Publishing type：Research paper (scientific journal)   Publisher：Japan Health Physics Society  

DOI： 10.5453/jhps.55.207

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Publishing type：Research paper (scientific journal)   Publisher：Japan Radioisotope Association  

DOI： 10.3769/radioisotopes.69.243

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Publishing type：Research paper (scientific journal)  

© 2019, Copyright © 2019 Taylor & Francis Group LLC. Purpose: We have proposed a mathematical model (WAM model) expressing increment of the dose-rate dependent mutation frequency caused by artificial radiations. In this model, it is defined that the pool of mutant cells in dynamic equilibrium in organisms. We verified the accuracy of the WAM prediction of mutation frequency in mice. Materials and methods: The theoretical values calculated by the WAM model were compared with the experimental values obtained from the large mouse genetics program at the Oak Ridge National Laboratory (ORNL). Results: Most of all the theoretical values in acute and chronic irradiation conditions nearly coincided with the experimental values. However, the theoretical value of the chronic conditions at the dose-rate of 0.8 R/min was significantly higher than its experimental value. This discordance was able to be minimized in the WAM assumption, when the period from the end of exposure to start mating was two weeks longer. Conclusions: As a result of comparison between experimental and theoretical data, the certainty of the WAM model was confirmed in mice and it was shown that the genetic influence varies depending on the dose-rate.

DOI： 10.1080/09553002.2019.1569772

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Language：English   Publishing type：Research paper (scientific journal)  

Purpose: This is a paper based on a talk given in the BER2018 conference by M. Bando. We first emphasize the importance of collaborations among scientists in various fields for the low dose/dose-rate effects on biological body. We make comparisons of quantitative estimations of mutation caused by the radiation exposure on various animals and plants using one mathematical model. We derive the importance of the spontaneous mutation at the DNA level, which provides the key to understand the biological evolution. We try to make a guide map to solve this problem and find that the mutation is an important stage of the pathway from the DNA damage to the macroscopic biological evolution. Materials and methods: We construct a mathematical model for the mutation, named as 'WAM' model, which takes into account the recovery effect. The model setting is regarded as an extension of the survival and the hazard functions. The WAM model is used to reproduce accumulated data of mutation frequency of animals and plants. Especially the model analysis shows that the dose-rate dependence is important to understand various mutation data. Results and conclusions: The WAM model is successful in reproducing various mutation data of animals and plants. We find that the inclusion of the dose rate is important to understand all the mutation data. Hence, we are able to develop the 'scaling law' to make the cross-species comparison of mutation frequency data. With this finding, we can extract the dominant effect on the mutation to be caused by the spontaneous mutation, and quantify this amount. We are able to write then the artificial radiation frequency by subtracting the spontaneous mutation. With this success, we estimate the origin of the spontaneous mutation as due to ROS, the order of which agrees to the spontaneous mutation.

DOI： 10.1080/09553002.2019.1606957

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Language：Japanese  

DOI： 10.11269/jjrsm.17.125

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Radioisotope Association  

DOI： 10.3769/radioisotopes.67.255

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：EDP Sciences  

We investigate the angular distribution of scission neutrons taking account of the effects of fission fragments. The time evolution of the wave function of the scission neutron is obtained by integrating the time-dependent Schrodinger equation numerically. The effects of the fission fragments are taken into account by means of the optical potentials. The angular distribution is strongly modified by the presence of the fragments. In the case of asymmetric fission, it is found that the heavy fragment has stronger effects. Dependence on the initial distribution and on the properties of fission fragments is discussed. We also discuss on the treatment of the boundary to avoid artificial reflections.

