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Title 403: Aspect Ratio Scaling of Core Turbulence
Name:Shigeyuki Kubota () Affiliation:University of California, Los Angeles
Research Area:Transport Model Validation Presentation time: Not requested
Co-Author(s): T.L. Rhodes, G. Wang, W.A. Peebles, G.J. Kramer
Description: Gyrokinetic microstability analyses indicate that low-k mode (ITG/TEM/micro-tearing) are sensitive to changes in the aspect ratio, beta, and Te/Ti. Here we propose similarity experiments in NSTX (A~1.3) and DIII-D (A~2-3) to look at the aspect ratio dependence of core turbulence properties. In particular, we will look at the turbulence radial correlation lengths determined from correlation reflectometry, since similar reflectometry hardware exists on both machines and the correlation length is a statistical property which allows a direct comparison between machines as well as with gyrokinetic codes.
Experimental Approach/Plan: The matched target plasmas (from the standpoint of NSTX) should be L-mode, beam-heated plasmas with Bt~0.6 T and peaked density profiles with ne0~2-3x10^13 cm-3 for good reflectometer access. He working gas for good density control. The target shot should have a long MHD-free period.
Background: Rewoldt et al. [Phys Plasmas 3, 1667 (1996)] initially demonstrated the stabilizing influence of the low aspect ratio on low-k modes, while more recent studies using linear GS2 analyses [Nucl Fusion 40, 677 (2000); Phys Plasmas 10, 2881 (2003)] with beta normal kept constant, have shown that beta is the dominant parameter and that the aspect ratio has little effect.
Resource Requirements: --
Diagnostic Requirements: Profile and fluctuation diagnostics. Profile and correlation reflectometers.
Analysis Requirements: --
Other Requirements: --