X-ray free electron laser observation of ultrafast lattice behaviour under femtosecond laser-driven shock compression in iron

Sano, Tomokazu*; Matsuda, Tomoki*; Hirose, Akio*; Terai, Tomoyuki*; Kakeshita, Tomoyuki*; Inubushi, Yuichi*; Sato, Takahiro*; Yabashi, Makina*; Shobu, Takahisa; 22 of others*

Scientific Reports (Internet), 13, p.13796_1 - 13796_10, 2023/08

https://doi.org/10.1038/s41598-023-40283-6

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.

The Deposition densities of radiocesium and the air dose rates in undisturbed fields around the Fukushima Dai-ichi Nuclear Power Plant; Their temporal changes for five years after the accident

Mikami, Satoshi; Tanaka, Hiroyuki*; Matsuda, Hideo*; Sato, Shoji*; Hoshide, Yoshifumi*; Okuda, Naotoshi*; Suzuki, Takeo*; Sakamoto, Ryuichi*; Ando, Masaki; Saito, Kimiaki

Journal of Environmental Radioactivity, 210, p.105941_1 - 105941_12, 2019/12

AA2019-0019.pdf:2.65MB

https://doi.org/10.1016/j.jenvrad.2019.03.017

The deposition densities of radiocesium and the air dose rates were repeatedly measured in a large number of undisturbed fields within the 80km zone that surrounds the Fukushima Dai-ichi Nuclear Power Plant site between 2011 and 2016, and features of their temporal changes were clarified. The average air dose rate excluding background radiation in this zone decreased to about 20% of the initial value during the period from June 2011 to August 2016, which was essentially a result of the radioactive decay of Cs with a half-life of 2.06y. The air dose rate reduction was faster than that expected from the decay of radiocesium by a factor of about two, with most of this reduction being attributed to the penetration of radiocesium into the soil. The average deposition densities of Cs and Cs in fields that were not decontaminated were found to have decreased nearly according to their expected radioactive decay, which indicated that the movement of radiocesium in the horizontal direction was relatively small. The effect of decontamination was apparently observed in the measurements of air dose rates and deposition densities. Nominally, the average air dose rates in the measurement locations were reduced by about 20% by decontamination and other human activities, of which accurate quantitative analysis is and continue to be a challenge.

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

https://doi.org/10.1126/science.aav7432

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Measurements and analyses of the distribution of the radioactivity induced by the secondary neutrons produced by 17-MeV protons in compact cyclotron facility

Matsuda, Norihiro; Izumi, Yuichi*; Yamanaka, Yoshiyuki*; Gando, Toshiyuki*; Yamada, Masaaki*; Oishi, Koji*

EPJ Web of Conferences, 153, p.07001_1 - 07001_6, 2017/09

https://doi.org/10.1051/epjconf/201715307001

Temperature of thermal spikes in amorphous silicon nitride films produced by 1.11 MeV C impacts

Kitayama, Takumi*; Nakajima, Kaoru*; Suzuki, Motofumi*; Narumi, Kazumasa; Saito, Yuichi; Matsuda, Makoto; Sataka, Masao*; Tsujimoto, Masahiko*; Isoda, Shoji*; Kimura, Kenji*

Nuclear Instruments and Methods in Physics Research B, 354, p.183 - 186, 2015/07

https://doi.org/10.1016/j.nimb.2014.11.002

Magnetic and Fermi surface properties of EuGa

Nakamura, Ai*; Hiranaka, Yuichi*; Hedo, Masato*; Nakama, Takao*; Miura, Yasunao*; Tsutsumi, Hiroki*; Mori, Akinobu*; Ishida, Kazuhiro*; Mitamura, Katsuya*; Hirose, Yusuke*; et al.

Journal of the Physical Society of Japan, 82(10), p.104703_1 - 104703_10, 2013/10

https://doi.org/10.7566/JPSJ.82.104703

Possible band termination of Rh

Sugawara, Masahiko*; Hayakawa, Takehito; Oshima, Masumi*; Toh, Yosuke; Osa, Akihiko; Matsuda, Makoto; Shizuma, Toshiyuki; Hatsukawa, Yuichi; Kusakari, Hideshige*; Morikawa, Tsuneyasu*; et al.

Physical Review C, 87(6), p.064319_1 - 064319_10, 2013/06

https://doi.org/10.1103/PhysRevC.87.064319

High-spin states of Rh were studied through in-beam -ray spectroscopy by using the reaction Zn(Cl, 2). The upper part of the band based on the g proton orbital was rearranged in fourparallel cascades. The negative-parity band with the configuration of (g)[(d(h)]was extended up to that is possibly a terminating state. The band based on the proton orbital was observed up to and its property was compared with those of neighboring odd-Z nuclei from the viewpoint of vibrational to rotational evolution along the band.

Possible antimagnetic rotation band and neutron alignment in Pd

Sugawara, Masahiko*; Hayakawa, Takehito; Oshima, Masumi*; Toh, Yosuke; Osa, Akihiko; Matsuda, Makoto; Shizuma, Toshiyuki; Hatsukawa, Yuichi; Kusakari, Hideshige*; Morikawa, Tsuneyasu*; et al.

Physical Review C, 86(3), p.034326_1 - 034326_11, 2012/09

https://doi.org/10.1103/PhysRevC.86.034326

High spin states of Pd have been studied through in-beam -ray spectroscopy by using the reaction Zn (Cl, 13). The band based on the neutron orbital has been extended to higher-spin states, and the band based on the neutron orbital has been somewhat revised. Many transitions decaying to these bands have been observed and consequently, several side bands have been established. Electric dipole transitions from the band to the band have been also observed. The structure of the band was discussed from the viewpoint of "antimagnetic rotation" based on a semiclassical particle plus rotor model taking neutron alignments into account.

Shape evolution in heaviest stable even-even molybdenum isotopes studied via Coulomb excitation

Wrzosek-Lipska, K.*; Zieliska, M.*; Hadyska-Klk, K.*; Hatsukawa, Yuichi; Iwanicki, J.*; Katakura, Junichi; Kisieliski, M.*; Koizumi, Mitsuo; Kowalczyk, M.*; Kusakari, Hideshige*; et al.

International Journal of Modern Physics E, 20(2), p.443 - 450, 2011/02

https://doi.org/10.1142/S0218301311017831

The quadrupole shape evolution in heaviest stable Mo isotopes is studied in terms of the shape coexistence phenomenon occurrence in this region of nuclear chart. Quadrupole deformation parameters of the Mo isotopes in the low-lying (ground and excited) 0 states were deduced using Coulomb excitation method. In all cases rich sets of electromagnetic reduced matrix elements were determined using the GOSIA code and then analyzed using the Quadrupole Sum Rules formalism. Discussion of the experimental results in comparison with the predictions of microscopic calculations within the general quadrupole collective Bohr Hamiltonian model is presented for Mo.