We aim at evaluating time evolutions of charge state distributions of target ions in internal targets formed by the self-confining RI ion target (SCRIT) technique. The charge state distribution of the target ions is important for optimizing the SCRIT performance, because the number of target ions escaping from the SCRIT is increasing with decreasing the mass-to-charge ratio (A/q) of the target ions. To quantitatively evaluate the charge state distribution, we developed the E-scanning method that separates target ions by their A/q using a fixed magnetic field and a scanning electric field in the E×B velocity filter. Results in the measurements with 138Ba ions, the 138Ba1+∼7+ ions trapped in the SCRIT were identified clearly, and their time evolutions were observed for the first time at a trapping time of 30 ∼ 300 ms.

We successfully performed electron scattering off unstable nuclei which were produced online from the photofission of uranium. The target ^{137}Cs ions were trapped with a new target-forming technique that makes a high-density stationary target from a small number of ions by confining them in an electron storage ring. After developments of target generation and transportation systems and the beam stacking method to increase the ion beam intensity up to approximately 2×10^{7} ions per pulse beam, an average luminosity of 0.9×10^{26}  cm^{-2} s^{-1} was achieved for ^{137}Cs. The obtained angular distribution of elastically scattered electrons is consistent with a calculation. This success marks the realization of the anticipated femtoscope which clarifies the structures of exotic and short-lived unstable nuclei.

The self-confining RI target (SCRIT) electron scattering facility has been constructed at RIKEN RI Beam Factory. The commissioning experiment was performed, and the luminosity was achieved to around 1027 cm−2 s−1 with stable ions at a 250 mA electron beam current. For the electron scattering with short-lived unstable nuclei, the radioactive isotope production was started at electron-beam-driven RI separator for SCRIT. Furthermore, new devices, the electron spectrometer window frame spectrometer for electron scattering and the cooler buncher system were constructed. After the setup of new devices, a first electron scattering experiment with short-lived nuclei will be performed soon.

The first elastic electron scattering has been successfully performed at the self-confining radioactive-isotope ion target (SCRIT) facility, the world's first electron scattering facility for SCRIT technique achieved high luminosity (over 10^{27}  cm^{-2} s^{-1}, sufficient for determining the nuclear shape) with only 10^{8} target ions. While ^{132}Xe used in this time as a target is a stable isotope, the charge density distribution was first extracted from the momentum transfer distributions of the scattered electrons by comparing the results with those calculated by a phase shift calculation.

The SCRIT (Self-Confining Radioactive-Isotope Ion Target) electron scattering facility has been constructed at the RIKEN RI Beam Factory. In the commissioning experiment, the ion-trapping properties of the SCRIT system were studied using stable ions. By using an electron spectrometer, the momentum transfer distribution of the electron elastic scattering of 132Xe was measured at 150, 200, and 300 MeV, and the charge density distribution was deduced. During the measurements, a luminosity of 1.8×1027 cm−2s−1 was achieved with a 250-mA electron beam and only 108 trapped ions. Production of RIs has begun in an electron-beam-driven RI separator, and developments are underway to increase the production rate of short-lived nuclei. Soon, measurements of electron elastic scattering by short-lived nuclei will be performed.