DOI： 10.1051/epjconf/201816900029

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC  

DOI： 10.1142/9789813229426_0069

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

We have investigated the dependence of the mutation frequency on the dose and dose rate of artificial radiation using the Whack-A-Mole (WAM) model that we recently proposed. In particular, we pay special attention to the case of long-term and low-dose-rate exposure. Our results indicate that the WAM model successfully describes the dose-rate dependence, and it can replace the so-called dose and dose-rate effectiveness factor (DDREF), which has been used for long, to account for the differences between high-dose-rate and low-dose-rate data. The basic properties of the WAM model are discussed with special emphasis on the dose-rate dependence in order to demonstrate how the dose-rate dependence, which is built into the model explicitly, plays a key role. Biological effects of long-term exposure to extremely low-dose-rate radiation are discussed in light of analysis of mega-mouse experiments using the WAM model. In the WAM model, the effects of long-term exposure show a saturation property, thus making it distinctly different from the linear no threshold (LNT)' hypothesis that predicts a linear increase of the effects with time.

DOI： 10.1080/00223131.2016.1164635

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Language：English   Publisher：GENETICS SOC JAPAN  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.2.0_2899

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.1.0_3426

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.2.0_2900

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.2.0_2898

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

We investigate the angular distribution of scission particles taking account of the effects of fission fragments. The time evolution of the wave function of the scission particle is obtained by integrating the time-dependent Schrodinger equation. The effects of the fission fragments are taken into account by means of the optical potentials. The angular distribution is strongly modified by the presence of the fragments. The attractive nuclear potential enhances the yield along the fragment axis for both neutrons and protons. For scission protons, the focusing effect due to the repulsive Coulomb field of the fragments is demonstrated. In the case of asymmetric fission, it is found that the heavy fragment has stronger effects. (C) 2015 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2015.04.005

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

We investigate the effects of the fission fragments on the angular distribution of scission neutrons. The time evolution of the wave function of the scission neutron is obtained by integrating the time-dependent Schrodinger equation. The effects of the re-absorption and scattering by the fission fragments are taken into account by means of the optical potential. The angular distribution is strongly modified by the presence of the fragments. Dependence on the magnitude of the absorption is discussed. Influence of the finiteness of the grid size is also discussed. (C) 2013 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2013.06.006

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

We study the angular distribution of the scission neutrons in a time dependent approach. This implies the numerical solution of the bi-dimensional time-dependent Schrodinger equation (TDSE) with time-dependent potential. To describe the axially symmetric extremely deformed nuclear shapes involved, we have used modified Cassini ovals. The Hamiltonian in cylindrical coordinates is discretized on a bi-dimensional grid, using finite difference approximations of the derivatives. The initial wave-functions for TDSE are the eigensolutions of the stationary Schrodinger equation whose potential corresponds to the pre-scission point (when the neck connecting the primary fission fragments starts to break). The time evolution is calculated by a Crank-Nicolson scheme until the neck dissappears (the post-scission point). The resulting wave-functions are then propagated keeping the last configuration to further intervals of time. We investigate the nucleus U-236 at different mass asymmetries. The numerical solutions can be used to evaluate relevant physical quantities. Among them, the current density, a key quantity in the angular distribution calculation. The angular distribution of the scission neutrons is a priori a way to separate them from other neutron components. Moreover our preliminary results show a striking similarity with the angular distribution of the neutrons evaporated from fully accelerates fragments. (C) 2013 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2013.06.005

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

We propose a Monte Carlo analysis that provides us with a useful diagnostic method to identify the nucleosynthesis paths giving helpful information to understand the nuclear burning mechanism in stellar evolution, connecting with network calculations. Applying the Monte Carlo analysis to the nucleosynthesis in the He shell flash model, we show that a. considerable change in synthesis paths occurs from (16)O to Ne isotopes depending on the reaction rate of (17)O(n, gamma)(18)O.

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Language：English   Publishing type：Research paper (international conference proceedings)  

Multi-modal fission has been systematically investigated for the series of isotopes of Fm and Cf. The multi-dimensional Langevin-type stochastic differential equation is used for the dynamical calculation. The primary fission mode changes from mass-asymmetric fission to mass-symmetric fission with the increase of neutron numbers for both Fm and Cf cases. © 2010 American Institute of Physics.

