DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 132: Momentum Transport Measurement Using Shape Modulation | ||
| Name: | C. Craig Petty ( |
Affiliation: | General Atomics |
| Research Area: | Rotation Physics | Presentation time: | Not requested | Co-Author(s): | W. Solomon |
| Description: | This experiment proposes to study momentum transport by modulating the plasma shape between upper/lower null (using a symmetric DND patch panel). The NBI power will be kept fixed so that the injected torque is not modulated, and the resulting changes in rotation can be fit using the "source free" form of the angular momentum transport equation. It would be interesting to perform this experiment in both ELMy and ELM-stabilized (either QH-mode or RMP) plasmas. In addition, this experiment may help to determine the effect of residual error fields on the apparent momentum diffusivity by varying the error field shot-to-shot. | ||
| Experimental Approach/Plan: | (1) Modulate dRsep at ~10 Hz from +1 cm to -1 cm in an otherwise stationary plasma with fixed NBI power. (2) Compare an ELMy H-mode plasma with a ELM-suppressed plasma. (3) If a hybrid discharge is used (as opposed to QH-mode), then compare the momentum transport modulation for a 3/2 NTM scenario vs. 4/3 NTM scenario since the resonant drag effects on error fields could be different. | ||
| Background: | It was noticed in 2006 that hybrid (H-mode) plasmas have higher toroidal rotation when the controlling X-point is away from the grad-B drift direction. This was verified for both signs of B. An initial attempt (2 shots) to measure the perturbed momentum transport by modulating dRsep positive/negative was not successful because NBI power feedback to keep beta_N fixed was utilized. This caused a problem because the link between rotation and confinement caused the NBI power (and therefore the injected torque) to modulate at the same frequency as the dRsep modulation. | ||
| Resource Requirements: | -- | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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