DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 125: Discharges with complete 2nd stable regime access | ||
| Name: | John Ferron ( |
Affiliation: | General Atomics |
| Research Area: | Stability | Presentation time: | Not requested | Co-Author(s): | -- |
| Description: | The goal is to further investigate discharges with ballooning mode second stable access across the entire radial profile. The primary task would be to demonstrate that the stability code prediction of second stable access is correct by producing a continuous series of discharges with and without full second stable access. Also of interest would be the relatively unusual MHD observed previously. The previous discharge demonstrated onset of a 3/1 tearing mode at high beta and qmin > 2 instead of the more commonly observed 2/1 mode. | ||
| Experimental Approach/Plan: | Shot 114723 would be reproduced first. This shot had a large gas puff in order to broaden the density and pressure profile. The pressure gradient profile was approximately flat with fairly large values in the region of rho = 0.7 where normally a dip in pressure gradient is observed in H-mode discharges. The gas puff amplitude would be scanned in order to vary the pressure profile. We would look for a transition between cases with relatively large pressure gradient in the outer portion of the discharge and cases with a pressure gradient dip more like standard H-mode. This transition would be correlated with calculations of the ballooning stability. Shot 114723 also had relatively broad electron temperature profile. Off-axis ECH heating could be used as a second method of varying the pressure gradient profile. | ||
| Background: | Shot 114723, a qmin > 2 case with very broad pressure profile, had ballooning mode second stable access across the entire profile according to stability analysis of the reconstructed equilibrium. This resulted from a very broad bootstrap current profile. It has been suggested that this is the first time that this has been observed. | ||
| Resource Requirements: | -- | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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