Transient transport experiments in the current-drive experiment upgrade spherical torus

T. Munsat, P. C. Efthimion, B. Jones, R. Kaita, R. Majeski, D. Stutman, G. Taylor
2002 Physics of Plasmas  
Electron transport has been measured in the Current-Drive Experiment Upgrade ͑CDX-U͒ ͑T. Jones, Ph.D. thesis, Princeton University, 1995͒ using two separate perturbative techniques. Sawteeth at the qϭ1 radius ͑r/aϳ0.15͒ induced outward-propagating heat pulses, providing time-of-flight information leading to a determination of e as a function of radius. Gas modulation at the plasma edge introduced inward-propagating cold pulses, providing a complementary time-of-flight based e profile
more » ... profile measurement. This work represents the first localized measurement of e in a spherical torus. Core ͑r/aϽ1/3͒ e values from the sawtooth study are 1 -2 m 2 /s, and from the gas modulation study are 1 -6 m 2 /s, increasing by an order of magnitude or more outside of the core region. Furthermore, the e profile exhibits a sharp transition near r/aϭ1/3. 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 e region. Comparisons are performed to several theoretical models, with measured e Ϸ5 -10ϫ neoclassical estimates in the core.
doi:10.1063/1.1428557 fatcat:jynstqxhprf33ctqzug4ahk4si