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Previously, we developed an α-TOF detector for correlated measurements of atomic masses and decay properties of radioactive isotopes using a multi-reflection time-of-flight mass spectrograph, and successfully demonstrated α-decay-correlated mass measurements of heavy and superheavy nuclides. In this work, we develop a β-TOF detector, an improvement upon the α-TOF detector, to extend this technology to β-decaying nuclides. Online commissioning with 81Ga yielded a measured half-life of 1.44(31) s, in agreement with the previous literature, and confirmed the efficiency of detecting a decay-correlated event to be consistent with the solid angle limitation.

A new multi-reflection time-of-flight mass spectrograph for nuclear mass measurements with high precision has been constructed at the SLOWRI facility at RIKEN-RIBF. We aim to couple this new device to a cryogenic gas cell operated at the BigRIPS facility of RIBF. It is part of the SLOWRI project for slowing down and stopping intense radioactive ion beams provided downstream of RIKEN’s superconducting ring cyclotron accelerator. In particular, this device is dedicated to be located at the end of the BigRIPS beam line to access ions that are presently guided to beam dumps during in-beam experiments. In this article the apparatus is described in detail.

We developed KEK Isotope Separation System (KISS) in RIKEN Nishina center to produce neutron-rich isotopes around N = 126 for the study of β-decay properties from astrophysical interests. The KISS is an argon-gas-cell-based on laser ion source with ISOL, and, therefore, allows us to extract heavy refractory elements and investigate neutron-rich isotopes around N = 126. We extracted the laser-ionized unstable nuclei in the vicinity of 198Pt, and performed β-γ spectroscopy and in-gas-cell laser ionization spectroscopy successfully.

We developed a multi-segmented proportional gas counter to perform β-decay spectroscopy of neutron-rich nuclei extracted from KEK Isotope Separation System (KISS). The 32 segmented gas counters allow us two-dimensional tracking of the events to identify β-ray events by discriminating background events. The detectors being by low-density material of thin aluminized Mylar foils and P10 gas enabled us to detect low energy electrons down to 100 keV. The absolute detection efficiency was 45% at Q β = 1 MeV, and the measured background event rate was 0.11 cps. The detector was applied to perform β-decay spectroscopy and hyperfine structure measurements of neutron-rich isotopes of Pt, Ir, and Os. We started to develop the gas counter with three-dimensional tracking by replacing the material of anode wire from BeCu to resistive thin carbon to reduce the background event rate below 0.01 cps.

Deexcitation $\ensuremath{\gamma}$ rays associated with an isomeric state of $^{186}\mathrm{Ta}$ were investigated. The isomers were produced in multinucleon transfer reactions between a $^{136}\mathrm{Xe}$ beam and a natural W target and were collected and separated by the KEK Isotope Separation System. Two $\ensuremath{\gamma}$ transitions with energies of 161.1(2) and 186.8(1) keV associated with an isomeric decay were observed for the first time. The half-life of the isomeric state of the neutral atom $^{186\mathrm{m}}\mathrm{Ta}$ was deduced as 17(2) s. Based on the comparison with the previous measurements of the isomeric state using the Experimental Storage Ring at GSI Darmstadt and the coupling of angular momenta of individual particle orbitals in odd-odd nuclei, a decay scheme of $^{186\mathrm{m}}\mathrm{Ta}$ was proposed.

