Plenarvorträge - DPG-Tagungen

Plasmaphysik Dienstag
Mode (“H-mode”) regime for its target of Q=10 (ratio of fusion power
and external heating power). Helium ash and impurity exhaust are mainly
due to an intermittent edge localized MHD instability (“ELMs”) which
can also lead to large momentary heat fluxes that are a challenge for the
power handling capability of plasma facing components. “Quiescent Hmode”
(QH-mode) is a new H-mode regime without ELMs, obtained in
several tokamaks (DIII-D, ASDEX Upgrade, JET, JT-60U) with neutral
beam injection in direction opposite to the plasma current, which causes
a strong population of beam ions outside of the core plasma, and a significant
radial current from lost ions. The impurity content in the plasma
is higher than in normal injection direction but similar in ELMy and
QH-mode phases with reversed injection, indicating comparable levels of
particle transport across the transport barrier. This may be connected
with benign continuous MHD activity observed instead of ELMs. The
edge pressure can be higher than in ELMing H-mode plasmas indicating
improved MHD stability. The physics of QH-mode and its extrapolation
to a reactor-size plasma are discussed.
Fachvortrag P 5.5 Di 12:10 Hörsaal D
A “Flight simulator” for ASDEX Upgrade plasmas — •L.
Höllt, W. Suttrop, L. Giannone, C. Sihler, A. C. C. Sips, D.
Zasche, and AUG Team — Max-Planck-Institut für Plasmaphysik,
EURATOM Association, D-85740 Garching
P 6 Staubige Plasmen I
A model for plasma discharges in the ASDEX Upgrade tokamak was
developed. It predicts the time evolution of the plasma density, stored
energy and flux consumtion. The model is based on empirical scalings
for confinement, power threshold for the transition to high-confinement
mode (“H-mode”), unfuelled density in H-mode and uses the request
waveform definitions as they are prepared for actual tokamak operation,
e.g. poloidal field coil currents, plasma current and deuterium gas influx.
The restriction to 0D global scalings used and no equilibrium calculation
done makes it a rather simple model which is fast to evaluate,
nevertheless the predictions show good agreement with experimental results.
Typical applications include consistency checks of tokamak discharges
before they are deployed for execution and empirical verification
of global scalings with measured time-dependent signals. The implementation
uses open-source tools (Scilab/Scicos - www.scilab.org, and MD-
Splus - www.mdsplus.org) which allow easy porting to other tokamaks
and different computer platforms.
Zeit: Dienstag 10:30–12:30 Raum: Hörsaal H
Fachvortrag P 6.3 Di 11:30 Hörsaal H
Large Area Mass Analyzer — •Mikhail Rashev — Max-Planck
institut für Kernphysik Saupfercheckweg 1 69117 Heidelberg
The presentation deals with the time-of-flight spectrometer for the
chemical analysis of cosmic dust particles in space. The instrument is
based upon impact ionization. This method is a high reliable method
for in-situ dust detection and is well established. Those instruments
flew on-board Helios, Galileo and are still in operation on-board Ulysses
and Cassini-Huygens missions. The new instrument has a large sensitive
area of 0.1m2 to have significant number of measurements far from dust
sources and a mass resolution M
∆M
≥ 100 which covers the most relevant
elements expected in cosmic dust. The instrument has a reflectron configuration
which allows to increase the mass resolution. Most of the ions
released during the impact are collected to the detector. The ion detector
consist of a large area ion-to-electron converter, an electron reflectron
and a microchannel plate detector.
Fachvortrag P 6.4 Di 11:50 Hörsaal H
Bestimmung der Ionenreibungskraft: Vergleich von Theorie und
Experiment — •Markus Hirt, Dietmar Block und Alexander
Piel — IEAP, AG Plasmadynamik, Christian-Albrechts-Universität,
24098 Kiel
Die Reibungskraft, die strömende Ionen auf ein Mikropartikel ausüben,
spielt eine wesentliche Rolle bei einer Vielzahl von dynamischen Effekten
in einem komplexen Plasma, z.B. bei der Entstehung des ’void’-Phänomens.
