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Journal Articles

Simultaneous determination of zircon crystallisation age and temperature; Common thermal evolution of mafic magmatic enclaves and host granites in the Kurobegawa granite, central Japan

Yuguchi, Takashi*; Yamazaki, Hayato*; Ishibashi, Kozue*; Sakata, Shuhei*; Yokoyama, Tatsunori; Suzuki, Satoshi*; Ogita, Yasuhiro; Sando, Kazusa*; Imura, Takumi*; Ono, Takeshi*

Journal of Asian Earth Sciences, 226, p.105075_1 - 105075_9, 2022/04

Simultaneous determination of the U-Pb age of zircon and concentration of titanium in a single analysis spot, using inductively coupled plasma mass spectrometry with laser ablation sample introduction, produces paired age and temperature data of zircon crystallisation, potentially revealing time-temperature ($$t-T$$) histories for evolved magma. The Kurobegawa granite, central Japan, contains abundant mafic magmatic enclaves (MMEs). We applied this method to evaluate MMEs and their host (enclosing) granites. Cooling behaviour common to both MMEs and host rocks was found between 1.5 and 0.5 Ma. Rapid cooling from the zircon crystallisation temperature to the closure temperature of biotite K-Ar system was within $$sim$$1 million year. Combining the obtained $$t-T$$ paths of MMEs and host rocks with petrological information can provide insights into magma chamber processes. This suggests that MME flotation, migration, and spread through the magma chamber ceased at 1.5-0.5 Ma, indicating the emplacement age of the Kurobegawa granitic pluton, as no large-scale reheating episodes have occurred since then.

Journal Articles

Chemical characterization of a volatile dubnium compound, DbOCl$$_3$$

Chiera, N. M.*; Sato, Tetsuya; Eichler, R.*; Tomitsuka, Tomohiro; Asai, Masato; Adachi, Sadia*; Dressler, R.*; Hirose, Kentaro; Inoue, Hiroki*; Ito, Yuta; et al.

Angewandte Chemie; International Edition, 60(33), p.17871 - 17874, 2021/08

 Times Cited Count:0 Percentile:0(Chemistry, Multidisciplinary)

The formation and the chemical characterization of single atoms of dubnium (Db, element 105), in the form of its volatile oxychloride, was investigated using the on-line gas phase chromatography technique, in the temperature range 350 - 600 $$^circ$$C. Under the exact same chemical conditions, comparative studies with the lighter homologs of group-5 in the Periodic Table clearly indicate the volatility sequence being NbOCl$$_3 > $$ TaOCl$$_3 geq$$ DbOCl$$_3$$. From the obtained experimental results, thermochemical data for DbOCl$$_3$$ were derived. The present study delivers reliable experimental information for theoretical calculations on the chemical properties of transactinides.

Journal Articles

Optimization of an isothermal gas-chromatographic setup for the chemical exploration of dubnium (Db, Z = 105) oxychlorides

Chiera, N. M.; Sato, Tetsuya; Tomitsuka, Tomohiro; Asai, Masato; Ito, Yuta; Shirai, Kaori*; Suzuki, Hayato; Tokoi, Katsuyuki; Toyoshima, Atsushi; Tsukada, Kazuaki; et al.

Journal of Radioanalytical and Nuclear Chemistry, 320(3), p.633 - 642, 2019/06

 Times Cited Count:1 Percentile:23.13(Chemistry, Analytical)

An isothermal gas-chromatographic (IGC) device has been developed and tested for on-line gas phase studies of volatile oxychlorides of short-lived group-5 transition metals. Radioisotopes of niobium and tantalum, produced in nuclear fusion evaporation reactions, are directly flushed into the IGC setup by an inert gas-jet. Oxychloride compounds are formed by the addition of SOCl$$_2$$ and O$$_2$$. Parameters influencing the formation and transport of NbOCl$$_3$$ and TaOCl$$_3$$ are investigated. For nuclides with half-lives ($$t_{1/2}$$) of about 30 s, an overall efficiency of 7% is obtained, rendering the IGC setup suitable for the chemical exploration of $$^{262}$$Db($$t_{1/2}$$ = 34s).

