-
16th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating, Sanya, China; 01/2010
-
[show abstract]
[hide abstract]
ABSTRACT: On WEGA stellarator electron Bernstein waves have been applied for plasma heating. The excitation of the electrostatic Bernstein waves was possible due to an efficient two-step OXB mode conversion process from electromagnetic waves. Overdense plasma operation was reached in argon and helium and, rather surprisingly, a supra-thermal electron component could be detected. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Contributions to Plasma Physics. 01/2010; 50(8):785-789.
-
21st Joint Russian-German Workshop on ECRH and Gyrotrons (STC-Meeting), Greifswald, Germany; 01/2009
-
AIP Conference Proceedings. 01/2009; 1187:441-448.
-
36th EPS Plasma Physics Conference, Sofia, Bulgaria; 01/2009
-
21st Joint Russian-German Workshop on ECRH and Gyrotrons (STC-Meeting), Greifswald, Germany; 01/2009
-
[show abstract]
[hide abstract]
ABSTRACT: Langmuir probes are used to study turbulent electrostatic fluctuations in the highly collisional plasmas of the WEGA stellarator. WEGA as a classical stellarator offers the opportunity to study fluctuations under various magnetic configurations. Two probe systems installed at WEGA give insight into the spatio-temporal structure of fluctuations. A poloidal array of 13 probes is used to study the properties in poloidal direction. Toroidally resolved measurements give insight into the three-dimensional structure of turbulence. To this end, a toroidally separated probe is placed on a field line intersecting the path of the poloidal array, as predicted by field line tracing calculations and verified experimentally by an electron gun. Probes are stationary biased to measure Isat and Φfl respectively. Fourier- and correlation-analysis techniques are applied to the data. The paper gives a survey of the general characteristics of fluctuations in WEGA. The scaling of turbulent structures is studied by varying the ion mass and the magnetic field strength over a wide range and is found to depend on the drift parameter ρs. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Beiträge aus der Plasmaphysik 06/2008; 48(5‐7):467 - 472.
-
M. Otte,
D. Andruczyk,
E. Holzhauer,
J. Howard,
R. König,
L. Krupnik,
H. P. Laqua,
O. Lischtschenko, S. Marsen,
J. Schacht,
J. Urban,
Y. Y. Podoba,
J. Preinhalter,
F. Wagner,
G. B. Warr,
A. Zhezhera
[show abstract]
[hide abstract]
ABSTRACT: In this article an overview is given on results from magnetic flux surface measurements, applied ECR heating scenarios for 2.45 GHz and 28 GHz, fluctuation and transport studies and plasma edge biasing experiments performed in the WEGA stellarator. Examples for the development of new diagnostics and the machine control system are given that will be used at Wendelstein 7-X stellarator, which is currently under construction in Greifswald.
AIP Conference Proceedings. 03/2008; 993(1):3-10.
-
[show abstract]
[hide abstract]
ABSTRACT: The ordinary-extraordinary-Bernstein-mode conversion process for overdense plasma heating with electron-Bernstein waves is demonstrated in the WEGA stellarator at low magnetic field (approximately 50 mT) at 2.45 GHz. For the first time the conversion from an O wave to an X wave is clearly demonstrated by probe measurements of amplitude and phase of the wave field in the conversion region and supported by two-dimensional full-wave calculations. The propagation and resonant absorption of the Bernstein wave is measured in fast power modulation experiments.
Physical Review Letters 07/2007; 98(25):255003. · 7.37 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: At the WEGA, which is a classical five period l=2 stellarator with a major radius of 0.72m and an aspect ratio of 6, electron Bernstein wave (EBW) heating by OXB-mode conversion was established for a frequency of 2.45GHz. Typical electron densities of 10^18 m−3, which is 12 times the cut-off density, with an electron temperature of <=20eV were achieved for 30s operation with an ECRH power of up to 26kW. The low temperature plasma allows the investigation both, the EBW power deposition and current drive profiles by probes. The first was performed by high frequency (12kHz) power modulation and coherent detection of the generated heat waves with Langmuir probes. The second was measured with a B -loop. The total EBW current was of up to 45A and the related normalised current drive efficiency was 0.48. The EBW propagation is strongly sensitive on the magnetic configuration. Both, the variation of rB along B and the shear can be changed individually, which makes WEGA an unique test bed for EBW propagation. As a result of the shear variation an EBW current reversal was found. The results were modelled by 3D ray-tracing calculations for the different magnetic configurations.
49th Annual Meeting of the Division of Plasma Physics, Orlando, FL, USA; 01/2007
-
34th Annual European Physical Society Conference on Controlled Fusion and Plasma Physics, Warsaw, Poland; 01/2007
-
Y. Y. Podoba,
H. P. Laqua,
G. B. Warr,
M. Schubert,
M. Otte, S. Marsen,
F. Wagner,
D. Andruczyk,
E. Holzhauer,
J. Preinhaelter,
J. Urban
Stellarator News. 01/2007;
-
-
-
Mateev, M.; Benova, E.: 36th European Physical Society Conference on Plasma Physics. Contributed Papers, European Physical Society (2009).
-
-
-
-
-