DOI： 10.1063/1.3455960

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Language：English   Publishing type：Research paper (scientific journal)  

In this paper we aim to construct a reliable theoretical framework to analyze nuclear reaction cross sections concerning the nucleosyntheses of light nuclei. To explain the reaction cross sections of 16O(n,γ) 17O and 16O(p, γ)17F, we propose a theoretical procedure combining an 16O+N model and the complex scaling method with the Lippmann-Schwinger solution for the complex-scaled Green's operator. We demonstrate that this procedure is a powerful tool in the analysis of the reactions observed in the lower-energy region including astrophysical energies.

DOI： 10.1143/PTP.121.375

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC  

DOI： 10.1142/9789812833433_0026

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Institute of Physics Inc.  

For the key reactions 16O(n,γ)17O and 17O(n,γ)18O on nucleosyntheses in stellar interior, the theoretical estimate for the cross section and reaction rate have been made. The careful description of the nuclear structure is important in very low energy regions. The Cluster Orbital Shell Model is adopted for reproducing the structure of the nuclei. Our results for the cross section of the 16O(n,γ)17O reaction are consistent with that of the microscopic two cluster model. The straightforward application becames possible to the case of the 17O(n,γ)18O reaction with a substantial reliance.

DOI： 10.1063/1.2943578

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Effect of the beta-delayed fission in r-process abundance is investigated with a realistic model for the fission fragment mass distribution (FFMD). The database for the FFMD is constructed based on the two-center shell model and multi-dimensional Langevin calculation. The beta-decay rates including neutron emission and beta-delayed fission are also newly calculated with 2nd version of the the gross theory. The differences appeared in the final element abundance calculated with and without fission process, with different beta-delayed fission rates are demonstrated.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：E D P SCIENCES  

The systematic data on the fission fragment mass distribution for nuclei ranging from Z = 88 to 120 relevant to the r-process nucleosynthesis is constructed in a semi-empirical way. The mass distribution is estimated from the potential energy surface by means of the liquid drop model with the shell energy correction and also by referring the results in the dynamical calculation of fission paths by the Langevin equation in the three-dimensional deformation space. The results are compared with the mass asymmetric values at the saddle point driven by the extended Thomas-Fermi Struchinsky integral (ETFSI) model. In the lighter nuclei Z < 100, our results are consistent with the values of ETFSI, on the other hand in the heavier nuclei our estimation gives a larger mass asymmetry and approaches to zero due to the decrease of shell effect beyond Z > 120.

DOI： 10.1051/ndata:07302

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

The fission fragments mass distribution (FFMD) which is the important nuclear information in the study of the r-process nucleosynthesis is estimated for the neutron-rich nuclei (Z>85) according to the theoretical investigation of the potential energy surface. The details for determining FFMD are discussed. In this paper, the network calculation on the r-process nucleosynthesis is also performed including the data of FFMD. The comparison of the results of the network calculation, with and without the fission processes, is shown.

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Language：English   Publishing type：Research paper (scientific journal)  

We apply our Monte Carlo method to the s-process element synthesis in the helium shell flash model for extremely metal-poor stars. We emphasize the importance of the reaction 17O(n γ)18O. It is presented that the uncertainty of this reaction rate affects the heaver elements abundance. We also discuss the variation of the O-Ne reaction paths with the uncertainty of the reaction rate of 17O(n γ)18O. © 2007 American Institute of Physics.

DOI： 10.1063/1.2713544

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Language：English   Publishing type：Research paper (scientific journal)  

Two kinds of stochastic integrals, Ito integral and Stratonovich integral, are applied for solving Langevin equation. In the case of the simplified Langevin equation for over-damped motion, the fission rate obtained with Stratonovich integral is significantly larger than that with Ito integral. On the other hand, in the case where the random force acts on the momentum variables, the two integrals give essentially the same results. The condition for the difference with two integrals to appear is discussed. The proper treatment of the double stochastic integral is necessary to obtain a high numerical accuracy. © 2007 American Institute of Physics.

DOI： 10.1063/1.2713551

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Language：English   Publishing type：Research paper (scientific journal)  

The nuclear fission barrier height has been estimated by means of the constraint Skyrme Hartree-Fock-Bogoliubov method. The potential energy surfaces obtained by the method are analyzed with the flooding method to find several saddle points. The results for U, Np, Bk isotopes are compared with the barrier derived from the extended Thomas-Fermi plus Strutinsky integral method. © 2007 American Institute of Physics.