The $\ensuremath{\beta}\text{\ensuremath{-}}\ensuremath{\gamma}$ spectroscopy of $^{195}\mathrm{Os}$ nucleus was performed at the KEK isotope separation system (KISS). The radioactive isotope of $^{195}\mathrm{Os}$ was produced by the multinucleon transfer reactions of $^{136}\mathrm{Xe}$ beams and $^{198}\mathrm{Pt}$ target. The isotope of interest was separated and extracted by using KISS, which is an argon-gas-cell based laser ion source with a mass separator. Those extracted isotopes are implanted into an aluminized mylar tape, which is surrounded by the multisegmented proportional gas counter (MSPGC) and four clover-type high-purity germanium (HPGe) detectors for the $\ensuremath{\beta}\text{\ensuremath{-}}\ensuremath{\gamma}$ spectroscopy. 27 $\ensuremath{\gamma}$-ray peaks were observed in coincidence with internal conversion electrons and x rays detected by the MSPGC. 21 of them were identified as $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$ rays of the $^{195}\mathrm{Os}$ ground state, where the energies of 19 $\ensuremath{\gamma}$-ray peaks agree with the literature values of transitions observed in $^{195}\mathrm{Ir}(n,\ensuremath{\gamma})$ reactions and two $\ensuremath{\gamma}$-ray peaks were newly found. The $\ensuremath{\beta}$-decay branching ratios of the $^{195}\mathrm{Os}$ ground state were deduced. The obtained log-$ft$ values range from $5.99(4)$ to $7.56(22)$, indicating all $\ensuremath{\beta}$-decay channels are the first forbidden transitions. It suggests that the spin-parity of the $^{195}\mathrm{Os}$ ground state is $3/{2}^{\ensuremath{-}}$, which is consistent with the systematical expectation. The $\ensuremath{\beta}$-decay half-life of the $^{195}\mathrm{Os}$ ground state was evaluated to be 6.5(4) min, which agrees well to the previously known value 6.5(11) min.

“Kawaii” is a Japanese word that represents an emotional value; it has positive meanings, such as cute, lovable, and small. In the 21st century, the emotional value accounts for a large part of consumers’ preference. The kawaii feeling might become a key factor for creating affective and pleasurable designs. In a behavior of watching photos, we have subjective, intuitive and strong preference based on our emotional values. In this study, as a study on the kawaii feeling, we conducted experiments to examine whether physiological responses of the brain can be measured when participants get the kawaii feeing in watching photos by the event-related potential (ERP) technique. We measured electroencephalogram of the participants while they were shown kawaii photos, uninteresting photos, and mosaic images. We found that event-related potentials were elicited in response to showing the kawaii photos and the uninteresting photos, while the mosaic photos did not elicit a particular response. ERPs elicited by the kawaii photos had the positive deflection in comparison with ones evoked by the uninteresting photos after about 300-400 msec from onsets of presenting the photos. We concluded that the physiological responses of the brain can be measured when participants get kawaii feeing in watching photos.

Mass-separated ${^{187}\mathrm{Ta}}_{114}$ in a high-spin isomeric state has been produced for the first time by multinucleon transfer reactions, employing an argon gas-stopping cell and laser ionization. Internal $\ensuremath{\gamma}$ rays revealed a ${T}_{1/2}=7.3\ifmmode\pm\else\textpm\fi{}0.9\text{ }\text{ }\mathrm{s}$ isomer at $1778\ifmmode\pm\else\textpm\fi{}1\text{ }\text{ }\mathrm{keV}$, which decays through a rotational band with perturbations associated with the approach to a prolate-oblate shape transition. Model calculations show less influence from triaxiality compared to heavier elements in the same mass region. The isomer-decay reduced $E2$ hindrance factor ${f}_{\ensuremath{\nu}}=27\ifmmode\pm\else\textpm\fi{}1$ supports the interpretation that axial symmetry is approximately conserved.

Hyperfine structure (HFS) measurements of neutron-rich iridium isotopes $^{196,197,198}\mathrm{Ir}$ ($Z=77,\phantom{\rule{0.16em}{0ex}}N=119$--121) were performed via in-gas-cell laser resonance ionization spectroscopy at the KEK Isotope Separation System. Magnetic dipole moments $\ensuremath{\mu}$ and isotope shifts were determined from the HFS spectra. The variation of mean-square charge radii and quadrupole deformation parameters of these isotopes were evaluated from the isotope shifts. The $\ensuremath{\mu}$ value of $^{197}\mathrm{Ir}$ agreed with a theoretical value based on the strong coupling model, and the Ir nucleus was interpreted as prolately deformed by the theoretical calculations. The $\ensuremath{\mu}$ values of $^{196,198}\mathrm{Ir}$ were also compared with semiempirical values calculated based on the strong coupling model. From the comparison, we can suggest the possible spin values of ${I}^{\ensuremath{\pi}}=1,{2}^{\ensuremath{-}}$ for $^{196}\mathrm{Ir}$ and ${I}^{\ensuremath{\pi}}={1}^{\ensuremath{-}}$ for $^{198}\mathrm{Ir}$.

