Yes (48)
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48
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Design and Preliminary Results of the COMPASS Power Supplies Filters
Havlíček, Josef; Zajac, Jaromír
2013 - English
The COMPASS tokamak uses rectifying thyristor converters as Power Supplies for the major slow coils circuits. 24-pulse thyristor converter is used for Toroidal Field circuit and 12-pulse converters are used for Magnetizing, Equilibrium and Shaping Field circuits. A noise generated by the switching of the converters negatively influences diagnostics measuring the plasma. The article describes design phase and some preliminary results of the filters for the Power Supplies
Keywords:
COMPASS tokamak; magnetic field; plasma
Fulltext is available at external website.
Design and Preliminary Results of the COMPASS Power Supplies Filters
The COMPASS tokamak uses rectifying thyristor converters as Power Supplies for the major slow coils circuits. 24-pulse thyristor converter is used for Toroidal Field circuit and 12-pulse converters ...
Absolute Sensitivity Calibration of Visible Spectroscopic Diagnostic and Temporal Evolution of First Window Transmittance at the COMPASS Tokamak
Naydenkova, Diana; Weinzettl, Vladimír; Stöckel, Jan; Háček, Pavel; Imríšek, Martin
2013 - English
An absolute calibration of spectroscopic systems is required to measure many important plasma parameters in tokamak discharges like impurity inflow, recycling and the effective ion charge. The procedure of the absolute calibration is described and technical issues and experimental limitations connected with the tokamak operation are discussed here. Namely, an influence of the first window transmittance and its evolution over experimental campaigns on the validity of the absolute calibration is investigated
Keywords:
COMPASS; tokamak; Visible Spectroscopic Diagnostic; Absolute Sensitivity; Calibration
Fulltext is available at external website.
Absolute Sensitivity Calibration of Visible Spectroscopic Diagnostic and Temporal Evolution of First Window Transmittance at the COMPASS Tokamak
An absolute calibration of spectroscopic systems is required to measure many important plasma parameters in tokamak discharges like impurity inflow, recycling and the effective ion charge. The ...
Observation of Sawtooth Oscillations in the COMPASS Tokamak
Imríšek, Martin; Havlíček, Josef; Weinzettl, Vladimír; Mlynář, Jan
2013 - English
The sawtooth instability in tokamak plasmas results in periodic relaxations of the core plasma density and temperature. The physics of sawtooth is still not fully understood. It is predicted that fusion-born alpha particles will lead to long sawteeth. However, longer sawteeth can seed other instabilities which cause further degradation of plasma confinement. This paper provides brief introduction into sawtooth physics and observations of sawtooth instability in COMPASS. Furthermore, evidence of triggering transition to high confinement regime by sawtooth crash is presented
Keywords:
Sawtooth; tokamak; soft-x ray; COMPASS
Fulltext is available at external website.
Observation of Sawtooth Oscillations in the COMPASS Tokamak
The sawtooth instability in tokamak plasmas results in periodic relaxations of the core plasma density and temperature. The physics of sawtooth is still not fully understood. It is predicted that ...
Observation and Prediction of Runaway Electrons in the COMPASS Tokamak
Papřok, R.; Krlín, Ladislav; Stöckel, Jan
2013 - English
In this paper we present new measurements of HXR radiation from the COMPASS tokamak by the use of scintillation detector, 21-pinhole CdTe semiconductor detector. This radiation is caused by the presence of highly energetic runaway electrons and in the case of Neutral Beam Injection by fusion products. We also present direct runaway electrons measurements by Cherenkov detector. We present a theoretical prediction of runaway production based on theoretical formula and experimental data from Thomson scattering and compare it with a simpler experimental method based on peak counting.
Keywords:
tokamak; COMPASS
Fulltext is available at external website.
Observation and Prediction of Runaway Electrons in the COMPASS Tokamak
In this paper we present new measurements of HXR radiation from the COMPASS tokamak by the use of scintillation detector, 21-pinhole CdTe semiconductor detector. This radiation is caused by the ...
Heat and Particle Deposition on the Plasma-Facing Components
Podolník, Aleš; Pánek, Radomír; Komm, Michael; Dejarnac, Renaud; Gunn, J. P.
2013 - English
The interaction of plasma with plasma-facing components (PFCs) in tokamaks is of increasing interest because of implications for ITER and next-step devices. The heat and particle fluxes interacting with solid objects can be studied by means of particle-in-cell (PIC) simulations. The aim of this work is to use the existing family of PIC codes SPICE to simulate the heat and particle flux distribution on PFCs. The output of the simulations is then used in new heat equation solver, which calculates the temperature of the PFCs. This solver provides us a testbed for the parallel sparse matrix code development as well as for the complex application aimed at study of the melting of tiles.
Keywords:
plasma; tokamak; ITER
Fulltext is available at external website.
Heat and Particle Deposition on the Plasma-Facing Components
The interaction of plasma with plasma-facing components (PFCs) in tokamaks is of increasing interest because of implications for ITER and next-step devices. The heat and particle fluxes interacting ...
First measurements with U-probe on the COMPASS tokamak
Kovařík, Karel; Ďuran, Ivan; Stöckel, Jan; Seidl, Jakub; Šesták, David; Brotánková, J.; Spolaore, M.; Martines, E.; Vianello, N.
