DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 63: Extreme Off-Axis ECCD | ||
| Name: | C. Craig Petty ( |
Affiliation: | General Atomics |
| Research Area: | Heating & Current Drive | Presentation time: | Not requested | Co-Author(s): | R. Prater, J. Lohr, M. Choi |
| Description: | Use the higher ECH power available this year and MSE system to test the physics of ECCD in the outer regions of the plasma, 0.5< rho_ec < 0.9, especially for cases where large trapping effects are expected. The current drive determined from MSE signals will be compared to theoretical models. | ||
| Experimental Approach/Plan: | These experiments can be done in either L-mode or H-mode plasmas, but H-mode is preferred since it is the standard operating mode for DIII-D. Co/counter current drive comparisons should be done. (1) Scan the ECCD location across the midplane radius on the high magnetic field side of the plasma from 0.5 < rho_ec < 0.9 by varying the toroidal magnetic field. (2) Scan the poloidal angle of the ECCD location at fixed rho by varying BT and the antenna steering for rho=0.5 and rho=0.8. (3) Scan the ECCD location vertically at a poloidal angle of 90 deg from 0.5 < rho_ec < 0.9 by varying the antenna steering. | ||
| Background: | Previous experiments on DIII-D have studied the effects of electron trapping and beta for ECH locations between 0.0 < rho_ec < 0.4 owing to limited power. However, many important applications of ECCD (such as NTM stabilization and AT sustainment) require current drive locations that are further off-axis. It is important to test the physics of ECCD in this situation so that predictive theoretical models can be used to guide the application of ECCD in future experiments. Furthermore, it is expected that the Ohkawa current drive mechanism (reverse ECCD from electron trapping) may dominate the Fisch-Boozer current drive mechanism (forward ECCD from reduced collisionality) far off axis, especially when the power deposition is on the low field side. It is important to test our theoretical models in this limit. | ||
| Resource Requirements: | NBI: Co and counter MSE beams, and at least 2 other sources.
EC: Minimum 5 gyrotrons. | ||
| Diagnostic Requirements: | MSE is critical. | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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