DOI： 10.1063/1.2713552

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Language：English   Publishing type：Research paper (scientific journal)  

The fission fragment mass distribution is estimated theoretically on about 2000 nuclides which might have a critical role on the r-process nucleosynthesis through fission (Z&gt
85). The mass distribution of fission fragment is derived by considering the location and the depth of valleys of potential energy surface near scission point of nuclei calculated by means of the liquid drop model with the shell energy correction by the Two-Center shell model. The guiding principle of determining the fission mass asymmetry is the behavior of the fission paths from the saddle to the scission point given by the Langevin calculation. © 2007 American Institute of Physics.

DOI： 10.1063/1.2713548

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We have made a study on the capture process of40,48Ca+208Pb systems with a dynamical approach based on the surface friction model. The deformation of the nuclei due to the mutual excitation is taken into account. We have calculated the capture cross sections for several values of the friction coefficients. It was shown that, in the cold fusion reactions, the friction parameters of the surface friction model needs to be reexamined. © 2007 American Institute of Physics.

DOI： 10.1063/1.2713553

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Language：Japanese   Publisher：素粒子論グループ 素粒子論研究 編集部  

DOI： 10.24532/soken.115.4_D29

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

The dependence of the capture and fusion excitation functions on the nuclear shell structure and initial orientation angles of the symmetry axis of the deformed projectile- and target-nucleus are explored by the dynamical model based on the dinuclear system concept and Langevin calculations. The fusion cross sections for O-16+U-238 and Ni-60+Sm-154 reactions obtained by averaging of the results for the all orientation angles are in good agreement with the experimental data. The capture and fusion cross sections for the O-16+U-238 reaction are nearly the same while those are different for the 60Ni+154Sm reaction due to presence of the hindrance to fusion as quasifission. The largest of the fusion cross section for the orientation angles of the reactants in the range 60 degrees < alpha(i) < 90 degrees (A) in comparison with that for angles 0 degrees < alpha(i) < 30 degrees (B) was explained by the increase of the quasifission contribution in the last case (B). The physical reason of this phenomenon is connected by the largest of the intrinsic fusion barrier B*(fus) in case (B) than that for the case (A). The observed difference between the excitation functions of evaporation residues for the Kr-86 + Xe-130 and Sn-124 + Zr-92 reactions is explained by the difference between the B*(fus) values which depend on the nuclear shell corrections.

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.61.2.1.0_24_2

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.61.1.1.0_41_4

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.61.2.1.0_24_3

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.61.2.1.0_24_1

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

We propose a Monte Carlo method to study the reaction paths in nucleosynthesis during stellar evolution. Determination of reaction paths is important to obtain the physical picture of stellar evolution. The combination of network calculation and our method gives us a better understanding of physical picture. We apply our method to the case of the helium shell flash model in the extremely metal poor star.

DOI： 10.1063/1.2234471

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Nuclear and Radiochemical Sciences  

DOI： 10.14494/jnrs2000.7.7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

The multi-modal fission of fermium nuclei is dynamically investigated. The multidimensional Langevin equation is used for the dynamical calculation. We use the potential energy taking account of the microscopic energy which depends on the excitation energy. We calculate the mass distribution and the total kinetic energy (TKE) distribution for Fm-256. We study the excitation energy dependence of the mass and TKE distributions. We find that the excitation energy dependence comes from the change in the contribution of each fission mode.

DOI： 10.1143/ptps.154.457

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

We have analyzed cold fusion reactions, especially, (HI(Heavy-Ion), xn) reactions with Pb-208 target series. The ratio a(f)/a(n) used in the statistical model is determined by fitting experimental data Gamma(n)/Gamma(total) for Z=102 and the extrapolative use is made for Z>103. Theoretical predictions for excitation functions in Pb-208(Ti-50, V-51, Cr-54, Mn-55, Fe-58, Co-59, Cu-65, Zn-70, xn) reactions are compared with experiments. We found that peak positions of (HI, xn) reactions except for the sub-barrier fusion enhancement effect stay almost constant when we increase the Z-number of compound nucleus from Z=104 to Z=110.

