DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 94: Physics of Safety Factor Resonance for n=3 RMP ELM Suppression | ||
| Name: | Max E. Fenstermacher ( |
Affiliation: | Lawrence Livermore National Laboratory |
| Research Area: | ELM Control & Pedestal Physics | Presentation time: | Not requested | Co-Author(s): | M.E. Fenstermacher |
| Description: | Expand scope of physics studies of the safety factor resonance window for ELM suppression with the n=3 I-coils. | ||
| Experimental Approach/Plan: | Perform a very systematic study of the physics determining the resonance window for n=3 ELM suppression with the I-coils. Scan plasma current up at fixed BT to produce a q95 down ramp from 4.2 to 3.2. Also scan Ip down to produce a q95 up ramp from 3.2 to 4.2 to look for differences due to build-up of edge current due to the Ip ramps. Change Ip ramp rate to look for differences in build-up of edge current. Do shot to shot fine q95 scan at edge of resonance window to eliminate the possibility of Ip ramps affecting the edge current. Carefully monitor edge plasma profiles (small wags and jogs for high resolution profiles) to determine if profiles remain the same during q ramps, ie. if window for suppression is due to something besides changes in pressure profile, vis. current transport (Snyder idea). | ||
| Background: | There is evidence from previous RMP ELM control experiments (see 128470, 472, 473, 474) that the physics that controls the density pumpout and therefore the significant changes to the edge pressure profile when the RMP is applied, may be less sensitive to a resonance window in edge safety factor than ELM suppression itself. Density pumpout is seen even for q95 far outside (q95=4.2) the resonance window for ELM suppression (q95=3.6 +- 0.1). Physics understanding here should go a long way toward ideas to expand the safety factor window for ELM suppression with new coil designs. | ||
| Resource Requirements: | Same resources as used for 2007 ISS ELM control experiments, see for example shot 128374 etc. I-coil maximum current with C_suplies, C-coil for optimum error field correction, 5 co-beams. | ||
| Diagnostic Requirements: | All pedestal and lower divertor diagnostics. Edge current measurements (especially simultaneously) with the Li-beam and co- plus counter-beam MSE would be highly desirable as would fast divertor IRTV. | ||
| Analysis Requirements: | All pedestal and lower divertor diagnostics. Edge current measurements (especially simultaneously) with the Li-beam and co- plus counter-beam MSE would be highly desirable as would fast divertor IRTV. | ||
| Other Requirements: | -- | ||
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