DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 35: High central fast wave current drive efficiency at high electon beta with 110 GHz EC preheating | ||
| Name: | Robert I. Pinsker ( |
Affiliation: | General Atomics |
| Research Area: | Fully Noninductive High Beta Operation | Presentation time: | Not requested | Co-Author(s): | F.W. Baity, J.C. Hosea, M. Porkolab, E. Fredd, J.M Lohr, A. Horton,R. Prater |
| Description: | Combine 6 gyrotrons-worth of central 110 GHz ECH (all launchers aimed at or near the center of the discharge without driving toroidal current) with the combined 60 MHz and ~90 MHz fast wave power. We would use the minimum neutral beam power necessary to create the sawtooth-free discharge in which the driven currents can be accurately measured, and to make the (MSE) measurement. Both L-mode and H-mode target discharges would be tried, although at full rf power, one would expect difficulty in keeping the discharge in L-mode. The basic scan would be a density scan, at each case obtaining at least a matching pair of discharges with co- and counter-current FW phasing. The object of the exercise would be to extend the range of central electon beta values, and hence of single-pass absorption of the FW power, considerably beyond what was possible without high power ECH. If time permits, comparison of the current drive efficiency of the 60 MHz and ~90 MHz systems could be performed - as the single-pass absorption increases, we expect at some point to observe more efficient current drive at higher launched parallel phase velocity (the higher frequency case). The experiment would seem to be the logical precursor to full utilization of the combined rf systems for AT work involving tailoring of the current profile. | ||
| Experimental Approach/Plan: | See description. | ||
| Background: | This experiment was tried on two days in the 2004-2005 campaign. However, technical problems prevented any useful data from being obtained. The DIII-D FWCD system was designed to be most efficient in a plasma with central electron temperature of about 10 keV, but the maximum electron temperature at which we have measured the FWCD efficiency to date is about 6 keV. The theoretical prediction is that the FWCD efficiency scales roughly linearly with central electron temperature, and all experiments to date have confirmed this prediction. | ||
| Resource Requirements: | Machine Time:
1 day Experiment Number of gyrotrons: 5 Number of neutral beam sources: 4 | ||
| Diagnostic Requirements: | MSE, all standard profile diagnostics. FIDE to check for evidence of interaction between FW and beam ions. | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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