Developments of 170Er, 204, 206, 207, 208Pb and 209Bi target wheels for reaction studies and synthesis of heaviest elements

Abstract

Target wheels and the target preparations of ∼450 μg/cm 2 thick Er, Pb and Bi isotopes sandwiched between C layers of 40 and 8 μg/cm 2 have been improved. By controlled high-vacuum evaporation a target uniformity per wheel was realized to 0.5% with deposition yields of 50.1 ± 0.9% on C backings in series. For the SHIP target wheel, a reduction of background, target temperature and unwanted activations were achieved. The standard method of weighing defined areas to characterize targets was supplemented by in-beam forward scattering. Further details were obtained from off-line γ-spectroscopy of irradiated targets. Recent and running experiments at GSI are aiming at the synthesis of heaviest elements with beams of 50Ti, 51V, 58Fe, 62Ni and 64Ni at energies near the Coulomb barrier on target wheels with 204, 206, 207, 208Pb and 209Bi. With the same experimental setup, neutron-deficient protactinium isotopes are produced at the UNILAC in reaction studies with a beam of 51V on targets of 170Er. The post-conference results of the synthesis of element 110 and element 111, obtained within the described experiment, are added in agreement with the Proceedings editors.