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Weekly Highlights
A more in depth investigation of the equilibrium and stability analysis of the bean and oval sawtooth experiments revealed some additional surprises. The growth rate does not fully follow the sawtooth cycle and is quite different in the two cases but new analysis shows that the local shear at q=1 tracks the ideal growth rates in both cases. None of the other key variables q0, qmin, r(q0) and r(qmin), is strongly correlated. Also, there is a small event about a third of the way into the sawtooth ramp in both cases, which causes a small drop in Te. The analysis revealed that for the bean case, the ideal unstable mode is a quasi-interchange until this event, after which the plasma becomes ideally stable for a sizeable fraction of the sawtooth period until, as reported earlier (see http://fusion.gat.com/theory/Weekly0407 and http://fusion.gat.com/theory/Weekly0908), the internal kink becomes unstable somewhat before the final sawtooth crash. For the oval, the growth rate drops after the event but the plasma is not fully stabilized and the mode remains a quasi-interchange throughout. The implications for interpreting the experimental observations are being worked through. | ||||||||||||||

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