National Repository of Grey Literature 11 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
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
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.
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
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.
Evaluation of the Financial Situation of a Company and Proposals to its Improvement
Seidl, Jakub ; Kožoušek, Tomáš (referee) ; Karas, Michal (advisor)
This bachelor’s thesis is focused on evaluation of financial situation of industrial company and suggestions for improvement for this situation in years 2011 to 2016 in P-D Refractories CZ a.s. First chapter of this bachelor’s thesis is focused on goals, methods and processes. Second part is interested in information about company and theoretical solution for financial analysis. Third chapter includes already analysis and evaluation of the state of company. Last chapter gives own suggestions for improvement of the situation in P-D Refractories CZ a.s.
Political behavior of the Andalusians
Seidl, Jakub ; Urban, Traian (advisor) ; Mejstřík, Martin (referee)
This study concerns the political behavior of the Andalusians and its reasons. In this autonomous community exists a traditional tendency to support the left-wing party PSOE. The object of this study is an analysis of this political trend and the aim is to explain why this phenomenon exists in the society. There is discovered the link between historical, sociopolitical and economical factors and the voting behavior of the Andalusians. The study is divided into a factographic and an analytical chapter. The first chapter includes a recapitulation of the results of autonomic elections and also there is an outline of the political behavior using the output of public opinion polls. These data are mentioned also in the next part of the study where are explained more deeply. The analytical chapter concerning the support of PSOE and its reasons is divided into parts following the character of the circumstanses affecting the political behavior. The first chapter is about historical factors, the second one about sociopolitical issues and the last one about economical factors. The main historical questions are the underdevelopment and poverty, the satisfaction paradox and the problem of latifundium. The sociopolitical factors include the political culture and nationalism and the chapter about economical...
Anomalous diffusion of plasma in tokamak edge region
Seidl, Jakub ; Krlín, Ladislav (advisor) ; Hrach, Rudolf (referee) ; Rohlena, Karel (referee)
Title: Anomalous diffusion of plasma in tokamak edge region Author: Jakub Seidl Tutoring institution: Institute of Plasma Physics AS CR, v.v.i. Supervisor: Doc. Ing. Ladislav Krlín, DrSc., IPP AS CR Consultant: RNDr. Radomír Pánek, Ph.D., IPP AS CR Abstract: This work provides brief introduction to the topic of plasma turbu- lence in tokamak edge region and several aspects of anomalous plasma diffusion are discussed. We use numerical code ESEL to model interchange turbulence and investigate properties of turbulent structures in different regimes of parallel trans- port. Means of experimental verification of the results are discussed. Results of the modelling are then used to interpret unexpected results experimentally obtained by electrostatic ball-pen probes on tokamak ASDEX Upgrade, mainly appearance of a 'bump' in power spectra of measured plasma potential. Next, we explain be- haviour of cross-correlation function of density signals measured by two spatially separated Langmuir probes in the vicinity of magnetic separatrix and we point out an ambiguity in interpretation of results of vorticity measurement made by set of floating Langmuir probes. In the last part, transport of plasma impurities by electrostatic turbulent potential is modelled. We identify reversal of radial particle velocity for particles with...
Anomalous Diffusion of Electrons in Tokamak by Their Interaction With Lower Hybrid Wave
Seidl, Jakub ; Krlín, Ladislav (advisor) ; Rohlena, Karel (referee)
Interaction of electrons with a lower-hybrid wave (LHW) is usually described using a quasilinear theory. It was shown formerly that in some cases the quasilinear approach is not proper. This work deals with an eect of spatial geometry of LHW spectra on a particle velocity diusion. Diusion coecient for various cases was computed and put to use to predict a long term evolution of an electron velocity distribution function. The computation was (on the contrary of previous papers) based on fully relativistic equations of motion. The results conrm that region of high electron acceleration is broadest just after the wave enters plasma and becomes narrower along its progress deeper into it. In the range of wave intensities over 105 V/m we found that the diusion becomes Lévy-walk. In the second part predictions of electron acceleration in front of LH grill of two dierent approaches were compared. We showed that the approach based on usage of Fourier expansion of potential gives only a rough estimate of the acceleration.
Radial propagation of L-mode structures in COMPASS tokamak
Kovařík, Karel ; Ďuran, Ivan ; Stöckel, Jan ; Seidl, Jakub ; Havlíček, Josef ; Háček, Pavel ; Spolaore, M. ; Vianello, N.
Various structures appear in the tokamak scrape-off layer (SOL) plasma with effects on plasma behavior. The filamentary probe recently introduced in the COMPASS tokamak allows measurement of electrostatic and magnetic properties of the filaments and their changes in dependence on distance from the last closed flux surface. This work presents evolution of the measured electromagnetic properties and their radial profiles as a part of the complex study of the processes in the SOL.
Study of Alfven Eigenmodes in Tokamak COMPASS
Markovič, Tomáš ; Stöckel, Jan ; Seidl, Jakub ; Melnikov, A. ; Medvedev, S.
Having both MHD and kinetic character plasma Alfven eigenmodes are signicant not only on the eld basic plasma research, but also on the eld of magnetic connement fusion. An introduction to basic physical principles of Alfven eigenmodes under MHD approximation is provided. Presented results of recent experiments on COMPASS suggest occurrence of toroidal Alfven eigenmodes in this tokamak, which is further supported by preliminary linear MHD code simulations, althought more studies will have to be conducted in the future to further investigate presented modes therein.
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.
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.

National Repository of Grey Literature : 11 records found   1 - 10next  jump to record:
See also: similar author names
2 Seidl, J.
4 Seidl, Jan
2 Seidl, Jaroslav
1 Seidl, Jiří
1 Seidl, Julian
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