Number of found documents: 507
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Dalekohledy typu Dall-Kirkham
Rail, Zdeněk; Ulrichová, Iva; Kuryshev, V.; Vápenka, David
2018 - Czech
Referát se zabývá optickými vadami dvojzrcadlových dalekohledů s elipsoidálními primárními a sférickými sekundárními zrcadly. Systém byl objeven na konci dvacátých let minulého století Horacem Dallem a Alanem Kirkhamem. Jeho optické prvky jsou snadno vyrobitelné a měřitelné. Tyto dalekohledy lze vybavit korektory a vytvořit z nich víceúčelové přístroje jak pro planetární pozorování, tak pro fotografování širokých zorných polí. Několik takových přístrojů bylo vyrobeno i v dílně Centra Toptec v Turnově. The paper deals with the optical aberrations of the two-mirror telescopes composed of the ellipsoidal primary and the spherical secondary mirrors. The system was discovered by Horace Dall and Alan Kirkham at the end of the Twenties of the 20th Century. Its optical elements are easy to manufacture and measure. These telescopes can be equipped by lens correctors and turned into multipurpose devices both for planetary observation and wide field photography. Several telescopes were manufactured in workshop of the Toptec Center in Turnov. Keywords: Two-mirror telescope; field corrector; optical aberrations; spherochromatic aberration; koma; astigmatism Available at various institutes of the ASCR
Dalekohledy typu Dall-Kirkham

Referát se zabývá optickými vadami dvojzrcadlových dalekohledů s elipsoidálními primárními a sférickými sekundárními zrcadly. Systém byl objeven na konci dvacátých let minulého století Horacem Dallem ...

Rail, Zdeněk; Ulrichová, Iva; Kuryshev, V.; Vápenka, David
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 - English
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. Keywords: Metastable β-titanium alloys; Porosity; Powder metallurgy; Spark plasma sintering Available at various institutes of the ASCR
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

Relativistic effects in plasma produced with sub-nanosecond 3-TW laser
Krása, J.; Klír, Daniel; Řezáč, Karel; Cikhardt, Jakub; Krůs, Miroslav; Velyhan, Andriy; Pfeifer, Miroslav; Dostál, Jan; Dudžák, Roman; Krupka, Michal; Kaufman, J.; Pisarczyk, T.; Kalinowska, Z.; Chodukowski, T.
2018 - English
This contribution deals with observations of relativistic electrons produced in a laser plasma interaction experiment at the PALS laser system operated at the Institute of Plasma Physics in Prague. The PALS laser is a near-infrared 3-TW iodine laser designed to deliver irradiance on target of 1016 Wcm2- in≈300 ps pulses at the wavelength of 1.315 μm. Various foils of 6 500 μm in thickness were irradiated with Iλ2 ≈5×1016 W cm-2 μm2 Under these conditions we have observed relativistic electrons expanding into the vacuum with maximum energy going beyond 4 MeV. The relativistically accelerated forward electrons escaping from the rear target surface were observed with the use of electron energy analysers. The observed electron energy spectra indicate that the applied laser intensity was increased by the thermal and relativistic self-focusing. The application of a unique femtosecond interferometry technique allowed us to observe bunches of thermal electrons occurring in the plasma expanding against the focused laser beam. Keywords: laser-produced plasma; relativistic electrons Fulltext is available at external website.
Relativistic effects in plasma produced with sub-nanosecond 3-TW laser

This contribution deals with observations of relativistic electrons produced in a laser plasma interaction experiment at the PALS laser system operated at the Institute of Plasma Physics in Prague. ...

Krása, J.; Klír, Daniel; Řezáč, Karel; Cikhardt, Jakub; Krůs, Miroslav; Velyhan, Andriy; Pfeifer, Miroslav; Dostál, Jan; Dudžák, Roman; Krupka, Michal; Kaufman, J.; Pisarczyk, T.; Kalinowska, Z.; Chodukowski, T.
Ústav fyziky plazmatu, 2018

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 - English
In this work we study properties of turbulent structures in the scrape-off layer (SOL) and edge plasma of the COMPASS tokamak. Two distinct types of coherent oscillations are observed: a) broadband high frequency branch rotating in the electron diamagnetic direction, appearing mainly in the confined region but protruding also to the SOL b) low-frequency blobs rotating in an opposite poloidal direction, formed in the vicinity of the radius of zero electric field. 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 fluctuations of the ion saturation current is positive even inside LCFS, distinguishable Gamma-distributed PDF, formed by the low-frequency fluctuations, arises in the near SOL and most of the fluctuations that form a positive skewness in the edge region disappear around LCFS. Keywords: plasma; tokamak; turbulence Fulltext is available at external website.
Fluctuations in the scrape-off layer and edge plasma of the COMPASS tokamak

In this work we study properties of turbulent structures in the scrape-off layer (SOL) and edge plasma of the COMPASS tokamak. Two distinct types of coherent oscillations are observed: a) broadband ...

