Dissociation of relativistic nuclei in peripheral interactions in nuclear track emulsion

Possibilities of the nuclear emulsion technique for the study of the systems of several relativistic fragments produced in the peripheral interactions of relativistic nuclei are discussed. The interactions of the ${}^{10}$B and ${}^9$Be nuclei in emulsion are taken as an example to show the manifestation of the cluster degrees of freedom in relativistic fragmentation. For the case of the relativistic ${}^9$Be nucleus dissociation it is shown that exact angular measurements play a crucial role in the restoration of the excitation spectrum of the alpha particle fragments. The energy calibration of the angular measurements by the ${}^9$Be nucleus enables one to conclude reliably about the features of internal velocity distributions in more complicated systems of relativistic $\alpha$ particles.