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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.

We demonstrated efficient two-color two-step laser ionization schemes in the combined use of λ

KOBRA (KOrea Broad acceptance Recoil spectrometer and Apparatus) facility being designed at Rare Isotope Science Project in Korea will be utilized to produce rare isotope beams by employing multi-nucleon transfer reactions at about 20 MeV/nucleon for studies of nuclear structure. KOBRA will also provide high suppression of beam induced background for direct measurements of radiative-capture cross sections in the astrophysical energy range. The present design status of the KOBRA facility is reported along with a brief introduction to the facility. We have studied the feasibility of production of 44 Ti based on the present design of KOBRA as an example, and calculated the intensity of 44 Ti secondary beam, to be about 105 particles per second, for 1 pnA 46 Ti primary beam with a carbon target for a beam energy of 25 MeV/nucleon. A Monte Carlo simulation with a ray-tracing code has been performed to show that recoil products 66 Se are well separated from a 65 As beam by KOBRA for the 65 As ( p , γ ) 66 Se reaction at a beam energy of 1 MeV/nucleon.

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 studied multinucleon transfer reactions in the 197Au+130Te system at Elab=1.07 GeV by employing the PRISMA magnetic spectrometer coupled to a coincident detector. For each light fragment we constructed, in coincidence, the distribution in mass of the heavy partner of the reaction. With a Monte Carlo method, starting from the binary character of the reaction, we simulated the de-excitation process of the produced heavy fragments to be able to understand their final mass distribution. The total cross sections for pure neutron transfer channels have also been extracted and compared with calculations performed with the grazing code.

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 studied the production of neutron-rich nuclides in multinucleon transfer collisions of stable and radioactive beams in the mass range A=40-60. We first presented our experimental cross section data of projectile fragments from the reaction of 40Ar(15 MeV/nucleon) with 64Ni, 58Ni and 27Al. We then compared them with calculations based on either the deep-inelastic transfer (DIT) model or the constrained molecular dynamics (CoMD) model, followed by the statistical multifragmentation model (SMM). An overall good agreement of the calculations with the experimental data is obtained. We continued with calculations of the reaction of 40Ar (15 MeV/nucleon) with 238U target and then with reactions of 48Ca (15 MeV/nucleon) with 64Ni and 238U targets. In these reactions, neutron-rich rare isotopes with large cross sections are produced. These nuclides, in turn, can be assumed to form radioactive beams and interact with a subsequent target (preferably 238U), leading to the production of extremely neutron-rich and even new isotopes (e.g. 60Ca) in this mass range. We conclude that multinucleon transfer reactions with stable or radioactive beams at the energy of around 15 MeV/nucleon offer an effective route to access extremely neutron-rich rare isotopes for nuclear structure or reaction studies., Comment: 28 pages, 11 figures

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.

Using a multireflection time-of-flight mass spectrograph located after a gas cell coupled with the gas-filled recoil ion separator GARIS-II, the masses of several $\alpha$-decaying heavy nuclei were directly and precisely measured. The nuclei were produced via fusion-evaporation reactions and separated from projectilelike and targetlike particles using GARIS-II before being stopped in a helium-filled gas cell. Time-of-flight spectra for three isobar chains, $^{204}$Fr-$^{204}$Rn-$^{204}$At-$^{204}$Po, $^{205}$Fr- $^{205}$Rn-$^{205}$At-$^{205}$Po-$^{205}$Bi, and $^{206}$Fr-$^{206}$Rn-$^{206}$At, were observed. Precision atomic mass values were determined for $^{204-206}$Fr, $^{204,205}$Rn, and $^{204,205}$At. Identifications of $^{205}$Bi, $^{204,205}$Po, $^{206}$Rn, and $^{206}$At were made with N$\leq$10 detected ions, representing the next step toward use of mass spectrometry to identify exceedingly low-yield species such as superheavy element ions., 多反射時間飛行質量分析装置を理化学研究所設置の気体充填型反跳分離装置-II型(GARIS-II)と連結したガスセルに配置し、$\alpha$崩壊連鎖を伴う重原子核の質量の直接測定を実施した。融合-蒸発反応で生成された原子核をGARIS-IIを用いて分離し、ヘリウムガスセルで止めて目的の原子核を捕集した。本実験で$^{204}$Fr-$^{204}$Rn-$^{204}$At-$^{204}$Po, $^{205}$Fr-$^{205}$Rn-$^{205}$At-$^{205}$Po-$^{205}$Bi及び$^{206}$Fr-$^{206}$Rn-$^{206}$Atの3つの同重体鎖の時間飛行スペクトルが観測された。その結果、$^{204-206}$Fr, $^{204,205}$Rn、そして$^{204,205}$Atの原子質量値が精密に決定された、今回の解析において、$^{205}$Bi, $^{204,205}$Po, $^{206}$Rn、そして$^{206}$Atの同定は10個以下という少量のイオン数でなされた。この成果は 次のステップとして実施する予定である(生成量が極少量の)超重元素イオンの質量分析につながる成果となる。

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.

