DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 165: Dependence of Turbulence and Transport on Te/Ti in Low Rotation L & H Modes | ||
| Name: | George R. McKee ( |
Affiliation: | University of Wisconsin, Madison |
| Research Area: | Transport Model Validation | Presentation time: | Requested | Co-Author(s): | C. Holland. T. Luce, C. Petty, T. Rhodes, D. Schlossberg, M. Shafer, G. Wang, A. White, L. Zeng |
| Description: | Examine the dependence of turbulence over a wide wavenumber range, spatial range and multiple fields, as well as particle, momentum and thermal transport on the electron to ion temperature ratio, Te/Ti, shown theoretically and experimentally to be a critical parameter for transport. The electron temperature profile will be self-similar as Te/Ti is varied, while other dimensionless parameters (rho*, nu*, q, beta) are kept nearly constant. | ||
| Experimental Approach/Plan: | Establish low power L-mode target plasma, with 2 balanced injection sources (minimize rotation), providing diagnosing beam for BES and CER, MSE (150R, 1/2-30L,330L), inner wall limited discharges to maintain L-mode conditions.
- Scan Te at constant Ti w/off-axis ECH heating, maintaining self-similar electron temperature profile shapes by varying ECH deposition location as necessary -Maintain constant Ti temperature at low rotation through adjustment of co/counter beam sources and power (previously in co-rotation discharges, rotation dropped significantly as Te increased during previous experiment) - Scan Ti at constant Te (via balanced NBI injection) - Scan Te and Ti at constant Beta (trade off ECH and NBI) as feasible - Increase density if necessary to further equilibrate temperatures - Obtain fluctuation data with all fluctuation diagnostics (expanded high-sensitivity BES, multi-wavenumber FIR, ECE, microwave back-scattering, correlation reflectometry, PCI, probes) -Examine particle diffusivity with helium puffs - Repeat experiment in H-mode plasmas | ||
| Background: | Numerous experiments have demonstrated that as Te/Ti, which is typically less than one in modern experiments, increases towards unity or above, transport increases, in general agreement with ITG-based turbulent transport theory. This experiment will seek to quantify the underlying turbulence mechanism giving rise to this dependence. Previous experiments have shown there to be a modest increase in low-wavenumber turbulence as Te is increased at constant Ti, however the experiments were not conclusive because of uncontrolled variation in the rotation and resulting ExB shear. This experiment will seek to investigate this issue in low-rotation discharges, now feasible with the balanced beam-injection, and also to investigate behavior in both L-mode and H-mode plasmas, as well as to employ the wide array of new and upgraded diagnostics. Of special note will be the capability to examine not only density but also electron temperature fluctuations with the newly implemented CECE diagnostic (UCLA).
These experiments will be simulated with TGLF and GYRO as reasonable to contribute to the effort to compare and challenges the codes and ultimately validate turbulence and transport simulations. | ||
| Resource Requirements: | Co and Counter beams, maximum ECH power (5 gyros) | ||
| Diagnostic Requirements: | All fluctuation diagnostics: BES, CECE, FIR (multi-wavelengths), correlation reflectometry, PCI, CO2 interferometer, Langmuir probes | ||
| Analysis Requirements: | Lots of transport and turbuelnce analysis required... | ||
| Other Requirements: | After experiment, simulate with modeling and nonlinear simulation codes (TGLF, GYRO, etc.). | ||
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