Ano (48)
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48
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RE beam generation in MGI disruptions on COMPASS.
Ficker, Ondřej; Mlynář, Jan; Macúšová, Eva; Vlainić, M.; Weinzettl, Vladimír; Urban, Jakub; Čeřovský, Jaroslav; Farník, Michal; Markovič, Tomáš; Papřok, Richard; Vondráček, Petr; Imríšek, Martin; Tomeš, Matěj; Havlíček, Josef; Varju, Jozef; Varavin, Mykyta; Bogár, Ondrej; Havránek, Aleš; Gospodarczyk, M.; Rabinski, M.; Jakubowski, M.; Malinovski, K.; Zebrowski, J.; Plyusnin, V.; Papp, G.; Pánek, Radomír; Hron, Martin
2017 - anglický
In the experiments with the massive gas injection (MGI) triggered disruptions in the COMPASS tokamak, post-disruptive runaway electron (RE) beams are generated occasionally. In this contribution, a relatively large set of discharges from the recent years is analysed in order to improve our understanding of the processes behind the beam generation. It seems that despite the low toroidal field applied in the discharges (typically 1.15 T) the magnetic perturbations may be small enough to allow the acceleration and confinement of the electrons. The influence of the different components and different sections of the frequency spectrum of the magnetic perturbations on the beam generation and RE beam current is examined. Fast visible camera images are also analysed. The relevance of COMPASS runaway electron experiments for large machines is discussed. Moreover, the potential of less common diagnostic tools (Cherenkov detector, vertical ECE, ...) to clarify the role of the pre-disruption fast electron population and the influence of prompt runaway electron losses in the current quench is discussed using the recent test measurements.
Klíčová slova:
RE; massive gas injection (MGI); disruptions; HXR; ECE; fast cameras
Dokument je dostupný na externích webových stránkách.
RE beam generation in MGI disruptions on COMPASS.
In the experiments with the massive gas injection (MGI) triggered disruptions in the COMPASS tokamak, post-disruptive runaway electron (RE) beams are generated occasionally. In this contribution, a ...
Microwave reflectometry for density profile and turbulence measurements on the COMPASS tokamak.
Bogár, Ondrej; Bílková, Petra; Böhm, Petr; Hron, Martin; Pánek, Radomír; Silva, A.; Zajac, Jaromír; Varavin, Mykyta
2017 - anglický
Microwave reflectometry is an established radar technique to acquire various scientific results in plasma fusion research. Fast electron density profile measurements are crucial for the study of fusion plasmas and the operation of fusion devices. Operation capability and first results of the reflectometry on the COMPASS tokamak are presented in this contribution.
Klíčová slova:
plasma; tokamak; COMPASS
Dokument je dostupný na externích webových stránkách.
Microwave reflectometry for density profile and turbulence measurements on the COMPASS tokamak.
Microwave reflectometry is an established radar technique to acquire various scientific results in plasma fusion research. Fast electron density profile measurements are crucial for the study of ...
Synthesis and applications of Intermetallics
Novák, P.; Salvetr, P.; Kříž, J.; Kubatík, Tomáš František
2015 - anglický
Intermetallic compounds, intermetallics, are characterized by interesting properties, such as e.g. excellent high -temperature oxidation resistance, shape memory or ability to store hydrogen reversibly. Their positive, but also negative, properties are a combination of the behaviour of metals and ceramics. Their wider application in industry is limited due to low room-temperature ductility and problematic production, associated with high melting points of many intermetallics, high reactivity of metals at high temperatures and problematic processing. In this paper, the overview of the methods for synthesis of intermetallic compounds is presented, ranging from conventional casting processes to modern powder metallurgy technologies. Selected interesting applications from industry and medicine, where their unique properties are used
Klíčová slova:
Intermetallic compounds; powder metallurgy technologies
Dokument je dostupný na externích webových stránkách.
Synthesis and applications of Intermetallics
Intermetallic compounds, intermetallics, are characterized by interesting properties, such as e.g. excellent high -temperature oxidation resistance, shape memory or ability to store hydrogen ...
Chemical aspects of antiballistic cermets preparation
Brožek, Vlastimil; Kubatík, Tomáš František; Chráska, Tomáš; Mušálek, Radek; Janata, Marek; Mastný, L.
