FREE ELECTRONIC LIBRARY - Thesis, documentation, books

Pages:     | 1 |   ...   | 9 | 10 || 12 | 13 |   ...   | 20 |


-- [ Page 11 ] --

An example of the EEDF for the radial position r = 56 mm in stationary phase of the plasma current for the shot #26402 is shown in Figure 1. The green line is a sum of the red one and the blue one. It is clearly seen that the EEDF is bi-Maxwellian. In Figure 2 the radial profiles of the two electron temperatures are presented. The fit with the experimental EEDF was obtained with an accuracy of 5%. It has to be noted that in the limiter shadow, r 85 mm, the EEDF is Maxwellian with a temperature of about 8 eV. In the same figure the results obtained by Stangeby method [5] (squares) are also presented. We must point out that the Stangeby method assumes a Maxwellian EDF of the electrons. Only the temperature of the high energetic fraction of electrons dominates [6,7] and can be evaluated. We estimate the density of the hot population of electrons at about 10% of the bulk electron density. Figure 3 shows the total electron densities at different radial positions. We compare the first derivative method results (dots) with the Stangeby method (squares) using the cold electron temperature only. The uncertainty in the first derivative method values evaluated does not exceed ± 30%. We see that the two methods show good agreement. Moreover, the first derivative method allows one to obtain in addition the “real” EEDF and the plasma potential values as well (Figure 4).

We have to note that, for those results, the raw data are not filtered. By using an advanced method based on an adaptive choice of the filtering and differentiating instrument functions, the 4x10

-3 electron density m

–  –  –

Part II - PHYSICS plasma parameters thus calculated are similar and we foresee that the advanced method will be useful for identifying the main modes of plasma turbulence.


[1] Arslanbekov R. R. et al., Plasma Sources Sci Technol. 3 (1994) 528 –538.

[2] Demidov V. I. et al., Phys Plasma 6 (1999) 350-358.

[3] Popov Tsv. K. et al., Journal of Physics: Conference Series 63 (2007) 012002.

[4] Martines E. et al., Plasma Phys. Control. Fusion 44 (2002) 351.

[5] Stangeby P. C., McCracken G. M., Nuclear Fusion 30 (1990) 1225-1379.

[6] Shoucri et al., Contrib. Plasma Phys. 38 (1998) 225.

[7] Batishchev O. V. et al., Phys. Plasma 4 (1997) 1672.

–  –  –

We present in this study the power loads in the ITER castellated PFCs by means of kinetic calculations during ELMs. The code used for this purpose has been developed at the IPP Prague and is adapted to such a tile gap geometry [1] by taking into account the specific geometry of the components, the inclination of the magnetic field lines and the gyration of the incoming particles.

–  –  –

Part II - PHYSICS TG and Ldep = 0.45 mm (-22%) for the PG, which is much greater than the geometric projection (Lgeo =0.018 mm for α = 2.1o).

For high plasma conditions, the effects of Te and Ti on the plasma deposition length inside the gap are not significant and the density plays a little role by increasing Ldep marginally (+15% when we double the density).

An important parameter is the inclination angle of the magnetic field lines with respect to the gap. Figure 2 shows the normalized power loads profiles in a TG for two angles, α = 2.1o (dotted line) & α = 1.2o (full line), and for the same plasma conditions (ne = 5.1019 m-3, Ti = Te = 2.5 keV, Bt = 5.9 T). The fluxes falling to the tile surface are in a ratio of a factor of 2 due to the different angles. However, the decrease of the wetted area inside the gap is only by 30%. We have a deposition of the power in the gap Ldep = 0.50 mm for α = 2.1o Figure 2: Normalized power deposition in a 0.5 mm whereas the deposition is Ldep = 0.35 mm for TG for an inclination angle of 2.1o (dotted line) and o α = 1.2o. It has to be noted that the peak value 1.2 (full line) at identical plasma conditions.

increases relatively to the incoming power to the tile with the smaller angle, but remains nevertheless lower in absolute value. We can note that the integrals of the curves shown in Figure 2 are identical due to this feature. This means that the total power inside the gaps is only dependant on the incoming power to the tiles. However, thanks to the change of the slope, by reducing α, the power loads inside the gap are spread differently and the wetted area reduced.

