DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2008 EXPERIMENTAL CAMPAIGN
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| Title | 384: Preferential Locking | ||
| Name: | Francesco Volpe ( |
Affiliation: | ORAU |
| Research Area: | General IP | Presentation time: | Requested | Co-Author(s): | R. La Haye, R. Prater, E.J. Strait |
| Description: | In case locking is imminent or has already happened, apply static n=1 error field "over-correction" to predetermine the toroidal phase of locking or readjust it, respectively, in such a way that the mode can be controlled by ECCD. | ||
| Experimental Approach/Plan: | Use three available dud detectors and a fourth one yet to be developed, based on real-time newspec, to predict or promptly recognize mode locking and trigger a control phase.
Control will consist of cw ECCD and various types of I-coil controls and NBI changes: in some initial shots, a slow travelling wave will be entrained to the mode to slowly drag it in the presence of ECCD. In this way, the island O-point and X-point will be illuminated, alternatively, with stabilizing/destabilizing consequences and an optimal set of I-coil currents will be determined. As a by-product, slowly dragging the island will also allow MSE measurements of current in its interior, which would represent the first measurement of current diffusion inside the island. Once the optimal settings are found, preferential locking yielding ECCD in the O-point can be tried directly, i.e. without slowly rotating the island first. Mode mitigation is expected. The optimization and preservation during the shot of the ECCD alignment will enable full suppression. Locking with ECCD in the X-point and no ECCD will offer terms of comparison. The controls should preferably be applied before locking (pre-emptive control, expected to be more efficient). Anyway, pre- and post-locking intervention will be compared. | ||
| Background: | Piggyback experiments in Sept.2006 and 1.5 dedicated day in June 2007 have demonstrated locked mode mitigation from 6 to 3G, according to external saddle loop measurements. June experiments took advantage of increased ECRH power, marginally sufficient for stabilization, but optimal ECCD alignment was achieved only transiently. Repeating the experiments with equivalent or higher power has the potential for full stabilization, if the alignment will be maintained for >400ms. This requirement can be achieved by means of the PCS "active tracking" algorithm already applied with success to the stabilization of rotating NTMs. | ||
| Resource Requirements: | up to 6 gyrotrons, real-time newspec | ||
| Diagnostic Requirements: | -- | ||
| Analysis Requirements: | -- | ||
| Other Requirements: | -- | ||
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