DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 56: Sustaining Low q(0) With Monster Sawtooth Control | ||
| Name: | C. Craig Petty ( |
Affiliation: | General Atomics |
| Research Area: | Core Integration (Steady-State Scenario) | Presentation time: | Not requested | Co-Author(s): | W. W. Heidbrink, R. I. Pinsker, J. Lohr |
| Description: | For the high li scenario, postpone or suppress the monster sawtooth crash for q(0)<<1 by using off-axis current drive to keep the current profile from becoming too peaked. The concept of q(0) control could also be tested transiently by using BT ramps. | ||
| Experimental Approach/Plan: | Create H-mode plasmas with "strongly" monotonic q profiles with co-NBI. Cryopumping should be used to control the density. Create a large population of fast ions to give monster sawteeth. Inject maximum co-ECCD off-axis around rho=0.35 to broaden the current profile and present q(0) from dropping to ~0.8. If that doesn't work, try adding some counter FWCD power. | ||
| Background: | To achieve a high internal inductance (which gives a high no-wall beta limit), the central safety factor needs to be less than unity. That can be achieved by stabilizing the m/n=1/1 mode using a sufficiently peaked fast ion pressure profile. However, if the ohmic current is significant then the current profile will continue to peak in time until a monster sawtooth crash occurs. Using off-axis current drive from ECCD, and perhaps counter on-axis current drive from FWCD, it is intended to halt the decrease in q(0) above the monster sawtooth crash limit. (Counter NBCD will not help because the counter current drive profile needs to be more peaked than the ohmic current profile.) It is expected that this experiment is contingent on the success of similar low-beta, low-density, monster-sawtooth stabilization experiments in the "Stability and Control" topical science area. | ||
| Resource Requirements: | NBI: At least 5 co sources.
EC: Minimum 5 gyrotrons. FW: Couple > 1 MW at 60 MHz. | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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