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Journal Articles

Excitation functions for production of Rf isotopes in the $$^{248}$$Cm + $$^{18}$$O reaction

Murakami, Masashi*; Goto, Shinichi*; Murayama, Hirofumi*; Kojima, Takayuki*; Kudo, Hisaaki*; Kaji, Daiya*; Morimoto, Koji*; Haba, Hiromitsu*; Kudo, Yuki*; Sumita, Takayuki*; et al.

Physical Review C, 88(2), p.024618_1 - 024618_8, 2013/08

 Times Cited Count:14 Percentile:68.19(Physics, Nuclear)

Production cross sections of Rf isotopes in the $$^{248}$$Cm + $$^{18}$$O reaction were measured at the beam energy range of 88.2 to 101.3 MeV by use of a gas-filled recoil ion separator. The excitation functions of $$^{260}$$Rf, $$^{261a}$$Rf, and $$^{262}$$Rf were obtained together with those of spontaneously fissioning nuclides which have few-second half-lives and have been assigned to $$^{261b}$$Rf and a longer-lived state of $$^{262}$$Rf. The excitation function of few-second spontaneously fissioning nuclide exhibited the maximum cross section at the $$^{18}$$O beam energy of 94.8 MeV. The shape of the excitation function was almost the same as that of $$^{261a}$$Rf, whereas it was quite different from those of $$^{260}$$Rf and $$^{262}$$Rf. A few-second spontaneously fissioning nuclide previously reported as $$^{261b}$$Rf and $$^{262}$$Rf observed in$$^{248}$$Cm + $$^{18}$$O reaction was identified as $$^{261b}$$Rf.

Journal Articles

New result in the production and decay of an isotope, $$^{278}$$113 of the 113th element

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sumita, Takayuki*; Wakabayashi, Yasuo*; Yoneda, Akira*; Tanaka, Kengo*; et al.

Journal of the Physical Society of Japan, 81(10), p.103201_1 - 103201_4, 2012/10

 Times Cited Count:156 Percentile:97.29(Physics, Multidisciplinary)

An isotope of the 113th element, $$^{278}$$113, was produced in a nuclear reaction with a $$^{70}$$Zn beam on a $$^{209}$$Bi target. We observed six consecutive $$alpha$$ decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector, in extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of $$^{262}$$Db and $$^{258}$$Lr both in decay energies and decay times. This indicates that the present decay chain consisted of $$^{278}$$113, $$^{274}$$Rg (Z = 111), $$^{270}$$Mt (Z = 109), $$^{266}$$Bh (Z = 107), $$^{262}$$Db (Z = 105), and $$^{258}$$Lr (Z = 103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads the unambiguous production and identification of the isotope $$^{278}$$113, of the 113th element.

Journal Articles

Sulfate complexation of element 104, Rf, in H$$_{2}$$SO$$_{4}$$/HNO$$_{3}$$ mixed solution

Li, Z.*; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Sato, Tetsuya; Sato, Nozomi; Kikuchi, Takahiro; Nagame, Yuichiro; Sch$"a$del, M.; Pershina, V.*; et al.

Radiochimica Acta, 100(3), p.157 - 164, 2012/03

 Times Cited Count:12 Percentile:68.26(Chemistry, Inorganic & Nuclear)

Journal Articles

Radiochemical study of sub-barrier fusion hindrance in the $$^{19}$$F+$$^{209}$$Bi reaction

Nishinaka, Ichiro; Kasamatsu, Yoshitaka*; Tanikawa, Masashi*; Goto, Shinichi*; Asai, Masato

Proceedings in Radiochemistry, 1(1), p.117 - 121, 2011/09

Unexpected steep falloff of fusion cross sections has recently been observed in heavy-ion fusion reactions at deep sub-barrier energies. In this study the fusion-fission cross sections for $$^{19}$$F+$$^{209}$$Bi at sub-barrier energies were determined by a radiochemical method in order to study sub-barrier fusion hindrance. We will discuss the sub-barrier fusion hindrance in heavy-mass systems, comparing the theoretical calculations and the systematics.

