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
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.
Ito, Yuta*; Schury, P.*; Wada, Michiharu*; Arai, Fumiya*; Haba, Hiromitsu*; Hirayama, Yoshikazu*; Ishizawa, Satoshi*; Kaji, Daiya*; Kimura, Sota*; Koura, Hiroyuki; et al.
Physical Review Letters, 120(15), p.152501_1 - 152501_6, 2018/04
Masses of Es, Fm and the transfermium nuclei Md, and No, produced by hot- and cold-fusion reactions, in the vicinity of the deformed neutron shell closure, have been directly measured using a multi-reflection time-of-flight mass spectrograph. The masses of Es and Md were measured for the first time. Using the masses of Md as anchor points for decay chains, the masses of heavier nuclei, up to Bh and Mt, were determined. These new masses were compared with theoretical global mass models and demonstrated to be in good agreement with macroscopic-microscopic models in this region. The empirical shell gap parameter derived from three isotopic masses was updated with the new masses and corroborate the existence of the deformed neutron shell closure for Md and Lr.
Sakanaka, Shogo*; Ago, Tomonori*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; Harada, Kentaro*; Hiramatsu, Shigenori*; Honda, Toru*; et al.
Proceedings of 11th European Particle Accelerator Conference (EPAC '08) (CD-ROM), p.205 - 207, 2008/06
Future synchrotron light sources based on the energy-recovery linacs (ERLs) are expected to be capable of producing super-brilliant and/or ultra-short pulses of synchrotron radiation. Our Japanese collaboration team is making efforts for realizing an ERL-based hard X-ray source. We report recent progress in our R&D efforts.
Nishitani, Tomohiro; Nakanishi, Tsutomu*; Yamamoto, Masahiro*; Okumi, Shoji*; Furuta, Fumio*; Miyamoto, Masaharu*; Kuwahara, Makoto*; Yamamoto, Naoto*; Naniwa, Kenichi*; Watanabe, Osamu*; et al.
Journal of Applied Physics, 97(9), p.094907_1 - 094907_6, 2005/05
no abstracts in English
Toyoshima, Atsushi; Miyashita, Sunao; Oe, Kazuhiro; Asai, Masato; Sato, Tetsuya; Tsukada, Kazuaki; Kitatsuji, Yoshihiro; Nagame, Yuichiro; Schdel, M.; Omtvedt, J. P.*; et al.
no journal, ,
We plan to determine the redox potential of seaborgium (Sg) in continuous experiments with a flow electrolytic column and a continuous solvent extraction SISAK. In this study, reduction experiments of its lighter homologues, Mo and W, were performed using the flow electrolytic column apparatus. After 200 L of the W radiotracer in 0.1 M HCl was introduced into the apparatus, 1000 L of 0.1 M HCl was fed into the electrode on which an potential was applied between -0.8 and 0.6 V. 1000 L was taken from the effluent from the electrode and was then mixed with 10 M hinokitiol in toluene with the same volume. After shaking for 1 min and then centrifuging for 30 s, 800 L was taken from each phase, which was then separately subjected to -ray spectrometry. As a result, the extraction yield of W was constant against the variation of the applied potential. It seems that once reduced W was again oxidized to the +6 state in the extraction procedure.
Oe, Kazuhiro; Tsukada, Kazuaki; Asai, Masato; Sato, Tetsuya; Toyoshima, Atsushi; Miyashita, Sunao; Nagame, Yuichiro; Schdel, M.; Kaneya, Yusuke*; Lerum, H. V.*; et al.
no journal, ,
We are planning to investigate the redox behavior of element 106, seaborgium (Sg). For the Sg study, we newly developed a continuous dissolution apparatus which dissolves the gas-jet transported nuclides produced in nuclear reactions into aqueous solution. The new apparatus has a hydrophobic membrane filter for separation of aqueous solution from the gas. We investigated the dissolution efficiencies with the apparatus for short-lived nuclides of molybdenum and tungsten which are lighter homologues of Sg. In the meeting, the dependence of the efficiencies on the aqueous- and gas-flow rates will be reported.
