Detector system for investigation of proton radioactivity and new elements at ship

Abstract

The velocity separator SHIP has been built at GSI, Darmstadt, for the investigation of evaporation residues produced in heavy ion compound nuclear reactions. Low level spectroscopic investigations down to production cross sections of 10 pb and half lives of 1 μs became possible due to the extremely high degree of separation from the projectile beam. The advantages of SHIP have been further improved with a newly developed position and time correlation method. 33 new nuclei could be identified in the element region between gadolinium and lead by correlation of successive alpha-decays of nuclei implanted into position-sensitive surface barrier detectors. In a search experiment for proton radioactivity in this region, the first proton radioactive nucleus beyond the proton dripline 151Lu could be identified, indicating the limit of radioactive nuclei on the neutron deficient side. In the region of the heavier elements ( Z ⩾ 98), nine new isotopes have been identified by parent daughter correlations. The decay properties of the heaviest known element, Z = 109, A = 266 could be measured in a decay of a single nucleus. Such an event has been observed in a two week irradiation of 209Bi targets with 58Fe projectiles.