PPPL-3615 is available in <a href="PPPL-3615.pdf">pdf</a> or 
<a href="PPPL-3615.ps">postscript</a> formats.

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<b>Observation of Compressional Alfv&#233n Modes during Neutral-beam Heating on the National Spherical Torus Experiment</b>
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<b>Authors:</b> E.D. Fredrickson, N. Gorelenkov, C.Z. Cheng, R. Bell, D. Darrow, D. Johnson, S. Kaye, B. LeBlanc, J. Menard, S. Kubota, and W. Peebles
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<b>Date of PPPL Report:</b> October 2001
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<b>Published in:</b> Phys. Rev. Lett. <b>87</b> (October 2001) 145001-1 thru 145001-4.</p>


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Neutral-beam-driven compressional Alfv&#233n eigenmodes (CAE) at frequencies below the ion cyclotron frequency have been observed and identified for the first time in the National Spherical Torus Experiment (NSTX). The modes are observed as a broad spectrum of nearly equally spaced peaks in the frequency range from approximately equal to 0.2 to approximately equal to 1.2 <font face = "symbol">w</font><sub>ci</sub>. The frequency has a scaling with toroidal field and plasma density consistent with Alfv&#233n waves.  The modes have been observed with high bandwidth magnetic pick-up coils and with a reflectometer.



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