DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 359: Structure of EHO and Connection to ELM precursor | ||
| Name: | Tom Osborne ( |
Affiliation: | General Atomics |
| Research Area: | ELM Control & Pedestal Physics | Presentation time: | Not requested | Co-Author(s): | J. Yu, G. McKee, P. Snyder, K. Burrell |
| Description: | Study structure of EHO with fast UCSD camera, BES, Magnetics, SXR and compare to ELM precursor. | ||
| Experimental Approach/Plan: | Create discharge which is transitioning between QH-mode and ELMing H-mode by adding CO beam beam power near threshold and look at structure of EHO in comparison to ELM precursor. Current up ramps might also be used to induce ELMs in QH-mode discharges. | ||
| Background: | The theory of P. Snyder for QH-mode proposes that the EHO is a rotational shear destabilized low n peeling ballooning instability. In previous studies where the CO NBI power was increased in QH-mode until ELMs reappeared in some cases n=1 EHOs grew to large amplitude preceeding the first ELM. A more rapidly growing mode is observed on magnetis as a precursor to the ELM also in this case. The link between the EHO and the mode usually associated with the ELM is unclear from the magnetic measurements. Filaments are observed associated with ELMs on several tokamaks and one would expect if there were a connection between the EHO and ELM instability to observed a transition between a steady perturbation and a rapidly ejected filament which could be important in understanding both the ELM instability and the EHO. An examination of the structure of the EHO and ELM presursors with fast cameras, BES, SXR, and magnetics combined may help to shead light on both the EHO and ELM instability. | ||
| Resource Requirements: | Rerverse IP, CO and CNTR beams for QH-mode. | ||
| Diagnostic Requirements: | UCSD fast camera, BES, SXR. Some gas puffing will probably be necessary to see anything on the camera. | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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