Miyashita, Sunao; Oe, Kazuhiro; Toyoshima, Atsushi; Sato, Tetsuya; Asai, Masato; Tsukada, Kazuaki; Nagame, Yuichiro; Schdel, M.; Kaneya, Yusuke*; Omtvedt, J. P.*; et al.
no journal, ,
For the experiments of the redox potentials of Sg, rapid separation between different oxidation states of Sg is needed. In this study, solvent extraction of hexavalent Mo and W, as the lighter homologues of Sg, from 1.0 mol/L hydrochloric acid solution into di-(2-ethylhexyl)phosphoric acid (HDEHP), 1-phenyl-3-metyl-4-benzoyl-5-pyrazolone (PMBP), N-benzoyl-N-pheny-hydroxylamine (BPHA) and 4-isopropyl-tropolone (HT) in toluene was carried out. When HDEHP and PMBP were used as extractant, extraction equilibrium of W was achieved within 5 and 1 hours respectively. On the other hand, when BPHA and HT were used, extraction equilibrium of W was quickly achieved within 1 minute in both extractants. Extraction kinetics of Mo using BPHA and HT was examined. Extraction kinetics of Mo was slower than that of W. Extraction equilibrium of Mo was achieved within 10 by BPHA and 3 minutes by HT. We concluded that HT is a suitable extractant for the Sg reduction experiment.
Miyashita, Sunao; Toyoshima, Atsushi; Oe, Kazuhiro*; Asai, Masato; Sato, Tetsuya; Tsukada, Kazuaki; Nagame, Yuichiro; Schdel, M.; Kaneya, Yusuke; Haba, Hiromitsu*; et al.
no journal, ,
Solvent extraction of Mo and W using 4-isopropyltropolone (Hinokitiol, HT) was investigated. Extraction mechanism of Mo and W with HT was examined by slope analysis. The slopse of the distribution ratio of Mo and W vs. [HT] in logarithmic scale are 1.88 and 1.54, respectively.
Miyashita, Sunao; Toyoshima, Atsushi; Oe, Kazuhiro*; Sato, Tetsuya; Asai, Masato; Tsukada, Kazuaki; Nagame, Yuichiro; Schdel, M.; Kaneya, Yusuke; Haba, Hiromitsu*; et al.
no journal, ,
The extraction behavior of hexavalent and reduced Mo and W were investigated when aqueous phase was 0.1 M HCl/0.9 M LiCl solution. The D value of Mo was changed from 10 to 1 when applied potential was near 0 to -0.2 V. On the other hand, the D value of W was not changed at all applied potentials in this experimental condition. Those results indicated that Mo was reduced by FEC, and the extraction behavior of reduced Mo was different from hexavalent Mo. In the case of W, W was not reduced or the D values of reduced W was same as hexavalent W.
Toyoshima, Atsushi; Miyashita, Sunao*; Asai, Masato; Sato, Tetsuya; Kaneya, Yusuke; Tsukada, Kazuaki; Kitatsuji, Yoshihiro; Nagame, Yuichiro; Schdel, M.; Lerum, H. V.*; et al.
no journal, ,
To carry out a continuous reduction experiment of Sg with the low production rates and the short half-life, we are developing a new chemistry assembly consisting of a membrane degasser (MDG), a flow electrolytic column (FEC), the continuous liquid-liquid extraction apparatus, and the liquid scintillation counting system (SISAK). Recently, we have begun preparatory studies with Mo and W isotopes. Aqueous solution dissolving Mo and W was successfully separated from a carrier gas. Redox couples of Mo(VI)/Mo(V) and W(VI)/W(V) in HCl have been characterized for their macro amounts. Extraction behavior of Mo(VI) and W(VI) between toluene containing hinokitiol (HT) and HCl was successfully observed by a batch method. On-line extractions of short-lived Mo and W were also carried out using SISAK and MDG. In the symposium, our present status of the preparation with Mo and W will be presented.