DOI： 10.1063/1.1737155

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Nuclear and Radiochemical Sciences  

DOI： 10.14494/jnrs2000.3.67

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Language：Japanese   Publisher：一般社団法人 日本物理学会  

DOI： 10.11316/jpsgaiyo.57.1.1.0_22_2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

In order to estimate the fission width for the case in which the Bohr-Wheeler model is inapplicable due to a fission barrier B-f similar or equal to 0, we introduce the mean first passage time method and discuss the usefulness of this method. By using this method, the fission decay time can be obtained without solving the Smoluchowski equation, which involves a time consuming calculation. This method is useful when we need to calculate the fission width with a vanishing fission barrier, as when we estimate the fusion evaporation residue cross section for superheavy nuclei with Z > 114.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

The dynamical process of synthesizing superheavy elements is studied on the basis of the fluctuation-dissipative dynamics. The whole process is divided into three stages, i.e., the approaching stage, the formation stage, and the surviving stage. For the study of the formation stage, a three-dimensional Langevin equation is used from the contact of two nuclei to calculate the competition between the complete fusion and the quasi-fission. We estimate the effects of the nuclear deformation on the fusion probability. The results are consistent with the experimental results. For the description of the surviving stage, a statistical model is used to estimate the competition between the fission and the evaporation process. In this stage, it is very important to include the temperature-dependent shell correction to the fission barrier and the collective enhancement of the level density. From the study of the isotope dependence of the production cross section, the survival probability is found to be very sensitive to the separation energy of neutron. The results show the importance of the use of neutron-rich beams and targets.

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.56.1.1.0_22_2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

The diffusion problem over a saddle is studied using a multidimensional Langevin equation. An analytical solution is derived for a quadratic potential and the probability to pass over the barrier deduced. A very simple solution is given for the one-dimensional problem and a general scheme is shown for higher dimensions.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

Dynamical reaction theories are reviewed for synthesis of superheavy elements. Characteristic features of formation and surviving are discussed with reference to possible incident channels. Theoretical predictions are presented on favorable incident channels and on optimum: energies for synthesis of Z = 114.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

Present status of the study of superheavy elements is reviewed. The dynamical process of synthesizing superheavy elements is studied on the basis of the fluctuation-dissipation dynamics. The whole process is divided into three stages, i.e., the approaching stage, the formation stage, and the surviving stage. For the study of the formation stage, a three-dimensional Langevin equation is used after the contact of two nuclei to calculate the competition between the complete fusion and the quasi-fission. For the description of the surviving stage, a statistical model is used to estimate the competition between the fission and the evaporation process. In this stage, it is very important to include the temperature-dependent shell correction to the fission barrier and the collective enhancement of the level density. From the study of the isotope dependence of the production cross section, the survival probability is found to be very sensitive to the separation energy of neutron. The results show the importance of the use of neutron-rich beams and targets.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

An overview of the present status of our knowledges is given on heavy-ion reaction mechanisms crucial for synthesis of the superheavy elements. Examples of the preliminary results are also given for Z=114.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

Dynamical reaction theory is presented for synthesis of superheavy elements. Characteristic features of formation and surviving are discussed, which combinedly determine final residue cross sections of superheavy elements. Preliminary results on Z=114 are also given.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

