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Journal Articles

Sodium-cooled Fast Reactors

Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.

Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07

https://shop.elsevier.com/books/sodium-cooled-fast-reactors/morishita/978-0-12-824076-2

This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.

Journal Articles

Production of $$^{266}$$Bh in the $$^{248}$$Cm($$^{23}$$Na,5$$n$$)$$^{266}$$Bh reaction and its decay properties

Haba, Hiromitsu*; Fan, F.*; Kaji, Daiya*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Komori, Yukiko*; Kondo, Narumi*; Kudo, Hisaaki*; Morimoto, Koji*; Morita, Kosuke*; et al.

Physical Review C, 102(2), p.024625_1 - 024625_12, 2020/08

https://doi.org/10.1103/PhysRevC.102.024625
 Times Cited Count：7 Percentile：50.83(Physics, Nuclear)

Journal Articles

Production of $$^{88}$$Nb and $$^{170}$$Ta for chemical studies of element 105, Db, using the GARIS gas-jet system

Huang, M.*; Haba, Hiromitsu*; Murakami, Masashi*; Asai, Masato; Kaji, Daiya*; Kanaya, Jumpei*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Kikutani, Yuki*; Komori, Yukiko*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 304(2), p.845 - 849, 2015/05

https://doi.org/10.1007/s10967-014-3877-4
 Times Cited Count：3 Percentile：23.69(Chemistry, Analytical)

A technique to utilize radioisotopes of Nb and Ta was developed for chemical studies of element 105, Db, by coupling a gas-jet transport system to the RIKEN gas-filled recoil ion separator (GARIS). The short-lived $$^{88}$$Nb and $$^{170}$$Ta were produced with nuclear reactions using a $$^{19}$$F beam whose energy was the same as that to produce $$^{262}$$Db. Then, they were separated with GARIS and extracted to a chemistry laboratory with the gas-jet transport system. By changing only magnetic field of GARIS and inserting an energy degrader and a shutter for recoil ions, we could deliver the $$^{88}$$Nb and $$^{170}$$Ta to a chemistry device for $$^{262}$$Db without changing other experimental conditions.

Journal Articles

Production of $$^{262}$$Db in the $$^{248}$$Cm($$^{19}$$F,5$$n$$)$$^{262}$$Db reaction and decay properties of $$^{262}$$Db and $$^{258}$$Lr

Haba, Hiromitsu*; Huang, M.*; Kaji, Daiya*; Kanaya, Jumpei*; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Murakami, Masashi*; Ozeki, Kazutaka*; Sakai, Ryutaro*; et al.

Physical Review C, 89(2), p.024618_1 - 024618_11, 2014/02

https://doi.org/10.1103/PhysRevC.89.024618
 Times Cited Count：27 Percentile：81.26(Physics, Nuclear)

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

https://doi.org/10.1103/PhysRevC.88.024618
 Times Cited Count：18 Percentile：70.08(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

https://doi.org/10.1143/JPSJ.81.103201
 Times Cited Count：178 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

Production of $$^{265}$$Sg in the $$^{248}$$Cm($$^{22}$$Ne,5$$n$$)$$^{265}$$Sg reaction and decay properties of two isomeric states in $$^{265}$$Sg

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

Physical Review C, 85(2), p.024611_1 - 024611_11, 2012/02

https://doi.org/10.1103/PhysRevC.85.024611
 Times Cited Count：56 Percentile：91.08(Physics, Nuclear)

Two isomeric states in $$^{265}$$Sg, i.e, $$^{265}$$Sg$$^{a}$$ and $$^{265}$$Sg$$^{b}$$ were produced in the $$^{248}$$Cm($$^{22}$$Ne,5$$n$$) reaction. Decay properties of $$^{265}$$Sg$$^{a,b}$$ were investigated with a rotating-wheel apparatus for $$alpha$$ and spontaneous fission (SF) spectrometry under low background condition attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. Based on genetically correlated $$alpha$$-$$alpha$$ (-$$alpha$$) and $$alpha$$-SF decay chains, 18 and 24 events were assigned to $$^{265}$$Sg$$^{a}$$ and $$^{265}$$Sg$$^{b}$$, respectively. The half-life and $$alpha$$-particle energy of $$^{265}$$Sg$$^{a}$$ were measured to be $$8.5^{+2.6}_{-1.6}$$ s and $$8.84 pm 0.05$$ MeV, respectively, and those of $$^{265}$$Sg$$^{b}$$ were $$14.4^{+3.7}_{-2.5}$$ s and $$8.69 pm 0.05$$ MeV.

