In this study, high spatial resolution Doppler backscattering measurements in JET have enabled new insights into the development of the edge Er. We observe fine-scale spatial structures in the edge Er well with a wave number kr[rho]i ≈ 0.4-0.8, consistent with stationary zonal flows, the characteristics of which vary with density. The zonal flow amplitude and wavelength both decrease with local collisionality, such that the zonal flow E x B shear increases. Above the minimum of the L-H transition power threshold dependence on density, the zonal flows are present during L mode and disappear following the H-mode transition, while below the minimum they are reduced below measurable amplitude during L mode, before the L-H transition.

Aspects of the macroscopic phenomenology of tokamak plasmas - relaxation, transport, and flow generation - are analyzed in the context of phase space dynamics. Particular problems of interest are: i) fluctuation entropy evolution with turbulence driven flows and its application to flow generation by heat flux driven turbulence, and ii) dynamical coupling between phase space structures and zonal flows and its implication for macroscopic relaxation and transport. In chapter 2, intrinsic toroidal rotation drive by heat flux driven turbulence in tokamak is analyzed based on phase space dynamics. In particular, the dynamics of fluctuation entropy with turbulence driven flows is formulated. The entropy budget is utilized to quantify tokamaks as a heat engine system, where heat flux is converted to macroscopic flows. Efficiency of the flow generation process is defined as the ratio of entropy destruction via flow generation to entropy production via heat input. Comparison of the results to experimental scaling is discussed as well. In chapter 3, dynamics of a single phase space structure (drift hole) is discussed for a strongly magnetized 3D plasma. The drift hole is shown to be dynamically coupled to zonal flows by polarization charge scattering. The coupled dynamics of the drift hole and zonal flow is formulated based on momentum budget. As an application, a bound on the self-bound drift hole potential amplitude is derived. The results show that zonal flow damping appears as a controlling parameter. In chapter 4, dynamics of both a single structure and multi-structures in phase space are discussed for a relevant system, i.e. trapped ion driven ion temperature gradient turbulence. The structures are dynamically coupled to zonal flows, since they must scatter polarization charge to satisfy the quasi-neutrality. The coupled evolution of the structures and flows is formulated as a momentum theorem. An implication for transport process is discussed as well. The transport flux is prescribed by dynamical friction exerted by structures on flows. The dynamical friction exerted by zonal flow is a novel effect and reduces transport by algebraically competing against other fluxes, such as a quasilinear diffusive flux.

Mexico City, Mexico, 5 - 9 December 2005

Here we describe recent measurements of the 2-D motion of turbulence in the edge and scrape-off layer (SOL) of the Alcator C-Mod tokamak. This data was taken using the outer midplane gas puff imaging (GPI) camera, which views a 6 cm radial by 6 cm poloidal region near the separatrix just below the outer midplane [1]. The data were taken in Ohmic or RF heated L-mode plasmas at 400,000 frames/sec for ≈50 msec/shot using a Phantom 710 camera in a 64 x 64 pixel format. The resulting 2-D vs. time movies [2] can resolve the structure and motion of the turbulence on a spatial scale covering 0.3-6 cm. The images were analyzed using either a 2-D cross-correlation code (Sec. 2) or a 2-D blob tracking code (Sec. 3).