The fusion-fission process for synthesizing superheavy elements is studied on the basis of the dissipative dynamics. We use a multi-dimensional Langevin equation for the first stage where the reaction system evolves from the contact configuration of two incident nuclei to the later time when the complete dissipation of the initial relative kinetic energy is accomplished, and a two-dimensional Smoluchowski equation for the following stage. The evaporation residue cross sections for superheavy elements have been shown to have an optimum value at a certain initial energy, due to the balance between the diffusibility for fusion at high temperature and the restoration of the shell correction energy against fission at low temperature. The isotope dependence is also discussed. The results show the impotence of the use of the neutron-rich beams and targets.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We study the dynamical process of synthesizing superheavy elements on the basis of the fluctuation-dissipative dynamics with a multi-dimensional diffusion model. A multidimensional Langevin equation is used from the contact of two nuclei. After the dissipation of relative kinetic energy, a two-dimensional Smoluchowski equation is adopted taking into account the temperature dependent shell correction energy. The fusion probability is large for high incident energies. For low incident energies, owing to the restoration of the shell correction energy, the survival provability against fission is large. The competition between the two factors results in the optimum energy at 20-30 MeV. A three-dimensional model is used for the treatment of mass-asymmetric incident channels.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

Fluctuation-dissipation dynamics is applied to the nearly mass-symmetric fusion reactions forming nuclei of Z > 80. We take into account the angular momentum of the system. The fusion cross section is calculated, and the hindrance of fusion is discussed. We estimate the amount of extra energy above the Coulomb barrier needed for fusion.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

Fusion-fission dynamics in superheavy elements is investigated by an approximate fluctuation-dissipation model, i.e., a diffusion model in the deformation space, assuming that the kinetic energy of the incident ion dissipates immediately after the contact. The probability accumulated inside the fission barrier is calculated by the one-dimensional Smoluchowski equation taking account of the temperature dependence of the shell correction energy. A new mechanism for an optimum condition is found as a compromise of two conflicting requirements: higher incident energy for larger fusion probability and lower excitation energy of compound nuclei for larger survival probability. Enhancements of the residue cross sections at the optimum condition are obtained for the cases in which the cooling is quick to restore the shell correction energy, combined with slow fissioning motion due to the strong friction. With symmetric combinations of incident ions, the (HI, 3-4n) channels show the enhancement. [S0556-2813(99)01501-0].

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Language：Japanese   Publisher：素粒子論グループ 素粒子論研究 編集部  

超重核を合成する融合・分裂反応の動的な過程は、揺動散逸動力学で記述される。異なる入射チャネルからの融合反応を調べるために変形自由度に質量非対称度を加えた多次元ランジュバン方程式を数値的に解く。入射時での質量非対称度が大きくなると、fusion hindranceが緩和され融合しやすくなるが、同時に合成系の励起エネルギーが高くなるため、分裂もしやすくなる。いくつかの異なる入射チャネルからの質量非対称融合・分裂反応について蒸発残留核断面積の計算を行い、超重核合成のための入射核、標的核の最適化について述べる。

DOI： 10.24532/soken.99.3_C60

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.54.1.1.0_32_3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AKADEMIAI KIADO  

Suitable target-projectile combinations for synthesis of the superheavy element Z = 114 are discussed for the case of the two isotopes A = 298 and A = 290, which are the neutron-rich isotope and the normal one, respectively. In our framework of estimating the evaporation residue cross section by using the Langevin or the diffusion equation, it is shown that the fusion reaction leading to a neutron-rich nucleus has an advantage around the entrance channel mass asymmetry parameter alpha = 0.65. On the contrary, lower mass asymmetry is favorable in the case of the normal nucleus, although the absolute value of the cross section is depressed drastically. We also present quantitatively the importance of neutron richness in the synthesis of superheavy elements.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have deduced the prescission time of hot nuclei as a function of the angular momentum from the light charged particle- and gamma ray-multiplicities measured simultaneously in coincidence with fully-damped binary decay fragments in the reaction of Ni-58 + Fe-56 at the incident energy of 10.0 MeV/nucleon. The prescission time was found to decrease as the angular momentum of the system increases. Theoretical calculations of the fissioning motion with the Langevin equation have shown that this dependence originates primarily from the change in the potential landscape due to the centrifugal energy. (C) 1998 Elsevier Science B.V.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

The fusion-fission process for synthesizing superheavy elements is studied on the basis of the dissipative dynamics. The nse a multi-dimensional Langevin equation for the first stage where the reaction system evolves from the contact configuration of two incident nuclei to the later time when the complete dissipation of the initial relative kinetic energy is accomplished, and a two-dimensional Smoluchowski equation for the following stage. The evaporation residue cross sections for superheavy elements have been shown to have an optimum value at a certain initial energy, due to the balance between the diffusibility for fusion at high temperature and the restoration of the shell correction energy against fission at low temperature. The isotope dependence is also discussed.