Für eine quantitative Beschreibung dieser Phänomene ist daher ein
grundlegendes Verständnis der Ionenreibungskraft notwendig. Es existieren
eine Vielzahl theoretischer Modelle [Barnes et al. 1992, Kilgore et al.
P 8 Plasma-Wand-Wechselwirkung I
1993, Khrapak et al. 2002, 2003], die sich im Wesentlichen durch die Wahl
der Abschirmlänge unterscheiden. Eine experimentelle Untersuchung der
Ionenreibungskraft ist daher notwendig, um die existierenden Modelle
kritisch prüfen zu können. In dem Experiment Dodo wurde die Ionenreibungskraft
an frei fallenden Mikropartikel in einem stossfreien Plasma
bestimmt. Sowohl bei hohen Ionenenergien (Ei = 3...45 eV) als auch
bei kleinen Energien (Ei ≈ 50 meV) können quantitative Vergleiche zwischen
Theorie und Experiment vorgenommen werden. Im Rahmen dieses
Vortrages werden die Ergebnisse der Untersuchungen vorgestellt und die
Anwendbarkeit der theoretischen Modelle diskutiert. Details des experimentellen
Aufbaus werden in einem Posterbeitrag dargestellt.
Fachvortrag P 6.5 Di 12:10 Hörsaal H
Dreidimensional ausgedehnte Staubwolken in einer kapazitiv
gekoppelten Hochfrequenzentladung — •Oliver Arp, Markus
Klindworth und Alexander Piel — Institut für Experimentelle und
Angewandte Physik der Christian-Albrechts-Universität zu Kiel, 24098
Kiel
Die Untersuchung von staubigen Plasmen in kapazitiv gekoppelten HF-
Entladungen ist im Labor häufig aufgrund der herrschenden Gravitationskraft
auf großflächige Staubverteilungen von geringer vertikaler Ausdehnung
in der unteren Randschicht der Entladung beschränkt.
Es ist jedoch unter bestimmten Bedingungen möglich, kleine konvexe
Staubwolken in der Entladung einzufangen. Im Gegensatz zu Experimenten
unter Mikrogravitationsbedingungen sind die hier untersuchten
dreidimensionalen Staubverteilungen nicht von dem ”Void”-Phänomen
betroffen. Die Struktur dieser Wolken wird mit Hilfe von Verfahren zur
dreidimensionalen Erfassung der Partikelpositionen analysiert.
Zeit: Dienstag 14:45–17:05 Raum: Hörsaal D
Fachvortrag P 8.2 Di 15:45 Hörsaal D
First results of the impact of the Dynamic Ergodic Divertor
DED on transport in the plasma edge of TEXTOR measured by
thermal atomic beam diagnostics — •Oliver Schmitz, Marcin
Jakubowski, Michael Lehnen, Ulrich Samm, Bernd Schweer,
and Bernhard Unterberg — Institut für Plasmaphysik, FZ Jülich,
Trilateral Euregio Cluster, EURATOM-Assoziation, 52425 Jülich, Germany
The Dynamic Ergodic Divertor (DED) has recently been installed in
the TEXTOR Tokamak. It consists of 16 magnetic coils wound helically
around inside the torus at the High Field Side (HFS). A magnetic field
pertubation resonant with different m and n mode numbers is induced to
the plasma edge of TEXTOR. An ergodic zone (long connection lengths
of the magnetic field to the wall) and a laminar zone (short connection
lengths) are formed. In this laminar zone the DED forms a helical divertor.
To investigate the impact of these pertubations on transport we
use beam emission spectroscopy of thermal atomic beams. The electron
density ne is measured by a thermal Lithium beam at the Low Field Side
(LFS). With the Helium beam diagnostics installed both at the LFS and
at the HFS of TEXTOR one can measure ne and the electron temperature
Te simultaneously.
In this contribution first indications of the effects of the DED on edge
transport, e.g. changes in the ne decay length, are presented. These find-