We performed in-gas-cell laser ionization spectroscopy of $^{194,196}\mathrm{Os}$, which were produced by multinucleon transfer reactions at the KEK Isotope Separation System (KISS). The nuclei of interest were identified through $\ensuremath{\beta}$-decay spectroscopy and a newly applied multireflection time-of-flight mass spectrograph (MRTOF-MS). From the study of laser resonance spectra, isotope shifts (ISs) of the transition ${\ensuremath{\lambda}}_{1}=247.758$ nm for $^{194}\mathrm{Os}$ and $^{196}\mathrm{Os}$ were measured for the first time. The change in the mean-square charge radius $\ensuremath{\delta}{\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}}^{192,A}$ and the quadrupole deformation parameter ${\ensuremath{\langle}{\ensuremath{\beta}}_{2}^{2}\ensuremath{\rangle}}^{1/2}$ were deduced from the IS measurements. The results were compared with the theoretical calculations and the predicted shape transition at $^{194}\mathrm{Os}$ is discussed.

Deexcitation $\ensuremath{\gamma}$ rays associated with an isomeric state of the $^{195}\mathrm{Os}$ were measured for the first time. The half-life of the isomeric state of the neutral atom $^{195\mathrm{m}}\mathrm{Os}$ was deduced. The isomers were produced in multinucleon transfer reactions between $^{136}\mathrm{Xe}$ beams and $^{198}\mathrm{Pt}$ targets, and were collected and separated by KEK Isotope Separation System. Analysis of $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ correlation and comparison with previous measurement of the isomeric state using the ESR at GSI Darmstadt suggests a possible decay scheme of $^{195\mathrm{m}}\mathrm{Os}$.

We present the first direct measurement of the atomic mass of a superheavy nuclide. Atoms of $^{257}$Db ($Z$=105) were produced online at the RIKEN Nishina Center for Accelerator-Based Science using the fusion-evaporation reaction $^{208}$Pb($^{51}$V, 2n)$^{257}$Db. The gas-filled recoil ion separator GARIS-II was used to suppress both the unreacted primary beam and some transfer products, prior to delivering the energetic beam of $^{257}$Db ions to a helium gas-filled ion stopping cell wherein they were thermalized. Thermalized $^{257}$Db$^{3+}$ ions were then transferred to a multi-reflection time-of-flight mass spectrograph for mass analysis. An alpha particle detector embedded in the ion time-of-flight detector allowed disambiguation of the rare $^{257}$Db$^{3+}$ time-of-flight detection events from background by means of correlation with characteristic $\alpha$-decays. The extreme sensitivity of this technique allowed a precision atomic mass determination from 11 events. The mass excess was determined to be $100\,063(231)_\textrm{stat}(132)_\textrm{sys}$~keV/c$^2$. Comparing to several mass models, we show the technique can be used to unambiguously determine the atomic number as $Z$=105 and should allow similar evaluations for heavier species in future work., Comment: Submitted to PRC as Rapid Comm., 5 pages, 4 figures

A multi-segmented proportional gas counter (MSPGC) with high detection efficiency and low-background event rate has been developed for β -decay spectroscopy. The MSPGC consists of two cylindrically aligned layers of 16 counters (32 counters in total). Each counter has a long active length and small trapezoidal cross-section, and the total solid angle of the 32 counters is 80% of 4 π . β -rays are distinguished from the background events including cosmic-rays by analyzing the hit patterns of independent counters. The deduced intrinsic detection efficiency of each counter was almost 100%. The measured background event rate was 0.11 counts per second using the combination of veto counters for cosmic-rays and lead block shields for background γ -rays. The MSPGC was applied to measure the β -decay half-lives of 198Ir and 199mPt. The evaluated half-lives of T 1 ∕ 2 = 9 . 8 ( 7 ) s and 12.4(7) s for 198Ir and 199mPt, respectively, were in agreement with previously reported values. The estimated absolute detection efficiency of the MSPGC from GEANT4 simulations was consistent with the evaluated efficiency from the analysis of the β - γ spectroscopy of 199Pt, saturating at approximately 60% for Q β > 4 MeV.

