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Reflectometry is currently used to monitor density fluctuations and turbulent correlation lengths in fusion plasmas. Various models have been used to interpret the experimental data and to determine the regimes of validity of the reflectometer fluctuation measurements. Heretofore, these models have not been validated by direct comparison with experiment. In this paper the first comparison between a controlled laboratory experiment and a one-dimensional numerical model is presented. It is found that the model is unable to predict the observed high degree of spatial localization and dependence on perturbation wave number. The implications of these disagreements are discussed, together with suggestions for their resolution. [ABSTRACT FROM AUTHOR]

Anomalous transport in fusion plasmas remains an enigma requiring explanation. A predictive capability is highly desirable if confinement enhancement regimes such as H mode or super shots are to be extrapolated to the next phase in development of the International Fusion program, epitomized, for example in ITER. Therefore, identification of the role that electrostatic turbulence plays in confinement is a critical issue requiring detailed experimental data capable of testing and challenging existing theoretical models. This article presents microturbulence measurements obtained on the DIII-D and TEXT tokamaks utilizing heterodyne, far-infrared collective scattering, and reflectometry techniques. The experimental systems are described on both machines and emphasis placed on results obtained during the L-H transition, ELM activity, and saturated ohmic operation where ion temperature gradient driven (ITGD) turbulence is theoretically predicted to exist. [ABSTRACT FROM AUTHOR]

Reflectometry is currently being used to investigate density fluctuations and turbulence in tokamak plasmas. However, there are unresolved questions about the spatial resolution and wave number sensitivity of this diagnostic method which impact the interpretation of the data. These questions are currently being addressed in a cylindrical, pulsed filament discharge plasma where ion acoustic waves (10-100 kHz) are launched toward the incident microwaves. Preliminary data supporting the spatially localized nature of reflectometry are presented. A computational model is also being developed to provide quantitative comparisons with experiment. [ABSTRACT FROM AUTHOR]