Spectroscopic analysis of normal and reversed ion flows in the DIII-D divertor

Abstract

Flow velocities of C+, C2+, B+, and D+ parallel to the magnetic field in the DIII-D [J. Luxon, P. Anderson, F. Batty et al., Plasma Physics Controlled Nuclear Fusion Research, Proceedings of the 11th International Conference, Tokyo, 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] divertor have been measured from Doppler shifts of spectral lines. In general, both normal flows (toward the target plate) and reversed flows (away from the target plate) are observed in the outer scrape-off layer with the reversed flows occurring near the separatrix. Following the transition from attached to partially detached conditions, normal flow velocities generally speed up while in some regions reversed flows are observed to slow down. In high density plasmas, deuteron velocities are reflected in Balmer line emission which originates mainly from atoms which have thermalized by charge exchange or which have been formed by recombination. Low-temperature areas of nearly stagnated deuteron flow have been observed. In these regions recombination should be efficient for neutralizing the divertor plasma.