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Ma, B.*; Teshigawara, Makoto; Wakabayashi, Yasuo*; Yan, M.*; Hashiguchi, Takao*; Yamagata, Yutaka*; Wang, S.*; Ikeda, Yujiro*; Otake, Yoshie*
Nuclear Instruments and Methods in Physics Research A, 995, p.165079_1 - 165079_7, 2021/04
Times Cited Count：1 Percentile：0.02(Instruments & Instrumentation)We have optimized a cold neutron moderator to be operated at the RIKEN accelerator-driven compact neutron source. We selected a safe and easy to manage material, mesitylene, as the RANS cold moderator. An efficient moderator system was designed by studying and optimizing a coupled cold neutron moderator of mesitylene at 20 K with a polyethylene (PE) pre-moderator at room temperature in the slab geometry with Particle and Heavy Ion Transport code System (PHITS) simulations. The parameters of mesitylene and PE thickness, the reflector, and the shielding configuration were studied to increase cold neutron intensities. Consequently, an integrated cold neutron intensity of 1.15
10
n/cm
/
A at 2 m from the neutron-producing target was finally achieved, which was 12 times higher than that of the current PE moderator. The results showed attractive application prospect of mesitylene as cold neutron moderator material.
Bh in the 
Cm(
Na,5
)Bh reaction and its decay propertiesHaba, 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
Times Cited Count：5 Percentile：56.79(Physics, Nuclear)
-decay properties of 
FrGhys, L.*; Andreyev, A. N.; Huyse, M.*; Van Duppen, P.*; Antalic, S.*; Barzakh, A.*; Capponi, L.*; Cocolios, T. E.*; Cubiss, J.*; Derkx, X.*; et al.
Physical Review C, 100(5), p.054310_1 - 054310_13, 2019/11
Times Cited Count：11 Percentile：81.7(Physics, Nuclear)
At revealed by in-source laser spectroscopyBarzakh, A. E.*; Cubiss, J. G.*; Andreyev, A. N.; Seliverstov, M. D.*; Andel, B.*; Antalic, S.*; Ascher, P.*; Atanasov, D.*; Beck, D.*; Biero
, J.*; et al.
Physical Review C, 99(5), p.054317_1 - 054317_9, 2019/05
Times Cited Count：9 Percentile：71.92(Physics, Nuclear)
AtCubiss, J.*; Andreyev, A. N.; Mitsuoka, Shinichi*; Nagame, Yuichiro; Nishio, Katsuhisa; Ota, Shuya*; Wakabayashi, Yasuo*; 60 of others*
Physical Review C, 97(5), p.054327_1 - 054327_19, 2018/05
Times Cited Count：27 Percentile：92.73(Physics, Nuclear)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：14 Percentile：71.07(Physics, Multidisciplinary)Excitation functions of quasielastic scattering cross sections for the 
Ca + 
Pb, 
Ti + Pb, and Ca + 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 Ca + Pb and Ti + Pb systems coincide with those of the 2n evaporation channel cross sections for the systems, while that of the Ca + 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.
-delayed fission of 
AmWilson, G. L.*; Takeyama, Mirei*; Andreyev, A. N.; Andel, B.*; Antalic, S.*; Catford, W. N.*; Ghys, L.*; Haba, Hiromitsu*; He
berger, F. P.*; Huang, M.*; et al.
Physical Review C, 96(4), p.044315_1 - 044315_7, 2017/10
Times Cited Count：5 Percentile：45.72(Physics, Nuclear)Ca + Cm 
Lv
at RIKEN-GARISKaji, 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：20 Percentile：79.07(Physics, Multidisciplinary)The fusion reaction of Ca + Cm Lv was studied using the gas-filled recoil-ion separator GARIS at RIKEN. A total of seven and spontaneous-fission decay chains were observed, which would originate from the reaction products of the element 116, 
Lv and 
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 
Cn or the production of the new isotope 
Lv.
Eichler, R.*; Asai, Masato; Brand, H.*; Chiera, N. M.*; Di Nitto, A.*; Dressler, R.*; D
llmann, Ch. E.*; Even, J.*; Fangli, F.*; Goetz, M.*; et al.
EPJ Web of Conferences, 131, p.07005_1 - 07005_7, 2016/12
Times Cited Count：2 Percentile：63.91In recent years gas-phase chemical studies assisted by physical pre-separation allowed for the productions and investigations of fragile single molecular species of superheavy elements. The latest highlight is the formation of very volatile hexacarbonyl compound of element 106, Sg(CO)
. Following this success, second-generation experiments were performed to measure the first bond dissociation energy between the central metal atom and the surrounding ligand. The method using a tubular decomposition reactor was developed and successfully applied to short-lived Mo(CO), W(CO), and Sg(CO).
