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Far-infrared magneto-optical measurements of superconducting NbN layer
Koláček, Jan ; Skrbek, L. ; Šindler, M. ; Tesař, Roman
Temperature dependence of far-infrared transmission of thin layer NbN deposited on SiO2 substrate has been measured at frequencies 0.40, 0.65 and 2.52 THz. The zero magnetic field data are in agreement with previous measurements. Additionally, temperature dependent transmission at 0.40 THz for parallel and perpendicular magnetic field orientation with respect to NbN layer from 1 to 10 tesla is reported. In order to interpret our data, we have calculated the transmission of the NbN layer using equations for complex conductivity. For zero magnetic field, the experimental and computed data are in good agreement. With increasing field, however, the experimental data start to deviate from the model prediction that neglects effects due to quantized vortices penetrating the superconductor. When moving, they absorb energy and affect both reflection and transmission. Presently, no way of calculating the complex conductivity in the presence of quantized vortices from the BCS theory is known.
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Total Electron Content Measurement Using Digisonde and GNSS
Kouba, Daniel ; Šauli, Petra
The digital pulse ionospheric sounder (Digisonde) of the University of Massachusetts Lowell has been operated in Pruhonice (geographic coordinates 50.0N, 14.6E) since 2004 for ionospheric study. Earlier, KEL Aerospace and ISP-42 ionosondes had also been operated. Hence, there is a long archive of bottomside ionospheric records for a period of about sixty years. In 2009, Topcon NET-G3 triple frequency Global Navigation Satellite System receiver will also be installed at the station, collocated with the Digisonde. GNSS receivers are becoming recognized as another source for ionospheric information. This year, the upgrade of Digisonde DPS-4 to model DPS-4D also will be realized. This new type will provide a much wider usage and expands the possibilities of our research. The GNSS and Digisonde measurements jointly will bring new improvements to the models of electron density profiles.
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Analýza výstupů klimatických modelů pomocí lineárních a nelineárních technik
Chládová, Zuzana
Regional climate models (RCMs) are currently one of regularly applied tools for localization of global climate models (GCMs) outcomes. This study is focused on analyses of mean daily temperature and precipitation using linear and nonlinear statistical techniques. 48 grid points of the regional climate models HIRHAM and RCAO and 29 meteorological stations of the Czech Republic were compared in the period 1961-1990. Mean annual courses of mean daily temperature and precipitation in the period 2071-2100 were analyzed at selected HIRHAM and RCAO grid points for A2 and B2 emission scenarios [IPCC, 2007]. Furthermore, time-delayed average mutual information (AMI) and autocorrelation function were analyzed. AMI and autocorrelation function were calculated for one selected time series of each grid point of the Czech Republic and Europe with a time lag varying from 1 to 10 days. The values of average mutual information were compared with values of autocorrelation function.
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Thermal Plasma Assisted Gasification of Polymers
Sforza, T. ; Charlier, C. ; Hrabovský, Milan ; Chumak, Oleksiy
Gasification of various hydrocarbons with help of thermal plasma is studied at the Institute of Plasma Physics. Such treatment can be way of recycling of polymer waste with production of high purity synthesis gas (syngas) mainly composed of hydrogen and CO. A plasma torch with hybrid stabilization of arc used in the reactor allows higher efficiency for gasification than other processes. This work is preparation of the experiment for gasification of PET. Basic description and analysis of the gasification reactor is done. Analysis of reaction taking place is made. On the base of derived information optimal composition flow rates and power balance of the process is calculated.
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Bellanova nestabilita u nečistot zachycených v turbulentních strukturách v okrajové vrstvě tokamaku
Seidl, J. ; Krlín, Ladislav
We present description of an electrostatic turbulent model ESEL and explain interchange mechanism leading to turbulence generation in tokamak scrape-off layer. After introducing theory of Bellan instability, threshold for particle detrapping from turbulent structures (blobs) due to their finite Larmor orbits is discussed for the case of turbulence simulated by the ESEL model. Since plasma potential as well as floating potential are available from the simulation, it is possible to evaluate error made by using experimentally obtained floating potential in simulations of particle diffusion. It is shown that due to bipolar nature of blobs the outflow of particles from the blob caused by Bellan instability can be, in certain conditions, asymmetric and localized mainly into its upper and inner boundary.
