Results 261 to 270 of about 4,141,636 (301)

Multi-shell transport model for L-H transition

Physics of Plasmas, 2017
A coupled model of transport, turbulence, and mesoscale flows is proposed, including turbulence spreading. The model consists of transport equations for plasma density and pressure coupled to a shell model of drift wave turbulence, which incorporates coupling to mesoscale flows via disparate scale interactions.
Berionni, Vincent, Morel, Pierre, Gürcan, Özgür   +2 more
openaire   +2 more sources

`Hidden' variables affecting the L-H transition

Plasma Physics and Controlled Fusion, 1998
Recent progress in experimental investigations, related to the determinant variables of the L-H transition, is reviewed in this paper. In particular, it is put forward that the `wall effect', which often produces spurious contributions to the various parametric dependences of the H-mode threshold power, may be an embodiment of the atomic processes ...
openaire   +1 more source

Ion collisionality and L–H transition in tokamaks

Physics of Fluids B: Plasma Physics, 1993
When the previous H-mode theory [K. C. Shaing and E. C. Crume, Jr., Phys. Rev. Lett. 63, 2369 (1989)] is extended to include a bi-Maxwellian ion distribution with both cold and hot ion components to model the effects of the non-Maxwellian distribution, the collisionality of the cold ions ν*ic becomes an irrelevant bifurcation parameter, as it is for ...
K. C. Shaing, P. J. Christenson
openaire   +1 more source

Edge ion parameters at the L–H transition on JET

Plasma Physics and Controlled Fusion, 2003
L–H transition experiments have recently been performed on JET to characterize the local edge ion parameters. Evidence of a threshold in the edge ion temperature to access the H-mode is presented and comparisons are made with edge electron temperature. These results provide the first scaling of pedestal ion temperature on JET.
Andrew, Y., Hawkes, N., O'Mullane, M., Sartori, R., Beurskens, M., Coffey, I., Joffrin, E., Loarte, A., McDonald, D., Prentice, R., Saibene, G., Suttrop, W., Zastrow, K., ASDEX Upgrade Team   +13 more
openaire   +2 more sources

Critical assessment of ion loss mechanisms for L-H transition

Plasma Physics and Controlled Fusion, 2000
Monte Carlo ion simulation of the tokamak edge, based on the neoclassical radial current balance, shows that a considerable E×B shear, relevant for turbulence suppression, can be generated by orbit losses. In contrast to earlier orbit loss models, no spontaneous bifurcation of the radial electric field Er is found. However, a bifurcation and a solitary
Kiviniemi, T., Heikkinen, J., Peeters, A., Kurki-Suonio, T., Sipilä, S.   +4 more
openaire   +3 more sources

Physics of GAM-initiated L–H transition in a tokamak

Plasma Physics and Controlled Fusion, 2016
Based on experimental observations using the TUMAN-3M and FT-2 tokamaks, and the results of gyrokinetic modeling of the interplay between turbulence and the geodesic acoustic mode (GAM) in these installations, a simple model is proposed for the analysis of the conditions required for L–H transition triggering by a burst of radial electric field ...
L G Askinazi, A A Belokurov, V V Bulanin, A D Gurchenko, E Z Gusakov, T P Kiviniemi, S V Lebedev, V A Kornev, T Korpilo, S V Krikunov, S Leerink, M Machielsen, P Niskala, A V Petrov, A S Tukachinsky, A Yu Yashin, N A Zhubr   +16 more
openaire   +1 more source

Theory of the L-H transition

1994
The theory of the L-H transition in tokamaks is discussed. A transport bifurcation model is presented, which predicts reasonably well several properties of the L-H transition in the DIII-D tokamak, including the evolution in time of the density and temperature profiles.
openaire   +2 more sources

Neoclassical transport and poloidal rotation at the L-H transition

Physica Scripta, 1995
We address the question of establishing if, and under what physical and boundary conditions, the neoclassical transport is quantitatively capable of establishing high gradients in a narrow layer at the edge of an auxiliary heated tokamak plasma, and of driving poloidal rotation in the absence of external momentum input and vanishing parallel viscous ...
G Gervasini, E Lazzaro, E Minardi
openaire   +2 more sources

Electron density evolution after L–H transitions and the L–H/H–L cycle in ASDEX Upgrade

Nuclear Fusion, 2012
Abstract The development of the electron density profile and its dependences after the L–H transition have been investigated. Only electron cyclotron resonance heated H-modes have been analysed to exclude core particle fuelling. While the density gradient in the edge transport barrier increases significantly after the L–H transition, the
Willensdorfer, M., Wolfrum, E., Scarabosio, A., Aumayr, F., Fischer, R., Kurzan, B., McDermott, R., Mlynek, A., Nold, B., Rathgeber, S., Rohde, V., Ryter, F., Sauter, P., Viezzer, E.   +13 more
openaire   +2 more sources

Transport modelling of L - H transition and barrier formation

Plasma Physics and Controlled Fusion, 1996
The mechanism of L - H transition and transport barrier formation is studied by the use of a one-dimensional transport code including plasma rotation and radial electric field. Particle transport simulation with a fixed temperature profile has indicated that the density profile is quite sensitive to the edge plasma temperature.
A Fukuyama, Y Fuji, S-I Itoh, M Yagi, K Itoh   +4 more
openaire   +1 more source