This paper presents our recent study on the production of neutron-rich rare isotopes with heavy-ion beams in the energy region of 15 MeV/nucleon. We present calculated production cross sections of neutron-rich nuclides from collisions of a 86 Kr (15 MeV/nucleon) beam with 238 U targets. Our calculations are based on a two-step approach: the dynamical stage of the collision is described with either the phenomenological Deep-Inelastic Transfer model (DIT), or with the microscopic Constrained Molecular Dynamics model (CoMD). The de-excitation of the hot heavy projectile fragments is performed with the Statistical Multifragmentation Model (SMM). We also performed calculations with a radioactive beam of 92 Kr (15 MeV/nucleon) with a target of 238 U and observed that the multinucleon transfer mechanism leads to very neutron-rich nuclides toward and beyond the astrophysical r-process path. In the future, we plan to experimentally investigate such reactions in the KOBRA spectrometer at the RISP facility in Korea. We conclude that the reaction mechanism at beam energies below the Fermi energy involving periph- eral nucleon exchange, constitutes a novel and effective route to access extremely neutron-rich isotopes toward the r-process path and the neutron drip-line.

In this contribution we summarize recent efforts to describe the production of rare isotopes with beams of 15–25 MeV/nucleon expected from low-energy facilities. We first present calculated production cross sections of proton-rich nuclides from collisions of stable beams of mass A∼60–80. Our calculations are performed with the phenomenological deep-inelastic transfer (DIT) model and the microscopic con- strained molecular dynamics model (CoMD). De-excitation of the excited quasipro- jectiles from the dynamical stage of the reaction is performed with the statistical multifragmentation model (SMM). In addition to the efforts on proton-rich nuclides, we investigated the possibility of producing neutron-rich rare isotopes in the mass range A∼180–200, i.e. near the third r-process peak of A=195. We performed calcu- lations for a 208Pb (15MeV/nucleon) beam and find that the multinucleon transfer mechanism leads to very neutron-rich nuclides in this mass range. We believe that our continued progress on the study of multinucleon transfer reactions using heavy- ion beams of 15–25 MeV/nucleon, can provide new opportunities in rare isotope research in the near future, as planned at the KOBRA facility of RISP in Korea.

The Rare Isotope Science Project (RISP) in Korea is developing the Rare Isotope (RI) Accelerator, RAON. The RAON is planned to be an advanced RI beam using isotope separation on-line (ISOL) with a high-power target. The main goal of the ISOL facility is to deliver high-quality, intense, neutron-rich (n-rich) beams to the experimental hall; for example 108 atoms per second of the 132Sn n-rich reference isotope. The RAON ISOL facility consists of mainly two systems. One is the RI production system of a high-power uranium fission target combined with the Forced Electron Beam Induced Arc Discharge (FEBIAD) ion source, Surface Ionization (SI) ion source and Resonance Ionization Laser Ion Source (RILIS), in which system the final goal for the RI production rate is 1014 fission per second. The other is the RI beam purification system, which is comprised of an RF beam cooler, a high resolution mass separator (HRMS), a charge breeder and a charge state separator, and the design goal is to deliver the RI beam with a mass resolving power up to 45,000 and with a limit of 6 × 105 background counts per second. The current status of the ISOL facility of the RISP is reported.

We developed a prototype laser ionization gas cell with a beam extraction system. This device is for use of PArasitic Laser Ion-Source (PALIS), which will be implemented into RIKEN’s fragment separator, BigRIPS as a part of SLOWRI. Off-line resonant laser ionization for stable Co, Cu, Fe, Ni, Ti, Nb, Sn, In and Pd inside the gas cell, ion extraction and transport to the high-vacuum region via SPIG and QMS have been confirmed (Sonoda et al, Nucl Instrum Meth B 295:1, 2013).

This paper proposes a robust adaptive control method for synchronization of uncertain chaotic neural networks with mixed delays. Uncertainty and disturbance in the networks are estimated by fuzzy disturbance observer without any prior information about them. The proposed control scheme with adaptive laws is derived based on Lyapunov-Krasovskii stability theory to guarantee the globally asymptotical synchronization between the networks. An example is illustrated to show the effectiveness of the proposed method.