The ERIS (electron-beam-driven RI separator for SCRIT) at the SCRIT electron scattering facility is an online isotope separator system for the electron scattering of unstable nuclei. Ion beams from the ERIS are transported to the FRAC (fringing-RF-fieldactivated ion beam compressor). The FRAC realizes the continuous injection followed by trapping, and after the appropriate accumulation time, pulsed beams from the FRAC are injected to the SCRIT system. During the accumulation inside the FRAC, some of the trapped ions escape through the entrance because the entrance potential is lower than the beam energy. In order to reduce the ratio of escaped ions to injected ions, it is necessary to shorten the opening period of the entrance and inject same number of ions as in the continuous injection. Ion stacking and pulse extraction are proposed, and we report the results obtained at the ERIS in this paper. Figure 1 shows a schematic drawing of the new ionization chamber of the ERIS. The new ionization chamber consists of a cathode, an ionization chamber (anode), and entrance and exit grids. The entrance and exit grids are connected to the ionization chamber through an insulator. The schematic potential structure of these electrodes is also shown in Fig. 1. The ion stacking and extraction are controlled by switching the voltage of the exit grid. Neutral atoms continuously enter the ionization chamber, passing through the cathode. They are ionized by electrons emitted from the surface of the cathode, which is kept at approximately 2000 ◦C. In the longitudinal direction, ions are trapped between the entrance and exit grids. The number of stacked ions inside the ionization chamber is determined by the ionization rate and ion-trapping lifetime. The properties of the ion stacking and pulse extraction at the ERIS were studied using 6-keV Xe ion beams. The voltages of the cathode, anode, and entrance grid were set to 0, 180, and 182 V, respectively. The exit-grid voltages at the stacking and extraction were 182 and 40 V, respectively. The typical pulse shape, measured at the entrance of the FRAC with a 1-ms stacking time and a 300-μs extraction period, is shown in Fig. 2(a). The pulse height is about five times larger than that of the continuous beam. Figure 2(b) shows the stacking ratio, which is the ratio of the total charge within a 300-μs pulse width to the total charge obtained by integrating the continuous beam over the stacking time and extraction period. This re-

A method for preparing lipid vesicles having suitable size for drug delivery (in a few hundred nanometer size) with high entrapment efficiency of hydrophilic molecules was developed. The lipid vesicles containing hydrophilic molecules in their internal compartments were formed from water-in-oil-in-water (W1/O/W2) multiple emulsions after the removal of organic solvent by evaporation under ambient condition. The primary W1/O emulsions were formed via homogenization by sonication of mixture of oil phase containing bilayer forming lipids, and the water phase containing hydrophilic molecules to be entrapped. The W1/O/W2 multiple emulsions were formed through microchannel (MC) emulsification by introducing the dispersed phase, i.e., (W1/O) emulsion, into the MC device in the presence of polymeric surfactants in the external water phase. The average size of the lipid vesicles formed, measured using dynamic light scattering and observed by transmittance electron microscopy, was 182 nm, and comparable with the size of the initial water droplet of the primary W1/O emulsion (192 nm), indicating that the vesicle size reflects the water droplet size of the primary W1/O emulsion. High entrapment yields for hydrophilic molecules, namely 89.3 ± 4.2% for calcein and 41.1 ± 3.3% for 5-fluorouracil, were achieved.

We have constructed the SCRIT electron scattering facility at RIKEN in order to realize electron scattering off unstable nuclei. Because electron scattering is the most powerful and reliable tool to study the internal structure of the atomic nuclei as demonstrated for many stable nuclei in the latter half of the 20th century, actualization of electron scattering for the unstable nuclei has been long awaited. Recently, we have performed a series of elastic electron scattering experiments with $^{132}$Xe target. The high luminosity of around 10$^{27}$~cm$^{-2}$s$^{-1}$ which is a minimum-requirement for electron scattering is achieved with using only 10$^8$ target ions. By comparing with a DWBA calculation assuming the two-parameter Fermi distribution as the nuclear charge density distribution, it is found that a root-mean-square of radius is consistent with that from the measurement of X-ray of muonic atom and an information of surface shape of $^{132}$Xe nucleus is extracted for the first time.

We report on development of a gas-jet transport system coupled to a surface ionization ion-source in the JAEA-ISOL (Isotope Separator On-Line) system. As a new aerosol material for the gas-jet system, CdI2, which has a low boiling point of 713 °C, is exploited to prevent deposition of the aerosol material on the surface of the ion-source. An additional filament is newly installed in the previous ion-source to provide uniform heating of an ionizer. The present system is applied to the measurement of absolute efficiencies of various short-lived lanthanide isotopes produced in nuclear reactions.