The same conclusions concerning this effect of the incident angle apply to the PGs. The curves are similar, the only difference between the types of gaps coming from the geometric effect described previously in Figure 1.

This work was performed in the frame of the EFDA Task: TW6-TPP-DAMTRAN "Report(ing) on the expected power deposition profiles onto ITER PFCs during steady-state and transient loads with realistic PFC geometry by PIC modeling".


[1] R. Dejarnac and J.P. Gunn, J. of Nucl. Mater. 363-365 (2007) 560-564.

–  –  –

Particle and power loads in tile gaps are of high interested since ITER plasma facing components will be castellated [1]. Previous experimental studies all show shot- or campaignaveraged results of deuterium and impurities deposition inside the gaps [2,3], but giving no information on how the plasma flows between the tiles. In order to investigate more deeply the physics of the plasma deposition, we have developed a special probe that can measure the ion saturation current profile along the gap (see Figure 1). The experimental data are compared to the results of self-consistent kinetic simulations performed by a 2D particle-in-cell code developed here at the IPP Prague and described in [4].

Figure 1: Picture of the 2 components of the dismantled "sandwich probe" for measuring the plasma deposition into a gap between tiles.

–  –  –

Part II - PHYSICS phenomenon is due to an asymmetry of the electric potential inside the gap as explained in [4] and is in good agreement with the numerical predictions.

2-Poloidal gaps Figure 3-a shows the ion saturation current distribution along a poloidal gap measured for different inclinations of the probe with the magnetic field lines. We observe exponential decays only for low angles (α≤32.8o) whereas the plasma seems to penetrate deeper and linearly for angles greater than 32.8o. The deposition shown here corresponds to the plasma facing side of the probe. The profiles calculated by our kinetic code are shown in Figure 3-b and we can observe that a similar behavior is well reproduced, with a non-exponential decay for high inclinations.

The absolute values are in the same range as in the experiment, however we notice that the deposition is in reality deeper, especially for the larger angles. More investigations must be undertaken to understand this result which is reproducible over all the angle scans we performed.

On the other side of the probe (plasma shadowed side), we do observe some signals but with an intensity 10 times lower. We explain this deposit by a "bump" on the potential profile inside Figure 3: Ion saturation profile along a poloidal gap measured by the probe (a) and calculated by the 2D self-consistent PIC code (b) for different inclinations with respect to the magnetic field lines (from 5o to 45o) and for the plasma facing side.

the gap, strong enough to repel the incoming ions towards the surface that is not directly wetted by the plasma [4]. Our simulations also reproduce the same asymmetry, plasma facing side/shadowed side. The absolute values at the entrance of the probe tend to be lower than the predicted ones but the radial deposition is in good agreement for all angles.

Conclusion We have developed a unique tool to measure the plasma deposition into a gap between tiles.

The experimental data confirm the numerical predictions we made with our 2D self-consistent numerical code. In the case of toroidal gaps, we have a quantitative and qualitative agreement.

However, in the case of poloidal gaps, it is only qualitatively acceptable. The 2-sided deposition is confirmed, with the good order of magnitude. This set of experiments confirms nevertheless the understanding of the plasma deposition in tile gaps presented in [4].


[1] W. Daener et al., Fusion Eng. Des. 61&62 (2002) 61.

[2] K. Krieger et al., J. of Nucl. Mater. 363-365 (2007) 870-876.

[3] A. Litnovsky et al., Phys. Scr. T128 (2007) 45-49.

[4] R. Dejarnac, J.P. Gunn, J. of Nucl. Mater. 363-365 (2007) 560-564.

