Sheared flow stabilization experiments in the ZaP flow Z pinch
The stabilizing effect of a sheared axial flow on the m=1 kink instability in Z pinches has been studied numerically with a linearized ideal magnetohydrodynamic model to reveal that a sheared axial flow stabilizes the kink mode when the shear exceeds a threshold. The sheared flow stabilizing effect...
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Veröffentlicht in: | Physics of Plasmas 2003-05, Vol.10 (5), p.1683-1690 |
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Hauptverfasser: | , , , , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | The stabilizing effect of a sheared axial flow on the
m=1
kink instability in Z pinches has been studied numerically with a linearized ideal magnetohydrodynamic model to reveal that a sheared axial flow stabilizes the kink mode when the shear exceeds a threshold. The sheared flow stabilizing effect is investigated with the ZaP (Z-Pinch) Flow Z-pinch experiment at the University of Washington. An axially flowing Z pinch is generated with a 1 m coaxial accelerator coupled to a pinch assembly chamber. The plasma assembles into a pinch 50 cm long with a radius of approximately 1 cm. An azimuthal array of surface mounted magnetic probes located at the midplane of the pinch measures the fluctuation levels of the azimuthal modes
m=1,
2, and 3. After the pinch assembles a quiescent period is found where the mode activity is significantly reduced. Optical images from a fast framing camera and a ruby holographic interferometer indicate a stable, discrete pinch plasma during this time. Multichord Doppler shift measurements of impurity lines show a large, sheared flow during the quiescent period and low, uniform flow profiles during periods of high mode activity. Z-pinch plasmas have been produced that are globally stable for over 700 times the theoretically predicted growth time for the kink mode of a static Z pinch. The plasma has a sheared axial flow that exceeds the theoretical threshold for stability during the quiescent period and is lower than the threshold during periods of high mode activity. |
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ISSN: | 1070-664X 1089-7674 |
DOI: | 10.1063/1.1558294 |