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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.

Summary form only given. A laser beam passing through plasma deflects due to a change in the line-integrated refractive index, which is attributed to an electron density gradient along the chord. By measuring the deflection angle of the laser beam, the electron density was obtained for an atmospheric pressure microwave-induced torch plasma generated in the ambient air. The diagnostic set-up, consisting of a low power He-Ne laser, a four channel segmented position-sensitive photodiode detector, and some relevant optical components, demands modest requirements of laser quality and optics alignments. The measured electron density was compared with that obtained by optical emission spectroscopy based on the measured Stark broadening width of the Balmer H-beta line emitted from the plasma. Both the multi channel deflection method and the optical emission method showed the same order of magnitude (~1015 cm-3) electron density values. Comparison of the detailed results will be presented.

The KSTAR (Korea Superconducting Tokamak Advanced Research) project is the major effort of the Korean National Fusion Program to design, construct, and operate a steady-state-capable superconducting tokamak. The project is led by Korea Basic Science Institute and shared by national laboratories, universities, and industry along with international collaboration. It is in the conceptual design phase and aims for the first plasma by mid 2002. The key design features of KSTAR are: major radius 1.8 m, minor radius 0.5 m, toroidal field 3.5 T, plasma current 2 MA, and flexible plasma shaping (elongation 2.0; triangularity 0.8; double-null poloidal divertor). Both the toroidal and the poloidal field magnets are superconducting coils. The device is configured to be initially capable of 20 s pulse operation and then to be upgraded for operation up to 300 s with non-inductive current drive. The auxiliary heating and current drive system consists of neutral beam, ICRF, lower hybrid, and ECRF. Deuterium operation is planned with a full radiation shielding.

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.

Theoretical and experimental studies of plasma diagnostic reflectometry have been undertaken as a collaborative research project between the Lawrence Livermore National Laboratory (LLNL) and the University of California Department of Applied Science Plasma Diagnostics Group under the auspices of the Laboratory Directed Research and Development Program at LLNL. Theoretical analyses have explored the basic principles of reflectometry to understand its limitations, to address specific gaps in the understanding of reflectometry measurements in laboratory experiments, and to explore extensions of reflectometry such as ultra-short-pulse reflectometry. The theory has supported basic laboratory reflectometry experiments where reflectometry measurements can be corroborated by independent diagnostic measurements.