We have developed a doughnut-shaped argon gas cell with a rotating target for the KEK Isotope Separation System (KISS). The new gas cell increased extraction yields for target-like fragments (TLFs) produced in multi-nucleon transfer (MNT) reactions. KISS is an on-line isotope separator, which makes use of a laser ion source combined with an argon gas cell as a gas catcher for TLFs. This system has been implemented for nuclear spectroscopy of neutron-rich isotopes in the region of N = 126 . A gas flow simulation was performed to optimize the design of the gas cell for efficient and fast transport of TLFs. To confirm the performance expected at the design stage, we performed off- and on-line experiments by using iridium atoms evaporated from a filament in the gas cell and TLFs produced by a 136 Xe beam and 198 Pt target system respectively. We could increase the extraction yield by more than an order of magnitude by applying a doughnut-shaped gas cell with a rotating target. Thus, we could perform nuclear spectroscopy in this heavy region with the use of KISS.

Various isotopes of Ac, Ra, Fr, and Rn were produced by fusion-evaporation reactions using a 48Ca beam. The energetic ions were stopped in and extracted from a helium gas cell. The extracted ions were identified using a multi-reflection time-of-fight mass spectrograph. In all cases, it was observed that the predominant charge state for the extracted ions, including the alkali Fr, was 2+.

Photography is closely related to the affection of individuals. Camera is one of the promising applications of affective computing. Emotion is essentially a personal characteristic, and it should be dealt with individually and not generically. Therefore, physiological signals are expected to be effective in the field of photography. Previous researches have shown that physiological signals are promising, but a huge amount of physiological data is needed to confirm its effectiveness in realistic situations. We constructed prototypes to investigate the usefulness of this concept in daily life without waiting for the accumulation of a huge amount of physiological data. In the prototypes, we employ three types of physiological signals, namely EOG (electrooculography), EEG (electroencephalogram), and ECG (electrocardiogram). We plan to use these prototypes to evaluate the usefulness and effectiveness of physiological signals in photograpny in the real world.

We report on the performance of a recently developed high-efficiency, low-background, three-dimensional tracking multi-segmented proportional gas counter (3DT-MSPGC), intended for β -decay spectroscopy of neutron-rich nuclei in the vicinity of neutron magic number N =126 at the KEK Isotope Separation System (KISS) facility. The 3DT-MSPGC uses two concentric cylindrical layers of proportional gas counters (16 per layer, 32 in total) featuring resistive anode wires (3 k Ω /cm). By independently measuring the charge deposition from both ends of each counter, we constrain β particle trajectories and determine where they intersect with the central axis of the 3DT-MSPGC. New compact charge-sensitive pre-amplifier modules, along with shaping amplifier and fast-timing amplifier modules, were developed to deduce the hit position by precisely measuring the charge deposition and timing. We have studied the performance of the 3DT-MSPGC in on- and off-line experiments. A longitudinal position resolution of ≤ 3.5 mm (FWHM) was achieved for each counter. The determination of the event trajectories allowed for suppression of background events, resulting in the background-event rate reaching 0.020(3) count-per-second (cps) while still maintaining a high-detection efficiency. This reduction of background is shown to improve the signal-to-noise ratio in determination of the half-life of 196Ir by a factor of 2.3(6), resulting in a significant improvement in achievable precision.

The technique of laser resonance ionization is employed for an element-selective ionization of multi-nucleon transfer reaction products which are stopped and neutralized in a gas cell filled with argon gas at 50 kPa. We have been searching for efficient laser ionization schemes for refractory elements of Z = 73–78 using a time-of-flight mass-spectrometer (TOF-MS) chamber. To evaluate the isotope shift and ionization efficiency for each candidate of the ionization scheme, isotope separation using the TOF-MS was devised. The TOF-MS was designed to separate the isotopes using two-stage linear acceleration with a mass resolving power M / Δ M of >350. A mass resolving power of 250 was experimentally confirmed by measuring the TOF of laser-ionized tantalum ( Z = 73) ions with mass number 181. We searched for a laser resonance ionization scheme of tantalum using the TOF-MS.

