DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 193: Transport Locality and ECH Deposition | ||
| Name: | Kenneth Gentle ( |
Affiliation: | University of Texas |
| Research Area: | Transport | Presentation time: | Not requested | Co-Author(s): | -- |
| Description: | The detailed analysis of the accurate Te(r,t) data now provided by the DIII-D ECE system for electron transport with modulated ECH [K.W. Gentle, et al, Phys. Plasmas 13, 012311 (2006)] produced some enigmatic results. If the full absorbed ECH is deposited in the expected resonance region, a nonlocal transport coefficient is required -- the transport coefficient cannot depend only on local parameters but must change directly with ECH power [cf. Stroth et al, Plasma Phys. Control. Fusion 38, 611 (1996).] However, if a modest fraction of the power is presumed to be deposited over a broader region (at very low power density) in a self-consistent manner, the analysis provides a determination of reasonable local transport coefficients. Resolving this question is critical to our understanding of electron thermal transport. If the transport were truly nonlocal, none of our theories or computational models would be correct. We would be missing some important new physics. On the other hand, if there is some subtle misunderstanding of our ECH configuration that is leading to a sort of tail on the deposition profile, we must understand and quantify the effect to interpret experimental results properly. These effects have been seen in modulated ECH for electron transport for several years, at least since 105663. (Our level of quantitative analysis has reached the level of being quite sensitive to such details.) | ||
| Experimental Approach/Plan: | The experiment would be to use several gyrotrons to deposit power at a resonance location near the center to give a large temperature rise but without nonlinear effects in the ECE temperature measurements. Each gyrotron would be applied separately to confirm its resonance location, which can be quite well determined from the signals from and single gyrotron, and then all would be used together to maximize the effect of lower power deposition at other radii. The search would include both Te(t) measurements to detect a break in slope coincident with ECH and modulation at high frequency, for which the signal, particularly the component in phase with ECH, represents local deposition rather than transport. | ||
| Background: | -- | ||
| Resource Requirements: | 2+ MW ECH | ||
| Diagnostic Requirements: | Fast ECE. Standard set for transport analysis. | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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