Visible imaging of edge fluctuations in TFTR

Abstract

Images of the visible light emission from the inner wall region of TFTR have been made using a rapidly gated, intensified TV camera. Strong "filamentation" of the neutral deuterium D^ light is observed when the camera gating time is <100 jisec during neutral-beam-heated discharges. These turbulent filaments vary in position randomly vs. time and have a poloidal wavelength of = 3-5 cm which is much shorter than their parallel wavelength of s: 100 cm. A second and new type of edge fluctuation phenomenon, which we call a "merfe," is also described. Merfes are a regular poloidal pattern of toroidally symmetric, small-scale marfes which move away from the inner midplane during the current decay after neutral beam injection. Some tentative interpretations of these two phenomena are presented.