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Journal Articles

First direct mass measurements of nuclides around $$Z$$ = 100 with a multireflection time-of-flight mass spectrograph

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

 Times Cited Count:11 Percentile:3.78(Physics, Multidisciplinary)

Masses of $$^{246}$$Es, $$^{251}$$Fm and the transfermium nuclei $$^{249-252}$$Md, and $$^{254}$$No, produced by hot- and cold-fusion reactions, in the vicinity of the deformed $$N=152$$ neutron shell closure, have been directly measured using a multi-reflection time-of-flight mass spectrograph. The masses of $$^{246}$$Es and $$^{249,250,252}$$Md were measured for the first time. Using the masses of $$^{249,250}$$Md as anchor points for $$alpha$$ decay chains, the masses of heavier nuclei, up to $$^{261}$$Bh and $$^{266}$$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 $$delta_{2n}$$ derived from three isotopic masses was updated with the new masses and corroborate the existence of the deformed $$N=152$$ neutron shell closure for Md and Lr.

Journal Articles

Observation of doubly-charged ions of francium isotopes extracted from a gas cell

Schury, P.*; Wada, Michiharu*; Ito, Yuta*; Kaji, Daiya*; Haba, Hiromitsu*; Hirayama, Yoshikazu*; Kimura, Sota*; Koura, Hiroyuki; MacCormick, M.*; Miyatake, Hiroari*; et al.

Nuclear Instruments and Methods in Physics Research B, 407, p.160 - 165, 2017/06

 Times Cited Count:3 Percentile:27.27(Instruments & Instrumentation)

Various isotopes of Ac, Ra, Fr, and Rn were produced by fusion-evaporation reactions using a $$^{48}$$Ca beam. The energetic ions were stopped in and extracted from a helium gas cell. The extracted ions were identified using a multi-reflection time-of-fight mass spectrograph. In all cases, it was observed that the predominant charge state for the extracted ions, including the alkali Fr, was 2+.

Journal Articles

New measurement of the $$^{8}$$Li($$alpha$$,n)$$^{11}$$B reaction in a lower-energy region below the Coulomb barrier

Das, S. K.*; Fukuda, Tomokazu*; Mizoi, Yutaka*; Ishiyama, Hironobu*; Miyatake, Hiroari*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Jeong, S. C.*; Ikezoe, Hiroshi*; Matsuda, Makoto; et al.

Physical Review C, 95(5), p.055805_1 - 055805_4, 2017/05

 Percentile:100(Physics, Nuclear)

Journal Articles

First online multireflection time-of-flight mass measurements of isobar chains produced by fusion-evaporation reactions; Toward identification of superheavy elements via mass spectroscopy

Schury, P.*; Wada, Michiharu*; Ito, Yuta*; Kaji, Daiya*; Arai, Fumiya*; MacCormick, M.*; Murray, I.*; Haba, Hiromitsu*; Jeong, S.*; Kimura, Sota*; et al.

Physical Review C, 95(1), p.011305_1 - 011305_6, 2017/01

AA2016-0638.pdf:0.71MB

 Times Cited Count:10 Percentile:8.11(Physics, Nuclear)

Using a multireflection time-of-flight mass spectrograph located after a gas cell coupled with the gas-filled recoil ion separator GARIS-II, the masses of several $$alpha$$-decaying heavy nuclei were directly and precisely measured. The nuclei were produced via fusion-evaporation reactions and separated from projectilelike and targetlike particles using GARIS-II before being stopped in a helium-filled gas cell. Time-of-flight spectra for three isobar chains, $$^{204}$$Fr-$$^{204}$$Rn-$$^{204}$$At-$$^{204}$$Po, $$^{205}$$Fr- $$^{205}$$Rn-$$^{205}$$At-$$^{205}$$Po-$$^{205}$$Bi, and $$^{206}$$Fr-$$^{206}$$Rn-$$^{206}$$At, were observed. Precision atomic mass values were determined for $$^{204-206}$$Fr, $$^{204,205}$$Rn, and $$^{204,205}$$At. Identifications of $$^{205}$$Bi, $$^{204,205}$$Po, $$^{206}$$Rn, and $$^{206}$$At were made with N$$leq$$10 detected ions, representing the next step toward use of mass spectrometry to identify exceedingly low-yield species such as superheavy element ions.

Journal Articles

Direct measurement of nanoscale lithium diffusion in solid battery materials using radioactive tracer of $$^{8}$$Li

Ishiyama, Hironobu*; Jeong, S.-C.*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Jung, H. S.*; Miyatake, Hiroari*; Oyaizu, Mitsuhiro*; Osa, Akihiko; Otokawa, Yoshinori; et al.