2013 - English
A complex electrostatic-magnetic probe diagnostics, baptized as ‘U-probe’, has been installed on COMPASS tokamak recently. Probe composes of two identical towers. Each tower houses 3 radially spaced sets of 3D coils, triple probe and rake probe – array of six Langmuir probes. The U-probe measures electric and magnetic properties of the filamentary structures in the edge plasma, particularly the floating potential profile and local magnetic field within the plasma filaments. Contribution presents first tests and results obtained.
Keywords:
plasma; tokamak
Fulltext is available at external website.
First measurements with U-probe on the COMPASS tokamak
A complex electrostatic-magnetic probe diagnostics, baptized as ‘U-probe’, has been installed on COMPASS tokamak recently. Probe composes of two identical towers. Each tower houses 3 radially spaced ...
Dust Observation in the COMPASS Tokamak Using Fast Camera
Odstrčil, M.; Mlynář, Jan; Weinzettl, Vladimír; Háček, Pavel; Berta, M.; Szabolics, T.; Bencze, A.
2013 - English
The dust grains were observed over a thousand discharges in the tokamak COMPASS. A novel method for semi-automatic extraction and tracking of dust grains using a relatively low frame-rate camera (370 fps) was proposed. Radiation lifetime, time evolution and the acceleration of the dust grains were studied. The measured dust velocities roughly correspond to a simple model. However, slow dust particles are signicantly aected by local plasma properties and initial release conditions that cannot be determined in our experiment
Keywords:
COMPASS; tokamak
Fulltext is available at external website.
Dust Observation in the COMPASS Tokamak Using Fast Camera
The dust grains were observed over a thousand discharges in the tokamak COMPASS. A novel method for semi-automatic extraction and tracking of dust grains using a relatively low frame-rate camera ...
Possible way to prepare nanoparticles from aerosols released at plasma deposition
Brožek, Vlastimil; Mastný, L.; Moravec, Pavel; Ždímal, Vladimír
2012 - English
During plasma deposition of powdered metals or inorganic compounds using WSP® generator, they interact with the plasma having temperature between 25000 and 30000 K. As a result, they melt, evaporate, thermally decompose, get ionized and/or react chemically both with plasma-forming medium and with the surrounding atmosphere or carrier gas. An experimental apparatus was constructed enabling us to capture aerosol particles emitted from the surface of the free flying particles (FFP) heated in a stream of plasma. In this work we studied content, composition and size distribution of nanosized particles of Ag and oxides of Al, Ti, Cr and W, released during plasma deposition process. These particles were analyzed by dynamic light scattering - photon correlation spectroscopy using instrument MALVERN, and with aerosol spectrometers SMPS 3936 and APS 3321.Concentration of aerosols containing nanoparticles of silver or metal oxides with diameters below 100 nm was found to be in the range 85 to
Keywords:
plasma spraying; aerosol technology; nanoparticles production; measurement of particle size distribution
Fulltext is available at external website.
Possible way to prepare nanoparticles from aerosols released at plasma deposition
During plasma deposition of powdered metals or inorganic compounds using WSP® generator, they interact with the plasma having temperature between 25000 and 30000 K. As a result, they melt, evaporate, ...
Production of nanoparticles utilizing water stabilized plasma
Bertolissi, Gabriele; Brožek, Vlastimil; Chráska, Tomáš; Mušálek, Radek; Neufuss, Karel; Mastný, L.; Sofer, Z.
2012 - English
Water stabilized plasma torch (WSP®) generates plasma jet with max. plasma velocity in the nozzle exit 7000m/s and temperature of 25000-30000 K. Reactants injected into the plasma jet undergo complicated radical reactions. Interaction of plasma with injected reactants depends on energy settings of the WSP plasma torch and lasts from 5 to 10 ms. Droplets of inorganic compound solution are fed to the plasma jet by pressurized spray nozzle device. Compounds of AgI,AlIII,TiIV,PtIV,VV, and CrVI undergo decomposition in the extremely high plasma temperature and the decomposed products are collected in liquid separators. Size of the produced nanoparticles in unsettled fraction is from 10 to 200 nm and depends primarily on concentration of inputting aerosol particles. In the case of 15 seconds reaction time and use of saturated solutions at 20°C, one can obtain colloidal solutions with silver, platinum, alumina, titania, vanadia, and chromia nanoparticles in concentrations of 3 to 180mg
Keywords:
Ag, Al, Ti, V, Cr, Pt – nanoparticles; nanoparticles morphology; plasma spraying; water stabilized plasma; photon spectroscopy; metallic nanoparticles; oxide nanoparticles
Fulltext is available at external website.
Production of nanoparticles utilizing water stabilized plasma
Water stabilized plasma torch (WSP®) generates plasma jet with max. plasma velocity in the nozzle exit 7000m/s and temperature of 25000-30000 K. Reactants injected into the plasma jet undergo ...
Using matlab for visualization of plasma dynamics by statystical processing of photograph sequences
Chumak, Oleksiy; Hrabovský, Milan
2011 - English
Short exposure photographs capturing the momentary state of the plasma radiation are often used for the primary characterization of discharges. Sequence of such images gives an impression about a variation of radiation intensity in different areas and can be used to describe the fluctuation intensity. This work presents a statistical procedure which produces brightness fluctuation intensity maps. Two realizations of the statistical procedure in Matlab environment are described and compared.
Keywords:
Plasma stability; jet fluctuations; statistical processing; entropy maps
Fulltext is available at external website.
Using matlab for visualization of plasma dynamics by statystical processing of photograph sequences
Short exposure photographs capturing the momentary state of the plasma radiation are often used for the primary characterization of discharges. Sequence of such images gives an impression about a ...
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