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Journal Articles

Determination of fusion barrier distributions from quasielastic scattering cross sections towards superheavy nuclei synthesis

Tanaka, Taiki*; Narikiyo, Yoshihiro*; Morita, Kosuke*; Fujita, Kunihiro*; Kaji, Daiya*; Morimoto, Koji*; Yamaki, Sayaka*; Wakabayashi, Yasuo*; Tanaka, Kengo*; Takeyama, Mirei*; et al.

Journal of the Physical Society of Japan, 87(1), p.014201_1 - 014201_9, 2018/01

 Times Cited Count:10 Percentile:72.43(Physics, Multidisciplinary)

Excitation functions of quasielastic scattering cross sections for the $$^{48}$$Ca + $$^{208}$$Pb, $$^{50}$$Ti + $$^{208}$$Pb, and $$^{48}$$Ca + $$^{248}$$Cm reactions were successfully measured by using the gas-filled recoil-ion separator GARIS. Fusion barrier distributions were extracted from these data, and compared with the coupled-channels calculations. It was found that the peak energies of the barrier distributions for the $$^{48}$$Ca + $$^{208}$$Pb and $$^{50}$$Ti + $$^{208}$$Pb systems coincide with those of the 2n evaporation channel cross sections for the systems, while that of the $$^{48}$$Ca + $$^{248}$$Cm is located slightly below the 4n evaporation ones. This results provide us helpful information to predict the optimum beam energy to synthesize superheavy nuclei.

Journal Articles

Study of the reaction $$^{48}$$Ca + $$^{248}$$Cm $$rightarrow$$ $$^{296}$$Lv$$^{ast}$$ at RIKEN-GARIS

Kaji, Daiya*; Morita, Kosuke*; Morimoto, Koji*; Haba, Hiromitsu*; Asai, Masato; Fujita, Kunihiro*; Gan, Z.*; Geissel, H.*; Hasebe, Hiroo*; Hofmann, S.*; et al.

Journal of the Physical Society of Japan, 86(3), p.034201_1 - 034201_7, 2017/03

 Times Cited Count:16 Percentile:79.57(Physics, Multidisciplinary)

The fusion reaction of $$^{48}$$Ca + $$^{248}$$Cm $$rightarrow$$ $$^{296}$$Lv$$^{ast}$$ was studied using the gas-filled recoil-ion separator GARIS at RIKEN. A total of seven $$alpha$$ and spontaneous-fission decay chains were observed, which would originate from the reaction products of the element 116, $$^{292}$$Lv and $$^{293}$$Lv. Decay properties observed in the chains are in good agreement with the previously published ones. However, one of the chains showed a discrepancy, indicating the new spontaneous-fission branch in $$^{285}$$Cn or the production of the new isotope $$^{294}$$Lv.

Journal Articles

Performance of new gas-filled recoil ion separator GARIS-II for asymmetric fusion reaction

Kaji, Daiya*; Morimoto, Koji*; Wakabayashi, Yasuo*; Takeyama, Mirei*; Yamaki, Sayaka*; Tanaka, Kengo*; Haba, Hiromitsu*; Huang, M.*; Murakami, Masashi*; Kanaya, Jumpei*; et al.

JPS Conference Proceedings (Internet), 6, p.030107_1 - 030107_4, 2015/06

Performance of the new gas-filled recoil ion separator GARIS-II was investigated using asymmetric $$^{22}$$Ne-induced fusion reactions. The use of He-H$$_{2}$$ mixture gas for the gas-filled magnet significantly reduced background scattered particles detected at the focal-plane Si detector, and increased a transmission of the asymmetric reaction products. A target-identification system was newly installed for efficient measurements of excitation functions without changing beam energy nor target.

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:142 Percentile:97.35(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

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:27 Percentile:78.3(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

Attempt to produce the 3rd chain of $$^{278}$$113

Morimoto, Koji*; Morita, Kosuke*; Kaji, Daiya*; Akiyama, Takahiro*; Goto, Shinichi*; Haba, Hiromitsu*; Ideguchi, Eiji*; Katori, Kenji*; Koura, Hiroyuki; Kudo, Hisaaki*; et al.

