SPATIAL PERIOD-DOUBLING INSTABILITY OF DENDRITIC ARRAYS IN DIRECTIONAL SOLIDIFICATION

A directional solidification study of succinonitrile doped with coumar in 152 was performed in which the pulling speed V-P was gradually redu ced in small steps. A spatial period-doubling instability was observed when V-P reached 17.4 mu m/s, in good quantitative agreement with the prediction of Warren and Langer [Phys. Rev. A 42, 3518 (1990)]. This experiment, in conjunction with two previous studies, conclusively dem onstrates the absence of a dynamical selection mechanism for the inter dendritic spacing lambda(1).