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有友 嘉浩*; 天野 翔太*; 奥林 瑞貴*; 栁 漠*; 西尾 勝久; 太田 雅久*
Physics of Atomic Nuclei, 83(4), p.545 - 549, 2020/07
被引用回数：0 パーセンタイル：0.00(Physics, Nuclear)For the success of synthesis of the superheavy elements Z 
118, it is indispensable to clarify the fusion-fission mechanism, which includes a role of the nuclear structure of colliding nuclei and the deformation in the fusion process. We develop the dynamical model to estimate the probability to produce new superheavy nuclei. To approach Island of Stability and synthesize new elements, we propose a new idea, which takes advantage of the shell structure in fusion and fission process.
Md with six-dimensional Langevin equation岡田 和記; 西尾 勝久; 和田 隆宏*; Carjan, N.*
no journal, ,
We calculate the fission process of Md with the multi-dimensional Langevin equation with the Cassini shape parameterization. To describe various fission modes, we use the six Cassini shape parameters 
, and apply them to the six-dimensional Langevin equation. The combination of these shape parameters can flexibly describe deformed nuclear shapes. This is the first attempt to calculate the Langevin dynamics in the six-dimensional collective coordinates. The resulting fragment mass and TKE distributions show the existence of three types of fission modes, consistent with the measurement data from JAEA. Furthermore, by increasing the excitation energy from 15 MeV to 18 MeV, the relative contribution of each mode is changed. With higher excitation energy, the short symmetric fission mode decreases significantly, and the asymmetric fission mode becomes dominant. It is considered that the shell effect corresponding to short symmetric fission is largely damped by the increase in excitation energy. Through analysis of fission paths obtained from these six-dimensional Langevin calculations, we expect to elucidate the physical origins and mechanisms of each fission mode.
岡田 和記; 西尾 勝久
no journal, ,
超重元素合成のために、核分裂をはじめとした核反応に関する実験、理論をさらに発展させていく必要がある。本講演では、現在原子力機構で行われている6次元Langevin方程式を用いた核分裂シミュレーションの現状と今後の計画について報告する。
岡田 和記; 西尾 勝久; 和田 隆宏*; Carjan, N.*
no journal, ,
日本原子力学会のシグマ調査専門委員会は、将来のJENDL核データ評価の取り組みとして、「核分裂ジェネレータ」を取り入れる評価方法を提言しており、原子核物理の基礎理論から構築された核分裂シミュレーションの実現が期待されている。本発表では6次元Cassini parameterを用いたLangevin方程式による核分裂計算の結果や今後の展望について報告する。
岡田 和記; 西尾 勝久; 和田 隆宏*; Carjan, N.*
no journal, ,
多次元Langevin方程式を用いた核分裂の動力学的アプローチは、核分裂過程の計算に広く用いられている。このアプローチは、核分裂片の質量分布や全運動エネルギー(TKE)分布といった、実験データと直接比較できる物理量を提供する。最近の原子力機構で実施されたMd核分裂の測定では、分裂片のmass-TKE分布が複数の異なる核分裂モードの存在を示している。この測定結果を理解するためには、様々な分裂片形状を記述できる高次元でのLangevin方程式を用いた動力学的計算が重要な役割を果たす。本研究では、フレキシブルに分裂片形状を記述するCassiniパラメータを採用し、の6次元Langevin方程式を解くことで、Mdの核分裂過程を計算する。
岡田 和記; 西尾 勝久; 和田 隆宏*; Carjan, N.*
no journal, ,
The dynamical approach to fission using the multi-dimensional Langevin equation has been extensively used as a practical model for calculating the fission observables, such as fission-fragment mass and total kinetic energy (TKE) distributions and their evolution with the excitation energy of compound nucleus. We investigated for the first time six-dimensional Langevin calculations with the Cassini shape parameterization. The largest dimension achieved in this work allows a more versatile description in fission under the highly flexible deformation space. For example, the appearance of several fission modes in the fission 
U is demonstrated, and the corresponding scission configuration is derived with high precision. In this presentation, we discuss the results of the fragment mass and TKE distributions and their dependence on the excitation energy of fissioning nuclei. Fission of neutron-rich fermium region offers a strict benchmark of the model. Our calculation explained a sudden change from mass-asymmetric fission of 
Fm to symmetric fission of Fm. Recently, the fission of 
in excited states was measured at JAEA. While the symmetric fission mode has a comparative yield with asymmetric mode at the excitation energy of 
= 15.0 MeV, the latter yield increases when extra excitation energy of only 3 MeV was given in Md
. The growth of AS mode with excitation energy, observed for the first time, and strong competition between the modes was explained in the present six-dimensional calculation.
岡田 和記; 西尾 勝久
no journal, ,
The dynamical approach to fission using the multi-dimensional Langevin equation plays an essential role in understanding the fission mechanism. This approach provides a description of the fission process from the ground state to scission by solving the time evolution of shape parameters. The key challenge is that the results largely depend on the choice of shape parameterization, especially when the number of parameters is small. The four- and five-dimensional two-center shell model has been applied as a practical model for representing typical fragment shapes. In our study, to account for various fission modes, we employ the Cassini shape parameterization, which can flexibly describe a wide range of deformed shapes through combinations of shape parameters. To reduce the dependence of the results on the parameterization, it is crucial to perform calculations in high-dimensional Cassini shape coordinates. In this seminar, we will discuss the current results and future plan of our study with the six-dimensional Cassini shape parameterization, computed with the supercomputer at JAEA.
岡田 和記; 西尾 勝久; 和田 隆宏*; Carjan, N.*
no journal, ,
The dynamical approach to fission using the multi-dimensional Langevin equation has been widely used for calculations of the fission process. This approach provides the fragment mass and total kinetic energy (TKE) distributions, which can be directly compared with experimental data across systems with various excitation energies. Recent measurements for the fission of Md conducted at JAEA indicate that the mass-TKE distributions consist of multiple distinct fission modes: short symmetric, asymmetric, and super-long symmetric fission. To understand these observations, dynamical calculations using the high-dimensional Langevin equation play an important role. In this study, we calculate the fission process of Md by solving the six-dimensional Langevin equation with Cassini shape parameterization. To describe various fission modes, we employ six Cassini shape parameters 
as the collective coordinates.