Journal Articles

Formation and thermochemical properties of oxychlorides of niobium (Nb) and tantalum (Ta); Towards the gas-phase investigation of dubnium (Db) oxychloride

Chiera, N. M.; Sato, Tetsuya; Tomitsuka, Tomohiro; Asai, Masato; Suzuki, Hayato*; Tokoi, Katsuyuki; Toyoshima, Atsushi; Tsukada, Kazuaki; Nagame, Yuichiro

Inorganica Chimica Acta, 486, p.361 - 366, 2019/02

 Times Cited Count:2 Percentile:24.66(Chemistry, Inorganic & Nuclear)

The formation of NbOCl$$_3$$ and TaOCl$$_3$$ and their adsorption behavior on quartz surfaces was explored by applying an isothermal gas-chromatographic method. Trace amounts of short-lived Nb and Ta isotopes were used. Adsorption enthalpy values ($$Delta H_{rm ads}$$) at zero surface coverage of -$$Delta H_{rm ads}$$(NbOCl$$_3$$) = 102 $$pm$$ 4 kJ/mol and -$$Delta H_{rm ads}$$(TaOCl$$_3$$) = 128 $$pm$$ 5 kJ/mol were determined by analyzing the chromatographic behavior of the Nb andTa complexes with a Monte-Carlo simulation method based on an adsorption-desorption kinetic model.By applying an empirical correlation, the experimental $$Delta H_{rm ads}$$ values were successively related to the macroscopic standard sublimation enthalpy, $$Delta H^circ _{rm subl}$$, as a measure of the volatility of each substance. The inferred sublimation enthalpies are in agreement with tabulated thermochemical values. Thus, the linear empirical correlation between $$Delta H_{rm ads}$$ and $$Delta H^circ _{rm subl}$$ for metal-oxychlorides was updated with the inclusion of the present data. According to the predicted $$Delta H^circ _{rm subl}$$(DbOCl$$_3$$), a $$Delta H_{rm ads}$$(DbOCl$$_3$$) value of 135 $$pm$$ 2 kJ/mol was extrapolated. The future accomplishment of comparative studies with DbOCl$$_3$$ under the same experimental conditions will provide valuable information on the volatility trend in Group-5 elements, together with an indication on the magnitude of relativistic effects on the electronic structure of dubnium.

Journal Articles

Density and X-ray emission profile relationships in highly ionized high-Z laser-produced plasmas

Yoshida, Kensuke*; Fujioka, Shinsuke*; Higashiguchi, Takeshi*; Ugomori, Teruyuki*; Tanaka, Nozomi*; Kawasaki, Masato*; Suzuki, Yuhei*; Suzuki, Chihiro*; Tomita, Kentaro*; Hirose, Ryoichi*; et al.

Applied Physics Letters, 106(12), p.121109_1 - 121109_5, 2015/03

 Times Cited Count:6 Percentile:32.7(Physics, Applied)

Journal Articles

Efficient extreme ultraviolet emission from one-dimensional spherical plasmas produced by multiple lasers

Yoshida, Kensuke*; Fujioka, Shinsuke*; Higashiguchi, Takeshi*; Ugomori, Teruyuki*; Tanaka, Nozomi*; Ohashi, Hayato*; Kawasaki, Masato*; Suzuki, Yuhei*; Suzuki, Chihiro*; Tomita, Kentaro*; et al.

Applied Physics Express, 7(8), p.086202_1 - 086202_4, 2014/08

 Times Cited Count:24 Percentile:75.15(Physics, Applied)

We demonstrate high conversion efficiency for extreme ultraviolet (EUV) emission at 6.5-6.7 nm from multiple laser beam-produced one-dimensional spherical plasmas. Multiply charged-state ions produce strong resonance emission lines, which combine to yield intense unresolved transition arrays in Gd, Tb, and Mo. The maximum in-band EUV conversion efficiency was observed to be 0.8%, which is one of the highest values ever reported due to the reduction of plasma expansion loss.

Journal Articles

EUV spectra from highly charged tin ions observed in low density plasma in LHD

Suzuki, Chihiro*; Kato, Takako*; Sato, Kuninori*; Tamura, Naoki*; Kato, Daiji*; Sudo, Shigeru*; Yamamoto, Norimasa*; Tanuma, Hajime*; Ohashi, Hayato*; Suda, Shintaro*; et al.

