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Journal Articles

Stochastic estimation of nuclear level density in the nuclear shell model; An Application to parity-dependent level density in $$^{58}$$Ni

Shimizu, Noritaka*; Utsuno, Yutaka; Futamura, Yasunori*; Sakurai, Tetsuya*; Mizusaki, Takahiro*; Otsuka, Takaharu*

Physics Letters B, 753, p.13 - 17, 2016/02

AA2015-0661.pdf:0.39MB

 Times Cited Count:12 Percentile:20.87(Astronomy & Astrophysics)

Nuclear level density plays an important role in applications to nuclear energy and nuclear astrophysics, dominating neutron-capture cross sections. In this paper, we propose a new, practical and accurate method of estimating nuclear level density within the framework of the nuclear shell model, and show its feasibility and usefulness. This method is based on the idea that the level density is obtained by the number of eigenstates that is represented as a contour integral in the complex plane. We first confirm the feasibility of this method using a small system in which the exact eigenstates are available, and then calculate parity-dependent level density in $$^{58}$$Ni, which cannot be calculated with direct eigenstate counting. We succeed in reproducing the experimental result that the $$2^+$$ and $$2^-$$ level densities are almost identical in low-energy regions, which cannot be obtained with conventional methods of estimating level densities.

Journal Articles

Phenomenological nuclear level densities using the KTUY05 nuclear mass formula for applications off-stability

Kawano, Toshihiko*; Chiba, Satoshi; Koura, Hiroyuki

Journal of Nuclear Science and Technology, 43(1), p.1 - 8, 2006/01

 Times Cited Count:42 Percentile:5.38(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Metastable states' population of uranium atoms produced by electron-beam heating

Oba, Hironori; Nishimura, Akihiko; Ogura, Koichi; Shibata, Takemasa

JAERI-Research 2000-033, 17 Pages, 2000/08

JAERI-Research-2000-033.pdf:0.65MB

no abstracts in English

Journal Articles

Fermi-gas model parametrization of nuclear level density

A.Mengoni*; Nakajima, Yutaka

Journal of Nuclear Science and Technology, 31(2), p.151 - 162, 1994/02

 Times Cited Count:97 Percentile:1.13(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Algebraic and geometric approaches to the collective enhancement of nuclear level densities

A.Mengoni*; G.Maino*; Ventura, A.*; Nakajima, Yutaka

Int. Conf. on Perspectives for the Interacting Boson Model on the Occasion of Its 20th Anniversary, 0, 421 Pages, 1994/00

no abstracts in English

JAEA Reports

HERMES: A Personal-computer program for calculation of the Fermi-gas model parameters of nuclear level density

A.Mengoni*; Nakajima, Yutaka

JAERI-M 93-177, 26 Pages, 1993/09

JAERI-M-93-177.pdf:0.81MB

no abstracts in English

Journal Articles

Evaluation of charge distribution in insulators by means of slanted etching

*; *; *; Yoshikawa, Masahito; *

Heisei-5-Nendo (Dai-37-Kai) Nihon Daigaku Riko Gakubu Gakujutsu Koenkai Koen Rombunshu; Zairyo, Bussei, p.135 - 136, 1993/00

no abstracts in English

Journal Articles

Thermal annealing effects on electric characteristics of MIS structures with nitride layers

*; *; Yoshikawa, Masahito; *

Heisei-5-Nendo (Dai-37-Kai) Nihon Daigaku Riko Gakubu Gakujutsu Koenkai Koen Rombunshu; Zairyo, Bussei, p.133 - 134, 1993/00

no abstracts in English

Journal Articles

Nuclear Level Density

Nippon Butsuri Gakkai-Shi, 25(9), p.631 - 644, 1970/00

no abstracts in English

Oral presentation

Large-scale shell-model study of strength function

Utsuno, Yutaka; Shimizu, Noritaka*; Otsuka, Takaharu*

no journal, , 

no abstracts in English

Oral presentation

Large-scale shell-model calculations for low- and high-lying states

Utsuno, Yutaka

no journal, , 

no abstracts in English

Oral presentation

Calculations of cross sections using the nuclear level density obtained from the microscopic nuclear structure calculation

