An isotope of the 113th element, i.e., 278 113, was produced in a nuclear reaction with a 70 Zn beam on a 209 Bi target. We observed six consecutive decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector under an extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of 262 Db and 258 Lr in both decay energies and decay times. This indicates that the present decay chain consisted of 278 113, 274 Rg (Z 111), 270 Mt (Z 109), 266 Bh (Z 107), 262 Db (Z 105), and 258 Lr (Z 103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads to the unambiguous production and identification of the isotope 278 113 of the 113th element.
The charge-state distributions and equilibrium charge states of uranium ( 238 U) and xenon ( 136 Xe) ions at 11 MeV=nucleon were determined using a gas charge stripper. A differential pumping system facilitated the increase of the nitrogen gas thickness up to 1:3 mg=cm 2 , which is sufficient for the most probable charge state to attain equilibrium. The charge states of 238 U attain equilibrium at 56.0, 56.6, and 55.7 in N 2 , Ar, and CO 2 media with thicknesses of 125, 79, and 126 g=cm 2 , respectively, while those of 136 Xe attain equilibrium at 40.5, 40.1, and 40.3 in N 2 , Ar, and CO 2 media with thicknesses of 163, 95, and 139 g=cm 2 , respectively. The equilibrium charge states of 136 Xe are acceptable for acceleration by the subsequent cyclotron. The measured data of 238 U were used to devise an empirical formula for the prediction of the equilibrium charge state in gaseous media over the energy region of 0:01-60 MeV=nucleon. The equilibrium charge state of 136 Xe as predicted by the devised formula is in good agreement with the data.
Development of a nondestructive, efficient electric-charge-stripping method is a key requirement for next-generation high-intensity heavy-ion accelerators such as the RIKEN Radioactive-Isotope Beam Factory. A charge stripper employing a low-Z gas is an important candidate applicable to high-intensity uranium beams for replacing carbon-foil strippers. In this study, a high-beam-transmission chargestripping system employing helium gas for 238 U beams injected at 10:8 MeV=u was developed and demonstrated for the first time. The charge-state evolution measured using helium in a thickness range of 0:24-1:83 mg=cm 2 is compared with theoretical predictions. Energy attenuation and energy spread due to the helium stripper are also investigated.
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