RIKEN Accelerator Progress Report, Vol.42, P. 15, 2009/00

In 2003-2007, we had performed an experiment to synthesize an element 113 by a $$^{209}$$Bi$$+$$ $$^{70}$$Zn reaction using a gas-filled recoil ion separator (GARIS) at RIKEN Nishina-Center. In a total of 241 days of net irradiation time experiment, two decay chains were observed and assigned from an isotope $$^{278}$$113. The cross section of the $$^{209}$$Bi($$^{70}$$Zn,n)$$^{278}$$113 reaction was determined to be 31$$^{+40}_{-20}$$ fb at that time. In order to increase the statistics of the decay property, we continued to produce more decay chains. The experiment was carried out from January 7 to March 31, 2008. The experimental conditions were identical to those used in the previous experiment. $$^{70}$$Zn ion beam of 353 MeV was extracted from RILAC. The net irradiation time was 83 days and the total dose of $$^{70}$$Zn was 2.28$$times10^{19}$$. In the present expriment any candidate of $$^{278}$$113 was not observed. Then combining the results of the present and previous experiments, the production cross section of $$^{278}$$113 was determined to be 22$$^{+29}_{-19}$$ fb.

Journal Articles

Experiment on synthesis of an isotope $$^{277}$$112 by $$^{208}$$Pb + $$^{70}$$Zn reaction

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Akiyama, Takahiro*; Goto, Shinichi*; Haba, Hiromitsu*; Ideguchi, Eiji*; Katori, Kenji*; Koura, Hiroyuki; Kudo, Hisaaki*; et al.

Journal of the Physical Society of Japan, 76(4), p.043201_1 - 043201_5, 2007/04

 Times Cited Count:132 Percentile:95.85(Physics, Multidisciplinary)

The production and decay of $$^{277}$$112 has been investigated using a gas-filled recoil ion separator in irradiations of $$^{208}$$Pb targets with $$^{70}$$Zn beam at 349.5 MeV. We have observed two $$alpha$$-decay chains that can be assigned to subsequent decays from $$^{277}$$112 produced in the 208 Pb($$^{70}$$Zn,n) reaction. After emitting four consecutive $$alpha$$-particles, the both chains ended by spontaneous fission decays of $$^{261}$$Rf and decay energies and decay times of the both chains obtained in the present work agree well with those reported by a group at Gesellschaft f$"u$r Schwerionenforschung (GSI), Germany. The present result gives the first clear confirmation of the discovery of $$^{277}$$112 and its $$alpha$$-decay products $$^{273}$$Ds reported previously.

Journal Articles

Observation of second decay chain from $$^{278}$$113

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Akiyama, Takahiro*; Goto, Shinichi*; Haba, Hiromitsu*; Ideguchi, Eiji*; Katori, Kenji*; Koura, Hiroyuki; Kikunaga, Hidetoshi*; et al.

Journal of the Physical Society of Japan, 76(4), p.045001_1 - 045001_2, 2007/04

 Times Cited Count:182 Percentile:97.44(Physics, Multidisciplinary)

The production and decay of $$^{278}$$113 has been investigated using a gas-filled recoil ion separator in irradiations of $$^{209}$$Bi targets with $$^{70}$$Zn beam at 353 MeV. We have observed one $$alpha$$-decay chain that can be assigned to subsequent decays from $$^{278}$$113 produced in the $$^{209}$$Bi($$^{70}$$Zn,n) reaction. After emitting four consecutive $$alpha$$-particles, the both chains ended by spontaneous fission decays of $$^{262}$$Db and decay energies and decay times of the both chains obtained in the present work agree well with those reported by our group in 2004. The present result gives the first clear confirmation of the discovery of $$^{278}$$113 and its $$alpha$$-decay products $$^{274}$$Rg reported previously.

Journal Articles

Experiments on synthesis of the heaviest element at RIKEN

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Akiyama, Takahiro*; Goto, Shinichi*; Haba, Hiromitsu*; Ideguchi, Eiji*; Kanungo, R.*; Katori, Kenji*; Kikunaga, Hidetoshi*; et al.

AIP Conference Proceedings 891, p.3 - 9, 2007/03

A series of experiments studying the productions and their decays of the heaviest elements have been performed by using a gas-filled recoil separator GARIS at RIKEN. Results on the isotope of the 112th element, $$^{277}$$112, and on that of the 113th element, $$^{278}$$113, are reviewed. Two decay chains which are assigned to be ones originating from the isotope $$^{277}$$112 were observed in the $$^{208}$$Pb($$^{70}$$Zn, n) reaction. The results provide a confirmation of the production and decay of the isotope $$^{277}$$112 reported by a research group at GSI, Germany, produced via the same reaction by using a velocity filter. Two decay chains, both consisted of four consecutive alpha decays followed by a spontaneous fission, were observed also in the reaction $$^{209}$$Bi($$^{70}$$Zn, n). Those are assigned to be the convincing candidate events of the isotope of the 113th element, $$^{278}$$113, and its daughter nuclei. $$^{274}$$Rg, $$^{270}$$Mt, $$^{266}$$Bh, and $$^{262}$$Db.

