The electrostatic separator VASSILISSA performance and experimental results

Within the past seven years the electrostatic separator VASSILISSA [A.V. Yeremin et al., Nucl. Instr, and Meth. A 274 (1989) 528; A 350 (1994) 608] has been used for the investigations of evaporation residues (ER) produced in heavy-ion induced complete fusion reactions. Two types of such studies were of specific interest to us, These are the synthesis of heavy (Z greater than or equal to 100) nuclides and investigations of heavy-ion fusion reactions leading to formation of neutron-deficient nuclei with Z greater than or equal to 82 and high excitation energy (60 MeV less than or equal to E* less than or equal to 200 MeV). In the course of the experimental work the optimization of the ion-optical and other systems of the separator including the improvements in the focal plane detector system has been made. As a result, the separation efficiency values ranging from 3 to 30% were achieved for ER's produced in the reactions with heavy ions from C-12 to Ti-48. The suppression factors > 10(19) for the full energy beam particles and > 10(4) for multinucleon transfer reaction products were achieved. The results of the performed experiments illuminating the separator performance and future plans of the separator upgrade are briefly presented.