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100 results on '"W7-AS Team"'

51. The Saturation of Beta in W7-AS

Author

Zarnstorff, M., Weller, A., Fredrickson, E., Knauer, J., Monticello, D., Reiman, A., Zegenhagen, S., W7-AS Team, and NBI Group

Published
2005

54. Impurity transport in the W7-AS stellarator

Author

Burhenn, R., Baldzuhn, J., Brakel, R., Ehmler, H., Giannone, L., Grigull, P., Knauer, J., Krychowiak, M., Hirsch, M., Ida, K., Maaßberg, H., McCormick, K., Pasch, E., Thomsen, H., Weller, A., W7-AS Team, ECRH Group, and NI Group

Published
2003

59. The Wendelstein W7-AS High Density H-Mode, A Mode for the Future?

Author

McCormick, K., Burhenn, R., Grigull, P., Baldzuhn, J., Bäumel, S., Brakel, R., Ehmler, H., Gadelmeier, F., Giannone, L., Hirsch, M., Holzhauer, E., Jaenicke, R., Klose, S., Knauer, J., Pasch, E., Thomsen, H., Werner, A., W7-AS Team, ECRH Team, and NBI Team

Published
2003

62. Impact of Island Geometry on Island Divertor Performance

Author

Feng, Y., Sardei, F., König, R., Massberg, H., Pasch, E., Ramasubramanian, N., Thomsen, H., Wagner, G. J., Wenzel, U., Grigull, P., McCormick, K., Kisslinger, J., Reiter, D., Bindemann, R., Ehmler, J. H., Giannone, L., Igitkhanov, Y., and W7-AS Team

Published
2003

63. Essential Elements of the High Density H-Mode on W7-AS

Author

McCormick, K., Burhenn, R., Grigull, P., Baldzuhn, J., Baeumel, S., Brakel, R., Ehmler, H., Gadelmeier, F., Giannone, L., Hirsch, M., Holzhauer, E., Igitkhanov, Y., Jaenicke, R., Klose, S., Knauer, J., Pasch, E., Thomsen, H., Werner, A., W7-AS Team, ECRH-Team, and NBI-Team

Published
2003

66. The spatial structure of edge fluctuations in the Wendelstein 7-AS stellarator

Author

Bleuel, J., Endler, M., Niedermeyer, H., Schubert, M., Thomsen, H., and W7-AS Team

Subjects
Astrophysics::Earth and Planetary Astrophysics
Abstract

In the scrape-off layer and outermost edge of the Wendelstein 7-AS (W7-AS) stellarator, fluctuations of, mostly, ion saturation current Isat and floating potentialΦfl have been measured with high poloidal, radial (both 2–3mm) and temporal (0.5 μs) resolution. Parallel to the magnetic field, measurements with two probe tips on the same magnetic field line were performed. The basic spatio-temporal structure of the fluctuations is presented in terms of correlation functions and of wavenumber–frequency (kf) spectra. They are characterized by the parameters of a fit function to the correlation function, which describe the spatio-temporal structure. The behaviour of these fluctuation parameters under variations of the discharge parameters is investigated. A high correlation of the fluctuations parallel to the magnetic field is documented, and we analyse, which frequency components contribute to this high correlation. In our radially and poloidally resolving measurements, we find that the fluctuation structures are inclined in the poloidal–radial plane at our position of measurement. The consequences of such inclined structures for the interpretation of measurements with one-dimensional arrays are discussed, with an emphasis on the risk of an erroneous interpretation of purely radially resolving measurements. There is strong evidence that this inclination is due to the local magnetic shear in W7-AS in conjunction with the high correlation of the fluctuations parallel to the magnetic field. A further contribution to the inclination may originate from the radial shear of the poloidal velocity of the fluctuations in the plasma edge. The different consequences of magnetic shear and velocity shear for an inclination of the fluctuations in the poloidal–radial plane are discussed.

