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 ≥ 100) nuclides and investigations of heavy-ion fusion reactions leading to formation of neutron-deficient nuclei with Z ≥ 82 and high excitation energy ( 60 MeV ≤ E ∗ ≤ 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 12C to 48Ti. The suppression factors > 1019 for the full energy beam particles and > 104 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.