–  –  –

In collaboration with:

H.P. Laqua, Association EURATOM – Max-Planck-Institute für Plasmaphysik, Greifswald We have adapted our EBW code to obtain a crude estimate of the profile of the current driven by

2.45 GHz wave. We investigated the dependence of the current profile on the central magnetic field and the temperature of the hot component.

WEGA plasmas are sustained by electron Bernstein wave heating. This produces a considerable suprathermal electron population. The fraction of this populations ranges up to ~20% and the temperature reaches 200 – 300 eV (compared to ~50 eV of the bulk electron population). These data are estimated from probe measurements and are only approximate. We have extended our EBW code to include the effects of the suprathermal electrons. Significantly different behaviour of the EBWs, compared to single component plasma, has been demonstrated by the simulations.

Even a modes fraction of suprathermal electrons enables very efficient absorption.

Current density profile was, for the first time, measured by a small Rogowski coil during our visit [1]. Therefore, we have concentrated on current drive studies. We have simulated the absorbed power corresponding to individual resonances (and components) and determined the corresponding direction of the driven current, supposing Fish-Boozer current drive mechanism.

The parallel wave vector direction of the EBWs can be reversed during the propagation through the plasma. The driven current direction has to be reversed analogously. Such behaviour has been observed experimentally [1]. We have investigated the effects of the central magnetic field and of the hot component on the EBW current drive.

Fig. 1. Distribution of the absorbed power between components and harmonics. Individual contributions are multiplied by the sign of vres=(ω-nωce)/k||. B(R0)=0.65Bce, T1=300eV.

Fig. 2. Hot component temperature scans. Summed Fig. 3. Central magnetic field scans. Summed components components of the absorbed power. Individual of the absorbed power. Individual contributions are contributions are multiplied by the sign of vres=(ω- multiplied by the sign of vres=(ω-nωce)/k||. T1=300eV nωce)/k||. B(R0)=0.65Bce.


[1] Laqua, H.P., et al., Bulletin of the American Physical Society, vol. 52, no. 16 (2007) 280

–  –  –

EFIT2006 is a modern version of the magnetic equilibrium reconstruction code EFIT, developed at UKAEA Culham. A parallel version of the code was desirable to accelerate the calculations.

EFIT2006 will be also used at IPP Prague for the COMPASS tokamak.

Parallelization of EFIT2006 [1] has started from scratch. It has been decided to implement a coarse grained parallel version of EFIT2006 [2], i.e. to parallelize the high level interface, so that a master process will serve other processes with input data for individual time slices. These processes (slaves) will perform the computation and send the results back to the master, where all the outputs will be written to a file or sent to a database. The parallel version should run on computer grids or clusters using the MPI interface.

EFIT2006 is an object oriented code in C++, which is very beneficial for understanding and enhancements, but parallelization using MPI requires rather complicated transmission of C++ objects. Fortunately, the Boost C++ libraries have recently been extended by an MPI library, which allows transmitting complex C++ objects very conveniently. A functional version of parallel EFIT2006 has been implemented and its performance has been tested. The results are shown in Fig. 1. A linear growth can be clearly seen, even though the benchmarks have been run on serial computers interconnected by rather slow Ethernet network.

EFIT2006 and all the necessary libraries have already been installed at IPP Prague.

Benchmarking results for the same inputs shows that the two installations are equivalent.

–  –  –

References :

[1] Appel, L.C., et al., 33rd EPS Conference on Plasma Physics, Rome (2006) [2] Havlíček, J. and Urban, J., WDS'07 Proceedings of Contributed Papers: Part II - Physics of Plasmas and Ionized Media (2007) 234-239 [3] K. Tani, M. Azumi and R. S. Devoto, J. Comput. Phys. 98 (1992) 332 We consider the the quasi-neutral self-consistent particle-in-cell (QPIC) simulation of a tokamak plasma scrape-off layer (SOL) bounded by two material walls – possibly divertor plates, limiters, probes, or a combination of these. At every time step of the simulation some ions and electrons reach the material walls, but suffer very different fates. The ions are absorbed by the walls and are lost from the simulation. A QPIC simulation satisfies local plasma quasineutrality so that during the simulation the plasma must also be globally neutral. It follows that not all electrons travelling to a wall are allowed to reach it: the total number of electrons lost to the walls must equal the total wall ion charge. If there is global charge balance at each wall, i.e if the ion and electron fluxes to a wall are equal, then the wall potential equals the floating potential. By definition, this floating potential is actually the energy of the most energetic electron which is reflected back into the plasma from it.

