On the fluctuation of line radiation emitted during aluminum micro-pellet ablation in magnetized plasmas

The phenomenon of striation observed during pellet ablation in hot magnetiz ed plasma is investigated experimentally injecting aluminum micro-pellets i nto MT-1M and TEXTOR-94 tokamak and W7-AS stellarator plasmas. Changes in p ellet cloud shape and temporal fluctuations of total emitted line radiation s are studied. Special attention is paid to the investigation of the depend ence of fluctuation frequency on pellet velocity. The results show that the light fluctuation frequency is characterized by a characteristic time rath er than by a characteristic length, and that the striation is caused by a p henomenon that occurs during the evolution of the ionized-pellet cloud. The compatibility of these experimental observations with different theories o f striation is discussed.