PPPL-3574 is available in <a href="PPPL-3574.pdf">pdf</a> or 
<a href="PPPL-3574.ps">postscript</a> formats.

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<b>Transient Transport Experiments in the CDX-U Spherical Torus</b>
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<b>Authors:</b> T. Munsat, P.C. Efthimion, B. Jones, R. Kaita, R. Majeski, D. Stutman, and G. Taylor
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<b>Date of PPPL Report:</b> June 2001
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<b>Published in: </b> Physics of Plasmas <b>9</b> (February 2002) 480-487 </p>


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Electron transport has been measured in CDX-U using two separate perturbative techniques. Gas modulation at the plasma edge was used to introduce cold-pulses which propagate towards the plasma center, providing time-of-flight information leading to a determination of <FONT FACE = "symbol">c</FONT FACE = "symbol"><sub>e</sub> as a function of radius. Sawteeth at the q = 1 radius (r/a ~ 0.15) induced heat-pulses which propagated outward towards the plasma edge, providing a complementary time-of-flight based <FONT FACE = "symbol">c</FONT FACE = "symbol"><sub>e</sub> profile measurement. This work represents the first localized measurement of <FONT FACE = "symbol">c</FONT FACE = "symbol"><sub>e</sub> in a spherical torus. It is found that <FONT FACE = "symbol">c</FONT FACE = "symbol"><sub>e</sub> = 1-2 m<sup>2</sup>/sec in the plasma core (r/a < 1/3), increasing by an order of magnitude or more outside of this region. Furthermore, the <FONT FACE = "symbol">c</FONT FACE = "symbol"><sub>e</sub> profile exhibits a sharp transition near r/a = 1/3. Spectral and profile analyses of the soft X-rays, scanning interferometer, and edge probe data show no evidence of a significant magnetic island causing the high <FONT FACE = "symbol">c</FONT FACE = "symbol"><sub>e</sub> region.



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