Tsukada, Kazuaki; Nagai, Yasuki*; Hashimoto, Shintaro; Minato, Futoshi; Kawabata, Masako*; Hatsukawa, Yuichi*; Hashimoto, Kazuyuki*; Watanabe, Satoshi*; Saeki, Hideya*; Motoishi, Shoji*
Journal of the Physical Society of Japan, 89(3), p.034201_1 - 034201_7, 2020/03
We found anomalously large yields of Ga, Ga, Zn and Cu by neutron irradiation on a ZnO sample in a polyethylene shield. Neutron beams are generated from the Be() reaction for 50 MeV deuterons. The yields obtained were more than 20 times larger than those in the unshielded sample. On the other hand, the yields of Ga, Ga, Zn and Cu from a metallic Zn sample and the yields of Cu, Ni and Zn from the ZnO and Zn samples were almost insensitive to the shield conditions. This finding would provide us a unique capability of accelerator neutrons to simultaneously produce a large amount of several radioisotopes, including proton induced reaction products, by using a single sample. The experimental data were compared with the yields estimated by using the Particle and Heavy Ion Transport code System and the result was discussed.
Minato, Futoshi; Tanimura, Yusuke*
European Physical Journal A, 56(2), p.45_1 - 45_18, 2020/02
For nuclei, three-body model of inert core can provide an understanding of pairing correlations in the ground state and spin-isospin excitations. However, residual core-nucleon interactions can impact the core nucleus significantly. The effect of core excitations thus has to be included for the detailed understanding of the ground state and the spin-isospin properties. We solve the three-body problem including core vibrational states to obtain the ground state as well as the spin-excitations. By including the effect of core excitation, (a) magnetic moment, (b) the enegy difference between the first and the excited states, (c) B(M1) and B(GT), are improved. It was also found that the root mean squares of distances between proton and neutron, and the center of mass of valence prton and neutron and core slightly increase.
Kunieda, Satoshi; Furutachi, Naoya; Minato, Futoshi; Iwamoto, Nobuyuki; Iwamoto, Osamu; Nakayama, Shinsuke; Ebata, Shuichiro*; Yoshida, Toru*; Nishihara, Kenji; Watanabe, Yukinobu*; et al.
Journal of Nuclear Science and Technology, 56(12), p.1073 - 1091, 2019/12
A new nuclear data library, JENDL/ImPACT-2018, is developed for an innovative study on the transmutation of long-lived fission products. Nuclear reaction cross- sections are newly evaluated for incident neutrons and protons up to 200 MeV for 163 nuclides including long-lived nuclei such as Se, Zr, Pd and Cs. Our challenge is an evaluation of cross-sections for a number of unstable nuclei over a wide energy range where the experimental data are very scarce. We estimated cross- sections based on a nuclear model code CCONE that incorporates an advanced knowledge on the nuclear structure theory and a model-parameterization based on a new experimental cross-sections measured by the inverse kinematics. Through comparisons with available experimental data on the stable isotopes, it is found that the present data give predictions of cross-sections better than those in the existing libraries.
Furutachi, Naoya; Minato, Futoshi; Iwamoto, Osamu
Physical Review C, 100(1), p.014610_1 - 014610_7, 2019/07
We investigated the probability distribution of thermal neutron capture cross sections () deduced stochastically with the resonance parameters randomly sampled from Wigner and Porter-Thomas distributions. We found that the typical probability distribution has an asymmetric shape. While there is a long tail on the large side due to a resonance happening to be close to the thermal energy, the multiresonance contribution considerably reduces the probability on the small side. We also found that the probability distributions have a similar shape if nuclei have an average resonance spacing sufficiently larger than an average radiation width. We compared the typical probability distribution with the distribution of the experimental values of 193 nuclei and found a good agreement between them.
