INTERNAL ANISOTROPY OF COLLISION CASCADES

It is shown that for collision cascades the global fractal dimension c annot give an adequate description of the geometrical structure becaus e it is insensitive to the internal anisotropy of the object arising f rom the directionality of cascade branches. Ln order to give a more el aborate description of the cascade, we introduce; an angular correlati on function, which takes into account the direction of the local growt h of the branches of the cascades. It is demonstrated that the angular correlation function gives a quantitative description of the directio nality and the interrelation of branches of the cascade. The power law decay of the angular correlation is evidenced and characterized by an exponent beta and an angular correlation length R-a different from th e radius of gyration R. It is demonstrated that the overlapping of sub cascades has a strong effect on the angular correlation.