8 results on '"Siller, G."'
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2. Density limit investigations on ASDEX
- Author
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Stabler, A, primary, McCormick, K, additional, Mertens, V, additional, Muller, E.R, additional, Neuhauser, J, additional, Niedermeyer, H, additional, Steuer, K.-H, additional, Zohm, H, additional, Dollinger, F, additional, Eberhagen, A, additional, Fussmann, G, additional, Gehre, O, additional, Gernhardt, J, additional, Hartinger, T, additional, Hofmann, J.V, additional, Kakoulidis, E, additional, Kaufmann, M, additional, Kyriakakis, G, additional, Lang, R.S, additional, Murmann, H.D, additional, Poschenrieder, W, additional, Ryter, F, additional, Sandmann, W, additional, Schneider, U, additional, Siller, G, additional, Soldner, F.X, additional, Tsois, N, additional, Vollmer, O, additional, and Wagner, F, additional
- Published
- 1992
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3. Experimental evidence for neoclassical ion transport effects in the H-transition of ASDEX
- Author
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Wagner, F., Bartiromo, R., Becker, G., Bosch, H.S., Eberhagen, A., Fussmann, G., Gehre, O., Gernhardt, J., Gierke, G.V., Clock, E., Gruber, O., Haas, G., Janeschitz, G., Karger, F., Keilhacker, M., Kislyakov, A., Klüber, O., Kornherr, M., Kotzé, P.B., Lackner, K., Lenoci, M., Lisitano, G., Mahdavi, A., Mayer, H.-M., McCormick, K., Meisel, D., Mertens, V., Müller, E.R., Murmann, H., Niedermeyer, H., Poschenrieder, W., Rapp, H., Ryter, F., Roth, J., Schneider, F., Siller, G., Smeulders, P., Söldner, F., Speth, E., Steinmetz, K., Steuer, K.-H., and Vollmer, O.
- Abstract
The H-mode develops in conditions of low and controlled recycling. The electron and ion collisionality parameters at the plasma periphery are close to, but above, one in the L-phase and drop below one in the H-phase. The realization of the H-phase is easier in the single-null than in the double-null configuration which has higher power and density thresholds. The increased H-mode accessibility of the single-null configuration requires the ion grad B-drift direction to be towards the stagnation point. The experimental observations are in agreement with a recent theory of the H-transition by Hinton.
- Published
- 1985
- Full Text
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4. Confinement and stability in ASDEX discharges close to the beta limit
- Author
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Becker, G., Gierke, G.V., Keilhacker, M., Bernhardi, K., Ditte, U., Eberhagen, A., Fussmann, G., Gehre, O., Gernhardt, J., Glock, E., Gruber, O., Haas, G., Hesse, M., Janeschitz, G., Karger, F., Kerner, W., Klober, O., Kornherr, M., Lackner, K., Lisitano, G., Mayer, H.M., Mccormick, K., Meisel, D., Mertens, V., Moller, E.R., Murmann, H., Niedermeyer, H., Poschenrieder, W., Rapp, H., Ryter, F., Schneider, F., Siller, G., Smeulders, P., Söldner, F., Speth, E., Steuer, K.-H., and Vollmer, O.
- Abstract
The highest ?-values derived from diamagnetic flux measurements in H-discharges are found to be close to the ?-limit due to kink and ideal ballooning modes. Both energy and particle confinement are degraded in these discharges and do not recover during the injection period. The energy confinement time decreases by a typical factor of two, the electron thermal diffusivity being correspondingly enhanced. Electron heat conduction is again found to be the dominant energy loss channel. The degradation of confinement close to the ideal-MHD limit suggests that kink and ballooning instabilities occur and are responsible for the enhanced transport. This conclusion is supported by the correlation with the pressure profile and by the result that global and local transport do not change in a reference discharge which is stable against ideal-MHD modes.
- Published
- 1985
- Full Text
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5. Heating and confinement in the ion cyclotron range of frequencies on the divertor tokamak ASDEX
- Author
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Steinmetz, K., Niedermeyer, H., Noterdaeme, J.-M., Wagner, F., Wesner, F., Bäumler, J., Becker, G., Becker, W., Bosch, H.S., Brambilla, M., Braun, F., Bracken, H., Dodel, G., Eberhagen, A., Fritsch, R., Fussmann, G., Gehre, O., Gernhardt, J., von Gierke, G., Glock, E., Gruber, O., Haas, G., Hofmann, J., Hofmeister, F., Holzhauer, E., Izvozchikov, A.B., Janeschitz, G., Karger, F., Keilhacker, M., Kislyakov, A., Klüber, O., Kornherr, M., Kotze, P.B., Lackner, K., Lisitano, G., Van Mark, E., Mast, K.F., Mayer, H.-M., McCormick, K., Meisel, D., Mertens, V., Müller, E.R., Murmann, H.D., Neuhauser, J., Pietrzyk, Z.A., Poschenrieder, W., Puri, S., Rapp, H., Roth, J., Rudyj, A., Ryter, F., Schneider, F., Setzensack, C., Siller, G., Smeulders, P., Söll, M., Speth, E., Söldner, F.X., Stäbler, A., Steuer, K.-H., Vollmer, O., Wedler, H., and Zasche, D.