Furutachi, Naoya*; Minato, Futoshi; Iwamoto, Osamu
Journal of Nuclear Science and Technology, 56(5), p.412 - 424, 2019/05
A phenomenological level density model that has different level density parameter sets for the state densities of the spherical and the deformed states, and the optimization of the parameters using the experimental data of the average s-wave neutron resonance spacing are presented. The transition to the spherical state from the deformed one is described using the parameters derived from a microscopic nuclear structure calculation. The nuclear reaction calculation has been performed by the statistical model using the present level density. Resulting cross sections for various reactions with the spherical, deformed and transitional target nuclei shows a fair agreement with the experimental data, which indicates the effectiveness of the present model. The role of the rotational collective enhancement in the calculations of those cross sections is also discussed.
Journal of Nuclear Science and Technology, 55(9), p.1054 - 1064, 2018/09
Incident neutron energy dependence of delayed neutron yields of uranium and plutonium isotopes are investigated. A summation calculation of decay and fission yield data is employed, and the energy dependence of the latter part is considered in a phenomenological way. Our calculation systematically reproduces the energy dependence of delayed neutron yields by introducing an energy dependence of the most probable charge and the odd-even effect. We also tested modification of the evaluated fission yield data of the JENDL/FPY-2011 by replacing fission yields of some important delayed neutron precursors with those of the present result. New yield data show improvements in delayed neutron yield, not changing accuracy of the original decay heat calculation.
Tsukada, Kazuaki; Nagai, Yasuki*; Hashimoto, Kazuyuki*; Kawabata, Masako*; Minato, Futoshi; Saeki, Hideya*; Motoishi, Shoji*; Ito, Masatoshi*
Journal of the Physical Society of Japan, 87(4), p.043201_1 - 043201_5, 2018/04
Koura, Hiroyuki; Minato, Futoshi; Iimura, Hideki
Nippon Genshiryoku Gakkai-Shi, 60(1), p.35 - 40, 2018/01
no abstracts in English
Minato, Futoshi; Fukui, Tokuro
EPJ Web of Conferences (Internet), 163, p.00037_1 - 00037_5, 2017/11
The capture reaction can be divided into two parts, that is the compound and direct processes. For most stable nuclei, the compound process occupies a large part of the neutron capture cross section. However, it has been pointed out that the direct process comes to play a comparable role to the compound one at a low energy in light and neutron-rich nuclei, where the number of resonance state at the neutron threshold energy is relatively small. In addition, there is an interference term between the direct and compound processes. However, it is usually neglected for most nuclei, because either of the compound or the direct process is more important than the other, its contribution becomes negligible. However, some experiment data have given an implication of the existence of the interference effect, and Mengoni and Otsuka reported that the experimental results of capture cross section can be described by taking into account it. It is then natural as a next step to have a concern whether the interference effect comes to play a role for neutron-rich nuclei as well. We therefore calculate the neutron capture reaction for neutron-rich nuclei and study the interference effect on it. We will present some results for neutron-rich nuclei and the interference effect becomes important.
Minato, Futoshi; Tsukada, Kazuaki*; Sato, Nozomi*; Watanabe, Satoshi*; Saeki, Hideya*; Kawabata, Masako*; Hashimoto, Shintaro; Nagai, Yasuki*
Journal of the Physical Society of Japan, 86(11), p.114803_1 - 114803_6, 2017/11
We have measured the yield of Mo, the mother nuclide of Tc used in nuclear diagnostic procedure. Mo was produced by Mo(,)Mo using neutrons with thermal energy up to about 40 MeV, provided by C(,). The Mo yield agrees with an estimated yield with the use of the latest data of C(,) and the evaluated cross section given in the JENDL. Based on this, a new calculation was carried out to produce Mo to seek for a good economical condition. Various conditions such as the MoO sample mass, the distance between the carbon target and the sample, the radius of the deuteron beam, and the neutron irradiation time were considered. The calculated Mo yield indicates that about 30% of the Mo demand in Japan can be fulfilled with a single accelerator. The elusion of Tc from the Mo twice per day would meet about 50% of the Mo demand.