Oral presentation

Production and decay properties of $$^{266}$$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, $$^{266}$$Bh, is the great-grand-daughter of $$^{278}$$113 that is produced in the $$^{209}$$Bi + $$^{70}$$Zn reaction. The identification was based on a genetic link to the known daughter nucleus $$^{262}$$Db by alpha-decays. The main purpose of this work is to provide further confirmation of the production and identification of the isotope $$^{278}$$113. As a present result, a state in $$^{266}$$Bh, which decays by an alpha emission with the energies ranging from 9.05 to 9.23 MeV, feeds a state in $$^{262}$$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, $$^{278}$$113, studied by a research group at RIKEN.

Oral presentation

Production and decay properties of $$^{266}$$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, , 

no abstracts in English

Oral presentation

Observation of new neutron-deficient actinide isotopes of $$^{234}$$Bk and $$^{230}$$Am

Kaji, Daiya*; Haba, Hiromitsu*; Kasamatsu, Yoshitaka*; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Ozeki, Kazutaka*; Sumita, Takayuki*; Yoneda, Akira*; Koura, Hiroyuki; et al.

no journal, , 

no abstracts in English

Oral presentation

GARIS-II commissioning, 1

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

no journal, , 

RIKEN group has been developing a new gas-filled recoil ion separator GARIS-II for research of superheavy element produced by actinide-based asymmetric fusion (hot fusion) reactions. The GARIS-II consists of five magnets with a Q-D-Q-Q-D configuration. Where, D and Q are dipole and quadrupole magnets, respectively. The test of GARIS-II was performed with the $$^{241}$$Am standard $$alpha$$-source and 0$$^{circ}$$ scattered ions from the $$^{208}$$Pb target. A solid angle of GARIS-II was measured to be about 18.4 msr, which was almost as same as a calculated value with the TRANSPORT cord. The image size at focal plane versus He-gas pressure in GARIS-II chamber was also measured with $$^{208}$$Pb ions.

Oral presentation

Confirmations of the synthesis of $$^{278}$$113 produced by the $$^{209}$$Bi($$^{70}$$Zn,n)$$^{278}$$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 $$^{209}$$Bi($$^{70}$$Zn,n)$$^{278}$$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 $$^{278}$$113. Both chains were connected into the previously known decays of $$^{266}$$Bh and $$^{262}$$Db via previously unknown decays of $$^{278}$$113, $$^{274}$$Rg, and $$^{270}$$Mt. Although the $$^{266}$$Bh was known nuclide, a number of atoms reported so far was limited. In order to study more precise decay property of the $$^{266}$$Bh, we performed the direct production of $$^{266}$$Bh by the $$^{248}$$Cm($$^{23}$$Na,5n)$$^{266}$$Bh reaction. In this experiment, the $$^{266}$$Bh was clearly identified from the correlation of the 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.

Oral presentation

Production and decay properties of $$^{277}$$Cn produced in the reaction of $$^{208}$$Pb+$$^{70}$$Zn

Sumita, Takayuki*; Morimoto, Koji*; Kaji, Daiya*; Ozeki, Kazutaka*; Katori, Kenji*; Sakai, Ryutaro*; Hasebe, Hiroo*; Haba, Hiromitsu*; Yoneda, Akira*; Yoshida, Atsushi*; et al.

no journal, , 

The decay property of $$^{277}$$Cn (atomic number, $$Z=112$$) produced in the $$^{208}$$Pb($$^{70}$$Zn, $$n$$) reaction was studied. The experiment was performed using the gas-filled recoil ion separator (GARIS) at the RIKEN liner accelerator facility (RILAC). The $$^{208}$$Pb target with about 630 $$mu$$g/cm$$^{2}$$ thickness was bombarded with 347.5, 351.5, and 355.5 MeV $$^{70}$$Zn beam. At the beam energy of 351.5 MeV, we observed one $$alpha$$-decay chain from $$^{277}$$Cn. The $$alpha$$-particle energy of $$^{277}$$Cn was $$11.07 pm 0.08$$ MeV and its lifetime was measured to be 0.370 ms. Including our previous result of the $$^{277}$$Cn production in 2004, the cross section of the $$^{208}$$Pb($$^{70}$$Zn, $$n$$) reaction is deduced to be $$0.17^{+0.16}_{-0.10}$$ pb.

Oral presentation

Monte-Carlo simulations for evaluation of the influence on the range and dose distribution of carbon ion beam by MRI magnetic field

Kakuta, Shion*; Iwai, Takeo*; Tokanai, Fuyuki*; Sato, Tatsuhiko

no journal, , 

Influence on the range and dose distribution of carbon ion beam by MRI magnetic field was investigated using the PHITS code. The PHITS simulation results agree with the corresponding data obtained from an analytical method based on the Bethe-Bloch equation, indicating the accuracy of the simulation.

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