Results 231 to 240 of about 723,509 (268)

A new model of the L–H transition in tokamaks*

Nuclear Fusion, 2012
Abstract A new model of the L–H transition in tokamaks is proposed, based on the criterion that the transition occurs when plasma turbulence and shear Alfvén waves compete in the vicinity of the last-closed flux surface. The model is used to predict the scaling of the H-mode access power, P L–H, with magnetic and plasma
W. Fundamenski, F. Militello, D. Moulton, D.C. McDonald   +3 more
openaire   +1 more source

A model for the L-H mode transition in Tokamaks

Nuclear Fusion, 1992
The ion orbit loss flux at the plasma edge is calculated, including the squeezing factor. A bifurcation solution is found by balancing the ion loss flux and the anomalous electron flux. At a certain level of anomalous electron flux, the plasma poloidal rotation increases with ion temperature.
Zhongtian Wang, G. Le Clair
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
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`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

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

L–H transition in tokamak plasmas: 1.5-D simulations

Journal of Nuclear Materials, 1999
Abstract Time-dependent theoretical models have been implemented in a 1.5-D transport code to describe the operational boundaries (L–H transition, ballooning limit) in terms of edge parameters. The width of the H-mode transport barrier (F. Wagner et al., Phys. Rev. Lett.
Janeschitz, G., Pacher, G., Igitkhanov, Y., Pacher, H., Pinches, S., Pogutse, O., Sugihara, M.   +6 more
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

Probabilistic theory of the L-H transition and causality

Plasma Physics and Controlled Fusion
Abstract The low-to-high confinement (L-H) transition is critical for understanding plasma bifurcations and self-organization in high-temperature fusion plasmas. This paper reports a probabilistic theory of the L-H transition, in particular, a probability density function of power threshold Qc for the first time ...
Eun-jin Kim, Abhiram Anand Thiruthummal
openaire   +1 more source

Warm-ion drift Alfvén turbulence and the L-H transition

Plasma Physics and Controlled Fusion, 1998
Computations of fluid drift turbulence treating ions and electrons on equal footing, including both temperatures, are conducted in a model toroidal geometry. The resulting `ion mixing mode' turbulence bears features of both electron drift-Alfven and ion temperature gradient turbulence, and nonlinear sensitivity to the relative strengths of the density ...
openaire   +2 more sources