Furutachi, Naoya; Minato, Futoshi; Iwamoto, Osamu

no journal, , 

Nuclear reaction calculations using the statistical model require information of the nuclear level density. While the phenomenological models such as Fermi Gas model are often used to calculate the nuclear level density in usual nuclear data evaluations, reliability of such level density depends on parameter adjustments using experimental values. Therefore, development of microscopic calculation methods that does not depend on parameter adjustments is desired. One of the microscopic methods to calculate the nuclear level density is the combinatorial method that uses single-particle levels obtained from Hartree-Fock theory, and its reliability has been discussed through the reproducibility of the s-wave neutron resonance spacing $$D_0$$. However, comparisons of cross sections with experiments are only preformed for (n,$$gamma$$) reaction of some nuclei, and is still insufficient. Therefore, in this work, we calculate the nuclear level density using the combinatorial method, and apply it to the nuclear reaction calculations such as (n,$$gamma$$) reaction and (n,2n) reaction calculations. The cross sections of these reactions adding to the s-wave neutron resonance spacing $$D_0$$ for stable nuclei are compared with the experiments systematically, and then the reliability of the nuclear level density is discussed.

Oral presentation

Interaction dependence of the nuclear level density calculated using Hartree-Fock-Bogoliubov theory

Furutachi, Naoya; Minato, Futoshi; Iwamoto, Osamu

no journal, , 

While Fermi Gas type phenomenological models are widely used to calculate the nuclear level density (NLD) of stable nuclei, it is important to develop a microscopic method to achieve reliable NLD for unstable nuclei. One of microscopic methods to calculate NLD is that based on the microscopic nuclear structure calculation using Hartree-Fock-Bogoliubov (HFB) theory. Since a effective nuclear interaction is basically the only input in HFB calculation, we investigated how the calculated NLD depends on it with special attention to the adopted pairing interaction, to discuss about the reliability of this method. Adding to SkM* force that was used in our previous study, SLy4, SkP, and UNEDF1 forces were used in HFB calculations of the present study. The statistical method was applied to derive NLD based on HFB calculation. We compared the s-wave resonance spacing D$$_0$$ derived from the calculated NLD with the experiments, and found better agreement with the results with SkP and UNEDF1 forces compared to those with SkM and SLy4 forces.

Oral presentation

Development of nuclear transmutation methods for converting LLFP into stable or short-lived nuclides, 15; Level densities of LLFPs and nuclei around LLFPs calculated based on the microscopic structure calculation

Furutachi, Naoya; Minato, Futoshi; Iwamoto, Osamu

no journal, , 

To establish a reasonable nuclear transmutation technology for long-lived fission products (LLFPs), it is important to improve precision of the nuclear data needed for the simulation of the nuclear transmutation. The level density is essential for the nuclear reaction calculation using the statistical model, and it has significant influence on the precision of the nuclear data evaluation. Although a phenomenological model such as Fermi Gas model is used in a usual nuclear data evaluation, it is considered that using a microscopic theory that has predictive power superior to a phenomenological model brings better precision for the nuclear data. In this study, to improve precision of the nuclear data of LLFPs and nuclei around LLFPs, the level densities needed for the nuclear data evaluation of those nuclei were derived based on the microscopic nuclear data calculation. In this derivation, we improved the calculation method to describe prcisely the effect of the deformation change with nuclear excitation. To analyze precision of the nuclear reaction calculation, we compared the cross sections of various reaction channel systematically with the experimental data of stable nuclei.

Oral presentation

Development of nuclear data evaluation method to improve precision of nuclear data for long-lived fission products

Furutachi, Naoya; Minato, Futoshi; Iwamoto, Osamu

no journal, , 

no abstracts in English

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