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

Microstructure of commercially pure titanium after cryogenic milling and spark Plasma sintering
Kozlík, J.; Harcuba, P.; Stráský, J.; Chráska, Tomáš; Janeček, M.
2018 - English
Commercially pure titanium was prepared by advanced powder metallurgy methods with the aim to produce the ultra-fine grained material. Cryogenic attritor milling was used as a first step to refine the microstructure at liquid argon temperatures to suppress recovery and dynamic recrystallization. Spark plasma sintering was subsequently employed to produce bulk material, exploiting its ability to achieve fully dense structure in short time and thus to reduce the grain growth. In order to understand the undergoing microstructural changes during the process, detailed investigation was performed after each preparation step. Powder morphology was changed significantly after milling, while particle fragmentation was only limited. Grain size after sintering was in micrometer scale, relatively independent of sintering conditions. Keywords: Cryogenic milling; Microstructure; Spark plasma sintering; Titanium Available at various institutes of the ASCR
Microstructure of commercially pure titanium after cryogenic milling and spark Plasma sintering

Commercially pure titanium was prepared by advanced powder metallurgy methods with the aim to produce the ultra-fine grained material. Cryogenic attritor milling was used as a first step to refine the ...

Kozlík, J.; Harcuba, P.; Stráský, J.; Chráska, Tomáš; Janeček, M.
Ústav fyziky plazmatu, 2018

Thin nitride layers as permeation barriers
Veverka, Jakub; Matějíček, Jiří; Lukáč, František; Pospíšil, D.; Cvrček, L.; Nemanič, V.
2018 - English
Permeation barriers represent one of the crucial fields in materials development for thermonuclear fusion. Primary objective of the barriers is to suppress the permeation of hydrogen isotopes (mainly tritium) from future thermonuclear fusion facilities. Secondary objective is to reduce their retention in structural materials. Expected reactor conditions put high demands on the material, as well as on the final barrier quality. Key properties are tritium permeation reduction, absence of defects (especially cracks), high-temperature stability and corrossion resistance, and compatibility with structural materials (mostly ferritic-martensitic steels). Thin nitride layers, identified as promising permeation barriers, were prepared by diffusion-based nitridation and physical vapour deposition (PVD), and characterized. Keywords: Permeation barriers; Nitride layers; PVD coating; Permeation measurement Available at various institutes of the ASCR
Thin nitride layers as permeation barriers

Permeation barriers represent one of the crucial fields in materials development for thermonuclear fusion. Primary objective of the barriers is to suppress the permeation of hydrogen isotopes (mainly ...

Veverka, Jakub; Matějíček, Jiří; Lukáč, František; Pospíšil, D.; Cvrček, L.; Nemanič, V.
Ústav fyziky plazmatu, 2018

Characterization of flame sprayed abradable seal NiCrAl-bentonite coatings
Houdková, Š.; Česánek, Z.; Schubert, J.; Lukáč, František; Bystrianský, M.
2018 - English
The NiCrAl-21% Bentonite abradable coating, deposited by flame spraying, was exposed to 720°C / 1 hour air-annealing to evaluate its resistance against heat-induced changes. The SEM and XRD microstructure evaluation was done. After the air-annealing, the increase of HR15Y surface hardness was recorded and accompanied with decrease of abradability evaluated by Progressive Readability Hardness (PAH) test, although no demonstrable microstructural changes was recorded by SEM. XRD analyses evidenced the formation of nickel oxides and ordered Ni3Al phase during the air-annealing. Besides the abradable coating evaluation, this work brings the verification of the potential of PAH for scratch hardness testing. The measurement provides the results with low scatter, compared to usual surface hardness testing, and enables to distinguish between the depth of indentation in loaded and unloaded state, pointing out to the elastic/plastic deformation ratio. Keywords: Abradability; Abradable seal; Flame spray; NiCrAl-Bentonite Available at various institutes of the ASCR
Characterization of flame sprayed abradable seal NiCrAl-bentonite coatings

The NiCrAl-21% Bentonite abradable coating, deposited by flame spraying, was exposed to 720°C / 1 hour air-annealing to evaluate its resistance against heat-induced changes. The SEM and XRD ...