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

https://doi.org/10.1143/JPSJ.78.064201
 Times Cited Count：30 Percentile：77.58(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.

JAEA Reports

Development of plasma neutralizer using DC arc discharge

Kashiwagi, Mieko; Okumura, Yoshikazu; Hanada, Masaya; Morishita, Takatoshi; Watanabe, Kazuhiro; Orita, Yoshitaka*; Horiike, Hiroshi*; Ido, Shuji*

JAERI-Tech 2001-046, 19 Pages, 2001/06

JAERI-Tech-2001-046.pdf:1.79MB

no abstracts in English

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

Alpha-decay spectroscopy of Rf and Lr isotopes

Asai, Masato; Haba, Hiromitsu*; Tsukada, Kazuaki; Sato, Nozomi; Kasamatsu, Yoshitaka*; Kaji, Daiya*; Morimoto, Koji*; Morita, Kosuke*; Sato, Tetsuya; Toyoshima, Atsushi; et al.

no journal, , 

Alpha-decay spectroscopy of odd-mass Rf and Lr isotopes was performed to establish proton and neutron single-particle orbitals. $$gamma$$ rays following the $$alpha$$ decay of $$^{259}$$Rf were observed for the first time through the $$alpha$$-$$gamma$$ coincidence measurement, and the neutron configuration of the ground state of $$^{259}$$Rf was assigned. It was found that the ground-state configuration of $$^{259}$$Rf is different from those of the lighter N = 155 isotones $$^{255}$$Fm and $$^{253}$$Cf. For the Lr isotopes, the proton configurations of the ground and isomeric states in $$^{255}$$Lr and the ground states of $$^{257}$$Lr and $$^{259}$$Lr were definitely identified through the high-resolution $$alpha$$ fine structure spectroscopy. Theoretical calculations based on the macroscopic-microscopic model revealed that the change of the ground-state configuration in the N = 155 isotones is strongly associated with the rapidly decreasing hexadecapole deformation with increasing atomic number.

Oral presentation

Production of $$^{261}$$Rf for chemical studies using the gas-jet transport system coupled to GARIS

Haba, Hiromitsu*; Oe, Kazuhiro*; Ozeki, Kazutaka*; Kasamatsu, Yoshitaka*; Kaji, Daiya*; Kudo, Yuki*; Komori, Yukiko*; Sato, Nozomi; Shinohara, Atsushi*; Morita, Kosuke*; et al.

no journal, , 

A gas-jet transport system for superheavy element chemistry has been coupled to the gas-filled recoil ion separator GARIS at the RIKEN linear accelerator. In this work, we have investigated the performance of the system using $$^{261}$$Rf produced in the $$^{248}$$Cm($$^{18}$$O,5$$n$$)$$^{261}$$Rf reaction. The present result demonstrates that the GARIS/gas-jet system is a promising approach to explore new frontiers in SHE chemistry: (1) the background radioactivities originating from unwanted reaction products are strongly suppressed, (2) the intense primary heavy-ion beam is absent in the gas-jet chamber, and hence high gas-jet transport efficiency is achieved, and (3) the beam-free conditions also make it possible to investigate new chemical systems that were not accessible before.

Oral presentation

Measurement of excitation functions of rutherfordium isotopes in $$^{248}$$Cm + $$^{18}$$O reaction

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

no journal, , 

Short-lived isomer $$^{261b}$$Rf were observed only in the decay chain of $$^{277}$$Cn or $$^{269}$$Hs, so far. In this work, we performed to confirm that the $$^{261b}$$Rf would be produced in the reaction of $$^{248}$$Cm +$$^{18}$$O simultaneously with the production of $$^{261a}$$Rf (T$$_{1/2}$$ = 68s) by using a gas-filled recoil ion separator (GARIS) at the RIKEN linear accelerator.