- Abstract
The paper summarizes the experiments performed with ion cyclotron resonance heating (ICRH) on ASDEX, from November 1984 until March 1986; the most interesting results are reported and discussed in detail. Heating and confinement studies using the hydrogen second harmonic scheme and the hydrogen minority scheme (PIC< 2.6 MW, tIC< 1.5 s) show a typical L-mode behaviour, i.e. a power dependent confinement degradation, which is rather similar to that found with neutral beam injection (NBI) heating. ICRH is accompanied by a slightly improved particle and energy confinement compared with that of NBI; this is also true for a combined ICRH + NBI scheme, up to Ptot? 4.5 MW, absorbed in the plasma. Particular efforts have been devoted to investigations of the second harmonic regime in H/D plasmas with nH/ne? 0.1 - 1, with a view to heating mixtures in reactor relevant plasmas. The achievement of H-mode transitions with ICRH alone in the hydrogen minority scheme at an absorbed RF power of about 1.1 MW supports the assumption of common confinement properties in auxiliary heated tokamaks, since they appear to be widely independent of the additional heating method. ICRH specific impurity problems, such as the strong release of iron from the vessel walls, have been overcome by applying extensive in situ wall carbonization. The mechanisms responsible for impurity generation have partly been identified and analysed; however, the problem still remains to be solved. Impurities preferentially released from the ICRH antenna do not pose problems.
- Published
- 1989
- Full Text
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6. Retention of gaseous and target produced impurities in the ASDEX divertor chamber
- Author
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Janeschitz, G., Fussmann, G., Kotzé, P.B., Mahdavi, A., Roth, J., Taglauer, E., Bartiromo, R., Becker, G., Bosch, H.S., Eberhagen, A., Gehre, O., Gernhardt, J., Von Gierke, G., Glock, E., Gruber, O., Haas, C., Karger, F., Keilhacker, M., Kislyakov, A., Klüber, O., Kornherr, M., Lenoci, M., Lisitano, G., Mayer, H.-M., McCormick, K., Meisel, D., Mertens, V., Müller, E.R., Murmann, H., Niedermeyer, H., Poschenrieder, W., Rapp, H., Ryter, F., Schneider, F., Siller, G., Smeulders, P., Söldner, F.X., Speth, E., Steinmetz, K., Steuer, K.-H., Vollmer, O., Wagner, F., and Wesner, F.
- Abstract
This letter reports on two experiments undertaken to evaluate the retention of gaseous and target produced impurities in the ASDEX divertor. The retention for gaseous impurities was determined by puffing Ar into the main chamber and simulating the time behaviour of the Ar XVI line intensity with a time dependent impurity transport code including a simple divertor model. During Ohmic heating a factor of 3 and 4.5 enhancement of impurity retention if found relative to the vacuum time constant (90 ms) of the divertor chamber, for ne= 2 × 1013cm?3and ne= 3.5 × 1013cm?3, respectively, while a drastic breakdown of the retention occurs during high power NI heating. - To deduce the retention of impurities generated at the divertor plates, a segment (3.5%) of the plates was covered with copper, a metal previously not used in ASDEX. By measuring the Cu influx at the target plates and the line intensity of the Cu XX line (11.38 Å) in the core plasma and by using the transport code, it is found that during NI heating (ne? 2 × 1013cm?3) Cu atoms originating from the target plates have a ? 3.5 times higher probability to penetrate into the core plasma than if they had when originating from the main chamber walls.
- Published
- 1986
- Full Text
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7. Experimental study of non-thermal electron generation by lower hybrid waves in the ASDEX tokamak
- Author
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Bartiromo, R., Hesse, M., Söldner, F.X., Burhenn, R., Fussmann, G., Leuterer, F., Murmann, H., Eckhartt, D., Eberhagen, A., Giuliana, A., Becker, G., Bosch, H.S., Brambilla, M., Brocken, H., Derfler, H., Gehre, O., Gernhardt, J., von Gierke, G., Glock, E., Gruber, O., Haas, G., Janeschitz, G., Karger, F., Keilhacker, M., Klüber, O., Kornherr, M., Kotzé, P.B., Lenoci, M., Lisitano, G., Mayer, H.M., McCormick, K., Meisel, D., Mertens, V., Müller, E.R., Münich, M., Niedermeyer, H., Poschenrieder, W., Rapp, H., Röhr, H., Ruhs, N., Ryter, F., Schmitter, K.H., Schneider, F., Siller, G., Smeulders, P., Steuer, K.-H., Vien, T., Vlases, G., Wagner, F., von Woyna, F., and Zouhar, M.
- Abstract
High resolution X-ray spectroscopy was used to evaluate the fractional population of non-thermal electrons generated when electromagnetic waves in the lower hybrid frequency range are launched in the ASDEX tokamak. In complete current drive discharges a typical value of 1% is found for this parameter, in agreement with a theoretical estimate. Furthermore, it is shown that the toroidal electric field is very effective in enhancing tail electron generation, as confimed by ? measurements, and that the wave penetration to the plasma centre is inhibited when interaction of the waves with plasma ions is the dominant damping mechanism.
- Published
- 1986
- Full Text
- View/download PDF
8. Transport simulation of neutral-beam-heated ASDEX plasma in the L and H regimes
- Author
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Becker, G., primary, Campbell, D., additional, Eberhagen, A., additional, Gehre, O., additional, Gernhardt, J., additional, Lackner, K., additional, Mayer, H.-M., additional, Meisel, D., additional, Murmann, H., additional, Rapp, H., additional, Stäbler, A., additional, Wagner, F., additional, Behringer, K., additional, Fussmann, G., additional, von Gierke, G., additional, Glock, E., additional, Haas, G., additional, Karger, F., additional, Keilhacker, M., additional, Klüber, O., additional, Kornherr, M., additional, Lisitano, G., additional, Lister, G.G., additional, Müller, E.R., additional, Niedermeyer, H., additional, Poschenrieder, W., additional, Röhr, H., additional, Schneider, F., additional, Siller, G., additional, Smeulders, P., additional, Söldner, F., additional, Speth, E., additional, Steinmetz, K., additional, Steuer, K.-H., additional, Szymanski, Z., additional, Venus, G., additional, and Vollmer, O., additional
- Published
- 1983
- Full Text
- View/download PDF
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