Houdková, Š.; Česánek, Z.; Schubert, J.; Lukáč, František; Bystrianský, M.
Ústav fyziky plazmatu, 2018

Oprava objektivu 160/2500 turnovské hvězdárny
Rail, Zdeněk; Melich, Zbyněk; Šrajer, Bohdan; Šípová, Gabriela; Kaucká, Iva; Franců, Helena; Melich, Radek
2018 - Czech
Tento referát přináší informace o opravě achromatického objektivu o průměru 160 mm a ohniskové vzdálenosti 2500 mm, vyrobeného v 70. letech ve Vývojové optické dílně ČSAV v Turnově. Refraktor s tímto dubletem se stal hlavním přístrojem místní hvězdárny. Spojka tohoto objektivu obsahovala šlíry a bylo ji nutné vyrobit novou This paper brings the information about repair of the achromatic objective lens of diameter 160mm and focal length 2500mm produced by the Development Optical Workshop of the ČSAV in Turnov. The refractor with this dublet has become the main telescope of a local astronomical observatory. The positive lens contained impurities – schlieren and it was necessary to produce a new lens and change it. Keywords: Achromatic dublet; aplanat; grinding; polishing; autocollimation test; optical aberrations Available at various institutes of the ASCR
Oprava objektivu 160/2500 turnovské hvězdárny

Tento referát přináší informace o opravě achromatického objektivu o průměru 160 mm a ohniskové vzdálenosti 2500 mm, vyrobeného v 70. letech ve Vývojové optické dílně ČSAV v Turnově. Refraktor s tímto ...

Rail, Zdeněk; Melich, Zbyněk; Šrajer, Bohdan; Šípová, Gabriela; Kaucká, Iva; Franců, Helena; Melich, Radek
Ústav fyziky plazmatu, 2018

Tmelený objektiv Steinheilova typu
Rail, Zdeněk; Franců, Helena; Ulrichová, Iva; Šípová, Gabriela; Jareš, Daniel; Kuryshev, V.; Vápenka, David
2018 - Czech
Tento referát se zabývá achromatickými dublety se vstupním členem z flintového skla. Optické řešení těchto objektivů navrhl německý fyzik Carl August Steinheil v polovině 19. století. V nedávné minulosti bylo několik těchto dubletů vyrobeno pro astronomické účely v naší dílně. V referátu popisujeme výpočet a technologický postup výroby tmeleného Steinheilova objektivu s rovinnou výstupní plochou. This paper analyses the achromatic dublets with an entrance lens of the flint glass. The objective lens of this construction were devised by German physician Carl August Steinheil in the half of the 19 th century. Several pieces of these dublets were manufactured for astronomical purposes in our workshop in the past. We discuse the mathematical evaluation and the method of manufacture of the glued Steinheil objective with plane exit surface. Keywords: Achromatic objective; apochromatic objective; spherochromatic aberration; coma Available at various institutes of the ASCR
Tmelený objektiv Steinheilova typu

Tento referát se zabývá achromatickými dublety se vstupním členem z flintového skla. Optické řešení těchto objektivů navrhl německý fyzik Carl August Steinheil v polovině 19. století. V nedávné ...

Rail, Zdeněk; Franců, Helena; Ulrichová, Iva; Šípová, Gabriela; Jareš, Daniel; Kuryshev, V.; Vápenka, David
Ústav fyziky plazmatu, 2018

Alternative Methods of Permeation Barriers Preparation
Veverka, Jakub; Matějíček, Jiří
2018 - English
Permeation barriers represent one of the crucial fields in materials development for thermonuclear fusion. Primary objective of the barriers is to suppress the permeation of hydrogen isotopes (mainly tritium) from future thermonuclear fusion facilities. Secondary objective is to reduce their retention in structural materials. Expected reactor conditions put high demands on the material, as well as on the final barrier quality. Key properties are tritium permeation reduction, absence of defects (especially cracks), high-temperature stability and corrossion resistance, and compatibility with structural materials (mostly ferritic-martensitic steels). Thin nitride layers, identified as promising permeation barriers, were prepared by diffusion-based nitridation and physical vapour deposition (PVD), and characterized. Keywords: Permeation barriers; Nitride layers; PVD coating; Permeation measurement Available at various institutes of the ASCR
Alternative Methods of Permeation Barriers Preparation

Permeation barriers represent one of the crucial fields in materials development for thermonuclear fusion. Primary objective of the barriers is to suppress the permeation of hydrogen isotopes (mainly ...

Veverka, Jakub; Matějíček, Jiří
Ústav fyziky plazmatu, 2018

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