KEK Isotope Separation System (KISS) has been developed at RIKEN to produce neutron rich isotopes with N = 126 to study the β -decay properties for application to astrophysics. The KISS is an element-selective mass-separation system which consists of an argon gas cell-based on laser ion source for atomic number selection and an ISOL mass-separation system. The argon gas cell of KISS is a key component to stop and collect the unstable nuclei produced in a multi-nucleon transfer reaction, where the isotopes of interest will be selectively ionized using laser resonance ionization. We have performed off- and on-line experiments to study the basic properties of the gas cell as well as of the KISS. We successfully extracted the laser-ionized stable 56 Fe (direct implantation of a 56 Fe beam into the gas cell) atoms and 198 Pt (emitted from the 198 Pt target by elastic scattering with a 136 Xe beam) atoms from the KISS during the commissioning on-line experiments. We furthermore extracted laser-ionized unstable 199 Pt atoms and confirmed that the measured half-life was in good agreement with the reported value.

The elastic scattering process for the nuclear reactions induced by the Radioactive Ion Beams 7Be and 8B on a 208Pb target was measured for the first time in the energy range around the Coulomb barrier. Extensive theoretical calculations within the framework of the optical model were performed. An excellent agreement between experimental data and theoretical predictions was achieved for the reaction 7Be + 208Pb, while a comprehensive understanding of the reaction dynamics induced by the more exotic projectile 8B is still far to be reached. Predictions of the cross section for the breakup for both systems will also be given., The 8B experiment was performed at RI Beam Factory operated by RIKEN Nishina Center and CNS, University of Tokyo. This work was supported by the Polish National Science Centre under Contract No. 2014/14/M/ST2/00738 (COPIN-INFN Collaboration), by JSPS KAKENHI (Nos. 16K05369, and 19K03883) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan and by the projects: CONACyT LN-294537 and DGAPA-PAPIIT IA103218.

We developed KEK Isotope Separation System (KISS) for the nuclear spectroscopy of the nuclei in the vicinity of N = 126. The spectroscopy is important to identify the explosive astrophysical environment for the formation of the third peak in the observed solar r-abundance pattern. We report the experimental results of in-gas-cell laser ionization spectroscopy and β-decay spectroscopy for the nuclei in the vicinity of 198Pt.

We usually use the word ‘like’ when we see good pictures, e.g. in social networks. When we choose a picture that evokes the feeling of ‘like’ out of many pictures, we evaluate each picture based on our subjective and intuitive preference. We hypothesized that physiological responses arise when participants watch pictures that evokes the feeling of ‘like’. In this study, we examined whether we can measure physiological responses when participants feel ‘to like’ a picture they choose among many pictures. We measured electroencephalogram, electrooculogram, electrocardiogram, and respiration of the participants while these are choosing the best picture from a set of pictures which had different setting of depth of field. We found that EEG responses appears when the participant watched the best pictures which evokes the feeling of ‘like’.

The masses of ^{246}Es, ^{251}Fm, and the transfermium nuclei ^{249-252}Md and ^{254}No, produced by hot- and cold-fusion reactions, in the vicinity of the deformed N=152 neutron shell closure, have been directly measured using a multireflection time-of-flight mass spectrograph. The masses of ^{246}Es and ^{249,250,252}Md were measured for the first time. Using the masses of ^{249,250}Md as anchor points for α decay chains, the masses of heavier nuclei, up to ^{261}Bh and ^{266}Mt, were determined. These new masses were compared with theoretical global mass models and demonstrated to be in good agreement with macroscopic-microscopic models in this region. The empirical shell gap parameter δ_{2n} derived from three isotopic masses was updated with the new masses and corroborates the existence of the deformed N=152 neutron shell closure for Md and Lr.