Introducing secondary electron emission changes the wall potentials and the wall charge balance.

Pages:     | 1 |   ...   | 9 | 10 || 12 | 13 |   ...   | 20 |

Similar works:

«Nokia C5–03 Bedienungsanleitung Ausgabe 2.2 2 Inhalt Inhalt Während eines Anrufs 25 Anrufbeantworter 26 Annehmen oder Abweisen von Sicherheit 5 Anrufen 26 Herausnehmen des Akkus 5 Telefonkonferenz 27 Kurzwahl einer Telefonnummer 27 Erste Schritte 6 Anklopfen 28 Einsetzen der SIM-Karte und des Sprachanwahl 28 Akkus 6 Protokoll 29 Einsetzen der Speicherkarte 8 Entfernen der Speicherkarte 10 Texteingaben 31 Aufladen des Akkus 10 Virtuelle Tastatur 31 Tasten und Komponenten 11 Handschrift 32...»

«STATE OF MICHIGAN COURT OF APPEALS GALIEN TOWNSHIP SCHOOL DISTRICT and FOR PUBLICATION DELTON-KELLOGG SCHOOLS, April 14, 2015 9:00 a.m. Plaintiffs-Appellees, v No. 317739 Ingham Circuit Court DEPARTMENT OF EDUCATION and LC No. 13-000367-AA SUPERINTENDENT OF PUBLIC INSTRUCTION, Defendants-Appellants. ON REMAND Before: SAAD, P.J., and OWENS and K.F. KELLY, JJ. PER CURIAM. In lieu of granting leave to appeal our decision in Galien Twp Sch Dist v Dep’t of Ed, 306 Mich App 410; 857 NW2d 659...»

«Die Real-Business-Cycle Theorie und ihre Relevanz für die Konjunkturanalyse Bernd Lucke Universität Hamburg von-Melle-Park 5 D-20146 Hamburg Germany email: lucke@hermes1.econ.uni-hamburg.de März 2002 1. Einführung Die Real-Business-Cycle-Theorie hat ihren Ursprung in zwei vor rund 20 Jahren erschienenen Artikeln von Kydland und Prescott (1982) sowie Long und Plosser (1983). Diese Artikel wirkten zur Zeit ihres Erscheinens revolutionär, denn sowohl inhaltlich als auch methodisch lagen sie...»

«NEWS RELEASE, | Release: 2864-88 Contact: Kate Hathaway ForRelease: February i, 1988 (202) 254-8630 WashingtomThe Commodity Futures Trading Commission released today the final staff report on stock index futures and related stock market activity during October 1987. The report analyzes the detailed data concerning the futures trading activities of major broker/dealers and institutional investors, along with certain pertinent aspects of their trading in the stock market. A detailed statistical...»

«An Excerpt From Analysis for Improving Performance: Tools for Diagnosing Organizations and Documenting Workplace Expertise by Richard A. Swanson Published by Berrett-Koehler Publishers Contents Preface xiii PART ONE Analysis: The Key to Improving Performance 1 1. Linking Improvement Programs to Important Organizational Goals 3 2. Theoretical Foundation of Performance Improvement 11 3. Case Study of Analysis for Performance Improvement 37 PART TWO Diagnosing Organizational Performance 47 4....»

«Issue 55 / e-Post / January 2011 Editor Welcome to the first edition of e-Post of 2011 and happy new year! In this issue, we offer you our selection of outstanding issues from 2010 on which we expect further news this year. For advice about any of the topics covered, please contact Martin Brewer, David Mills, Gillie Scoular or your usual Mills & Reeve contact. If you would like to receive information about key developments more quickly, please sign up to an email alert or RSS feed from our blog...»