We investigate the possibilities of producing neutron-rich nuclides in projectile fission of heavy beams in the energy range of 20 MeV/nucleon expected from low-energy facilities. We report our efforts to theoretically describe the reaction mechanism of projectile fission following a multinucleon transfer collision at this energy range. Our calculations are mainly based on a two-step approach: the dynamical stage of the collision is described with either the phenomenological Deep-Inelastic Transfer model (DIT), or with the microscopic Constrained Molecular Dynamics model (CoMD). The deexcitation/fission of the hot heavy projectile fragments is performed with the Statistical Mul- tifragmentation Model (SMM). We compared our model calculations with our previous experimental projectile-fission data of 238U (20 MeV/nucleon)+208Pb and 197Au (20 MeV/nucleon)+197Au and found an overall reasonable agreement. Our study suggests that projectile fission following periph- eral heavy-ion collisions at this energy range offers an effective route to access very neutron-rich rare isotopes toward and beyond the astrophysical r-process path.

is one of three genetic loci conferring strain-specific resistance to (SMV). The locus has been mapped to a 154-kb region on chromosome 14, containing a cluster of five nucleotide-binding leucine-rich repeat (NB-LRR) resistance genes. High sequence similarity between the candidate genes challenges fine mapping of the locus. Among the five, Glyma14g38533 showed the highest transcript abundance in 1 to 3 h of SMV-G7 inoculation. Comparative sequence analyses were conducted with the five candidate NB-LRR genes from susceptible (-type) soybean [ (L.) Merr.] cultivar Williams 82, resistant (-type) cultivar Hwangkeum, and resistant lines L29 and RRR. Sequence comparisons revealed that Glyma14g38533 had far more polymorphisms than the other candidate genes. Interestingly, Glyma14g38533 gene from -type lines exhibited 150 single-nucleotide polymorphism (SNP and six insertion-deletion (InDel) markers relative to -type line, Furthermore, the polymorphisms identified in three -type lines were highly conserved. Several polymorphisms were validated in 18 -type resistant and six -type susceptible lines and were found associated with their disease response. The majority of the polymorphisms were located in LRR domain encoding region, which is involved in pathogen recognition via protein-protein interactions. These findings associating Glyma14g38533 with -type resistance to SMV suggest it is the most likely candidate gene for .

International audience; Production of neutron-rich nuclei around N = 126 by multinucleon transfer reactions has recently gained a renewal of interest both theoretically and experimentally. We are now advancing the KISS project at RIKEN to produce those nuclei by multinucleon transfer reactions and measure their lifetimes to investigate the astrophysical environments of the r-process. To investigate the relevance of the production mechanism, we performed measurements for the reaction system 136Xe + 198Pt, using the spectrometer VAMOS++ and the gamma-ray array EXOGAM at GANIL. Cross sections deduced from the measurements for neutron-rich nuclei around N = 126 show a modest enhancement when compared with the GRAZING calculations, indicating the advantage of the multinucleon transfer reactions as compared with fragmentation for production of N = 126 neutron-rich isotones. The possibility for production of neutron-rich nuclei around uranium beyond N = 126 by multinucleon transfer reactions is also discussed.

This work aims at investigating the projectile binding energy influence on the reaction dynamics, introducing new results and new data analysis methods in order to overcome some typically encountered problems, such as the identification of reaction products differing by few mass units and the discrimination of direct reaction processes. The $^{17}\mathrm{O}+^{58}\mathrm{Ni}$ collision was studied at five near-barrier energies employing a compact experimental setup consisting of four double-sided silicon strip detectors (DSSSDs). Different reaction processes, namely the elastic and inelastic scattering and the $1n$ stripping, were discriminated by means of a detailed analysis of the experimental energy spectra based on Monte Carlo simulations. The elastic scattering angular distributions were investigated within the framework of the optical model using Woods-Saxon and double-folding potentials. The total reaction cross sections were extracted and the reduced cross sections compared with those obtained for $^{17}\mathrm{F}$ (${S}_{p}=0.600$ MeV), the mirror nucleus of $^{17}\mathrm{O}$ (${S}_{n}=4.143$ MeV), and for the tightly bound $^{16}\mathrm{O}$ projectile. The $^{17}\mathrm{O}+^{58}\mathrm{Ni}$ total reaction cross sections were larger than those for $^{16}\mathrm{O}$ on the same target at the lowest energies studied, becoming identical, within errors, as the incident energy increased above the Coulomb barrier. This behavior was related to a strong contribution from the $1n$-stripping channel at the lowest energies.