Lawrencium, with atomic number 103, has an isotope with a half-life of 27 seconds; even so, its first ionization potential has now been measured on an atom-at-a-time scale and agrees well with state-of-the-art theoretical calculations that include relativistic effects. The most dramatic modern revision of Mendeleev's periodic table of elements came in 1944 when Glenn T. Seaborg placed a new series of elements, the actinides (atomic numbers 89–103), below the lanthanides. In this issue of Nature, Yuichiro Nagame and colleagues report the first measurement of one of the basic atomic properties of element 103 (lawrencium), namely its first ionization potential. Lawrencium is only accessible via atom-at-a-time synthesis in heavy-ion accelerators, so experimental investigations of its properties are rare. Nagame and colleagues were able to reduce the number of atoms required to measure the ionization potential from billions to thousands, and these results — in agreement with the latest theoretical calculations — show that the last valence electron in lawrencium is the most weakly bound one in all actinides and any other element beyond group 1 of the periodic table. This signature — in a region of the periodic table where the sheer size of the atoms means that relativistic effects play a crucial role — confirms the end of the actinide series at element 103. The chemical properties of an element are primarily governed by the configuration of electrons in the valence shell. Relativistic effects influence the electronic structure of heavy elements in the sixth row of the periodic table, and these effects increase dramatically in the seventh row—including the actinides—even affecting ground-state configurations1,2. Atomic s and p1/2 orbitals are stabilized by relativistic effects, whereas p3/2, d and f orbitals are destabilized, so that ground-state configurations of heavy elements may differ from those of lighter elements in the same group. The first ionization potential (IP1) is a measure of the energy required to remove one valence electron from a neutral atom, and is an atomic property that reflects the outermost electronic configuration. Precise and accurate experimental determination of IP1 gives information on the binding energy of valence electrons, and also, therefore, on the degree of relativistic stabilization. However, such measurements are hampered by the difficulty in obtaining the heaviest elements on scales of more than one atom at a time3,4,5. Here we report that the experimentally obtained IP1 of the heaviest actinide, lawrencium (Lr, atomic number 103), is electronvolts. The IP1 of Lr was measured with 256Lr (half-life 27 seconds) using an efficient surface ion-source and a radioisotope detection system coupled to a mass separator. The measured IP1 is in excellent agreement with the value of 4.963(15) electronvolts predicted here by state-of-the-art relativistic calculations. The present work provides a reliable benchmark for theoretical calculations and also opens the way for IP1 measurements of superheavy elements (that is, transactinides) on an atom-at-a-time scale.

Production cross-sections of the isotope Lr-256 in the Cf-249,Cf-250,Cf-251 + B-11, Am-243 + O-18, and Cm-248 + N-14 reactions were measured using a He/KCl gas-jet transport system and a rotating wheel alpha-particle detection apparatus. The alpha-particle energy of Lr-256 was distributed from 8.3 to 8.7 MeV and its half-life, T-1/2, was measured to be 28 +/- 1 s. The maximum cross sections in the Cf-249 (B-11, 4n)Lr-256 and Am-243(O-18, 5n)Lr-256 reactions were determined to be 122 +/- 36 nb at the beam energy of 63 MeV and 26 +/- 7 nb at 96 MeV, respectively. In the Cm-248(N-14, 6n)Lr-256 reaction, the cross section was measured to be 27 +/- 10 nb at 91 MeV.

Abstract Production cross-sections of the isotope 256Lr in the 249,250,251Cf +11B, 243Am +18O, and 248Cm +14N reactions were measured using a He/KCl gas-jet transport system and a rotating wheel α-particle detection apparatus. The α-particle energy of 256Lr was distributed from 8.3 to 8.7 MeV and its half-life, T 1/2, was measured to be 28 ± 1 s. The maximum cross sections in the 249Cf(11B, 4n)256Lr and 243Am(18O, 5n)256Lr reactions were determined to be 122 ± 36 nb at the beam energy of 63 MeV and 26 ± 7 nb at 96 MeV, respectively. In the 248Cm(14N, 6n)256Lr reaction, the cross section was measured to be 27 ± 10 nb at 91 MeV.