-delayed fission and decay of 
AtTruesdale, V. L.*; Andreyev, A. N.; Ghys, L.*; Huyse, M.*; Van Duppen, P.*; Sels, S.*; Andel, B.*; Antalic, S.*; Barzakh, A.*; Capponi, L.*; et al.
Physical Review C, 94(3), p.034308_1 - 034308_11, 2016/09
Times Cited Count：9 Percentile：60.65(Physics, Nuclear)
and W(CO)Usoltsev, I.*; Eichler, R.*; Wang, Y.*; Even, J.*; Yakushev, A.*; Haba, Hiromitsu*; Asai, Masato; Brand, H.*; Di Nitto, A.*; Dllmann, Ch. E.*; et al.
Radiochimica Acta, 104(3), p.141 - 151, 2016/03
Times Cited Count：29 Percentile：95.75(Chemistry, Inorganic & Nuclear)Conditions of the production and decomposition of hexacarbonyl complexes of short-lived Mo and W isotopes were investigated to study thermal stability of the heaviest group 6 hexacarbonyl complex Sg(CO). A tubular flow reactor was tested to decompose the hexacarbonyl complexes and to extract the first bond dissociation energies. A silver was found to be the most appropriate reaction surface to study the decomposition of the group 6 hexacarbonyl. It was found that the surface temperature at which the decomposition occurred was correlated to the first bond dissociation energy of Mo(CO) and W(CO), indicating that the first bond dissociation energy of Sg(CO) could be determined with this technique.
) cross-sections using multi-nucleon transfer reactionsMakii, Hiroyuki; Ota, Shuya*; Ishii, Tetsuro; Wakabayashi, Yasuo*; Furutaka, Kazuyoshi; Nishio, Katsuhisa; Nishinaka, Ichiro; Chiba, Satoshi; Igashira, Masayuki*; Czeszumska, A.*
Nuclear Instruments and Methods in Physics Research A, 797, p.83 - 93, 2015/10
Times Cited Count：4 Percentile：36.12(Instruments & Instrumentation)We have installed new experimental apparatus to measure 
rays from highly excited states populated by the multi-nucleon transfer reactions with heavy-ion projectiles to determine the (
) cross sections by means of the surrogate reaction method. Apparatus consists of two anti-Compton LaBr
(Ce) spectrometers to measure the rays and a Si 
-
detector system to detect outgoing projectile-like particles. Reactions of 153-MeV 
O beams with 
Gd and 
Gd targets were used to study the performance of apparatus. By using the LaBr(Ce) scintillators with relatively large volume (101.6 mm in diameter and 127 mm in length), we have successfully measured rays from the compound nuclei, which have excitation energy above neutron separation energy, populated by Gd(O, 
O)Gd and Gd(O, O)
Gd two-neutron transfer reactions. The present study has demonstrated high capability of apparatus to measure the de-excitation rays in the compound nuclei produced by the multi-nucleon transfer reactions for determination of the () cross sections by using the surrogate reaction method.
Hg formed in fusion reactions of 
Ar + 
SmNishio, Katsuhisa; Andreyev, A. N.*; Chapman, R.*; Derkx, X.*; Dllmann, C. E.*; Ghys, L.*; Heberger, F. P.*; Hirose, Kentaro; Ikezoe, Hiroshi*; Khuyagbaatar, J.*; et al.
Physics Letters B, 748, p.89 - 94, 2015/09
Times Cited Count：34 Percentile：90.89(Astronomy & Astrophysics)- spectroscopy using Si-Ge detector array installed at focal plane of GARISKaji, Daiya*; Morimoto, Koji*; Wakabayashi, Yasuo*; Takeyama, Mirei*; Asai, Masato
JPS Conference Proceedings (Internet), 6, p.030106_1 - 030106_4, 2015/06
A Si-Ge detector array was newly installed at the focal plane of the gas-filled recoil ion separator GARIS to perform - (X-rays) spectroscopy for superheavy nuclei. The performance of the array was tested using the 
Pb(Ca,2n)
No and Pb(Ca,xn)
No [x=1,2,3] reactions. rays originating from the decay of No and 
No were clearly observed in prompt coincidence with the particles.
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 
Ne-induced fusion reactions. The use of He-H
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.