Fukui, Tokuro*; Minato, Futoshi
Physical Review C, 96(5), p.054608_1 - 054608_8, 2017/11
Shizuma, Toshiyuki*; Hayakawa, Takehito*; Daito, Izuru*; Ogaki, Hideaki*; Miyamoto, Shuji*; Minato, Futoshi
Physical Review C, 96(4), p.044316_1 - 044316_10, 2017/10
The low-lying dipole strength in Cr was measured in nuclear resonance fluorescence experiments using a quasi-monochromatic, linearly polarized photon beam. The parities of the excited dipole states were determined by the intensity asymmetry of resonantly scattered -rays with respect to the polarization plane of the incident photon beam. The summed magnetic dipole (M1) strength was determined as at excitation energies between 7.5 and 12.1 MeV; the summed electric dipole (E1) strength was obtained as fm. The observed M1 and E1 strengths were compared via random phase approximation calculations using the Skyrme interaction. The effects of 2 particle-2 hole configuration mixing and tensor force on dipole strength distributions were investigated.
Minato, Futoshi; Iwamoto, Osamu; Minomo, Kosho*; Ogata, Kazuyuki*; Iwamoto, Nobuyuki; Kunieda, Satoshi; Furutachi, Naoya
EPJ Web of Conferences (Internet), 146, p.12032_1 - 12032_4, 2017/09
Phenomenological optical potential is known to be able to describe the elastic scattering process. It is applied widely to the nuclear data evaluation of the cross section. Many kinds of the optical potential have been studied so far. However, the parameters in the phenomenological optical potentials are determined so as to reproduce existing experimental data, so that use of it for unmeasured nuclei such as neutron-rich nuclei is not necessarily reliable. Recently, a new optical potential derived from the microscopic effective reaction theory (MERT) was proposed. Since the formulation of MERT is based on the NN effective interaction, any parameterizations in the optical potential aren't needed. Therefore, it is capable of calculating nuclei whose scattering cross section isn't measured. We incorporate the optical potentials of MERT in code CCONE and start nuclear data evaluation of several nuclei. In this work, we discuss difference of cross sections evaluated by MERT's optical potentials and conventional phenomenological ones.
Iwamoto, Osamu; Shibata, Keiichi; Iwamoto, Nobuyuki; Kunieda, Satoshi; Minato, Futoshi; Ichihara, Akira; Nakayama, Shinsuke
EPJ Web of Conferences (Internet), 146, p.02005_1 - 02005_6, 2017/09
Acta Physica Polonica B; Proceedings Supplement, 10(1), p.131 - 138, 2017/00
The random phase approximation (RPA) is one of the useful approaches to describe a collective motion of nuclei. However, RPA intrinsically considers only 1 particle-1 hole (1p1h) excitations, as a result it fails to describe the width of the excited states, for example the Gamow-Teller (GT) state. To include higher-order particle-hole excitations, one can extend RPA to Second RPA (SRPA) which includes 2p2h excitations in a similar way to RPA with the quasi-boson-approximation (QBA). However, it fails to describe the GT distribution even with those model. A part of the problem may arise from the use of QBA. In past studies, SRPA was compared with exact solution using the Lipkin Model and the validity of application of QBA to them was examined. In this work, we examine proton-neutron SRPA (pnSRPA) in SU(4) basis. SU(4) is naturally required in this case to take into account two different particles having two levels each. The first and second excited states are calculated by the diagonalization of Hamiltonian and pnSRPA.
Kunieda, Satoshi; Iwamoto, Osamu; Iwamoto, Nobuyuki; Minato, Futoshi; Okamoto, Tsutomu; Sato, Tatsuhiko; Nakashima, Hiroshi; Iwamoto, Yosuke; Iwamoto, Hiroki; Kitatani, Fumito; et al.
JAEA-Conf 2016-004, p.41 - 46, 2016/09
Neutron- and proton-induced cross-section data are required in a wide energy range beyond 20 MeV, for the design of accelerator applications. New evaluations are performed with recent knowledge in the optical and pre-equilibrium model calculations. We also evaluated cross-sections for p+Li and p+Be which have been highly requested from a medical field. The present high-energy nuclear data library, JENDL-4.0/HE, includes evaluated cross-sections for incident neutrons and protons up to 200 MeV (for about 130 nuclei). We overview substantial features of the library, i.e., (1) systematic evaluation with CCONE code, (2) challenges for evaluations of light nuclei and (3) inheritance of JENDL-4.0 and JENDL/HE-2007. In this talk, we also focus on the results of benchmark calculation for neutronics to show performance of the present library.
