DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 69: Electron Heat Pinch | ||
| Name: | C. Craig Petty ( |
Affiliation: | General Atomics |
| Research Area: | Transport | Presentation time: | Not requested | Co-Author(s): | T. C. Luce |
| Description: | (1) Demonstrate the existence of an electron heat pinch with convincingly small error bars. (2) Determine if the electron heat pinch is dependent upon the sign of the magnetic shear as predicted by some theories. | ||
| Experimental Approach/Plan: | (1) Reproduce the previous best cases of the heat pinch using the maximum ECH power available this year (up to 6 gyrotrons). The poloidal steering of the ECH antenna will allow variation of the heating location at constant target parameters. (2) Modulate the ECH power to obtain direct evidence on inward heat transport. (3) Use early off-axis ECH in low density plasmas to form negative shear discharges with rho_qmin > rho_ech. Measure the behavior of the Te profile as the q profile relaxes to a low shear state. (4) Repeat at several different densities (different Te) to vary the amount of shear reversal. | ||
| Background: | Understanding electron transport requires that the effects of diffusion and convection be distinguished, and the heat pinch issue falls squarely into this area. The inward transport effect seen with off-axis ECH remains a severe challenge to the theoretical community. Previous experiments using low field side, second harmonic launch found a negative electron heat flux near the plasma center, in support of the old 60 GHz ECH data from 1989-1990. However, due to higher ion temperatures, even in the ohmic phase, than 1989-1990, the error bars include positive (although small) values for the electron thermal diffusivity. This experiment will use the higher ECH power available this year to increase the separation betweem Te and Ti and thus reduce the error bars. Furthermore, the theoretical heat pinch model of coupled transport between Grad-J and Grad-T can be tested by comparing the non-diffusive electron transport for positive and negative shear plasmas. | ||
| Resource Requirements: | NBI: At least 2 sources.
EC: Mimimum of 5 gyrotrons. | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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