Nuclear Instruments and Methods in Physics Research B, 376, p.379 - 381, 2016/06

 Times Cited Count:2 Percentile:57.25(Instruments & Instrumentation)

Journal Articles

Nanoscale diffusion tracing by radioactive $$^{8}$$Li tracer

Ishiyama, Hironobu*; Jeong, S.-C.*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari*; Oyaizu, Mitsuhiro*; Katayama, Ichiro*; Osa, Akihiko; Otokawa, Yoshinori; et al.

Japanese Journal of Applied Physics, 53(11), p.110303_1 - 110303_4, 2014/11

 Times Cited Count:3 Percentile:78.29(Physics, Applied)

Journal Articles

A Multi-reflection time-of-flight mass spectrograph for short-lived and super-heavy nuclei

Schury, P. H.*; Wada, Michiharu*; Ito, Yuta*; Naimi, S.*; Sonoda, Tetsu*; Mita, Koki*; Takamine, Aiko*; Okada, Kunihiro*; Wollnik, H.*; Chon, S.*; et al.

Nuclear Instruments and Methods in Physics Research B, 317(Part B), p.537 - 543, 2013/12

 Times Cited Count:13 Percentile:15.14(Instruments & Instrumentation)

A multi-reflection time-of-flight (MRTOF) mass spectrograph has been implemented at RIKEN to provide high-precision mass measurements of very short-lived nuclei. Of particular interest are mass measurements of r-process nuclei and trans-uranium nuclei. In such nuclei, the MRTOF can perform on par with or better than traditional Penning trap systems. We demonstrate that the MRTOF-MS is capable of accurately attaining relative mass precision of $$delta$$m/m $$<$$ 10$$^{-7}$$ and describe it's utility with heavy, short-lived nuclei.

Journal Articles

Development of a resonant laser ionization gas cell for high-energy, short-lived nuclei

Sonoda, Tetsu*; Wada, Michiharu*; Tomita, Hideo*; Sakamoto, Chika*; Takatsuka, Takaaki*; Furukawa, Takeshi*; Iimura, Hideki; Ito, Yuta*; Kubo, Toshiyuki*; Matsuo, Yukari*; et al.

Nuclear Instruments and Methods in Physics Research B, 295, p.1 - 10, 2013/01

 Times Cited Count:17 Percentile:9.29(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Tilted-foil technique for producing a spin-polarized radioactive isotope beam

Hirayama, Yoshikazu*; Mihara, Mototsugu*; Watanabe, Yutaka*; Jeong, S. C.*; Miyatake, Hiroari*; Momota, Sadao*; Hashimoto, Takashi*; Imai, Nobuaki*; Matsuta, Kensaku*; Ishiyama, Hironobu*; et al.

European Physical Journal A, 48(5), p.54_1 - 54_10, 2012/05

 Times Cited Count:2 Percentile:77.83(Physics, Nuclear)

Journal Articles

GEM-MSTPC; An Active-target type detector in low-pressure He/CO$$_{2}$$ mixed gas

Ishiyama, Hironobu*; Yamaguchi, Kanako*; Mizoi, Yutaka*; Watanabe, Yutaka*; Das, S. K.*; Hashimoto, Takashi*; Miyatake, Hiroari*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Oyaizu, Mitsuhiro*; et al.

Journal of Instrumentation (Internet), 7(3), p.C03036_1 - C03036_14, 2012/03

 Times Cited Count:6 Percentile:57.36(Instruments & Instrumentation)

We developed an active-target type gas counter operating with low He/CO$$_{2}$$ (10%) detector gas for application in studying low-energy nuclear reactions using radioactive beams. A 400-$$mu$$m-thick gas electron multiplier (THGEM) was used as the proportional counter for high injection rate capability. We examined the gas gain stability and the influence of ion feedback on particle tracks at high beam injection rates of up to 10$$^{5}$$ particles per second (pps) using a low-energy $$^{12}$$C beam. From the result of this examination, we found that the THGEM was found to be applicable for our active target at high injection rates of up to 10$$^{5}$$ pps.

Journal Articles

Low-background prebunching system for heavy-ion beams at the Tokai radioactive ion accelerator complex

Okada, Masashi*; Niki, Kazuaki*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Ishiyama, Hironobu*; Jeong, S. C.*; Katayama, Ichiro*; Miyatake, Hiroari*; Oyaizu, Mitsuhiro*; Watanabe, Yutaka*; et al.