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PIC simulace pravoúhlých a seříznutých štěrbin ve zkušebním limiteru tokamaku TEXTOR
Komm, M. ; Pekarek, Z. ; Pánek, Radomír ; Matveev, D. ; Kirschner, A. ; Litnovsky, A.
In this paper, we present results of Particle-In-Cell simulations of the plasma behavior in the vicinity of gaps in castellated plasma-facing components. We studied gaps in the test limiter of TEXTOR, which is a plasma-facing component designed for studies of impurity transport and fuel retention, mainly via hydrocarbon layer formation. The castellated limiter tiles have been analyzed using the postmortem techniques and first attempts of impurity transport modelling were done using the 3DGAP code [Matveev et al., 2008]. In order to improve the agreement between modeling and experiment, realistic plasma particle flux distribution needs to be included in the code. For this purpose, a series of PIC simulations for varying plasma conditions was performed by using the SPICE2 code [Dejarnac et al., 2008]. Plasma behavior inside the gaps is discussed and semi-empiric characterization via generic fitting procedure is proposed
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Ozařovací testy Hallových senzorů
Kovařík, Karel ; Ďuran, Ivan ; Oszwaldowski, M. ; Viererbl, L.
A principally new diagnostic method has to be developed to complement the magnetic measurements in true steady state regime of operation of future fusion reactors. One of the options is the use of diagnostics based on Hall sensors that are well established in experimental physics and industry, although it is rarely implemented in the fusion plasma physics due to short pulse operation of majority of present day tokamaks. There are two main issues associated with the use of Hall sensors in harsh environment of future fusion reactors i.e. low survival temperature of presently available commercial transducers and questionable stability of these mostly semiconductor sensors under neutron irradiation. Hall sensors based on InSb thin film layers are presently being evaluated as one of the perspective options for ITER ex-vessel steady state magnetic sensors. Here, the compatibility with vacuum vessel baking temperature of 220 oC and with the peak life time neutron fluence of 1018 n/
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Kontrola vakua a plynového systému pro tokamak COMPASS
Janky, F. ; Pereira, T.V. ; Santos, B.A. ; Hron, Martin
This paper is aimed at creating a vacuum and a gas handling subsystem. The new vacuum and the gas handling subsystem was developed at IPP/Prague after the COMPASS tokamak reinstallation. It was necessary to build a system which can operate 24/7 and be fully autonomous. A firmware programmed in the C programming language controls devices connected to the vacuum and the gas handling subsystem. The firmware is programmed at dsPICr Microchip r embedded at a board assembled at IST Lisbon. The vacuum and the gas handling are connected through fiber optics to a server computer and can be controlled remotely through a workstation situated at the control room
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Navrh filtru pro detekci Thomsonovym rozptylem na tokamaku COMPASS
Aftanas, Milan ; Scannell, R. ; Bílková, Petra ; Böhm, Petr ; Weinzettl, Vladimír ; Walsh, M.
Reinstalled tokamak COMPASS, originally from Culham Science Centre, is now operating at the Institute of Plasma Physics, Prague and many new optical diagnostics are being developed [Sestak et al, 2009]. For measurement of electron temperature and density profiles, high resolution incoherent Thomson scattering spectroscopy based on Nd:YAG laser and avalanche photodiodes is under development now. The paper outlines part of the design of this diagnostic - proper choice of spectral filters. The design of filters is shown and its evaluation taking into account different angle of scattered light is introduced. Error bars of the electron temperature, density and pressure are determined with respect to assumed electron temperature and density profiles and to required high spatial resolution at the pedestal region.
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