator (COL).\nBe aware that it is not purpose of this document to ...

Kredba, Jan; Steiger, Lukáš; Tomka, David; Václavík, Jan
Ústav fyziky plazmatu, 2018

Výzkumná zpráva Projekt MidFree 2. etapa
Beneš, Jiří; Karabyn, Vasyl; Matoušek, Ondřej; Špína, Michal
2018 - český
Výzkumná zpráva popisující tvorbu inženýrského modelu k predikci možností potlačení problematických povrchových struktur. Research report describing the creation of an engineering model to predict possibilities of suppressing problematic surface structures. Klíčová slova: vibration analysis; MSF simulation Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Výzkumná zpráva Projekt MidFree 2. etapa

Výzkumná zpráva popisující tvorbu inženýrského modelu k predikci možností potlačení problematických povrchových struktur....

Beneš, Jiří; Karabyn, Vasyl; Matoušek, Ondřej; Špína, Michal
Ústav fyziky plazmatu, 2018

Využití holografie pro měření a charakterizaci povrchu
Kaván, František
2018 - český
Tento výzkum je zaměřen na využití digitální holografie pro měření tvaru optických a jiných ploch. Pro první experimenty jsme použili standardní metodu dvojvlnné holografické interferometrie. Ta posloužila jako reference. Hlavním zaměřením je však Frequency Sweeping Digital Holography (FSDH) neboli skenovací digitální holografie, která využívá plynule přeladitelných DFB laserových diod. Přesnost této metody lze dále vylepšit spojením měření z více vlnových délek - více diod. Při spojení je možno pomocí této metody dosáhnout přesnosti až 2 µm. This research focuses on the use of digital holography for measuring the shape of optical and other surfaces. For the first experiments, we used a standard double-wave holographic interferometry method. This served as a reference. However, the main focus is Frequency Sweeping Digital Holography (FSDH), or scanning digital holography, which utilizes fluently translatable DFB laser diodes. The accuracy of this method can be further improved by combining measurements from multiple wavelengths - multiple diodes. When combined, this method can achieve accuracy of up to 2 μm. Klíčová slova: holography; measurement Dokument je dostupný na externích webových stránkách.
Využití holografie pro měření a charakterizaci povrchu

Tento výzkum je zaměřen na využití digitální holografie pro měření tvaru optických a jiných ploch. Pro první experimenty jsme použili standardní metodu dvojvlnné holografické interferometrie. Ta ...

Kaván, František
Ústav fyziky plazmatu, 2018

Realizace tenkých vrstev na optických komponentech
Budasz, Jiří
2018 - český
Zpráva se zabývá realizací tenkých vrstev na optických elementech určených pro funkční vzorky a prototypy. Popisuje rovněž zátěžové testování soustav vrstev na vzorcích. The report describes the realisation of the thin films coatings at the optical elements used for prototyping. It involves the testing of the coatings at sample substrates as well. Klíčová slova: High reflective coatings; testing; laser Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Realizace tenkých vrstev na optických komponentech

Zpráva se zabývá realizací tenkých vrstev na optických elementech určených pro funkční vzorky a prototypy. Popisuje rovněž zátěžové testování soustav vrstev na vzorcích....

Budasz, Jiří
Ústav fyziky plazmatu, 2018

Stabilita optického monitoru při depozici 42-vrstvého interferenčního „bandpass“ filtru 520-590 nm
Žídek, Karel
2018 - český
V této zprávě popisujeme stabilitu depozice komplikovaných soustav tenkých vrstev, které byly navrženy jako interferenční filtr s pásmovou propustností. Jde o 42 vrstev TiO2 a SiO2, které jsou monitorovány jednak tzv. krystalovým a optickým monitorem tloušťky. Diskutujeme případ, kdy je návrh IF průběžně upravován podle reálné tloušťky deponovaných vrstev. We report on stability of a deposition process of a complex system of thin layers. The layers were designed as a 42-layer bandpass interference filter. The layers of TiO2 and SiO2 were monitored both by the means of a crystal and an optical thickness monitor. We discuss the case when the design of the interference filter is continuously adapted according to the real thickness of the already deposited layers. Klíčová slova: thin layer deposition; thickness monitor; interference filter; deposition stability Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Stabilita optického monitoru při depozici 42-vrstvého interferenčního „bandpass“ filtru 520-590 nm

V této zprávě popisujeme stabilitu depozice komplikovaných soustav tenkých vrstev, které byly navrženy jako interferenční filtr s pásmovou propustností. Jde o 42 vrstev TiO2 a SiO2, které jsou ...

