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Journal Articles

Control of the size of etchable ion tracks in PVDF; Irradiation in an oxygen atmosphere and with fullerene C$$_{60}$$

Kitamura, Akane; Yamaki, Tetsuya*; Yuri, Yosuke*; Koshikawa, Hiroshi*; Sawada, Shinichi*; Yuyama, Takahiro*; Usui, Aya; Chiba, Atsuya*

Nuclear Instruments and Methods in Physics Research B, 460, p.254 - 258, 2019/12

 Times Cited Count:1 Percentile:23.13(Instruments & Instrumentation)

Poly(vinylidene-fluoride) (PVDF) film is suitable for investigation of the size of etchable ion tracks because we can clearly judge the finish of the track etching and the surrounding bulk area remains due to the high chemical stability. Thereby we can measure the radius of ion tracks of each ion. In this study, we focused on two irradiation conditions for controlling the size of etchable ion tracks of PVDF films. One was irradiation in an oxygen atmosphere and the other was a fullerene (C$$_{60}$$$$^{+}$$) cluster beam irradiation. SEM observation showed that the size of pores became larger by irradiation in an oxygen atmosphere. It was found that the oxidation of ion tracks widened the size of etchable ion tracks. The C$$_{60}$$$$^{+}$$ irradiation caused larger etchable tracks on the PVDF surface. The result could represent the effect of local and simultaneous collisions by the swift aggregated ions.

Journal Articles

FE-SEM observation of chains of nanohillocks in SrTiO$$_{3}$$ and Nb-doped SrTiO$$_{3}$$ surfaces irradiated with swift heavy ions

Kitamura, Akane; Ishikawa, Norito; Kondo, Keietsu; Yamamoto, Shunya*; Yamaki, Tetsuya*

Nuclear Instruments and Methods in Physics Research B, 460, p.175 - 179, 2019/12

 Times Cited Count:1 Percentile:23.13(Instruments & Instrumentation)

Irradiation at grazing incidence formed chains of multiple hillocks on the surface of strontium titanate (SrTiO$$_{3}$$) and titanium oxide (TiO$$_{2}$$). They were observed with an atomic force microscope (AFM), however, the AFM measurement gives resolution errors in a nanometer order due to the curvature of the probe tip. To prevent these errors, a field emission scanning electron microscope (FE-SEM) would be a better option for observation. In this study, we performed SEM observations for the chains of the multiple hillocks. Single crystals of SrTiO$$_{3}$$ and TiO$$_{2}$$ were irradiated with 200 MeV $$^{136}$$Xe$$^{14+}$$ in the tandem accelerator at JAEA-Tokai. It was revealed that a lot of isolated hillocks were formed in a line on these surface. The diameter and the interval of those hillocks are discussed in comparison to AFM observation.

Journal Articles

Development of cation and anion exchange membranes for saline water concentration using high-energy heavy-ion beams

Sawada, Shinichi*; Yasukawa, Masahiro*; Koshikawa, Hiroshi*; Kitamura, Akane; Higa, Mitsuru*; Yamaki, Tetsuya*

Nihon Kaisui Gakkai-Shi, 73(4), p.208 - 216, 2019/08

For applications to saline water concentration by electrodialysis, we prepared nano-structure-controlled cation and anion exchange membranes (CEMs and AEMs) by a so-called ion-track grafting technique. This new technique involves irradiation of a polymer substrate with an MeV-GeV heavy-ion beam to form the nano-sized cylindrical ion tracks and the graft polymerization only into the ion tracks for the creation of one-dimensional transport pathways. A 25-$$mu$$m-thick poly(ethylene-co-tetrafluoroethylene) film was irradiated with 560 MeV $$^{129}$$Xe or 310 MeV $$^{84}$$Kr. The irradiated films were immersed in grafting solutions of ethyl p-styrenesulfonate (EtSS) and chloromethylstyrene (CMS), and then subjected to the hydrolysis of EtSS units and quaternization of CMS units to prepare CEMs and AEMs, respectively. These CEMs and AEMs showed lower resistance than the commercially-available membranes even at the very low water uptake. This would be due to the signifcantly-effcient transport of ions through the unique one-dimensional highly-connected transport pathways. In the saline water concentration experiment, a pair of our CEM and a commercial AEM or vice versa led to a higher salt concentration in the concentration chamber than did a pair of the commercial membranes. This result demonstrated great applicability of our ion-track-grafted CEMs and AEMs for saline water concentration.

Journal Articles

FE-SEM observations of multiple nanohillocks on SrTiO$$_{3}$$ irradiated with swift heavy ions

Kitamura, Akane; Ishikawa, Norito; Kondo, Keietsu; Fujimura, Yuki; Yamamoto, Shunya*; Yamaki, Tetsuya*

Transactions of the Materials Research Society of Japan, 44(3), p.85 - 88, 2019/06

Swift heavy ions can create nanosized hillocks on the surfaces of various ceramics. When these materials are irradiated with swift heavy ions at normal incidence, each ion impact results in the formation of a single hillock on the surfaces. In contrast, irradiation at grazing incidence forms chains of multiple hillocks on the surface, for example, for strontium titanate (SrTiO$$_{3}$$). So far, chains of multiple hillocks have been investigated using atomic force microscopy (AFM). It should be noted that AFM measurements involve systematic errors of several nanometers due to the finite size of the probe tip. Consequently, it is possible that the image of one hillock may merge with that of a neighboring hillock even if the two hillocks are well separated. In contrast to AFM, field-emission scanning electron microscopy (FE-SEM) is a useful technique for obtaining higher-resolution images. In this study, we observed multiple nanohillocks on the surfaces of SrTiO$$_{3}$$ using FE-SEM. Crystals of SrTiO$$_{3}$$(100) and 0.05 wt% Nb-doped SrTiO$$_{3}$$(100) were irradiated with 350 MeV Xe ions, respectively, at grazing incidence, where the angle between the sample surface and the beam was less than 2$$^{circ}$$. On the SrTiO$$_{3}$$ surface, a chain of periodic nanohillocks is created along the ion path. In contrast, black lines accompanied by hillocks are observed on the Nb-doped SrTiO$$_{3}$$ surface.

