DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 110: Role of coherent modes on edge pedestal and ELM behavior | ||
| Name: | Dmitry Rudakov ( |
Affiliation: | University of California, San Diego |
| Research Area: | Boundary | Presentation time: | Not requested | Co-Author(s): | Role of coherent modes on edge pedestal and ELM behavior |
| Description: | 1. Test models of coherent modes in H-mode pedestal regions, including esp. scaling with [1] rotation shear, [2] electric field shear, [3] pressure gradient, and [4] collisionality 2. Check effect of the I-coil induced erogodic fields on the coherent modes 3. Use inter-machine comparisions to help separate the contributions of the individual drives | ||
| Experimental Approach/Plan: | 1. Establish low power high density (ne/nG ~ 1) H-mode with quasi-coherent or coherent pedestal modes 2. vary momentum input-toroidal rotation (change balance of co and counter NBI) 3. density scan (puff and pump) 4. vary edge pressure gradient with edge localized ECH 5. use I-coils to test the effect of ergodic fields on the coherent modes 6. characterize edge profiles, fluctuations, and flows with boundary diagnostics, reciprocating probes, CER, ... | ||
| Background: | 1. Various types of quasi-coherent, coherent, or harmonic edge modes have been observed in the pedestal region of many devices (D3D, Asdex-Upgrade, C-Mod, H-1, etc.) and have been associated with increased levels of cross-field transport that permit steady-state H-mode operation without Type I ELMs 2. Theoretical models for pedestal coherent modes are based on [1] toroidal rotation shear, [2] Er shear, [3] pressure gradient drive, and/or [4] edge collisionality 3. DIII-D is an excellent facility for testing these theories because it can obtain edge coherent modes which can vary significantly in their character (electrostatic vs. electromagnetic; particle and heat transport vs. heat transport only, etc.) 4. DIII-D has a way to control (by using I-coils) ergodic magnetic fields that were shown to affect ELMs and are likely to affect the coherent modes as well. | ||
| Resource Requirements: | Machine Time: 1 day Experiment
Plasma Control System Development Number of gyrotrons: 2 Number of neutral beam sources: 4 (including co and counter) | ||
| Diagnostic Requirements: | 1. CER for edge Er and toroidal rotation 2. X-point probe for parallel flow (separatrix must be reachable with probe from bottom of machine) 3. full profile and edge diagnostics 4. edge current profile diagnostic if available | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | 1. I-coils 2. Edge ECH 2. Pumping for control of edge collisionality | ||
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