DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 440: Plasma startup with compensating n=1(=3) error magnetic field components before the plasma ignition with I-coil feedback | ||
| Name: | Michio Okabayashi ( |
Affiliation: | Princeton Plasma Physics Laboratory |
| Research Area: | General PCO | Presentation time: | Not requested | Co-Author(s): | -- |
| Description: | Plasma startup is a complex process since the poloidal magnetic field pattern at the plasma ignition time t= 0 can be not only 2-dimensional but also 3-dimensional due to the non-axis-symmetric error field and the eddy currents induced on the metallic materials. The flux pattern, not only n=1, but higher n may exist in addition to the n=0 component around t = 0.
The 2-minensional Bp null point moves around inside the vacuum vessel and then the plasma will capture the helical flux in an unpredicted manner during low temperature period. Here, it is proposed: Using I-coil and/or c-coil, we turn on the feedback process to null out the magnetic field n=1 (=3 if needed) from before t=zero This feedback should reduce the helical component in the vacuum field and reduce the helical flux capturing in break down. This may minimize the appearance of magnetic island formation t=0-10 msec time range, improving the discharge evolvement in later time. | ||
| Experimental Approach/Plan: | Proof of principle experiment
(1) Fast feedback will be applied with taup =100 microsec of PCS before t=0. We will try first the I-coil with SPA connection. (2) If the n=3 component is high, it will be tried to carry out the n=1 and n=3 feedback simultaneously. The C-coil will be used together, if needed (3) The effectiveness of ECH before t=0 is tested | ||
| Background: | -- | ||
| Resource Requirements: | -- | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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