In this contribution we describe the first results obtained for the investigation of the elastic scattering process in the reactions induced by the Radioactive Ion Beams 7Be and 8B on a 208Pb target at Coulomb barrier energies. The experimental data were analyzed within the framework of the optical model in order to extract the total reaction cross section. The comparison with data available in literature for reactions induced on 208Pb by light ions in the mass range A = 6-8 shows that the loosely-bound 8B has the largest reactivity.

We developed an in situ radiotracer method for diffusion studies in solids using short-lived α-emitting 8Li tracer. In the method, while implanting a pulsed 8Li beam into a solid material of interest, the α particles emitted into the implantation side of the sample surface were detected as a function of time. By changing the implantation depth and the detection angle against the sample surface according to lithium diffusivity (deep implantation and large angle with a large solid angle, or shallow implantation and small angle with a narrow solid angle), the method can be sensitive to a wide range of diffusion length ranging from micrometer scale to nanometer scale per second. The feasibility of the method was demonstrated by measuring the lithium diffusion coefficients to the order of 10−12 cm2/s in lithium ionic conductors.

We have developed a laser ion source for the target-like fragments (TLFs) produced in multi-nucleon transfer (MNT) reactions. The operation principle of the source is based on the in-gas laser ionization and spectroscopy (IGLIS) approach. In the source TLFs are thermalized and neutralized in high pressure and high purity argon gas, and are extracted after being selectively re-ionized in a multi-step laser resonance ionization process. The laser ion source has been implemented at the KEK Isotope Separation System (KISS) for β-decay spectroscopy of neutron-rich isotopes with N = 126 of nuclear astrophysical interest. The simulations of gas flow and ion-beam optics have been performed to optimize the gas cell for efficient thermalization and fast transporting the TLFs, and the mass-separator for efficient transport with high mass-resolving power, respectively. To confirm the performances expected at the design stage, off-line experiments have been performed by using 56Fe atoms evaporated from a filament in the gas cell. The gas-transport time of 230 ms in the argon cell and the measured KISS mass-resolving power of 900 are consistent with the designed values. The high purity of the gas-cell system, which is extremely important for efficient and highly-selective production of laser ions, was achieved and confirmed from the mass distribution of the extracted ions. After the off-line tests, on-line experiments were conducted by directly injecting energetic 56Fe beam into the gas cell. After thermalization of the injected 56Fe beam, laser-produced singly-charged 56Fe+ ions were extracted. The extraction efficiency and selectivity of the gas cell in the presence of plasma induced by 56Fe beam injection as well as the time profile of the extracted ions were investigated; extraction efficiency of 0.25%, a beam purity of >99% and an extraction time of 270 ms. It has been confirmed that the performance of the KISS laser ion source is satisfactory to start the measurements of lifetimes of the β-decayed nuclei with N = 126 .

We have developed an in situ and nanoscale Li diffusion measurement method in Li battery materials using an α-emitting radioactive 8Li tracer. In this method, while implanting a low-energy (8 keV) 8Li beam, the α particles emitted at a small angle (10°) relative to the sample surface were detected as a function of time. Measurement for Li diffusion coefficients in a spinel phase LiMn2O4 (LMO) thin film has been started, which is used as an electrode in a Li ion secondary battery. An obvious Li diffusion effect in LMO was observed at the sample temperature of 623 K, and the further measurement is underway.

The KEK Isotope Separation System has been developed to study the β -decay properties of the neutron-rich nuclei around the neutron magic number N = 126. These properties are essential for understanding the origin of the third peak in the r-process element abundance pattern. The detector system for β -decay spectroscopy at the KEK Isotope Separation System should have high detection efficiency for low-energy β -rays, and should be operated under a low-background environment. The detector system of the KEK Isotope Separation System consists of β -ray telescopes and a tape transport system. The solid angle covered by the β -ray telescopes is as large as 75% of 4 π in total. The Q β -value dependence of the detection efficiency was estimated by Geant4 simulation. The background rate was 0.09 cps using a veto counter system and Pb shields. This background rate allows us to measure the lifetime of 202Os.

