L-H confinement mode dynamics in three-dimensional state space

Abstract

DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise dces not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. AbstractThe dynamical model for the L-H confinement mode transitions consisting of three ordinary differential equations (3-ODE model) for the essential state variables is proposed.The model is derived from the energy balance equations for the resistive pressure-gradient-driven turbulence and describes temporal evolutions of three characteristic variables (u. k. f) the potential energy contained in the pressure gradient, the turbulent kinetic energy and the shear flow energy. The energy input to the peripheral plasma region is included as an external control parameter in the model. The model equations have stationary solutions corresponding to the L and H modes. We obtain the L to H and H to L transition with the energy input parameter cha_ed. The type of the L.H transition, whether a first-order or second-order transition, is shown to be determined by the shear flow damping coefficient. We also find the pstameter region in which the H merle stationary, solution becomes unstable and bifurcates to the iim,t cycle which shows p,_riodic oscillations characteristic of the ELM confinement state I_STRIBUTION OF THIS DOCUMENT 18 UNLIM|TF...J_

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