Journal Articles

Extraction of chromatographic behavior of Rf, Zr, and Hf in HCl solution with styrenedivinylbenzene copolymer resin modified by TOPO (trioctylphosphine oxide)

Toyoshima, Atsushi; Kasamatsu, Yoshitaka*; Tsukada, Kazuaki; Asai, Masato; Ishii, Yasuo; Tome, Hayato*; Nishinaka, Ichiro; Sato, Tetsuya; Nagame, Yuichiro; Sch$"a$del, M.; et al.

Journal of Nuclear and Radiochemical Sciences, 11(1), p.7 - 11, 2010/06

The extraction behavior of rutherfordium (Rf) into trioctylphosphine oxide (TOPO) from 2.0 - 7.0 M HCl solution was studied together with that of the homologues Zr and Hf. The extracted yields of Rf, Zr, and Hf increased with an increase of HCl concentration, and the sequence of their extraction was Zr $$>$$ Hf $$geq$$ Rf. It is suggested that the stability of the RfCl$$_{4}$$$$cdot$$2(TOPO) complex is lower than that of the corresponding species of the homologues.

Journal Articles

Anionic fluoro complex of element 105, Db

Kasamatsu, Yoshitaka*; Toyoshima, Atsushi; Asai, Masato; Tsukada, Kazuaki; Li, Z.; Ishii, Yasuo; Tome, Hayato*; Sato, Tetsuya; Kikuchi, Takahiro; Nishinaka, Ichiro; et al.

Chemistry Letters, 38(11), p.1084 - 1085, 2009/10

 Times Cited Count:14 Percentile:46.79(Chemistry, Multidisciplinary)

We report on the characteristic anion-exchange behavior of the superheavy element dubnium (Db) with atomic number Z = 105 in HF/HNO$$_{3}$$ solution at the fluoride ion concentration [F$$^{-}$$] = 0.003 M. The result clearly demonstrates that the fluoro complex formation of Db is significantly different from that of the group-5 homologue Ta in the 6th period of the periodic table while the behavior of Db is similar to that of the lighter homologue Nb in the 5th period.

Journal Articles

Decay properties of $$^{266}$$Bh and $$^{262}$$Db produced in the $$^{248}$$Cm + $$^{23}$$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

 Times Cited Count:30 Percentile:79(Physics, Multidisciplinary)

Decay properties of an isotope $$^{266}$$Bh and its daughter nucleus $$^{262}$$Db produced by the $$^{248}$$Cm($$^{23}$$Na,5$$n$$) reaction were studied by using a gas-filled recoil separator coupled with a position-sensitive semiconductor detector. $$^{266}$$Bh was clearly identified from the correlation of the known nuclide, $$^{262}$$Db. The obtained decay properties of $$^{266}$$Bh and $$^{262}$$Db are consistent with those observed in the $$^{278}$$113 chain, which provided further confirmation of the discovery of $$^{278}$$113.

Journal Articles

Adsorption of Db and its homologues Nb and Ta, and the pseudo-homologue Pa on anion-exchange resin in HF solution

Tsukada, Kazuaki; Haba, Hiromitsu*; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko*; Kasamatsu, Yoshitaka; Nishinaka, Ichiro; Ichikawa, Shinichi; Yasuda, Kenichiro; Miyamoto, Yutaka; et al.

Radiochimica Acta, 97(2), p.83 - 89, 2009/02

 Times Cited Count:20 Percentile:78.88(Chemistry, Inorganic & Nuclear)

Anion-exchange chromatography of element 105, dubnium (Db), produced in the $$^{248}$$Cm($$^{19}$$F, 5n)$$^{262}$$Db reaction is investigated together with the homologues Nb and Ta, and the pseudo-homologue Pa in 13.9 M hydrofluoric acid (HF) solution. The distribution coefficient (K$$_{d}$$) of Db on an anion-exchange resin is successfully determined by running cycles of the 1702 chromatographic column separations. The result clearly indicates that the adsorption of Db on the resin is significantly different from that of the homologues and that the adsorption of anionic fluoro complexes of these elements decreases in the sequence of Ta $$approx$$ Nb $$>$$ Db $$geq$$ Pa.