International audience; Precision mass measurements of ^63Cu, ^64–66Zn, ^65–67Ga, ^65–67Ge, ^67As, ^79,81Br, ^79Kr, ^80,81Rb, and ^79,80Sr were performed with a multireflection time-of-flight mass spectrograph. The masses of these nuclides were determined by the single reference method using isobaric references. In order to obtain precise results, time-of-flight drift compensations were performed and a phenomenological fit function was employed. Consequently, in the case of ^65Ga, a mass uncertainty of 2.1 keV, corresponding to a relative precision of \(\delta m/m = 3.5 \times 10^{ - 8}\), was obtained and the mass value is in excellent agreement with the 2016 Atomic Mass Evaluation.

Magnetic dipole moment and mean-square charge radius of $^{199}$Pt ($I^{\pi}=$ 5/2$^-$) have been evaluated for the first time from the investigation of the hyperfine splitting of the $\lambda_1=$ 248.792 nm transition by in-gas-cell laser ionization spectroscopy. Neutron-rich nucleus $^{199}$Pt was produced by multi-nucleon transfer reaction at the KISS where the nuclear spectroscopy in the vicinity of $N=$ 126 is planed from the aspect of an astrophysical interest as well as the nuclear structure. Measured magnetic dipole moment $+$0.63(13)$\mu_{\rm N}$ is consistent with the systematics of those of nuclei with $I^{\pi}=$ 5/2$^-$. The deformation parameter $| ^{1/2}|$ evaluated from the isotope shift indicates the gradual shape change to spherical shape of platinum isotopes with increasing neutron number toward $N=$ 126.

The $^{8}\mathrm{Li}(\ensuremath{\alpha},n)^{11}\mathrm{B}$ reaction is regarded as the key reaction in the inhomogeneous big bang and in type-II supernova nucleosynthesis. Recently, the importance of this reaction to solving the $^{7}\mathrm{Li}$ problem, i.e., the inconsistency between the predicted and the observed primordial $^{7}\mathrm{Li}$ abundances, has also been noted. The most recent cross-section data published by our collaboration group in 2006 [H. Ishiyama et al., Phys. Lett. B 640, 82 (2006)] cover the 0.7- to 2.6-MeV energy region in the center-of-mass system. Here, we present additional data spanning the 0.45- to 1.8-MeV energy region. Thus, the predominant energy region for the big bang nucleosynthesis, corresponding to ${T}_{9}=1$ (where ${T}_{9}$ is a temperature unit equivalent to ${10}^{9}$ K), is almost completely spanned by the previous [H. Ishiyama et al., Phys. Lett. B 640, 82 (2006)] and present results together.

High-precision mass measurements of $^{63}$Cu, $^{64-66}$Zn, $^{65}$Ga, $^{65-67}$Ge, $^{67}$As, $^{78,81}$Br, $^{80}$Rb, and $^{79}$Sr were performed utilizing a multireflection time-of-flight mass spectrograph combined with the gas-filled recoil ion separator GARIS-II. In the case of $^{65}$Ga, a mass uncertainty of 2.1 keV, corresponding to a relative precision of $\delta m / m = 3.5\times10^{-8}$, was obtained and the mass value is in excellent agreement with the 2016 Atomic Mass Evaluation. For $^{67}$Ge and $^{81}$Br, where masses were previously deduced through indirect measurements, discrepancies with literature values were found. The feasibility of using this device for mass measurements of nuclides more neutron-deficient side, which have significant impact on the $rp$-process pathway, is discussed., Comment: 15 pages, 6 figures, 1 table

The scattering process of weakly-bound nuclei at Coulomb barrier energies provides deep insights on the reaction dynamics induced by exotic nuclei. Within this framework, we measured for the first time the scattering process of the short-lived Radioactive Ion Beam (RIB) 8B (Sp = 0.1375 MeV) from a 208Pb target at 50 MeV beam energy. The 8B RIB was produced by means of the in-flight facility CRIB (RIKEN, Japan) with an average intensity on target of 10 kHz and a purity about 25%. Elastically scattering ions were detected in the angular range θc.m. = 10 ◦ -160 ◦ by means of the detector array EXPADES. A preliminary optical model analysis indicates a total reaction cross section of about 1 b, a value, once reduced, 2-3 times larger than those obtained for the reactions induced by the stable weakly-bound projectiles 6,7Li on a 208Pb target in the energy range around the Coulomb barrier.