Furutachi, Naoya; Minato, Futoshi; Iwamoto, Osamu
JAEA-Conf 2016-004, p.93 - 98, 2016/09
To investigate feasibility of the nuclear transmutation of long-lived fission products (LLFPs), nuclear data used in the simulation calculation of transmutation system is essential. To improve the precision of simulation calculation, the nuclear data of various nuclei produced via nuclear transmutation of LLFPs involved in the simulation is also important. Since wide range of nuclei are expected to be produced depends on the method of transmutation, and there are no available experimental data for some of them, a systematic information based on a microscopic calculation is desirable. In this work, we have performed microscopic nuclear structure calculation to derive the structure parameters used in the nuclear data evaluation. We have calculated deformation parameters and ground-state spin and parities for Z = 30-55 medium nuclei including odd-even and odd-odd nuclei, expected to be produced via the transmutation of Se, Zr, Pd and Cs, using Hartree-Fock-Bogoliubov (HFB) theory. The calculation was done by HFBTHO code. The results are compared with the available experimental data, and reliability of the prediction with the present method is discussed.
Shibata, Keiichi; Iwamoto, Nobuyuki; Kunieda, Satoshi; Minato, Futoshi; Iwamoto, Osamu
JAEA-Conf 2016-004, p.47 - 52, 2016/09
It is required to estimate radioactive products accurately for the decommissioning of LWRs. We have developed the neutron-induced activation cross-section file for this purpose. The products consist of 227 nuclides with half-lives larger than 30 days and 12 nuclides with very long half-lives. Target nuclei were selected by considering possible paths leading to the required products. The activation cross sections of these targets were taken from JENDL-4.0, JENDL/A-96 and the post JENDL-4.0 evaluations. As a result, we produced the activation cross-section file with 302 nuclides. Comparing with other evaluations, there exists a large difference especially for the capture cross sections leading to meta-stable states. The data will be released in FY2016 after achieving further improvements.
EPJ Web of Conferences (Internet), 122, p.10001_1 - 10001_13, 2016/06
Nuclear beta-decay and delayed neutron (DN) emission is important for the -process nucleosynthesis after the freeze-out and stable and safe operation of nuclear reactors. Even though radioactive beam facilities have enabled us to measure beta-decay and DN branching ratio of neutron-rich nuclei apart from the stability line in the nuclear chart, there are still a lot of nuclei which one cannot investigate. In particular, information on DN is rather scarce than that of . To predict and DN branching ratios, we recently developed a method which comprises QRPA and Hauser-Feshbach model. In this work, we calculate fission fragments with . We obtain the RMS deviation from experimental half-life of 5.06. However, there are odd-even staggering when looking at theoretical along an isotopic chain, which is not observed experimentally. There are also deviations of DN branching ratios. We discuss the cause of these problems and how to remedy them.
Physical Review C, 93(4), p.044319_1 - 044319_11, 2016/04
Two-particle two-hole (2p2h) effect on Gamow-Teller (GT) transition for neutron-rich nuclei is studied by the second Tamm-Dancoff-Approximation (STDA) with the Skyrme interaction. Unstable O and Si, and stable Ca nuclei are chosen to study quenching and fragmentation of the GT strengths. The correlation of 2p2h configurations induces 20% quenching and downward shift of GT giant resonances (GTGRs). The residual interaction exchanging angular momentum by , appeared in the tensor force part as well as the central force part, gives a meaningful effect to the GT distributions. 15 to 20% of the total GT strengths are brought to high energy region above GTGRs. In particular, the tensor force brings strengths to high energy more than 60 MeV. STDA calculation with a small model space for 2p2h configuration is also studied and experimental data of Ca is reproduced successfully.