DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 371: Inducing 3/2 NTMs in hybrid discharges by means of ECRH | ||
| Name: | Francesco Volpe ( |
Affiliation: | ORAU |
| Research Area: | Core Integration (Advanced Inductive) | Presentation time: | Requested | Co-Author(s): | R. La Haye |
| Description: | ECRH slightly outside q=3/2 to provoke a local flattening of pressure, thus a Bootstrap deficit and therefore a 3/2 NTM when desired, for example in hybrid discharges. | ||
| Experimental Approach/Plan: | Very simple, with ECRH, perpendicular launch and deposition slightly outside q=3/2. A toroidal field scan (within the shot, or from shot to shot) will allow to find the best location. | ||
| Background: | NTMs are not always undesired instabilities: small 3/2 NTMs, for example, are desirable in "hybrid" discharges, where they help to prevent sawteeth. Occasional difficulties were encountered recently (March 2007) in reproducing hybrid scenarios with "natural" 3/2 NTMs. The purpose of this proposal is to develop a tool to trigger these modes on demand, when required. It might also shed light on the physics of seeding, and permit accurate measurement of the NTM growth rate, although under "artificial" conditions, which can be contrasted with predictions from the Rutherford equation. In particular, the flattening of the pressure profile is expected to affect the Bootstrap term in the Rutherford equation and, to a higher order, to make Delta' less negative. The presence of other NTMs in the plasma (typically 4/3, in the absence of 3/2) is not expected to constitute a problem, as ECRH will be deposited outside the 3/2 surface and thus even farther from the 4/3 one. | ||
| Resource Requirements: | -- | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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