An investigation was made on the energy resolution of an active-target type gas counter operating in low-pressure He/CO2 mixed gas for studies of nuclear reactions such as (?, n) and (?, p) using radioactive nuclear beams (RNBs). The dependencies of effective gain and energy resolution on different parameters such as drift field, induction field and GEM voltages were studied. The energy resolution with adequate electric field configuretaion was found to be 3% in ?. DOI: http://dx.doi.org/10.3329/jbas.v37i2.17553 Journal of Bangladesh Academy of Sciences, Vol. 37, No. 2, 139-144, 2013

We demonstrated efficient two-color two-step laser ionization schemes in the combined use of λ1 ∼ 250 nm and λ2 = 307.9 nm, which are applicable to heavy refractory elements with an atomic number in the wide range of Z = 69–78. We investigated newly observed ionization schemes of tantalum and tungsten atoms in an argon-gas-cell-based laser ion source for the efficient ionization of atoms of unstable nuclei through the two-color two-step laser resonance ionization technique. We experimentally determined the ionization cross sections from the measured saturation curves by solving the rate equations for the ground, intermediate, and ionization continuum populations. Hyperfine structures of these elements were also studied to deduce the isotope-shift, pressure-shift, and pressure-broadening in the resonance spectra of the excitation transitions in the argon gas cell. The electronic factor F255 of the excitation transition λ1 = 255.2115 nm between the ground and intermediate states was deduced from the measured isotope shifts of stable 182,183,184,186W isotopes. The ionization schemes investigated here are applicable to extract any isotopes of these elements by considering the measured pressure shift and nuclear isotope shift in optimizing the wavelength λ1.

Nuclear parameters such as lifetimes and masses of the waiting point nuclei of r-process nucleosynthesis are significant to investigate its astrophysical environment. However, the difficulty in the production of extremely neutron-rich nuclei at the 126 neutron closed shell makes their experimentalstudies unfeasible. Therefore, the theoretical nuclear models play crucial roles in the simulation of the r-process nucleosynthesis. The systematic nuclear spectroscopy of the neutron-rich nuclei around the 126 neutron closed shell provides significant inputs to those theoretical models to improve their predictability for the waiting point nuclei. We are developing KEK Isotope Separation System (KISS) to perform the systematic nuclear spectroscopy of those neutron-rich nuclei. The nuclei of interest are produced by multi-nucleon transfer reactions between 136Xe and 198Pt. The experimental study demonstrated its promising potential to produce them. We have successfully performed the β­γ spectroscopy and the laser ionization spectroscopy at KISS using the nuclear production by the multi-nucleon transfer reactions.

The tilted-foil method for producing spin-polarized radioactive isotope beams has been studied using the re-accelerated radioactive 8 Li and 123 In beams produced at Tokai Radioactive Ion Accelerator Complex (TRIAC) facility. We successfully produced polarization in a 8 Li beam of 7.3(5)% using thin polystyrene foils (4.2 μg/cm 2 ). The systematic study of the nuclear polarization as a function of the number of foils and beam energy has been performed, confirming the features of the tilted-foil technique experimentally. After the study, a spin-polarized radioactive 123 In beam, which is the heaviest ever polarized in its ground state by this method, has been successfully generated by the tilted-foil method, for the nuclear spectroscopy around the doubly magic nucleus 132 Sn.

We are developing in situ diffusion measurements in solids using short-lived radioactive ion beams provided from an isotope separator on-line (ISOL). We examined the feasibility of a new in situ nanoscale diffusion measurement method using a radioactive 8 Li tracer by computer simulations. Under moderate experimental conditions, we have found that the detection limit of lithium diffusion coefficient can be improved to a low value of 1 × 10 - 12 cm 2 / s . Also, in situ sodium diffusion measurement in Na battery materials can be applicable using a radioactive 20 Na tracer. We found Na diffusion coefficients can be measured, ranging from 10 - 6 to 10 - 10 cm 2 / s by computer simulations.