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Ion Heating and Velocity Fluctuation Measurements in MST Sanjay Gangadhara, Darren Craig, David Ennis, Gennady Fiskel and the MST team University of Wisconsin-Madison.

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Presentation on theme: "Ion Heating and Velocity Fluctuation Measurements in MST Sanjay Gangadhara, Darren Craig, David Ennis, Gennady Fiskel and the MST team University of Wisconsin-Madison."— Presentation transcript:

1 Ion Heating and Velocity Fluctuation Measurements in MST Sanjay Gangadhara, Darren Craig, David Ennis, Gennady Fiskel and the MST team University of Wisconsin-Madison General CMSO meeting, Princeton, NJ October 5-7, 2005

2 Motivation for Impurity Ion Measurement Anomalous Ion Heating T i (r,t) MHD Dynamo Momentum Transport v(r,t) Energy and Particle Transport

3 Outline CHERS Experimental Setup First Spatially Resolved Measurement of Ion Heating at a Sawtooth Crash First Spatially Resolved Measurement of Velocity Fluctuations in the Core

4 Ion Doppler Spectroscopy (IDS) For any Doppler shifted and broadened spectral line: Width Ion Temperature Centroid Shift Ion Velocity Area Relative Ion Density

5 Charge Exchange Recombination Spectroscopy (CHERS) Stimulated emission of the impurity ions due to charge exchange recombination with neutral beam atoms Charge exchange measurement is localized to the intersection of the line of sight and the beam path (~ 2 cm)

6 CHERS on MST Two fiber bundles allow for a simultaneous measurement of the charge exchange component and the background Measure the spectrum of the n=7 to n=6 transition of C +5 ( ~ nm) with a 100 kHz bandwidth

7 A Higher Energy and Longer Pulse DNB Installed on MST Neutral particle energy increase from 30 keV to 50 keV Longer duration of the pulse from 3 ms to 20 ms

8 Outline CHERS Experimental Setup First Spatially Resolved Measurement of Ion Heating at a Sawtooth Crash First Spatially Resolved Measurement of Velocity Fluctuations in the Core

9 Localized Heating On-Axis is Observed During a Sawtooth Crash Heating occurs on a fast time scale (~ 100 s) Cooling time scale is much longer (~ 1 ms)

10 Temperature Profile Evolution During the Crash Suggests Global Heating

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14 Ion heating is strongest in the center and edge but active throughout the entire plasma volume Non-uniform heating of different radial positions Cooling fastest in the edge

15 Comparison with Bulk Ions Indicates Larger Impurity Heating during Crash Comparable temperatures for bulk and impurity ions away from sawteeth Impurity heating at the sawtooth crash stronger than for the bulk

16 Impurity Ion Heating appears to be localized during m=0 bursts An increase in T i during burst is only observed outside of mid-radius

17 Outline CHERS Experimental Setup First Spatially Resolved Measurement of Ion Heating at a Sawtooth Crash First Spatially Resolved Measurement of Velocity Fluctuations in the Core

18 Ensembles of similar plasmas are generated to reduce measurement noise levels 0.5 ms time windows were selected away from sawtooth crashes Method for Computing Coherence of Velocity Fluctuations with Magnetic Modes

19 Summary of Coherence Between Velocity Fluctuations and Magnetic Modes Strong coherence with high n mode numbers at the mid- radius Modest coherence with the dominant n=6 magnetic mode Velocity fluctuations are much less global than magnetic fluctuations

20 MHD Dynamo The dynamo term depends on the magnitude of the fluctuating parameters along with their coherence ( g ) and phase difference ( d ) Within the error bars, the sum of the on-axis dynamo could encompass the prediction

21 Future Work Collect more data with the new diagnostic neutral beam to improve error bars on all measurements Adding toroidal & radial measurement capability gives: T || vs T ^ vs Examine the dynamo during a sawtooth crash Simultaneous measurement of the Hall dynamo spatial structure during and away from sawteeth

22 Summary First localized measurement of impurity ion temperature Heating at the sawtooth crash is global Impurity ions heated stronger than the bulk First localized measurement of impurity ion velocity fluctuations in the core Velocity fluctuations not as global as magnetic fluctuations Small dynamo in the core possibly consistent with expectations between sawteeth


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