DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 293: Minimum Contact Startup in DIII-D | ||
| Name: | Jim Leuer ( |
Affiliation: | General Atomics |
| Research Area: | Model based Control | Presentation time: | Not requested | Co-Author(s): | A. Hyatt, M. Walker, D. Humphreys |
| Description: | Plasma breakdown and initial plasma current ramp are produced primarily with a circular plasmas. The plasma edge is scraped-off on the inner or outer wall. This leads to loss of volt-second and impurity influx. Presently, only when substantial current is present in the plasma is is possible to divert and move the plasma off the wall surface. We will attempt to divert the plasma at the earliest possible time to limit the interactions with the wall. Low magnetic signal and issues with vertical feedback of elongated plasmas presently preclude early divertor formation. We will investigate the signals and determine if feed back is possible at an earlier time. Model based studies (including eddy currents) to improve the signal resolution required for early vertical stabilization will be explored. Other methods of detecting vertical position will also be explored to determine if other non-magnetic signals can be used for stabilizaiton. These signals include light emission from the inner and outer walls and impurity radiation from the core. Early ECH or diagnostic N-Beam may provide some indication of the plasma center and allow feed-back for vertical control. | ||
| Experimental Approach/Plan: | Initially effort will be to observer the signals of typical breakdown to develop those diagnostics that can provide positional plasma position resolution required for early utilization of feed back vertical control. We will request early EC and beams to quantify if these systems can be used diagnostics for centroid detection. Much of this work will be done in a piggy-back, observer, mode without need for experimental time. However, some diagnostic systems may require modification and/or timing changes to provide the required signal and time resolution. Following model/diagnostic development, we anticipate staged implementation of the techniques in the PCS to augment our existing startup scenario. | ||
| Background: | Traditional breakdown is based on simple null formation and feed-forward current or flux programing. Many modern modeling tools and non-magnetic diagnostics signals can be used to expand the capability of optimizing breakdown and initial current ramp. DIII-D is the perfect machine to explore this area of research and will provide ITER, KSTAR, EAST and other machines with new tools, diagnostics and methods to optimize their plasma startup. | ||
| Resource Requirements: | NBI sources especially tangential, EC | ||
| Diagnostic Requirements: | All diagnostics with significant signal at breakdown and initial current ramp | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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