Journal of Physics; Conference Series, 163, p.012019_1 - 012019_4, 2009/06

 Times Cited Count:9 Percentile:93.21

We have measured EUV spectra from highly charged tin ions in low density plasmas produced in the Large Helical Device (LHD). The well known dense spectral structure around 13.5 nm is measured when the plasma is rapidly cooled and approaching radioactive collapse, while the sparse spectrum with several unidentified discrete lines from 13.8-14.6 nm is observed if the plasma is cooled more slowly. The dominant charge states in the former case are Sn$$^{11+}$$ -Sn$$^{14+}$$. The latter case may be explained by considering the spectral lines from charge states higher than Sn$$^{19+}$$.

Oral presentation

A Basic study for solidification of low level liquid waste including high density sodium with iron phosphate glass

Saito, Akihito*; Iwata, Masayuki*; Sato, Hayato*; Arai, Tsuyoshi*; Nagayama, Katsuhisa*; Suzuki, Tatsuya*; Horiguchi, Kenichi; Sugaya, Atsushi

no journal, , 

no abstracts in English

Oral presentation

Development of a Monte Carlo simulation code for analyses of adsorption and desorption behavior of short-lived isotopes in a surface ion-source

Tokoi, Katsuyuki; Sato, Tetsuya; Eichler, R.*; Ito, Yuta; Tomitsuka, Tomohiro; Suzuki, Hayato*; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi*; Chiera, N. M.; et al.

no journal, , 

We developed a new experimental method combining vacuum chromatography and surface ionization, and applied this to investigate adsorption behavior of lawrencium (Lr, Z =103) on a surface of high temperature metallic tantalum. The adsorption behavior of Lr was similar to that of lutetium having low volatility among lanthanide elements. In this work, a Monte Carlo simulation code has been newly developed to study ionization and chromatographic behavior of short-lived atoms. In the presentation, we will report the details of a developed simulation code and calculation results.

Oral presentation

Spontaneous fission measurements for nuclei around neutron-rich Fm region produced by using an $$^{254}$$Es target

Asai, Masato; Tsukada, Kazuaki; Hirose, Kentaro; Toyoshima, Atsushi; Tomitsuka, Tomohiro; Chiera, N. M.; Ito, Yuta; Makii, Hiroyuki; Nagame, Yuichiro; Nishio, Katsuhisa; et al.

no journal, , 

Spontaneous fissions of $$^{256}$$Fm, $$^{258}$$Fm, and $$^{259}$$Lr have been measured using an $$^{254}$$Es target at the JAEA Tandem Accelerator Facility. These three nuclei show different fission properties: the asymmetric fission, the high total-kinetic-energy (TKE) symmetric fission, and the low TKE symmetric fission, and the mechanisms of these three fissions should be very different. It is of great interest to elucidate how these differences occur. We have produced $$^{256,258}$$Fm in multinucleon-transfer reactions with a $$^{254}$$Es target and $$^{18}$$O projectiles, and produced $$^{259}$$Lr in the $$^{248}$$Cm($$^{15}$$N,4n) fusion-evaporation reaction. The reaction products were mass-separated with a gas-jet-coupled on-line isotope separator, and were delivered into a rotating wheel alpha- and fission-fragment detection system. By comparing the mass and TKE distributions deduced from the present experimental data, we will discuss the differences in fission mechanism among $$^{256}$$Fm, $$^{258}$$Fm, and $$^{259}$$Lr.

Oral presentation

Development of a slow atomic beam source for superheavy elements

Tomitsuka, Tomohiro; Tokoi, Katsuyuki; Sato, Tetsuya; Ito, Yuta; Suzuki, Hayato*; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Chiera, N. M.; Goto, Shinichi*; et al.

no journal, , 

In order to experimentally determine the ground state electronic configurations of Superheavy element atoms, we have developed a slow Atomic Beam Source (ABS) using a high-temperature nozzle type cavity. In this study, we conducted an off-line experiment using stable isotopes of Cd to examine the extraction of the Cd beams. A symmetrical beam distribution with respect to the atomic beam edge was obtained. The obtained results, together with Monte-Carlo simulations for atomic beam profiles, will be presented.