A radioactive isotope (RI) separator named ERIS (electron-beam-driven RI separator for SCRIT) was constructed at the SCRIT (Self-Confining Radioactive isotope Ion Target) electron scattering facility at RIKEN RI Beam Factory and has been in operation since 2013. Recently, ion stacking and pulse extraction were developed at ERIS to improve the dc-to-pulse conversion efficiency of a radio-frequency quadrupole cooler buncher. Using a surface-ionization ion source, long-time stacking inside ERIS was realized and a dc-to-pulse conversion efficiency of more than 50% was achieved with a relatively small amount of buffer gas.

The SCRIT electron scattering facility, aiming at electron scattering off short-lived unstable nuclei, has been constructed at the RIKEN RI Beam Factory. This facility consists of a racetrack microtron (RTM), an electron storage ring (SR2) equipped with the SCRIT system, and a low-energy RI separator (ERIS). SCRIT (self-confining radioactive isotope ion targeting) is a novel technique to form internal targets in an electron storage ring. Experiments for evaluating performance of the SCRIT system have been carried out using the stable 133Cs1+ beam and the 132Xe1+ beam supplied from ERIS. Target ions were successfully trapped in the SCRIT system with 90% efficiency at a 250mA electron beam current, and luminosity exceeding 1026/(cm2s) was maintained for more than 1s. Electrons elastically scattered from the target ions were successfully measured. Applicability of the SCRIT system to electron scattering for unstable nuclei has been established in experiments.

The tilted-foil method for producing spin-polarized radioactive isotope beams has been studied for the application to nuclear physics and materials science, using the radioactive nucleus 8Li ( \(\ensuremath I^{\pi}=2^+\) , g = 0.82678(9) , \(\ensuremath T_{1/2}=0.838(6)\) s) produced at the Tokai Radioactive Ion Accelerator Complex (TRIAC). We successfully produced polarization in a 8Li beam of \(\ensuremath 7.3\pm0.5\) % using 15 thin polystyrene foils (4.2 \(\ensuremath \mu \mathrm{g/cm}^2\) fabricated especially for this purpose. A systematic study of the nuclear polarization as a function of the number of foils, beam energy, tilt angle and foil material has been performed, confirming the features of the tilted-foil technique experimentally. The contributions made to the nuclear polarization of 8Li nuclei by the atomic states was investigated.

We investigated the ion-loss distribution on the sidewall of an electron cyclotron resonance (ECR) plasma chamber using the 18-GHz ECR charge breeder at the Tokai Radioactive Ion Accelerator Complex (TRIAC). Similarities and differences between the ion-loss distributions (longitudinal and azimuthal) of different ion species (i.e., radioactive 111In1+ and 140Xe1+ ions that are typical volatile and nonvolatile elements) was qualitatively discussed to understand the element dependence of the charge breeding efficiency. Especially, the similarities represent universal ion loss characteristics in an ECR charge breeder, which are different from the loss patterns of electrons on the ECRIS wall.

A spin-polarized radioactive 123In (I π , g = 1.220(2) , T 1/2 = 5.97(5) s) beam has been successfully generated by the tilted-foil method. This nuclide is the heaviest ever polarized in its ground state by this method. Using the ISOL-based re-acceleration-type facility TRIAC, an 123Ing.s. beam of 305 keV/nucleon went through a stack of 15 carbon foils with a tilt angle of 70° , and an asymmetry of 0.76 ± 0.25% of β-decays was observed by the β-NMR technique. The asymmetry shows that the tilted-foil method combined with a re-acceleration facility is useful for producing spin-polarized beams for applications such as nuclear physics and materials science.