Oral presentation

Homogeneous liquid-liquid extraction of radioactive particles based on pH-dependent phase separation phenomenon of fluorinated surfactants

Nakagawa, Taichi; Suzuki, Reika*; Matsueda, Makoto; Terashima, Motoki; Horita, Takuma; Oka, Toshitaka; Kitatsuji, Yoshihiro; Takagai, Yoshitaka*

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

Production of $$^{265}$$Sg via the $$^{248}$$Cm($$^{22}$$Ne,5$$n$$)$$^{265}$$Sg reaction

Haba, Hiromitsu*; Oe, Kazuhiro*; Ozeki, Kazutaka*; Kasamatsu, Yoshitaka*; Kaji, Daiya*; Kikunaga, Hidetoshi*; Kudo, Hisaaki*; Kudo, Yuki*; Komori, Yukiko*; Sato, Nozomi; et al.

no journal, , 

RIKEN group has investigated the performance of the system using an isotope of element 106, $$^{265}$$Sg, produced in the $$^{248}$$Cm($$^{22}$$Ne,5$$n$$) reaction. Alpha-particles of $$^{265}$$Sg separated with a GAs-filled Recoil Ion Separator (GARIS) and extracted to a chemistry laboratory were successfully identified with a rotating wheel system for $$alpha$$-spectrometry under low background conditions. As a result, two isomeric states in $$^{265}$$Sg, $$^{265a}$$Sg ($$alpha$$-particle energy $$E_{alpha} = 8.84$$ MeV, half-life $$T_{1/2} = 6.7$$ s) and $$^{265b}$$Sg ($$E_{alpha} = 8.69$$ MeV, $$T_{1/2} = 15$$ s), were identified. The cross sections for the $$^{248}$$Cm($$^{22}$$Ne,5$$n$$) reactions at 118 MeV were roughly evaluated to be 200 pb for $$^{265a}$$Sg and 170 pb for $$^{265b}$$Sg.

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

$$alpha$$-$$gamma$$ and high-resolution $$alpha$$ fine-structure spectroscopy for the heaviest nuclei

Asai, Masato; Haba, Hiromitsu*; Tsukada, Kazuaki; Sato, Nozomi; Kasamatsu, Yoshitaka*; Kaji, D.*; Morimoto, Koji*; Morita, Kosuke*; Sato, Tetsuya; Toyoshima, Atsushi; et al.

no journal, , 

Alpha-gamma and high-resolution $$alpha$$ fine-structure spectroscopy of Rf and Lr isotopes was performed to clarify the nuclear structure of superheavy nuclei. $$gamma$$ rays following the $$alpha$$ decay of $$^{259}$$Rf were observed for the first time through the $$alpha$$-$$gamma$$ coincidence measurement, and the neutron configuration of the ground state of $$^{259}$$Rf was assigned. It was found that the ground-state configuration of $$^{259}$$Rf is different from those of the lighter N = 155 isotones $$^{255}$$Fm and $$^{253}$$Cf. For the Lr isotopes, the proton configurations of the ground and isomeric states in $$^{255}$$Lr and the ground states of $$^{257}$$Lr and $$^{259}$$Lr were definitely identified through the high-resolution $$alpha$$ fine structure spectroscopy. Theoretical calculations based on the macroscopic-microscopic model revealed that the change of the ground-state configuration in the N = 155 isotones is strongly associated with the rapidly decreasing hexadecapole deformation with increasing atomic number.

Oral presentation

High-resolution $$alpha$$ fine-structure spectroscopy for studying nuclear structure of heavy nuclei

Asai, Masato; Haba, Hiromitsu*; Sato, Nozomi; Kasamatsu, Yoshitaka*; Kaji, Daiya*; Morimoto, Koji*; Morita, Kosuke*; Shima, Yosuke*; Shibata, Michihiro*; Tsukada, Kazuaki; et al.

no journal, , 

We have developed high-resolution $$alpha$$ fine-structure spectroscopy for studying nuclear structure of short-lived heavy actinide nuclei. It has been demonstrated that spin-parities and single-particle configurations of the ground state of a parent nucleus as well as excited states in a daughter nucleus can be determined only through the measured $$alpha$$ singles spectrum. To achieve a good $$alpha$$ energy resolution of $$sim$$11 keV, conditions to make a thin $$alpha$$ source have been optimized. Using this technique, we have identified proton single-particle configurations of $$^{rm 255g}$$Lr, $$^{rm 255m}$$Lr, $$^{257}$$Lr, and $$^{259}$$Lr for the first time.

21 (Records 1-20 displayed on this page)