International audience; An experiment was performed at LNL to obtain information concerning the yield distributions in both the 132Sn (N = 82) and the 208Pb (N = 126) regions of the nuclide chart. The experimental set-up was composed of the large-acceptance magnetic spectrometer PRISMA to detect the light partner of the reaction, in conjunction with a recently installed ancillary set-up to detect the heavy partner.

We investigated the reaction dynamics induced by the 7Be,8B+208Pb collisions at energies around the Coulomb barrier. Charged particles originated by both the col- lisions were detected by means of 6 ΔE-Eres telescopes of a newly developed detector array. Experimental data were analysed within the framework of the Optical Model and the total reaction cross-sections were compared together and with the 6,7Li+208Pb colli-sion data. According to the preliminary results, 7Be nucleus reactivity is rather similar to the 7Li one whereas the 8B+208Pb total reaction cross section appears to be much larger than those measured for reactions induced by the other weakly-bound projectiles on the same target.

This paper proposes a robust adaptive controller design method for synchronization of a complex dynamical network with uncertainty and disturbance. A fuzzy disturbance observer is used to estimate the overall disturbances without any prior knowledge about them. The proposed control method globally asymptotically synchronizes the network using adaptation laws obtained by using Lyapunov stability theory. The proposed method is applied to two chaotic systems and the results show the effectiveness of the approach.

This paper proposes a robust adaptive backstepping synchronization method for a class of uncertain chaotic systems. Unknown factors including system uncertainties and external disturbances are estimated by a fuzzy disturbance observer. By use of the fuzzy disturbance observer, any prior information about the unknown factors is not need. The proposed method using the estimated values guarantees the global synchronization for chaotic systems with mismatched uncertainties in the sense of uniform ultimate boundedness. Finally, numerical examples are presented to show the effectiveness of the method.

This paper proposes an adaptive control method to achieve the lag synchronization between uncertain complex dynamical network having delayed coupling and a non-identical reference node. Unknown parameters of both the network and reference node are estimated by adaptive laws obtained by Lyapunov stability theory. With the estimated parameters, the proposed method guarantees the globally asymptotical synchronization of the network in spite of unknown bounded disturbances. The effectiveness of our work is verified through a numerical example and simulation.

The KEKCB is an electron cyclotron resonance ion source (ECRIS) operating at the microwave frequency of 18 GHz and has successfully operated as the charge breeder at Tokai Radioactive Ion Accelerator Complex (TRIAC). Following an overview of the TRIAC, the recent operating results of the KEKCB have been demonstrated. Special attention was paid on the element-dependent charge breeding efficiency and the beam impurity originating from the ECR plasma of the KEKCB.

Expérience GANIL/VAMOS/EXOGAM; International audience; Absolute cross sections for isotopically identified products formed in multinucleon transfer in the136Xe + 198Pt system at ∼ 8 MeV=nucleon are reported. The isotopic distributions obtained using a largeacceptance spectrometer demonstrated the production of the “hard-to-reach” neutron-rich isotopes forZ < 78 around the N = 126 shell closure far from stability. The main contribution to the formation of theseexotic nuclei is shown to arise in collisions with a small kinetic energy dissipation. The presentexperimental finding corroborates for the first time recent predictions that multinucleon transfer reactionswould be the optimum method to populate and characterize neutron-rich isotopes around N = 126 whichare crucial for understanding both astrophysically relevant processes and the evolution of “magic” numbersfar from stability.

The excitation function of the 8 Li(d, t) 7 Li reaction was directly measured using 8 Li beam irradiating a deuterated polyethylene target at center-of-mass system beam energies ( E cm ) between 0.3 and 1.2 MeV. This is the first cross section measurement of the above reaction below E cm = 1.5 MeV , covering Gamow peaks for 1 – 3 × 10 9 K of astrophysical interest. A broad resonance-like structure was observed at around E cm = 0.8 MeV . The astrophysical reaction rate deduced from the present result is far larger than the previously reported values estimated from extrapolation of data observed at higher energies, roughly by one order of magnitude at about 1 × 10 9 K .

A gated multiple-sampling and tracking proportional chamber (GMSTPC) has been made for the study of ( α , n) and (p, n) type reactions of astrophysical interest induced by low-energy radioactive nuclear beam. It consists of a drift-space region, a proportional-counter region divided into 24 segments and a gating grid. The GMSTPC is placed in such a way that the beam enters directly into its drift space, so that the chamber gas also acts reaction targets. The gating grid allows the gas multiplication of electrons only when it is triggered by neutron signals. Under the operation of this gating grid, almost no pulse-height defects have been observed up to 40 kHz beam-injection rates. Characteristics and performance of the GMSTPC are reported. We also describe some details of a whole detector system including a time-of-flight counter, a neutron-counter wall consisting of 28 plastic-scintillator bars and the GMSTPC, with which three-dimensional trajectories and energies of both charged particles and neutrons can be measured event by event. The measured efficiency of the detector system as well as the analysis efficiency in the case of the Li 8 ( α , n ) reaction are also given.

