DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 278: Density pump-out studies in USN divertored, RMP discharges | ||
| Name: | Zeke Unterberg ( |
Affiliation: | ORISE/ORNL |
| Research Area: | ELM Control & Pedestal Physics | Presentation time: | Not requested | Co-Author(s): | T. Petrie |
| Description: | The goal of these discharges would be to assess the effect of divertor geometry on edge particle transport during the RMP and to expand the database of RMP effects to different divertor geometries. In particular, the upper divertor geometry is more ITER-like with the dome between inner and outer strike point plenums as opposed to the lower divertor with only an outer baffle. The different geometry of the upper divertor would lead to different neutral particle and recycling characteristics during RMP discharges. These would most likely be caused by the proximity of the OSP (ISP) to the throat of the outer (inner) plenum. The OSP proximity to the plenum throat is known to have strongly coupled influence on density control and ELM suppression during LSN, RMP discharges with grad_B toward the divertor. USN discharges have the benefit of: a) an inner plenum and cyro-pump, and b) fast-neutral-particle (ASDEX) ionization gauge heads in ISP plenum, OSP plenum, and private flux region of the divertor. This could lead to more detail measurements of temporal and spatial neutral particle evolution during the RMP. Combined with the D_alpha and the upper divertor Langmuir probe array data, this could give a relatively full assessment of particle transport in the divertor during an RMP discharge. It is thought with potentially greater access to plenum pumping there would be a greater effect on particle pumpout and/or transport during the RMP. Another potentially interesting question is how pumping on in the ISP region effects ELM suppression in the RMP? | ||
| Experimental Approach/Plan: | A fiducial USN RMP discharge would be the initial focus. This experiment could either be a piggyback with Petrie�??s ROF ID169 proposal where grad-B would be out of the divertor or a flip of the B-tor to focus on discharges with grad-B toward the x-point, which have shown ELM suppression in LSN RMP shots. From there, scans of I_coil magnitude at different q95s to determine the optimal resonances for density pump out, and sweeps of the OSP and/or ISP for optimal particle exhaust and/or to assess changes in pumping would be desirable. For instance, the latter would provide information on the density pump out as a function of perturbation strength even without ELM suppression. Finally, variations in plasma shape with the aim being to access lower-triangularity, ITER-like shapes (similar to shot 126006 in LSN discharges) would further help in characterizing the effects of this divertor type on future machines. | ||
| Background: | -- | ||
| Resource Requirements: | Standard for H-mode and RMP experiments. Would need to reverse the direction of B-tor for experiments with grad-B toward the divertor. | ||
| Diagnostic Requirements: | upper divertor Langmuir probe array; upper filterscope array, upper divertor ASDEX gauges, plus standard diagnostics for RMP experiments. | ||
| Analysis Requirements: | possibly 2D and/or 3D edge fluid code modeling | ||
| Other Requirements: | -- | ||
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