2015 - anglický
The paper aims to demonstrate the possibilities of metal-ceramic material deposition on different types of metal or ceramic substrates using plasma deposition. A number of self-supporting components and the preparation of metal-braced composites are described and the results of plasma depositions of two particular extremely hard ceramic materials, boride and nitride of titanium are presented. The plasma deposition of these material is performed in technological conditions which prevent undesirable high-temperature oxidation. The paper describes deposition conditions that may lead to materials suited to create anti-ballistic protection and complicated shapes or improve parameters of surface layers of present anti-ballistic ceramics.
Klíčová slova:
Anti-ballistic ceramics; armour ceramics; plasma spraying; titanium boride; plasma spraying; titanium nitride
Dokument je dostupný na externích webových stránkách.
Chemical aspects of antiballistic cermets preparation
The paper aims to demonstrate the possibilities of metal-ceramic material deposition on different types of metal or ceramic substrates using plasma deposition. A number of self-supporting components ...
Mechanical and chemical properties of plasma sprayed bronze CuAl10 coating on magnesium and magnesium alloy AZ91
Kubatík, Tomáš František; Vilémová, Monika; Mušálek, Radek; Janata, Marek
2015 - anglický
The most common magnesium alloy AZ91 is widely used as a structural material, but its use is limited at higher temperatures and high humidity. Plasma spraying is a technology that allows to prepare protective metallic and nonmetallic coatings on a wide variety of substrates including magnesium and its alloys. In this study, CuAl10 was plasma sprayed on magnesium and magnesium alloy AZ91 with the aim to study corrosion resistance of the magnesium substrates. The work focuses on optimization of the plasma spraying process, on chemical composition of the coatings, on interface between the coating and substrate, as well as on adhesive strength of the coatings. The coating were deposited after two passes of the spraying torch resulting in thickness of 150 micro m on magnesium substrate and 110 micro m on AZ91 substrate. Chemical microanalysis showed that deposition of CuAl10 alloy on magnesium results in formation of an intermetallic layer at the interface. The layer provides a
Klíčová slova:
Magnesium alloy AZ91; Plasma spraying
Dokument je dostupný na externích webových stránkách.
Mechanical and chemical properties of plasma sprayed bronze CuAl10 coating on magnesium and magnesium alloy AZ91
The most common magnesium alloy AZ91 is widely used as a structural material, but its use is limited at higher temperatures and high humidity. Plasma spraying is a technology that allows to prepare ...
Structural and Mechanical Characterization of Spark Plasma Sintered Tungsten
Čech, J.; Haušild, P.; Kocmanová, Lenka; Matějíček, Jiří
2015 - anglický
The main objective of this paper is to describe the microstructure and mechanical properties of spark plasma sintered tungsten. The indentation tests, which are very advantageous because of their semi-nondestructive character and low requirements on the volume of investigated material, were carried out using Berkovich and spherical indenters. Indentation techniques with spherical indenters are less frequently used than those with sharp indenters but they offer variation of strain with the indentation depth and, therefore, they could be used for determination of stress-strain curves. Local stress-strain behavior obtained by this method showed good correspondence with the results of compression tests. Observation of the microstructure and the fracture surfaces helped to explain some phenomena which occurred during the mechanical testing
Klíčová slova:
tungsten; SPS; instrumented indentation
Dokument je dostupný na externích webových stránkách.
Structural and Mechanical Characterization of Spark Plasma Sintered Tungsten
The main objective of this paper is to describe the microstructure and mechanical properties of spark plasma sintered tungsten. The indentation tests, which are very advantageous because of their ...
Unfolding of energies of fusion products measured by the activation probe at JET
Ficker, Ondřej; Mlynář, Jan; Bonheure, G.; Murari, A.; Popovichev, S.
2015 - anglický
Providing a detection method for diagnostic of charged fusion products in tokamaks presents a major challenge, while its absolute calibration with a sufficient accuracy and its capability to withstand harsh fusion reactor environment will be required. A novel type of detector that meets most of these requirements, based on an activation probe, was tested in JET and other European facilities. This probe proved to be extremely robust due to its simple construction. It is equipped with samples of well defined isotopic abundance. The amounts of activated nuclei due to the reactions in these materials could be measured via ultra-low-level gamma spectroscopy. The feasibility of the proton spectrum reconstruction from measured activities is examined in this contribution with the help of the algorithm based on the Tikhonov regularisation constrained by minimum Fisher information. The reliability of the method was previously illustrated using synthetic proton data.