Žídek, Karel
Ústav fyziky plazmatu, 2018

Electric probe measurements in the anode area of a DC arc plasma torch at low pressure
Ondáč, Peter; Mašláni, Alan; Hrabovský, Milan
2018 - anglický
We measured radial profiles of the electric field, plasma electrical potential and electron temperature in the hot anode area of a hybrid water-argon DC arc plasma torch with an external anode. The measurements were made under different values of the ambient pressure, during the restrike mode with a constricted anode arc attachment or during a supersonic mode with a diffuse anode arc attachment. The results provide first experimental data on plasma electrical potential in that anode area. Klíčová slova: plasma; arc; anode; low pressure; electric probes Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Electric probe measurements in the anode area of a DC arc plasma torch at low pressure

We measured radial profiles of the electric field, plasma electrical potential and electron temperature in the hot anode area of a hybrid water-argon DC arc plasma torch with an external anode. The ...

Ondáč, Peter; Mašláni, Alan; Hrabovský, Milan
Ústav fyziky plazmatu, 2018

The effect of spark plasma sintering on the porosity and mechanical properties of Ti-15Mo alloy
Terynková, A.; Kozlík, J.; Bartha, K.; Chráska, Tomáš; Dlabáček, Zdeněk; Stráský, J.
2018 - anglický
Metastable β-titanium alloys are receiving much interest for various applications such as aircraft industry and medicine thanks to their excellent mechanical properties and biocompatibility. The common way of preparing the titanium alloys is hindered by its production costs. Powder metallurgy (PM) approach is a promising route for cost-effective fabrication of titanium alloys due to possibility of near net shaping. In this study, binary biomedical Ti-15Mo alloy was prepared by PM. Gas atomized powder was sintered by spark plasma sintering (SPS) above the β-transus temperature of the studied alloy. The compaction of the powders was accomplished by short-time sintering. The effect of the time of sintering on the porosity and the microhardness in centre part as well as in periphery part of the sample was investigated. The samples revealed significant inhomogeneity the porosity increases with the distance from the centre of the specimen. With increasing sintering times the porosity decreases and simultaneously the microhardness increases. Klíčová slova: Metastable β-titanium alloys; Porosity; Powder metallurgy; Spark plasma sintering Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The effect of spark plasma sintering on the porosity and mechanical properties of Ti-15Mo alloy

Metastable β-titanium alloys are receiving much interest for various applications such as aircraft industry and medicine thanks to their excellent mechanical properties and biocompatibility. The ...

Terynková, A.; Kozlík, J.; Bartha, K.; Chráska, Tomáš; Dlabáček, Zdeněk; Stráský, J.
Ústav fyziky plazmatu, 2018

OLGA – efficient full wave code for the coupling of LH grills
Preinhaelter, Josef; Hillairet, J.; Urban, Jakub
2018 - anglický
The full wave code OLGA, for determining the coupling of a single row lower hybrid launcher (waveguide grills) to the plasma, is extended to handle multirow multijunction active passive structures (like the C3 and C4 launchers on TORE SUPRA) by implementing the scattering matrix formalism. The extended code is still computationally fast because of the use of (i) 2D splines of the plasma surface admittance in the accessibility region of the k-space, (ii) high order Gaussian quadrature rules for the integration of the coupling elements and (iii) utilizing the symmetries of the coupling elements in the multiperiodic structures. The extended OLGA code is benchmarked against the ALOHA-1D, ALOHA-2D and TOPLHA codes for the coupling of the C3 and C4 TORE SUPRA launchers for several plasma configurations derived from reflectometry and interferometery. Unlike nearly all codes (except the ALOHA-1D code), OLGA does not require large computational resources and can be used for everyday usage in planning experimental runs. In particular, it is shown that the OLGA code correctly handles the coupling of the C3 and C4 launchers over a very wide range of plasma densities in front of the grill. Klíčová slova: lower hybrid waves; coupling; large multirow multijunction grills; tokamak; full-wave Dokument je dostupný na externích webových stránkách.
OLGA – efficient full wave code for the coupling of LH grills

The full wave code OLGA, for determining the coupling of a single row lower hybrid launcher (waveguide grills) to the plasma, is extended to handle multirow multijunction active passive structures ...

Preinhaelter, Josef; Hillairet, J.; Urban, Jakub
Ústav fyziky plazmatu, 2018

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