Poloidal asymmetry and gradient drive in core electron density and temperature fluctuations on the Texas Experimental Tokamak-Upgrade

Abstract

Electron temperature and density fluctuations are measured in the core of the Texas Experimental Tokamak-Upgrade (TEXT-U) [P. H. Edmonds, E. R. Solano, and A. J. Wootton, in Proceedings of the 15th Symposium on Fusion Technology, Utrecht (Elsevier Science, Amsterdam, 1989), Vol. 1, p. 342] plasma across the poloidal cross section. The high spatial resolution of the heavy-ion beam probe (HIBP) and correlation radiometry of electron cyclotron emission (CRECE) reveal that both the density and temperature fluctuations are strongly poloidally asymmetric. Temperature fluctuation measurements indicate a broadband drift wave feature localized near the plasma equatorial plane on both the high- and low-field sides, which is consistent with density fluctuation measurements by far infrared (FIR) scattering. In contrast, the HIBP observes this feature localized only to the low-field side. Excellent spatial resolution allows us to investigate whether changes in the gradient affect the fluctuation amplitudes. We find that indeed, the temperature fluctuations increase with the electron temperature gradient. Results also link density fluctuations to changes in the density gradient.