DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 282: Test J-K Park theory of tokamak error field correction | ||
| Name: | Michael J. Schaffer ( |
Affiliation: | General Atomics |
| Research Area: | Error Fields | Presentation time: | Not requested | Co-Author(s): | LaHaye, Strait, Scoville, J-K Park (expected) |
| Description: | Find the best empirical correction by varying more I-coil degrees of freedom than the usual amplitude and toroidal phase angle in an otherwise hard-wired current distribution. Specifically, connect a 1.7 kA SPA to each I-coil so that all 12 coil currents can be independently set. Then vary the toroidal "phasing" angle between the upper and lower I-coil sets, in addition to the usual parameters. Compare the best empirical correction with analysis by J-K Park with his IPEC code. The result may help to further establish the theory. | ||
| Experimental Approach/Plan: | Use the previously developed Ohmic, low-density, locked-mode error field test plasma and technique. Connect one 1.7 kA SPA to each of the 12 I-coils, in order to make any physically possible current distribution. Operate the plasma at sufficiently low Bt, Iplas and density that locked modes can be made with no more than 1.7 kA maximum in any coil. Vary the "phasing" angle between the upper and lower I-coil sets, in addition to the usual current magnitude and global toroidal phase of the current distribution. Start from the past experimental correction and, if available, a prediction from J-K Park. Determine empirically the best correction. | ||
| Background: | Tokamaks are distressingly sensitive to non axisymmetric magnetic field errors. A 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. If this theory is verified, it will provide a systematic, practical way to design and operate tokamak error field correction systems. | ||
| Resource Requirements: | I-coil system essential.
Ohmic plasmas --- no NBI. | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | Compare experiment result with theory. Requires collaboration by J-K Park with his IPEC code. | ||
| Other Requirements: | -- | ||
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