Physical Review Special Topics; Accelerators and Beams, 15(3), p.030101_1 - 030101_10, 2012/03

 Times Cited Count:1 Percentile:87.28(Physics, Nuclear)

Journal Articles

Adhesion improvement of HIVIPP $$^{12}$$C targets on Au backings

Sugai, Isao*; Takeda, Yasuhiro*; Kawakami, Hirokane*; Ota, Naoto*; Makii, Hiroyuki; Miyatake, Hiroari*

Nuclear Instruments and Methods in Physics Research A, 655(1), p.24 - 33, 2011/11

 Times Cited Count:2 Percentile:75.84(Instruments & Instrumentation)

Journal Articles

Proton resonance elastic scattering in inverse kinematics on the medium heavy nucleus $$^{68}$$Zn

Imai, Nobuaki*; Hirayama, Yoshikazu*; Ishiyama, Hironobu*; Jeong, S.-C.*; Miyatake, Hiroari*; Watanabe, Yutaka*; Makii, Hiroyuki; Mitsuoka, Shinichi; Nagae, Daisuke*; Nishinaka, Ichiro; et al.

European Physical Journal A, 46(2), p.157 - 160, 2010/11

 Times Cited Count:2 Percentile:74.1(Physics, Nuclear)

Journal Articles

Barrier distribution of quasi-elastic backward scattering in very heavy reaction systems

Mitsuoka, Shinichi; Ikezoe, Hiroshi; Nishio, Katsuhisa; Watanabe, Yutaka*; Jeong, S. C.*; Ishiyama, Hironobu*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari

International Journal of Modern Physics E, 19(5&6), p.989 - 996, 2010/07

 Percentile:100(Physics, Nuclear)

We have measured quasi-elastic scattering cross sections in reactions of $$^{48}$$Ti, $$^{54}$$Cr, $$^{56}$$Fe, $$^{64}$$Ni and $$^{70}$$Zn + $$^{208}$$Pb, relating to Pb-based cold fusion reactions for super-heavy elements 104, 106, 108, 110 and 112, respectively. A thin target of $$^{208}$$Pb was bombarded by heavy-ion beams supplied from the JAEA tandem-booster accelerator with changing the beam energy in steps of 1.5 MeV. The barrier distributions were derived from the first derivative of the excitation functions measured at backward angles of 172$$^{circ}$$, 168$$^{circ}$$ and 162$$^{circ}$$. The centroid of the barrier distributions showed a deviation from several predicted barrier heights toward the low energy side. The shape of the barrier distributions was well reproduced by the results of a coupled-channel calculation taking account of the coupling effects of the collective vibrational excitations in the projectile and target nuclei. We have recently obtained similar results in heavier reactions of $$^{76}$$Ge and $$^{86}$$Kr + $$^{208}$$Pb.

Journal Articles

Superdeformation in asymmetric $$N$$$$>$$$$Z$$ nucleus $$^{40}$$Ar

Ideguchi, Eiji*; Ota, Shinsuke*; Morikawa, Tsuneyasu*; Oshima, Masumi; Koizumi, Mitsuo; Toh, Yosuke; Kimura, Atsushi; Harada, Hideo; Furutaka, Kazuyoshi; Nakamura, Shoji; et al.

Physics Letters B, 686(1), p.18 - 22, 2010/03

 Times Cited Count:26 Percentile:13.74(Astronomy & Astrophysics)

A rotational band with five $$gamma$$-ray transitions ranging from 2$$^+$$ to 12$$^+$$ states was identified in $$^{40}$$Ar. The deduced transition quadrupole moment of 1.45 $$pm$$0.15 eb indicates that the band has a superdeformed shape. The nature of the band is revealed by cranked Hartee Fock Bogoliubov calculations and a multiparticle-multihole configuration is assigned to the band.

Journal Articles

A New measurement of the astrophysical $$^8$$Li(d,t)$$^7$$Li reaction

Hashimoto, Takashi; Ishiyama, Hironobu*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari; Jeong, S.-C.*; Tanaka, Masahiko*; Yoshikawa, Nobuharu*; Nomura, Toru*; et al.

Physics Letters B, 674(4-5), p.276 - 280, 2009/04

 Times Cited Count:5 Percentile:56.05(Astronomy & Astrophysics)

The excitation function of the $$^8$$Li(d,t)$$^7$$Li reaction was directly measured using $$^8$$Li beams at E$$_{mathrm{cm}}$$ = 0.3, 0.4, 0.5, 0.7, 0.8, 1.0, 1.1, and 1.2 MeV with CD$$_2$$ targets. The beam energies covered the Gamow peaks for 1$$sim$$3$$times$$10$$^9$$ K. Large cross sections were observed at around E$$_{mathrm{cm}}$$ = 0.8 MeV, implying a resonance state located at 22.4 MeV in $$^{10}$$Be. The present astrophysical reaction rate is higher in one order magnitude than the presently adopted rate at around 1$$times$$10$$^9$$ K.