Journal Articles

Long-term erosion and re-deposition of carbon in the divertor region of JT-60U

Goto, Yoshitaka*; Tanabe, Tetsuo*; Ishimoto, Yuki*; Masaki, Kei; Arai, Takashi; Kubo, Hirotaka; Tsuzuki, Kazuhiro*; Miya, Naoyuki

Journal of Nuclear Materials, 357(1-3), p.138 - 146, 2006/10

 Times Cited Count:26 Percentile:85.47(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Thermal properties of redeposition layers in the JT-60U divertor region

Ishimoto, Yuki; Goto, Yoshitaka*; Arai, Takashi; Masaki, Kei; Miya, Naoyuki; Oyama, Naoyuki; Asakura, Nobuyuki

Journal of Nuclear Materials, 350(3), p.301 - 309, 2006/05

 Times Cited Count:21 Percentile:80.79(Materials Science, Multidisciplinary)

Thermal properties of the redeposition layer on the inner plate of the W-shaped divertor of JT-60U have been measured with laser flash method for the first time so as to estimate transient heat loads onto the divertor. Measurement of a redeposition layer sample of more than 200 m thick showed following results: (1) the bulk density of the redeposition layer is about half of that of carbon fiber composite material; (2) the specific heat of the layer is roughly equal to that of the isotropic graphite; (3) the thermal conductivity of the redeposition layer is two orders of magnitude smaller than that of the carbon fiber composite. The difference between the divertor heat loads and the loss of the plasma stored energy becomes smaller taking account of thermal properties of the redeposition layer on the inner divertor, whereas estimated heat loads due to the ELMs is still larger than the loss. This is probably caused by the poloidal distribution of the thermal properties and heat flux asymmetry inherent in the device.

Journal Articles

Deuterium depth profiling in JT-60U W-shaped divertor tiles by nuclear reaction analysis

Hayashi, Takao; Ochiai, Kentaro; Masaki, Kei; Goto, Yoshitaka*; Kutsukake, Chuzo; Arai, Takashi; Nishitani, Takeo; Miya, Naoyuki

Journal of Nuclear Materials, 349(1-2), p.6 - 16, 2006/02

 Times Cited Count:10 Percentile:58.04(Materials Science, Multidisciplinary)

Deuterium concentrations and depth profiles in plasma-facing graphite tiles used in the divertor of JT-60U were investigated by NRA. The highest deuterium concentration of D/$$^{12}$$C of 0.053 was found in the outer dome wing tile, where the deuterium accumulated probably through the deuterium-carbon co-deposition. In the outer and inner divertor target tiles, the D/$$^{12}$$C data were lower than 0.006. Additionally, the maximum (H+D)/$$^{12}$$C in the dome top tile was estimated to be 0.023 from the results of NRA and SIMS. OFMC simulation showed energetic deuterons caused by NBI were implanted into the dome region with high heat flux. Furthermore, the surface temperature and conditions such as deposition and erosion significantly influenced the accumulation process of deuterium. The deuterium depth profile, SEM observation and OFMC simulation indicated the deuterium was considered to accumulate through three processes: the deuterium-carbon co-deposition, the implantation of energetic deuterons and the deuterium diffusion into the bulk.

Journal Articles

Hydrogen isotope distributions and retentions in the inner divertor tile of JT-60U

Oya, Yasuhisa*; Hirohata, Yuko*; Tanabe, Tetsuo*; Shibahara, Takahiro*; Kimura, Hiromi*; Oyaizu, Makoto*; Arai, Takashi; Masaki, Kei; Goto, Yoshitaka*; Okuno, Kenji*; et al.

Fusion Engineering and Design, 75-79, p.945 - 949, 2005/11

 Times Cited Count:9 Percentile:54.04(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Retention of hydrogen isotopes in divertor tiles used in JT-60U

Hirohata, Yuko*; Shibahara, Takahiro*; Tanabe, Tetsuo*; Oya, Yasuhisa*; Arai, Takashi; Goto, Yoshitaka*; Masaki, Kei; Yagyu, Junichi; Oyaizu, Makoto*; Okuno, Kenji*; et al.

