DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 306: Completion of MP 2007-01-02: Investigate direct effect of RMP on ELM Stability | ||
| Name: | Richard A. Moyer ( |
Affiliation: | University of California, San Diego |
| Research Area: | ELM Control & Pedestal Physics | Presentation time: | Requested | Co-Author(s): | Moyer, Evans, Joseph, Fenstermacher, Wade |
| Description: | The goal of this experiment is to determine whether or not the RMP has a direct effect on ELM stabilization independent of the enhanced transport which leads to a reduction in the pedestal pressure gradient. We will use the separability of time scales between the transport/density pumpout (= 250 ms) and MHD response (< 1 ms) in order to separate these two effects by applying an a.c. oscillation (a few tens of Hz) around a sub-critical RMP amplitude for ELM suppression. This a.c. oscillilation will carry the RMP amplitude over the threshold for suppression and back on a time scale with is too fast for the transport to follow, but slow relative to the Alfven, reconnection and resistive times that govern MHD response. | ||
| Experimental Approach/Plan: | 1) Re-establish robust n = 3 RMP ELM suppression in a low collisionality, ITER-similar shape as on June 24, 2007. 2) Reduce the d.c. I-coil current below the level needed for suppression and add an a.c. oscillation on a 10-30 Hz frequency. 3) Characterize the ELM behavior, and the pedestal and boundary plasma response. | ||
| Background: | RMP ELM control results in ITER-similar shapes suggest that ELM suppression may be the result of not only reducing the edge pressure gradient, but of also shifting the stability boundary. This result raising the possibilty of a direct effect of the RMP on ELM stability separate from the effect of enhanced transport reducing the pedestal pressure gradient.
This experiment was initially attempted during the June 24 2007 run day, but due to limited machine availablity, we were not able to obtain a conclusive result. This proposal is to complete this portion of the experiment, describes in MP 2007-01-02 | ||
| Resource Requirements: | 1/2 run day
lower cryopumps n = 3 a.c. I coil operation | ||
| Diagnostic Requirements: | CER, Thomson scattering, profile reflectometry
fast and Mirnov magnetics pedestal diagnostics, filterscopes, SXR reciprocating probes BES, FIR scattering, PCI, reflectometry, correlation ECE IRTVs (fast TEXTOR camera if available) fast framing UCSD camera, DiMES camera, Xpoint tangential TV | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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