DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 216: Measurement of Zonal Flows in the H-mode pedestal | ||
| Name: | Lothar Schmitz ( |
Affiliation: | University of California, Los Angeles |
| Research Area: | Transport | Presentation time: | Requested | Co-Author(s): | G. Wang, G. McKee, T.L. Rhodes, W.A. Peebles, A.E. White, T. A. Carter |
| Description: | Zonal Flows, including low frequency ZFs and Geodesic Acoustic Modes (GAMs), are thought to regulate local turbulence levels. We propose simultaneous low and intermediate-k fluctuation measurements, along with poloidal flow measurements (<v pol> and v~ pol) in ELM-free H-mode in the transport barrier (pedestal) region. The observed increase of fluctuations after initial suppression at the L-H transition will be investigated with regard to changes in flow patterns. | ||
| Experimental Approach/Plan: | In DIII-D, the average and time dependent poloidal flow in the H-mode pedestal can be measured simultaneously with low-k and medium k density fluctuations spectra by Doppler reflectometry. (2cm-1< k pol < 5 cm-1), combined with BES (k pol < 3 cm-1). Doppler reflectometry can also measure the instantaneous correlation of the flow amplitude with the density fluctuation level. Four x-mode reflectometry channels (50-70 Ghz) can obtain a radial flow profile for pedestal densities n ped < 2.5x 10^13 cm^-3. The outer gap should be chosen to allow the edge CER chords to cover the pedestal region to obtain the mean flow profile with high spatial resolution. | ||
| Background: | There is experimental evidence of the interaction of low frequency ZF flows and broadband density fluctuations from the Compact Helical Device (CHS) and JFT-2M. These measurements were done with Heavy-Ion Beam Probes and edge Langmuir probes.
In DIII-D, GAMs and low frequency ZFs have been measured by BES and Doppler reflectometry, and signatures of low frequency ZFs in the H-mode pedestal have been recently detected by Doppler reflectometry. | ||
| Resource Requirements: | USN plasmas with outer gap adjusted to allow edge CER measurements, 150 Beam constant for BES | ||
| Diagnostic Requirements: | Four channel Doppler reflectometry, BES, FIR low/intermediate k, CECE, profile reflectometry | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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