DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 300: QH-mode with co-injected neutral beams | ||
| Name: | Keith Burrell ( |
Affiliation: | General Atomics |
| Research Area: | ELM Control & Pedestal Physics | Presentation time: | Not requested | Co-Author(s): | M.E. Fenstermacher, P. Gohil, W.M. Solomon, C.J. Lasnier,T.H. Osborne, P.B. Snyder |
| Description: | Attempt to create QH-mode with dominant co-injection. | ||
| Experimental Approach/Plan: | Start with a plasma similar to 128502 but which the plasma current in
the standard direction. Utilize the usual QH-mode recipe to minimize particle inventory to keep density as low as possible. Explore variations in plasma up-down balance and strike point location relative to the pumps to minimize density. Do current scan from 1.3 MA down to 0.7 MA to exploit the improved peeling-ballooning stability at high q. Explore use of I-coil perturbations to induce increased particle transport | ||
| Background: | The peeling-ballooning mode theory has allowed us to understand
QH-mode operation. ELM-free QH-mode edges lie in the region of parameter space that are predicted to be stable to ELMs. This is achieved by working to lower the edge density and pressure to move the H-mode edge into this region of parameter space. The enhanced particle transport due to the EHO is a key part of this. The peeling-ballooning mode theory, however, makes no prediction of the sign of the plasma current. Accordingly, if we can achieve the correct edge density and pressure, the theory predicts that we can achieve QH-mode with co neutral beam injection. In the 2006 and 2007 campaigns, we developed plasma shapes with enhanced edge stability margins. These are high-triangularity, double-null plasmas which exploit the new cryopumps for density control. The goal of the present experiment is to see if our density control is good enough for this shape to achieve QH-mode with all co-injection. A companion experiment proposed by T. Osborne will explore use of the I-coil perturbations at non-resonant q-values as a means of density control. | ||
| Resource Requirements: | Standard current direction. 7 NBI sources. | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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