PPPL-3757 is available in <a href="PPPL-3757.pdf">pdf</a> format (8.7 MB).

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<b>Enhanced Conversion of Thermal Electron Bernstein Waves to the Extraordinary Electromagnetic Mode on the National Spherical Torus Experiment (NSTX)</b>
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<b>Authors:</b> G. Taylor, P.C. Efthimion, B. Jones, B.P. LeBlanc, J.R. Wilson, J.B. Wilgen, G.L. Bell, T.S. Bigelow, R. Maingi, D.A. Rasmussen, R.W. Harvey, A.P. Smirnov, F. Paoletti, and S.A. Sabbagh </p>

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<b>Date of PPPL Report:</b> October 2002
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<b>Published in:</b> Physics of Plasmas <b>10</b> No. 5 (May 2003) 1395-1401.</p>


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A four-fold increase in the conversion of thermal electron Bernstein waves (EBW) to the extraordinary mode (X-mode) was measured when the density scale length (L<sub>n</sub>) was progressively shortened by a local Boron nitride limiter in the scrape-off of an ohmically heated National Spherical Torus Experiment (NSTX) plasma [M. Ono, S. Kaye, M. Peng, et al., Proceedings 17th IAEA Fusion Energy Conference (IAEA, Vienna, Austria, 1999), Vol. 3, p. 1135]. The maximum conversion efficiency approached 50% when L<sub>n</sub> was reduced to 0.7 cm, in agreement with theoretical predictions that used locally measured L<sub>n</sub>. Calculations indicate that it is possible to establish L<sub>n</sub> &#60; 0.3 cm with a local limiter, a value predicted to attain approximately 100&#37; EBW conversion to the X-mode in support of proposed EBW heating and current drive scenarios.




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