Intruder configurations in Ne at the transition into the island of inversion; Detailed structure study of Ne

Wang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.

Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08

https://doi.org/10.1016/j.physletb.2023.138038

Detailed -ray spectroscopy of the exotic neon isotope Ne has been performed using the one-neutron removal reaction from Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

https://doi.org/10.1038/s41550-020-01271-2

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

Research plan on geosphere stability for long-term isolation of radioactive waste; Scientific programme for fiscal years 2012

Asamori, Koichi; Niwa, Masakazu; Hanamuro, Takahiro; Yamada, Kunimi; Kusano, Tomohiro; Makuuchi, Ayumu; Takatori, Ryoichi; Kokubu, Yoko; Ishimaru, Tsuneari; Umeda, Koji

JAEA-Review 2012-024, 44 Pages, 2012/07

JAEA-Review-2012-024.pdf:1.29MB

The concept of geological disposal of HLW in Japan is based on a multi-barrier system which combines a stable geological environment with a robust barrier system. Potential geological host formations and their surroundings are chosen, in particular, for their long-term stability, taking into account the fact that Japan is located in a tectonically active zone. This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of HLW in JAEA, in fiscal year 2012. The objectives and contents in fiscal year 2012 are described in detail based on the outline of 5 years plan (fiscal years 2010-2014). In addition, the planed framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques.

Decay properties of Bh and Db produced in the Cm + Na reaction

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sato, Nozomi*; Sumita, Takayuki*; Yoneda, Akira*; Ichikawa, Takatoshi*; et al.

Journal of the Physical Society of Japan, 78(6), p.064201_1 - 064201_6, 2009/06

https://doi.org/10.1143/JPSJ.78.064201

Decay properties of an isotope Bh and its daughter nucleus Db produced by the Cm(Na,5) reaction were studied by using a gas-filled recoil separator coupled with a position-sensitive semiconductor detector. Bh was clearly identified from the correlation of the known nuclide, Db. The obtained decay properties of Bh and Db are consistent with those observed in the 113 chain, which provided further confirmation of the discovery of 113.

Production and decay properties of Bh and its daughter nuclei

Morimoto, Koji*; Morita, Kosuke*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sato, Nozomi; Sumita, Takayuki*; Yoneda, Akira*; Ichikawa, Takatoshi*; et al.

no journal, , 

A nuclide, Bh, is the great-grand-daughter of 113 that is produced in the Bi + Zn reaction. The identification was based on a genetic link to the known daughter nucleus Db by alpha-decays. The main purpose of this work is to provide further confirmation of the production and identification of the isotope 113. As a present result, a state in Bh, which decays by an alpha emission with the energies ranging from 9.05 to 9.23 MeV, feeds a state in Db, which decays by alpha emission and by SF with a previously known half-life. The result provided a further confirmation of the production and identification of the isotope of the 113th element, 113, studied by a research group at RIKEN.

Confirmations of the synthesis of 113 produced by the Bi(Zn,n)113 reaction

Morimoto, Koji*; Morita, Kosuke*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sato, Nozomi; Sumita, Takayuki*; Yoneda, Akira*; Ichikawa, Takatoshi*; et al.

no journal, , 

We performed the experiment to synthesize an isotope of the element 113 produced by a Bi(Zn,n)113 reaction using a gas-filled recoil ion separator (GARIS) at RIKEN. Two decay chains were observed, and assigned to those originating from an isotope 113. Both chains were connected into the previously known decays of Bh and Db via previously unknown decays of 113, Rg, and Mt. Although the Bh was known nuclide, a number of atoms reported so far was limited. In order to study more precise decay property of the Bh, we performed the direct production of Bh by the Cm(Na,5n)Bh reaction. In this experiment, the Bh was clearly identified from the correlation of the nuclide, Db. The obtained decay properties of Bh and Db are consistent with those observed in the 113 chain, which provided further confirmation of the discovery of 113.

Experimental demonstration of neutron resonance measurement using laser-driven neutron source

Lan, Z.*; Yogo, Akifumi*; Mirfayzi, S. R.*; Hayakawa, Takehito*; Koizumi, Mitsuo; Wei, T.*; Shi, B.*; Ishimoto, Takashi*; Golovin, D.*; Mori, Takato*; et al.

no journal, , 

Neutron resonance absorption by laser-driven source; Toward "Single Shot" analysis

Yogo, Akifumi*; Lan, Z.*; Hayakawa, Takehito*; Arikawa, Yasunobu*; Abe, Yuki*; Mirfayzi, S. R.*; Koizumi, Mitsuo; Mori, Takato*; Wei, T.*; Fujioka, Shinsuke*; et al.

no journal, , 

no abstracts in English

High-speed atomic thermometer using single shot of laser-driven neutron pulse

Lan, Z.*; Yogo, Akifumi*; Hayakawa, Takehito*; Wei, T.*; Kamiyama, Takashi*; Sato, Hirotaka*; Arikawa, Yasunobu*; Mirfayzi, R.*; Koizumi, Mitsuo; Abe, Yuki*; et al.

no journal, , 

Nuclear thermometer using single pulse of laser-driven neutron source

Lan, Z.*; Hayakawa, Takehito*; Wei, T.*; Kamiyama, Takashi*; Sato, Hirotaka*; Arikawa, Yasunobu*; Mirfayzi, S. R.*; Koizumi, Mitsuo; Abe, Yuki*; Mori, Takato*; et al.

no journal, ,