Oral presentation

Formation and thermochemical properties of oxychlorides of Nb and Ta; Towards the gas-phase investigation of the Superheavy Element dubnium (Db) oxychloride

Chiera, N. M.; Sato, Tetsuya; Asai, Masato; Suzuki, Hayato*; Tokoi, Katsuyuki; Tomitsuka, Tomohiro; Toyoshima, Atsushi; Tsukada, Kazuaki; Nagame, Yuichiro

no journal, , 

Oral presentation

Development of a CFD-BASED simulation method for cesium penetration into concrete

Miyahara, Naoya*; Maejima, Hayato*; Suzuki, Eriko; Osaka, Masahiko; Sato, Isamu*

no journal, , 

In the decommissioning of the Fukushima-Daiichi Nuclear Power Station, a large amount of radioactive concrete waste should be generated. For the waste management, its appropriate treatment based on the accurate information of the inventory and the contamination aspect of radioactive Cs is of importance. In particular, accurate estimation for Cs penetration into concrete by immersion to the contaminated water should be required. Thus, we have launched a development of CFD-based simulation method which is expected to help evaluate the Cs penetration behavior into concrete. In this presentation, a first trial simulation is given for the reproduction of experimental result for Cs penetration into homogeneous concrete for confirmation of the applicability of this method by considering the most basic physical parameter, Cs diffusion.

Oral presentation

Spontaneous fission measurements for neutron-rich Fm isotopes using an $$^{254}$$Es target

Asai, Masato; Tsukada, Kazuaki; Hirose, Kentaro; Toyoshima, Atsushi; Tomitsuka, Tomohiro; Chiera, N. M.; Ito, Yuta; Makii, Hiroyuki; Nagame, Yuichiro; Nishio, Katsuhisa; et al.

no journal, , 

Spontaneous fissions of neutron-rich heavy actinide isotopes $$^{256}$$Fm, $$^{258}$$Fm, and $$^{259}$$Lr have been measured at the JAEA Tandem accelerator facility. $$^{256}$$Fm and $$^{258}$$Fm were produced in a multinucleon transfer reaction with an $$^{18}$$O beam and an extremely rare $$^{254}$$Es target with a half-life of 276 days. Reaction products were mass-separated with an on-line isotope separator (ISOL). A transition between the typical asymmetric mass distribution and a very sharp symmetric one was clearly observed between $$^{256}$$Fm and $$^{258}$$Fm, while the spontaneous fission of $$^{259}$$Lr was found to exhibit mixture of three different fission modes.

Oral presentation

Spontaneous fission studies for neutron-rich Fm and Lr isotopes

Asai, Masato; Tsukada, Kazuaki; Hirose, Kentaro; Toyoshima, Atsushi*; Tomitsuka, Tomohiro*; Chiera, N. M.*; Ito, Yuta; Makii, Hiroyuki; Nagame, Yuichiro*; Nishio, Katsuhisa; et al.

no journal, , 

We have studied spontaneous fission of neutron-rich Fm and Lr isotopes. The neutron-rich Fm isotopes were produced with the $$^{254}$$Es target and the $$^{18}$$O beam delivered by the JAEA tandem accelerator. The neutron-rich Lr isotope were produced with the $$^{248}$$Cm target and the $$^{15}$$N beam. Reaction products were mass-separated with an on-line isotope separator (ISOL), which enabled us to obtain non-contaminated samples and to measure fission fragments precisely. From the deduced fission-fragment mass and total kinetic energy distributions, we have obtained a new insight into the competition between the symmetric and asymmetric fission which is characteristic in this neutron-rich region.

Oral presentation

Fission properties of $$^{258}$$Md produced in the $$^{4}$$He+$$^{254}$$Es reaction

Nishio, Katsuhisa; Hirose, Kentaro; Makii, Hiroyuki; Orlandi, R.; Kean, K. R.*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi*; Sato, Tetsuya; Ito, Yuta; et al.

no journal, , 

no abstracts in English

Oral presentation

Spontaneous fission measurements for neutron-rich Fm and Lr isotopes using $$^{254}$$Es target

Asai, Masato; Tsukada, Kazuaki; Hirose, Kentaro; Toyoshima, Atsushi*; Tomitsuka, Tomohiro*; Chiera, N. M.*; Ito, Yuta; Makii, Hiroyuki; Nagame, Yuichiro*; Nishio, Katsuhisa; et al.

