DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 74: Is the 3/2 NTM Worth Suppressing in Hybrid Discharges? | ||
| Name: | C. Craig Petty ( |
Affiliation: | General Atomics |
| Research Area: | Core Integration (Advanced Inductive) | Presentation time: | Not requested | Co-Author(s): | T. C. Luce, P. A. Politzer, M. Murakami |
| Description: | Use co-ECCD near the q=3/2 surface to (1) suppress the 3/2 NTM, and (2) drive enough off-axis current to keep q(0) above unity. Compare the plasma performance to the normal passive hybrid cases with the 3/2 NTM with the same amount of electron heating. | ||
| Experimental Approach/Plan: | Study hybrid plasmas with q95=4.4. (1) Use enough co-ECCD at q=3/2 location to suppress the 3/2 NTM. Use the remaining co-ECCD at a radius best suited for driving enough off-axis current to raise q(0) above unity. (2) Compare these plasmas with ECH (heating only - no current drive) at the same density and beta_n. | ||
| Background: | The 3/2 NTM in hybrid discharges is not completely benign because it decreases the confinement time by ~15% (compared to 4/3 NTM hybrids) and it slows the plasma rotation. However, the ECCD required to suppress the 3/2 mode is not free. The question is whether the hybrid scenario on ITER would achieve a higher Q by using the ECCD to suppress the 3/2 NTM, or live with the lower confinement time (but less auxiliary heating power). Since the ECCD also changes the Ti/Te ratio in a direction unfavorable to transport in DIII-D, it is important to include that effect in the "passive" 3/2 NTM hybrid cases. | ||
| Resource Requirements: | NBI: All 7 sources are required.
EC: Minimum 5 gyrotrons. | ||
| Diagnostic Requirements: | MSE is critical. | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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