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.53.2.1.0_32_4

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

We measured gamma-ray multiplicity and light charged particle (LCP) multiplicity simultaneously in coincidence with binary decay fragments in the reactions of Kr-84 (10.6 and 8.5 MeV/nucleon) + Al-37 and Ni-58 (10.0 MeV/nucleon) + Fe-56, We-observed the prescission time and charge distribution of heavy fragments as a function of the angular momentum of the system applying the mea sured gamma-ray multiplicity as an angular momentum filter. The deduced prescission time becomes smaller as the angular momentum of the system increases. For Kr-84 27 Al, the fusion-fission reaction seems to occur dominantly only at the angular momentum similar to 70 (h) over bar fr, which is concluded from the dependence of prescission proton multiplicity on the total kinetic energy (TKE). The charge distribution of binary decay fragments changes from the symmetric mass division to asymmetric one with increasing the gamma-ray multiplicity.

DOI： 10.1063/1.55138

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

We study the dynamical process of synthesizing superheavy elements on the basis of the fluctuation-dissipative dynamics with a multi-dimensional diffusion model. To treat the effect of the initial kinetic energy properly, a multi-dimensional Langevin equation is used for the first stage of the process, from the contact of two nuclei to the time when the relative kinetic energy dissipates completely For the description of the second stage, a two-dimensional Smoluchowski equation is adopted taking into account the temperature dependent shell correction energy and the cooling due to the neutron evaporations is treated with the statistical model. The fusion probability is large for high incident energies due to the strong diffusion. For low incident energies, owing to the restoration of the shell correction energy, fission is suppressed and the survival provability is large. The competition between these two factors results in the optimum energy around 20-30 MeV. From the study of the isotope dependence of the production cross section, the importance of the use of neutron-rich nuclei is remarked.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Starting from the contact configuration of colliding nuclei: the evolution of the nuclear shape is simulated in two-dimensional deformation space fixing the asymmetry by means of the Langevin equation under the influence of the one body dissipation. It is quantitatively shown that, in heavy mass region, the asymmetry of the entrance channel plays an important role to get an optimum fusion probability in connection with the extra barrier to be overcome. It is necessary to take into account this effect together with the excitation energy at Bass barrier to consider the optimum target-projectile combination for the synthesis of super heavy elements.

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.53.1.1.0_40_4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

A dynamical theory is proposed for nuclear reactions leading to residues of superheavy elements. Fusion and fission processes are treated consistently by a diffusion equation which describes a time-dependent probability distribution in the collective coordinate or deformation space. The potential energy in the equation is time-dependent, because cooling due to particle evaporation gradually restores the shell correction energy which gives rise to a potential pocket essential for the stabilization of the superheavy elements around Z = 114 and N = 184. It is shown that there is an optimum initial excitation energy or incident energy of reactions as the result of a compromise between two conflicting requirements; higher energies which favour larger fusion probabilities and lower energies which favour larger residue probabilities or a quicker restoration of the shell-correction energy. A promising experimental direction is suggested.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A diffusion model is proposed for the dynamical treatment of the synthesis of superheavy elements. Fusion-fission process is analyzed by one-dimensional Smoluchowski equation with liquid drop model potential of no pocket and the temperature dependent shell correction energy which generates the pocket around the spherical shape. Competition between fission and neutron evaporation is taken into account in terms of the continuous cooling by neutron evaporation. The evaporation residue cross sections of superheavy elements have been shown to have an optimum value at a certain temperature, due to the balance between the diffusibility for fusion at high temperature and the restoration of the shell correction energy against fission at low temperature. The isotope dependence of the evaporation residue cross section is found to be very strong. Neutron rich compound system with small neutron separation energy is favorable for larger cross section because of the quick restoration of the shell correction energy.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The fusion-fission process in heavy systems is analyzed by the Smoluchowski equation with the finite-range droplet model potential of no pocket and the temperature-dependent shell correction energy which generates the pocket around the spherical shape. The evaporation residue cross sections of superheavy elements have been shown to have an optimum value at a certain initial temperature, due to the balance between the diffusibility for fusion at high temperature and the restoration of the shell correction energy against fission at low temperature.