Nb and 
Ta for chemical studies of element 105, Db, using the GARIS gas-jet systemHuang, 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
Times Cited Count：3 Percentile：28.28(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 Nb and Ta were produced with nuclear reactions using a 
F beam whose energy was the same as that to produce 
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 Nb and Ta to a chemistry device for Db without changing other experimental conditions.
Even, J.*; Ackermann, D.*; Asai, Masato; Block, M.*; Brand, H.*; Di Nitto, A.*; Dllmann, Ch. E.*; Eichler, R.*; Fan, F.*; Haba, Hiromitsu*; et al.
Journal of Radioanalytical and Nuclear Chemistry, 303(3), p.2457 - 2466, 2015/03
Times Cited Count：14 Percentile：78.53(Chemistry, Analytical)Rapid In situ synthesis of metal carbonyl complexes has been demonstrated using short-lived isotopes produced in nuclear fission and fusion reactions. The short-lived isotopes with high recoil energy directly react with carbon-monoxides and form carbonyl complexes. Only highly volatile complexes were fast transported in a gas stream to counting and chemistry devices. Short-lived Mo, Tc, Ru, Rh, W, Re, Os, and Ir were found to form volatile carbonyl complexes, while no volataile complex of Hf and Ta were detected. This technique has been applied to a chemical investigation of the superheavy element Sg (atomic number 106), and will be applicable to various fields of nuclear science with short-lived transition metal isotopes.
Even, J.*; Yakushev, A.*; Dllmann, Ch. E.*; Haba, Hiromitsu*; Asai, Masato; Sato, Tetsuya; Brand, H.*; Di Nitto, A.*; Eichler, R.*; Fan, F. L.*; et al.
Science, 345(6203), p.1491 - 1493, 2014/09
Times Cited Count：59 Percentile：83.25(Multidisciplinary Sciences)A new superheavy element complex, a seaborgium carbonyl, has been successfully synthesized, and its adsorption property has been studied using a cryo-thermochromatography and -detection apparatus COMPACT. Nuclear reaction products of short-lived 
Sg preseparated with a gas-filled recoil ion separator GARIS at RIKEN were directly injected into a gas cell filled with He/CO mixture gas, and chemical reaction products of volatile carbonyl complexes were trasported to COMPACT. The Sg carbonyl complex detected with COMPACT was found to be very volatile with adsorption enthalpy of 
50 kJ/mol, from which we have concluded that this complex should be a Sg hexacarbonyl Sg(CO). This is the first synthesis of organometallic compounds of transactinide elements for which only simple inorganic comounds have been synthesized so far.
(Ce) spectrometer for measurement of surrogate reactionsMakii, Hiroyuki; Ota, Shuya*; Ishii, Tetsuro; Nishio, Katsuhisa; Nishinaka, Ichiro; Furutaka, Kazuyoshi; Wakabayashi, Yasuo*; Chiba, Satoshi*; Igashira, Masayuki*
Nuclear Data Sheets, 119, p.361 - 364, 2014/05
Times Cited Count：0 Percentile：0.02(Physics, Nuclear)Anti-Compton LaBr(Ce) spectrometers have been installed at JAEA-Tokai tandem accelerator facility in order to measure the rays from the highly excited states produced by surrogate reactions. Each spectrometer consists of a central LaBr(Ce) detector with a diameter of 10.2 cm and a length of 12.7 cm, and an annular BGO detector with a thickness of 2.5 cm and a length of 25.4 cm. In this contribution, we will present the results of performance test using the standard ray source and high-energy rays from the 
Al(p,)
Si reaction, and a measurement plan for (n,) cross sections using a surrogate reaction at JAEA-Tokai tandem accelerator facility.
Kawata, Norio; Wakabayashi, Shuji; Hanai, Tasuku; Yamaguchi, Yasuo; Nonaka, Nobuyuki; Scharmer, C.*
Proceedings of International Conference on Nuclear Security; Enhancing Global Efforts (CD-ROM), 10 Pages, 2014/03
The ISCN of the JAEA provides effective trainings in order to strengthen nuclear security for emerging nuclear power countries in Asia to realize Japan's National Statement at the Washington Nuclear Security Summit in April 2010. As a part of these activities, the ISCN has developed the PPEF and the VR training system, which are training tools to implement experience-oriented and interactive lessons. These two facilities are mutually complemented and contribute to deeper understandings through actual practices in addition to the classroom lesson. The ISCN initiated its full-scale training from 2012 JFY, and these two facilities received more than 450 trainees or vistors from Japan and over-sea countries. This paper provides the basic concepts and outlines of these two facilities and the training programs that use them for teaching the nuclear security.