Published
2002

72. Island divertor experiments on the W7-AS stellarator

Author

Gadelmeier, F., Grigull, P., McCormick, K., Brakel, R., Burhenn, R., Ehmler, H., Feng, Y., Giannone, L., Hartmann, D., Hildebrandt, D., Jaenicke, R., Kisslinger, J., Klinger, T., Knauer, J., König, R., Naujoks, D., Pasch, E., Sardei, F., Wagner, F., Wenzel, U., Werner, A., and W7-AS Team

Published
2002

91. ICRF Experiments on the Stellarator W7-AS

Author

Hartmann, D., Cattanei, G., Lyon, J., Plyusnin, V., ICRF-Group, and W7-AS Team, Max Planck Institute for Plasma Physics, Max Planck Society

Published
1997

92. Plasma Radiation with Local Impurity Injection into a Magnetic Island of W7-AS Stellarator and the Separatix of AUG Tokamak

Author

Hildebrandt, D., Rohde, V., Brakel, R., Elsner, A., Fiedler, S., Fuchs, J., Giannone, L., Goerner, C., Grigull, P., Hacker, H., Herre, G., Kastelewicz, H., Napiontek, B., Naujoks, D., Neu, R., Suttrop, W., W7-AS Team, Max Planck Institute for Plasma Physics, Max Planck Society, and ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society

Published
1997

96. Inter-machine validation study of neoclassical transport modelling in medium- to high-density stellarator-heliotron plasmas

Author

A. Wakasa, Robert Wolf, Y. Feng, C. Suzuki, H. Yamada, M. W. Jakubowski, A. Lopez-Fraguas, H. Maaßberg, T. Morisaki, Yu. Turkin, J. Miyazawa, M. Yokoyama, K. Tanaka, J. Geiger, Yasuhiro Suzuki, Andreas Dinklage, W As Team, S. Murakami, M. Isaev, C. D. Beidler, E. Ascasibar, D. Lopez-Bruna, M. Yoshinuma, R. Seki, Katsumi Ida, J. Baldzuhn, José Luis Velasco, S. Satake, Juan Miguel Insúa Arévalo, David Gates, N. A. Pablant, S. Kobayashi, LHD Experimental Group, and W7-AS Team

Subjects
Physics, Nuclear and High Energy Physics, Work (thermodynamics), Ambipolar diffusion, Plasma, Condensed Matter Physics, Electron transport chain, law.invention, law, Electric field, Atomic physics, Scaling, Stellarator, Energy (signal processing)
Abstract

A comparative study of energy transport for medium- to high-density discharges in the stellarator-heliotrons TJ-II, W7-AS and LHD is carried out. The specific discharge parameters are chosen to apply a recently concluded benchmarking study of neoclassical (NC) transport coefficients (Beidler et al 2011 Nucl. Fusion 51 076001) to perform this validation study. In contrast to previous experiments at low densities for which electron transport was predominant (Yokoyama et al 2007 Nucl. Fusion 47 1213), the current discharges also exhibit significant ion energy transport. As it affects the energy transport in 3D devices, the ambipolar radial electric field is addressed as well. For the discharges described, ion-root conditions, i.e. a small negative radial electric field were found. The energy transport in the peripheral region cannot be explained by NC theory. Within a 'core region'(r/a < 1/2 ~ 2/3), the predicted NC energy fluxes comply with experimental findings for W7-AS. For TJ-II, compliance in the core region is found for the particle transport and the electron energy transport. For the specific LHD discharges, the core energy transport complied with NC theory except for the electron energy transport in the inward-shifted magnetic configuration. The NC radial electric field tends to agree with experimental results for all devices but is measured to be more negative in the core of both LHD and TJ-II. As a general observation, the energy confinement time approaches the gyro-Bohm-type confinement scaling ISS04 (Yamada et al 2005 Nucl. Fusion 45 1684). This work is carried out within the International Stellarator-Heliotron Profile Database (www.ipp.mpg.de/ISS and http://ishpdb.nifs.ac.jp/index.html).

Published
2013
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