Fusion Science and Technology, 48(1), p.557 - 560, 2005/07

 Times Cited Count:3 Percentile:24.81(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Development of the level difference measurement technique of a graphite tile with coarseness meter, 2

Yagisawa, Hiroshi; Arai, Takashi; Goto, Yoshitaka*

Heisei-16-Nendo Osaka Daigaku Sogo Gijutsu Kenkyukai Hokokushu (CD-ROM), 4 Pages, 2005/03

no abstracts in English

Journal Articles

Retention characteristics of hydrogen isotopes in JT-60U

Masaki, Kei; Sugiyama, Kazuyoshi*; Hayashi, Takao; Ochiai, Kentaro; Goto, Yoshitaka*; Shibahara, Takahiro*; Hirohata, Yuko*; Oya, Yasuhisa*; Miya, Naoyuki; Tanabe, Tetsuo*

Journal of Nuclear Materials, 337-339, p.553 - 559, 2005/03

 Times Cited Count:26 Percentile:84.7(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Hydrogen retention in divertor tiles used in JT-60 for hydrogen discharge period

Hirohata, Yuko*; Shibahara, Takahiro*; Tanabe, Tetsuo*; Arai, Takashi; Goto, Yoshitaka*; Oya, Yasuhisa*; Yoshida, Hajime*; Morimoto, Yasutomi*; Yagyu, Junichi; Masaki, Kei; et al.

Journal of Nuclear Materials, 337-339, p.609 - 613, 2005/03

 Times Cited Count:13 Percentile:66.44(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Measurement of deuterium and tritium retentions on the surface of JT-60 divertor tiles by means of nuclear reaction analysis

Ochiai, Kentaro; Hayashi, Takao; Kutsukake, Chuzo; Goto, Yoshitaka*; Masaki, Kei; Arai, Takashi; Miya, Naoyuki; Nishitani, Takeo

Journal of Nuclear Materials, 329-333(Part1), p.836 - 839, 2004/08

 Times Cited Count:4 Percentile:29.9(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

In-out asymmetry of low-$$Z$$ impurity deposition on the JT-60 divertor tiles

Masaki, Kei; Yagyu, Junichi; Miyo, Yasuhiko; Goto, Yoshitaka*; Arai, Takashi; Hayashi, Takao; Kodama, Kozo; Sasajima, Tadayuki; Kaminaga, Atsushi; Tanabe, Tetsuo*; et al.

Journal of Nuclear Materials, 329-333(Part1), p.845 - 848, 2004/08

 Times Cited Count:0 Percentile:0.01(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Transmission electron microscopy of redeposition layers on graphite tiles used for open divertor armor of JT-60

Goto, Yoshitaka*; Arai, Takashi; Yagyu, Junichi; Masaki, Kei; Kodama, Kozo; Miya, Naoyuki

Journal of Nuclear Materials, 329-333(1), p.840 - 844, 2004/08

 Times Cited Count:15 Percentile:69.15(Materials Science, Multidisciplinary)

TEM and Selected Area Diffraction (SAD) were made on nm-structures of redeposition layers on graphite tiles used in the lower-X-point divertor of JT-60. The tiles were used in the 1988 experimental campaign in which 300 divertor discharges and 1500 limiter discharges were made. TEM observations were made at poloidal and/or toroidal sections at two positions on the inboard side of the inner-separatrix strike point. Layer structures in 0-6micron depths were correlated to the last 40-shots in the campaign. Columnar structures corresponded to divertor discharges of additional heating power below 10MW. Lamellar structures were due to limiter discharges or to the higher power divertor discharges. Carbon-Mo, Ti or carbon-Ni, Fe, Cr, Ti codeposition layers were ascribed to disruptive shots. From analyses on poloidal orientation of the column axes and graphene sheets composing columns, the observed columnar structures were ascribed to both low adatom-migration due to the low deposition temperatures and also to self-shadowing effects due to inclined incidence of carbon impurity ions.

Journal Articles

Erosion and re-deposition in JT-60U

Goto, Yoshitaka*

Kaku Yugoro, (11), p.34 - 37, 2004/03

Recent results of erosion and re-deposition studies are reported for graphite tiles from W-shaped divertor region of JT-60U. The tiles were operated in Jun. 1997 - Oct. 1998 periods in which more than 3000 D-D discharge experiments were made with all-carbon walls with 2-times boronizations and inner-private flux pumping. Erosion depth was estimated by using dial gauge, while deposition was measured with SEM. On the outer divertor target, erosion was found dominant, while on the inner target, re-deposition was found to be dominant. No continuous deposition layers on the dome top. Observed in/out asymmetry is attributable to in/out asymmetry of plasma particle conditions in front of the divertor plates. Columnar structures in the redeposition layers corresponded to the lower heat-flux zone, while lamellar structures were found in the overlayers in the higher heat-flux zone near the separatrix strike point.

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