The heaviest currently known nuclei, which have up to 118 protons, have been produced in $^{48}\mathrm{Ca}$ induced reactions with actinide targets. Among them, the element tennessine (Ts), which has 117 protons, has been synthesized by fusing $^{48}\mathrm{Ca}$ with the radioactive target $^{249}\mathrm{Bk}$, which has a half-life of 327 d. The experiment was performed at the gas-filled recoil separator TASCA. Two long and two short $\ensuremath{\alpha}$ decay chains were observed. The long chains were attributed to the decay of $^{294}\mathrm{Ts}$. The possible origin of the short-decay chains is discussed in comparison with the known experimental data. They are found to fit with the decay chain patterns attributed to $^{293}\mathrm{Ts}$. The present experimental results confirm the previous findings at the Dubna Gas-Filled Recoil Separator on the decay chains originating from the nuclei assigned to Ts.
Direct mass measurements in the region of the heaviest elements were performed with the Penning-trap mass spectrometer SHIPTRAP at GSI Darmstadt. Utilizing the phase-imaging ion-cyclotron-resonance mass-spectrometry technique, the atomic masses of $^{251}\mathrm{No}$ ($Z=102$), $^{254}\mathrm{Lr}$ ($Z=103$), and $^{257}\mathrm{Rf}$ ($Z=104$) available at rates down to one detected ion per day were determined directly for the first time. The ground-state masses of $^{254}\mathrm{No}$ and $^{255,256}\mathrm{Lr}$ were improved by more than one order of magnitude. Relative statistical uncertainties as low as $\ensuremath{\delta}m/m\ensuremath{\approx}{10}^{\ensuremath{-}9}$ were achieved. Mass resolving powers of 11 000 000 allowed resolving long-lived low-lying isomeric states from their respective ground states in $^{251,254}\mathrm{No}$ and $^{254,255}\mathrm{Lr}$. This provided an unambiguous determination of the binding energies for odd-$A$ and odd-odd nuclides previously determined only indirectly from decay spectroscopy.
In modern rare isotope facilities, ion cooling and bunching lies at the heart of the ion transfer along a low-energy beam line that consists of several differential pumping stages. We present a conceptual design of an ion guide as an alternative to the conventional linear Radio-Frequency Quadrupole (RFQ) for cooling and bunching rare isotopes. The ion guide is composed of stacked ring electrodes of varying apertures, to which a confining RF potential following a rectangular waveform is applied. The thicknesses of the rings and the gaps in between are varied accordingly to maximize the confining volume and to reduce ion losses. Ion transport within the ion guide is facilitated by a lower-frequency wave traveling on top of the higher-frequency confining field. The former is induced by locally adjusting the duty cycle of the rectangular waveform of the confining potential. Design parameters are first calculated by analytical studies and then optimized by ion trajectory simulations with SIMION®. The results show that the ion guide enables high ion transmission and produces well focused ion bunches. It will be used in the NEXT project—an experimental study of atomic masses of Neutron-rich EXotic nuclei produced in multi-nucleon Transfer reactions.