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.52.1.1.0_40_3

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.52.2.1.0_50_1

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.52.2.1.0_49_3

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Language：English   Publishing type：Research paper (scientific journal)  

The fusion-fission process in heavy systems is analyzed by the Smoluchowski equation with the finite-range droplet model potential of no pocket and the temperature-dependent shell correction energy which generates the pocket around the spherical shape. The evaporation residue cross sections of superheavy elements have been shown to have an optimum value at a certain initial temperature, due to the balance between the diffusibility for fusion at high temperature and the restoration of the shell correction energy against fission at low temperature. © 1997 The American Physical Society.

DOI： 10.1103/PhysRevC.55.R1011

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyoj.1996.1.0_56_2

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyoj.1996.1.0_57_1

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyoj.1995.1.0_88_1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/0375-9474(93)90034-u

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

DOI： 10.1103/physrevlett.70.3538

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Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.70.3538/fulltext

Language：English   Publishing type：Research paper (scientific journal)  

Multi-dimensional Langevin approach to nuclear dissipative phenomena is presented. We solve two-dimensional Langevin equation numerically without any approximations for the study of induced fission dynamics. Transient time of the symmetric fission of 213At is calculated and discussed in comparison with empirically deduced value. Fragment kinetic energy distribution is calculated and compared with experiments. © 1992.

DOI： 10.1016/0375-9474(92)90778-I

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

DOI： 10.1103/physrevc.41.2147

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Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevC.41.2147/fulltext

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

DOI： 10.1103/physrevc.41.160

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Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevC.41.160/fulltext

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

DOI： 10.1103/physrevc.38.2063

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Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevC.38.2063/fulltext

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1143/ptp.80.502

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1143/ptp.80.488

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1143/ptp.79.19

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

DOI： 10.1103/physrevlett.58.2190

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Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.58.2190/fulltext

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1143/ptp.76.837

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1143/ptp.75.619

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1143/ptp.75.754

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1143/ptp.75.458

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1143/ptp.75.198

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

DOI： 10.1143/ptp.70.1599

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：一般社団法人日本物理学会  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

More than 30 years have been passed since the prediction was made for the existence of the superheavy elements (SHE). It is now reported that SHE are synthesized in the laboratories. In this manuscript, we explain what SHE are and then, by looking back history, we discuss the purpose and the interest of the search for SHE. The present status of the experiments of synthesizing SHE is reviewed. We also discuss our theoretical study of the reaction process and present the prediction of the evaporation residue cross section of SHE via heavy-ion fusion reaction. Future perspectives are also given.

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Language：Japanese   Publisher：一般社団法人日本物理学会  

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Language：Japanese   Publisher：一般社団法人日本物理学会  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：English   Publisher：Soryushiron Kenkyu  

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Language：Japanese   Publisher：Soryushiron Kenkyu  

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J-GLOBAL

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：素粒子論グループ 素粒子研究編集部  

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Language：Japanese   Publisher：物性研究刊行会  

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10938027

Language：Japanese   Publisher：Soryushiron Kenkyu  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Language：Japanese   Publisher：素粒子論グループ 素粒子研究編集部  

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Language：English   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

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Event date： 2018

Venue：Chhicago, IL, USA  

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Venue：Chhicago, IL, USA  

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Venue：Charlotte, NC, USA  

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Venue：Paris, France  

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Venue：Charlotte, NC, USA  

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Venue：Paris, France  

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Venue：Paris, France  

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Venue：Sanibel Island, FL, USA  

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Venue：Neuherberg, Germany  

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Venue：Opatija, Croatia  

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Venue：Ｓｉｎａｉａ, Romania  

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Venue：Vienna, Austria  

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Venue：Vienna, Austria  

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