A Ramsey's method with pulsed neutrons is proposed. A Ramsey signal, which is a neutron spin rotation about a static magnetic field for a time interval between two separated oscillatory fields, is observed as a function of a neutron time of flight (TOF) in this method. The neutron spin rotation or the RF oscillation is used as a clock of the neutron velocity measurement which ranges from cold to epithermal neutron energies. This method together with the TOF measurement can be used for neutron inelastic scattering experiments. In addition, this method can be applied to the measurement of magnetic and pseudomagnetic fields in matter, and also to neutron spin manipulation for spin dependent scattering.

An accurate exclusive measurement of the 8 Li( α , n) 11 B reaction cross sections has been carried out successfully by using a highly efficient detector system and high-purity low energy 8 Li-beam. The excitation function obtained with high statistics in the energy region from 0.9 to 2.7 MeV in the center-of-mass system is reported. The present cross sections show that the averaged ratio of total cross section to the inverted neutron capture cross section is 4 ∼ 5. Some details of the experimental method are also described.

The effect of the nuclear shell structure on the heavy-ion fusion reaction was investigated for the reaction systems 8 2 Se + 1 3 8 Ba, 8 2 Se + 1 3 4 Ba, 1 6 O + 2 0 4 Pb, 8 6 Kr + 1 3 4 Ba, 8 6 Kr + 1 3 8 Ba and 8 2 Se + n a t . Ce. Evaporation residues for these fusion reactions were measured using a recoil mass separator (JAERI-RMS) near Coulomb barrier region. The measured evaporation residue cross sections for the reactions 8 2 Se + 1 3 8 Ba and 8 6 Kr + 1 3 8 Ba were two orders of magnitude and one order of magnitude larger than those for the reactions 8 2 Se + 1 3 4 Ba and 8 6 Kr + 1 3 4 Ba, respectively, at the excitation energy region of 10 ∼ 30 MeV. The evaporation residue cross sections were compared with those of the other reaction systems that make the same or similar compound nuclei as the present reaction systems. It was found that the evaporation residue cross sections correlate strongly with the sum of the shell energies for both projectile and target nuclei, i.e. the evaporation residue cross sections increase as the sum of the shell energy decreases.

We have studied, by a computer simulation, the feasibility of the radiotracer method for diffusion studies using short-lived radioactive nuclear beams as tracers. We have considered two typical examples of radiotracers that will be available in KEK-JAERI RNB facility, 18F (half-life: 1.8 h, β+-emitter) and 8Li (half-life: 0.83 s, α-emitter). The sample is set on a given temperature and irradiated by the tracer beams for a time-duration. In the case of 18F, the serial sectioning technique by the ion-beam-sputtering device is assumed to obtain the concentration-depth profile of the tracer diffused during the irradiation time. In the case of 8Li, the simulation reveals that the time-dependent yields of α particles can be used as a measure of the diffusivity of the tracer in a non-destructive way. The present method could be applied to measure rather large diffusion coefficients of various radiotracers with a short measuring time.

The dependence of the fusion reaction on the nuclear shell structure was investigated for the two reaction systems 82Se + 138Ba and 82Se + 134Ba, where the nucleus 138Ba has a closed neutron shell N=82, while the nucleus 134Ba has a neutron number 78. Evaporation residues for these fusion reactions were measured near the Coulomb barrier region. The measured evaporation residue cross sections for the reaction system 82Se + 138Ba were two orders of magnitude larger than those for the reaction system 82Se + 134Ba in the excitation energy region of 20–30 MeV. The evaporation residue cross sections were compared with those of the other reaction systems that produce the same compound nucleus as the present systems. It was found that the fusion reaction 82Se + 138Ba occurs without hindrance, while that of 82Se + 134Ba is considerably hindered, as commonly observed in the massive reaction system with the charge product ZpZt>1800 of projectile and target. This suggests the importance of the shell closure N=82 in the heavy-ion fusion reaction.

A new ISOL-based radioactive nuclear beam (RNB) facility has been constructed as a joint project of the High Energy Accelerator Research Organization (KEK) and the Japan Atomic Energy Research Institute (JAERI) at the Tandem accelerator of the Tokai site of JAERI. It uses heavy-ion linacs and related equipment of the presently closed KEK-RNB facility. Fission fragments with energy from 0.1 to 8 MeV/u will be available at this facility.