Klíčová slova:
fusion products; nuclear activation; protons; spectra
Dokument je dostupný na externích webových stránkách.
Unfolding of energies of fusion products measured by the activation probe at JET
Providing a detection method for diagnostic of charged fusion products in tokamaks presents a major challenge, while its absolute calibration with a sufficient accuracy and its capability to withstand ...
Poisson Equation Solver Parallelisation for Particle-in-Cell Model
Podolník, Aleš; Komm, Michael; Dejarnac, Renaud; Gunn, J. P.
2014 - anglický
Numerical simulations based on PIC technique like the SPICE2 model developed at IPP ASCR are often used in tokamak plasma physics to investigate the interaction of edge plasma with plasma-facing components. The SPICE2 model has been parallelised with the exception of the Poisson equation solver which considerably slows down the simulations. It is now being upgraded to a parallelised version to be efficient enough to perform more demanding tasks like the ITER tokamak baseline scenario edge plasma whose conditions like high density (up to 1020 m−3) and low temperature (1–2 eV) result in simulations taking several months to compute. Performance and scaling are compared for different cases in order to choose the optimal candidate for aforementioned applications.
Klíčová slova:
plasma; tokamak; ITER
Dokument je dostupný na externích webových stránkách.
Poisson Equation Solver Parallelisation for Particle-in-Cell Model
Numerical simulations based on PIC technique like the SPICE2 model developed at IPP ASCR are often used in tokamak plasma physics to investigate the interaction of edge plasma with plasma-facing ...
Thermal Coatings for Glass Industry
Chráska, Pavel; Neufuss, Karel
2014 - anglický
A new type of plasma torch with combined stabilization of electric arc by water vortex and gas flow is presented. This hybrid water/gas stabilization offers the possibility of adjusting plasma jet parameters within a wide range from high-enthalpy low-density plasmas typical for liquid stabilized torches to lower enthalpy higher density plasmas generated in gas stabilized torches. Moreover, gas flow in the cathode part protects a cathode tip and thus a consumable graphite cathode used in water-only stabilized plasma torches could be replaced by a fixed tungsten cathode. Examples of hybrid WSP torch utilization for high temperature application are given.
Klíčová slova:
glass melts; high temperature loading; glass forming tools; service life; coatings
Dokument je dostupný na externích webových stránkách.
Thermal Coatings for Glass Industry
A new type of plasma torch with combined stabilization of electric arc by water vortex and gas flow is presented. This hybrid water/gas stabilization offers the possibility of adjusting plasma jet ...
THERMAL AND MECHANICAL PROPERTIES OF TUNGSTEN COMPACTS PREPARED BY SPS
Nevrlá, Barbara; Vilémová, Monika; Matějíček, Jiří
2014 - anglický
Tungsten is a promising candidate material for use in the tokamak device aimed at future production of nuclear fusion power. Here, tungsten is intended for the application in the part called first wall,with the function of a heat-resistant plasma facing armor.In the present work,two fractions of tungsten powder (2 and 4 μm) were used to prepare two consolidated samples by spark plasma sintering (SPS),using a combination of pressure,temperature and electric power.This sintering technique produces samples of near theoretical density which is positive for the application.Tungsten compacts were then studied to determine some basic thermal and mechanical properties, namely thermal conductivity using the laser-flash method and hardness by Vickers test.The measurements were focused on thermal conductivity of the compacts because high thermal conductivity is crucial for the material of tokamak first wall,loaded by high heat flux from the plasma.High hardness is desirable for good resistance
Klíčová slova:
spark plasma sintering; tungsten; thermal properties
Dokument je dostupný na externích webových stránkách.
THERMAL AND MECHANICAL PROPERTIES OF TUNGSTEN COMPACTS PREPARED BY SPS
Tungsten is a promising candidate material for use in the tokamak device aimed at future production of nuclear fusion power. Here, tungsten is intended for the application in the part called first ...
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