Journal Articles

On-line diffusion tracing in Li ionic conductors by the short-lived radioactive beam of $$^{8}$$Li

Jeong, S.-C.*; Katayama, Ichiro*; Kawakami, Hirokane*; Watanabe, Yutaka*; Ishiyama, Hironobu*; Imai, Nobuaki*; Hirayama, Yoshikazu*; Miyatake, Hiroari; Sataka, Masao; Sugai, Hiroyuki; et al.

Japanese Journal of Applied Physics, 47(8), p.6413 - 6415, 2008/08

 Times Cited Count:5 Percentile:72.85(Physics, Applied)

A non-destructive and on-line diffusion tracing in Li ionic conductors has been demonstrated. As a tracer, pulsed beam of $$^{8}$$Li was implanted into LiGa. By analyzing the time dependent yield of the $$alpha$$-particles decaying from $$^{8}$$Li, diffusion coefficients were extracted with a high accuracy. The ordering of Li vacancies in the Li-deficient $$beta$$ phase of LiGa was observed for the first time in terms of the Li diffusion.

Journal Articles

KEKCB electron cyclotron resonance charge breeder at TRIAC

Imai, Nobuaki*; Jeong, S.-C.*; Oyaizu, Mitsuhiro*; Arai, Shigeaki*; Fuchi, Yoshihide*; Hirayama, Yoshikazu*; Ishiyama, Hironobu*; Miyatake, Hiroari; Tanaka, Masahiko*; Okada, Masayuki*; et al.

Review of Scientific Instruments, 79(2), p.02A906_1 - 02A906_3, 2008/02

 Times Cited Count:12 Percentile:41.29(Instruments & Instrumentation)

KEKCB is an 18 GHz Electron Cyclotron Resonance (ECR) ion source and is a charge breeder device for converting mass-separated 1$$^+$$ radioactive ions to multi-ionized ones by utilizing an axial injection technique to the ECR plasma. It is a part of the Tokai Radioactive Ion Accelerator Complex (TRIAC) facility. Based on the developments so far, converting efficiencies for metal elements, such as barium and indium, and for gaseous elements, such as krypton and xenon, are improved to be 7 $$%$$ and 2 $$%$$, respectively. And it is confirmed that the efficiency is nearly the constant for short-lived (t$$_{1/2}$$ $$ge$$ 1 sec) isotopes. Background ions mixed in the output beams are supressed to be 600 pps from 10$$^8$$ pps by applying all aluminum electrodes and high pressure pure-water cleanings.

Journal Articles

Diffusion of $$^{8}$$Li short-lived radiotracer in Li ionic conductors of NaTl-type intermetallic compounds

Sugai, Hiroyuki; Sataka, Masao; Okayasu, Satoru; Ichikawa, Shinichi; Nishio, Katsuhisa; Mitsuoka, Shinichi; Nakanoya, Takamitsu; Osa, Akihiko; Sato, Tetsuya; Hashimoto, Takashi; et al.

Defect and Diffusion Forum, 273-276, p.667 - 672, 2008/00

Journal Articles

A New measurement of the astrophysical $$^8$$Li($$alpha$$, n)$$^{11}$$B reaction

Ishiyama, Hironobu*; Hashimoto, Takashi; Ishikawa, Tomoko*; Watanabe, Yutaka*; Das, S. K.*; Miyatake, Hiroari; Mizoi, Yutaka*; Fukuda, Tomokazu*; Tanaka, Masahiko*; Fuchi, Yoshihide*; et al.

Physics Letters B, 640(3), p.82 - 85, 2006/09

 Times Cited Count:30 Percentile:13.18(Astronomy & Astrophysics)

The excitation function of the $$^{8}$$Li($$alpha$$,n)$$^{11}$$B reaction was measured while identifying the final state event by event in the region of E$$_{rm{cm}}$$ = 0.7 - 2.6 MeV using a highly efficient detector system and a low-energy $$^8$$Li beam. The results are much improved both in statistics and precisions, and show smaller cross sections than those of previous measurements by a factor of more than 2 in the low-energy region of E$$_{rm{cm}}le$$ 1.5 MeV. A resonance-like structure is found at around E$$_{rm{cm}}$$ = 0.85 MeV.

62 (Records 1-20 displayed on this page)