DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 270: Simultaneous correction of B-coil bus and F-coil offset errors | ||
| Name: | Michael J. Schaffer ( |
Affiliation: | General Atomics |
| Research Area: | Error Fields | Presentation time: | Not requested | Co-Author(s): | LaHaye, Strait, Scoville (expected) |
| Description: | Develop an improved empirical correction for left-handed (standard) plasmas, by independently and simultaneously correcting the two main known sources of error, (a) the F-coil offsets from the B-coil, and (b) the B-coil current feed at 30 degrees. The I-coil and the C-coil should both be tried for the F-coil offset correction role. It is expected that one or both of these corrections will be better than the presently used empirical corrections. The result will also be used to test J-K Park's new theory of error correction. | ||
| Experimental Approach/Plan: | Use the previously developed Ohmic, low-density, locked-mode error field test plasma and technique. The starting point for the empirical search for best correction will start from past experiments and from calculations of error fields informed by J-K Park's new theory. If time permits, empirical corrections will be developed using the I-coil for both functions | ||
| Background: | An exploratory experiment in 2007 showed that the I-coil nearest to the 30 deg feed (the IL30 coil) applied alone is effective at reducing the locked mode error symptom. On the other hand, The C-coil and especially the I-coil are thought to be good at correcting the F-coil offset error. Therefore, it is hypothesized that independently correcting both error fields simultaneously will be more effective than previously used corrections.
New theory by J-K Park et al, PRL (accepted 2007) explains previous DIII-D empirical error correction semiquantitatively, via the coupling between the external error and correction fields with the least stable ideal MHD plasma mode, whose non axisymmetric currents strongly dominate inside the plasma. This theory will be used to help choose the starting point for the empirical best correction search. | ||
| Resource Requirements: | I-coil and C-coil systems essential.
Ohmic plasmas --- no NBI. | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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