«SPATIAL-TEMPORAL ANALYSES OF CLIMATE ELEMENTS, VEGETATION CHARACTERISTICS AND SEA SURFACE TEMPERATURE ANOMALY Yitea Seneshaw Getahun SPATIAL-TEMPORAL ANALYSES OF CLIMATE ELEMENTS, VEGETATION CHARACTERISTICS AND SEA SURFACE TEMPERATURE ANOMALY A Case study in Gojam, Ethiopia Dissertation supervised by Professora Ana Cristina Costa, PhD Dissertation co-supervised by Professor Jorge Mateu, PhD Professor Edzer Pebesma, PhD February 2012 ii ACKNOWLEDGEMENTS First and foremost I would like to express...»

«Technology in secondary mathematics education: The role of calculators* Barry Kissane School of Education Murdoch University Murdoch WA Australia 6150 B.Kissane@Murdoch.edu.au Abstract The significance of hand-held technologies for secondary school mathematics education is analysed. In many secondary school mathematics classrooms in many countries, including Thailand, student access to sophisticated ICT facilities is either very limited or non-existent, so that hand-held technologies of...»

«Harry’s (in)complete Guide to independent Bottlers of Single Malt Scotch Whiskies Ein Führer zu den Pullenquellen von Harald Kirsch Version 4.4g September 2008 The Guide INHALTSVERZEICHNIS INHALTSVERZEICHNIS Vorwort History Artikel I. Unabhängige Abfüller Abschnitt 1.01 Wm Cadenhead Abschnitt 1.02 Gordon & MacPhail Abschnitt 1.03 Signatory Abschnitt 1.04 Douglas Laing Abschnitt 1.05 James MacArthur Abschnitt 1.06 Hart Brothers Abschnitt 1.07 Vintage Malt Whisky Company Abschnitt 1.08 Ian...»

«Journal of Statistics Education, Volume 19, Number 2(2011) Enhancing Students’ Inferential Reasoning: From Hands-On To “Movies” Pip Arnold Cognition Education, New Zealand Maxine Pfannkuch Chris J. Wild Matt Regan Stephanie Budgett The University of Auckland, New Zealand Journal of Statistics Education Volume 19, Number 2(2011), www.amstat.org/publications/jse/v19n2/pfannkuch.pdf Copyright © 2011 by Pip Arnold, Maxine Pfannkuch, Chris J. Wild, Matt Regan and Stephanie Budgett all rights...»

«5 Interactivity as Media Reflection between Art and Science Monika Fleischmann and Wolfgang Strauss Fraunhofer Institute for Intelligent Analyze and Information Systems, MARS-Exploratory Media Lab / eCulture Factory, 53754 Sankt Augustin / 28199 Bremen, Germany {Monika.Fleischmann,Wolfgang.Strauss}@iais.fraunhofer.de http://www.iais.fraunhofer.de/mars.html, http://netzspannung.org/about/mars/projects/ Abstract. This article describes the evolution of interactivity in the media arts ranging from...»

«Robert Gary Žakula, MA “Pleased to be assisted even by the Devil Himself”: Recollection, Reprieve, and the U.S. Intervention of Grenada, 1983 “Oh God! Oh God! They have turned their guns on the People!,” screamed progressive Prime Minister Maurice Bishop, deposed leader of the Grenadian Revolution. On October 19, 1983, under the direction of Marxist-Leninist ideologues like Deputy Prime Minister Bernard Coard and General Hudson Austin, soldiers used automatic weapons and armored cars...»

<<  HOME   |    CONTACTS
2016 www.thesis.xlibx.info - Thesis, documentation, books

Materials of this site are available for review, all rights belong to their respective owners.
If you do not agree with the fact that your material is placed on this site, please, email us, we will within 1-2 business days delete him.