DOE OSTI2011
Briefly stated, the goal of this combined experiment/theory milestone was to improve our knowledge of the physics processes that control the H-mode pedestal by applying models of these mechanisms to experimental data. A concerted and coordinated effort of experimental, theory and modeling activities has examined several physics mechanisms of interest, and has met the goals of the milestone. A few noteworthy results will be noted here. The activity has applied peeling-ballooning theory to all three machines, and increased confidence that the theory predicts the ultimate limits to pedestal height in an ELMing plasma. The activity has expanded the range of conditions for testing of the EPED model, and increased confidence in the ability of the model to compute the pedestal pressure height in medium aspect ratio tokamaks. Kinetic neoclassical models have been used to verify that an important analytic model for the pedestal bootstrap current has good accuracy in many regimes of interest but needs correction at high collisionality. A benchmarking effort between electromagnetic gyrokinetic codes has provided increased understanding of how to use these codes in the pedestal, and has laid the groundwork for using these codes to study linear stability of gyrokinetic modes in and on top of the pedestal. Comparisons of data and models have led to successful simulations of a quasi-coherent mode in C-Mod and to the tentative identification of a high frequency mode in DIII-D. A kinetic neoclassical model qualitatively agrees with some features of pedestal density profiles. A paleoclassical transport model quantitatively predicts some features of the electron temperature profiles in NSTX and DIII-D. The milestone activity also laid the groundwork for future advancements in understanding and predicting the pedestal. All three machines obtained a wealth of pedestal data under a wide variety of operating conditions. Some of these data have been analyzed already, and the analysis and comparison with models will provide important results over the next year or two. Many codes were improved in significant ways in order to model data under the challenging conditions of the pedestal. In addition, new and strengthened collaborations were established between experiment, modeling and theory, and these efforts include providing mechanisms for sharing experimental data. All of these efforts will continue to provide major benefits to future pedestal studies. Much of the experimental and modeling work performed to support this milestone is reported in detail in the research contributions to this report. Here, a summary of results from the various contributions, as they pertain to several proposed pedestal physics processes, is discussed here. Emphasis is placed on mechanisms for which there are results from one or more machines or one or more models. Work from preceding quarterly reports is used for some of this summary. At the end of this summary, a brief summary of implications for ITER and implications for future work will be presented.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