no journal, , 

Neutron-rich fermium isotopes $$^{256}$$Fm and $$^{258}$$Fm and lawrencium isotope $$^{259}$$Lr were produced in the multinucleon transfer reaction on $$^{254}$$Es target with heavy-ion beam and in the heavy-ion fusion reaction on $$^{248}$$Cm target with $$^{15}$$N beam, respectively. Reaction products were mass-separated with an on-line isotope separator (ISOL), and spontaneous fission (SF) of these isotopes were measured. It was found that the mass distribution of the SF of $$^{256}$$Fm was asymmetric, while that of $$^{258}$$Fm was sharp symmetric, which confirmed the previous experimental results. On the other hand, the SF of $$^{259}$$Lr seemed to contain both symmetric and asymmetric mass distributions. On the basis of the present results of the mass and total kinetic energy distributions, we discussed the mechanism of fission for these isotopes.

Oral presentation

Discovery of $$^{234}$$Np isomer and its decay properties

Asai, Masato; Suekawa, Yoshihide*; Higashi, Masato*; Kamada, Hiroki*; Tobe, Teruhisa*; Andreyev, A. N.; Hirose, Kentaro; Ito, Yuta; Makii, Hiroyuki; Nishio, Katsuhisa; et al.

no journal, , 

A new isomer $$^{234m}$$Np with a half-life of $$sim$$9 min has been discovered. It was produced in the reaction of $$^{233}$$U target with $$^{6}$$Li beam at JAEA tandem accelerator, and was identified through characteristic X-ray measurement and mass separation with an on-line isotope separator (ISOL). Gamma-ray singles, gamma-gamma coincidence, and internal-conversion electron measurements were performed. It was revealed that the $$^{234m}$$Np decays mostly through an isomeric E4 transition followed by an M1 transition, and that the spin-parity of the $$^{234m}$$Np should be 5$$^{+}$$. The results are introduced in detail, and the nuclear structure of the $$^{234m}$$Np are discussed.

Oral presentation

Decay and nuclear structure of $$^{234}$$Np isomer

Asai, Masato; Suekawa, Yoshihide*; Higashi, Masato*; Kamada, Hiroki*; Tobe, Teruhisa*; Andreyev, A. N.; Hirose, Kentaro; Ito, Yuta; Makii, Hiroyuki; Nishio, Katsuhisa; et al.

no journal, , 

We have carried out experiments to study nuclear structure of the new isomer $$^{234m}$$Np which we discovered recently. The $$^{234m}$$Np was produced in the reaction of $$^{233}$$U target with $$^{6}$$Li beam at JAEA tandem accelerator, and was mass-separated with an on-line isotope separator (ISOL). The half-life was determined accurately through LX-ray measurements. The $$gamma$$ transition emitted by following the isomeric transition was successfully observed through LX-$$gamma$$ coincidence measurements. Moreover, the multipolarities of the $$gamma$$ transitions were determined with internal-conversion electron measurements. On the basis of these experimental results, We have clarified excitation energy, spin-parity, and nuclear structure of $$^{234m}$$Np.

Oral presentation

On-line isothermal gas chromatographic behavior of oxychlorides of group-5 elements, Nb, Ta, and Db

Sato, Tetsuya; Chiera, N. M.*; Tomitsuka, Tomohiro; Tokoi, Katsuyuki*; Suzuki, Hayato*; Ito, Yuta; Asai, Masato; Shirai, Kaori*; Inoue, Hiroki*; Adachi, Sadia*; et al.

no journal, , 

The influence of strong relativistic effects on chemical properties has been interesting in the superheavy element region. Their chemical properties, however, have not been investigated sufficiently because of experimental difficulties owing to their low production rates and short half-lives. In order to elucidate the chemical properties of dubnium (Db, Z = 105), we have conducted on-line isothermal gas chromatographic experiments of oxychloride of group-5 elements. We confirmed the formation of volatile oxychlorides of Db and its lighter homologs Nb and Ta by using $$^{262}$$Db (half-life, $$T_{1/2}$$ = 33.8 s), $$^{88}$$Nb ($$T_{1/2}$$ = 14.5 min.), and $$^{170}$$Ta ($$T_{1/2}$$ = 6.76 min.), respectively. We successfully determined the adsorption enthalpies of the oxychlorides of each element on the quartz surface from their isothermal gas chromatographic behavior. The obtained volatility sequence of the group-5 elements is found to be Nb $$>$$ Ta $$geq$$ Db.

26 (Records 1-20 displayed on this page)