Upgrade of the dubna gas-filled recoil separator for the synthesis of superheavy nulcei in ~244 Pu + ~48 Ca reaction

摘要

Preparing experiments on the synthesis of superheavy nuclei with Z=114 in the reaction ~244Pu+~48Ca, we modifed the Dubna gas-filled recoil separator and its detection system and carried out bombardments of the lead targets with ~48 Ca projectiles. We studied excitation functions for the reactions ~206pb(~48Ca,1-4n) and ~204,207,208Pb(~48Ca,2n). Maximum cross sections for evaporation of 1-3 neutrons in the reaction ~206 Pb+~48Ca were measured to be sigma _1n = 60 nb, sigma _2n=500nb, and sigma _3n=30nb; an upper limit of 0.2 nb was obtained for the 4n channel. In the bombardment of ~204 Pb target by 217-MeV ~48Ca production cross sections for evaporation of 2 neutrons from compound nuclei ~256No, ~255No, and ~252No were measured to be 2.1 um b, 1.3 um b, and 10 nb, respectively. Collection efficiency of the separator was estimated to be approx 45