Journal Articles

Fluoropolymer-based nanostructured membranes created by swift-heavy-ion irradiation and their energy and environmental applications

Yamaki, Tetsuya*; Nuryanthi, N.*; Kitamura, Akane; Koshikawa, Hiroshi*; Sawada, Shinichi*; Voss, K.-O.*; Severin, D.*; Tautmann, C.*

Nuclear Instruments and Methods in Physics Research B, 435, p.162 - 168, 2018/11

 Times Cited Count:4 Percentile:56.63(Instruments & Instrumentation)

We used individual single-ion tracks in fluoropolymers with diameters of tens to hundreds of nanometers; chemical etching and ion-track grafting enabled us to develop ion-track and proton-conductive membranes, respectively. In the ion-track membranes of PVDF, strongly-LET-dependent etching was found, so the pore shape as well as the size was exclusively controlled by the track structures. We performed the ion-track grafting of styrene into ETFE to develop nanostructure-controlled proton exchange membranes (PEMs) for applications in PEM fuel cells. Our ion beam technology to develop fluoropolymer-based nanostructures has the potential to apply in the field of filtration processes and fuel cell devices. This would make it possible to provide new microfiltration technology for water treatment, sterilization, petroleum refining and dairy processing.

Journal Articles

Research on nanostructure-controlled functional membranes using high-energy ion beams; Fluoropolymer-based porous and ion-exchange membranes

Yamaki, Tetsuya*; Kitamura, Akane; Sawada, Shinichi*; Koshikawa, Hiroshi*

Nihon Kaisui Gakkai-Shi, 72(2), p.62 - 74, 2018/04

This review paper is devoted to two topics, i.e., fluoropolymer-based porous and ion-exchange membranes, both of which include the creation of nanostructure-controlled functional membranes with high-energy ion beams. Latent tracks of the MeV-GeV heavy ions in a polymer foil can sometimes be chemically etched out to form a membrane with micro- and nano-sized through-pores, the so-called ion-track membrane. Our focus is on ion-track membranes of poly (vinylidene fluoride) (PVDF) and cation- and anion-exchange membranes (CEMs and AEMs, respectively).

Journal Articles

Ion track etching of PVDF films irradiated with fast C$$_{60}$$$$^{+}$$ cluster ions

Kitamura, Akane; Yamaki, Tetsuya*; Chiba, Atsuya*; Usui, Aya

QST-M-8; QST Takasaki Annual Report 2016, P. 37, 2018/03

We investigated the track-etched surface of PVDF films irradiated with C$$_{60}$$$$^{+}$$ cluster ions, comparing the data with C$$^{+}$$ monoatomic ions. PVDF films were irradiated with 6 MeV C$$_{60}$$$$^{+}$$ cluster ions. The energy of the each carbon ion is 100 keV/atom; thus, for comparison, the PVDF films were also irradiated with 100 keV C$$^{+}$$ ions. SEM and AFM observation showed that the surface irradiated with C$$_{60}$$$$^{+}$$ cluster ions apparently possessed flat-bottomed pores with an average diameter and depth of approximately 400 and 250 nm, respectively. On the other hand, track-etched pores were also formed on the surface irradiated with C$$^{+}$$ ions, but their morphology was irregular or obscure. In the irradiation with the C$$_{60}$$$$^{+}$$ cluster ions, the surface diameter of track-etched pores increased with increasing the etching time. The tracks of the 100 keV C$$^{+}$$ ions seemed to be hardly developed by the etching when the time. In conclusion, the C$$_{60}$$$$^{+}$$ cluster ions irradiation caused a large size of etchable tracks on the PVDF surface. The result could represent the effect of local and simultaneous collision by the aggregated ions.

Journal Articles

Preparation of nano-structure controlled ion-exchange membranes by ion beams and their application to seawater concentration

Yamaki, Tetsuya*; Goto, Mitsuaki*; Sawada, Shinichi*; Koshikawa, Hiroshi*; Kitamura, Akane; Higa, Mitsuru*

QST-M-8; QST Takasaki Annual Report 2016, P. 35, 2018/03

We prepared ion exchange membranes by a heavy-ion-track grafting method, and then used them for seawater concentration process. Both the water uptake and resistance were lower for our ion-track grafted membranes than for the conventional $$gamma$$-ray-grafted membranes. The results would be because local and high-density energy deposition due to the ion beam enabled us to control the membrane structure in a nanometer scale. We demonstrate our membranes are suitable for this application.

Journal Articles

Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex, 2; Neutron scattering instruments

Nakajima, Kenji; Kawakita, Yukinobu; Ito, Shinichi*; Abe, Jun*; Aizawa, Kazuya; Aoki, Hiroyuki; Endo, Hitoshi*; Fujita, Masaki*; Funakoshi, Kenichi*; Gong, W.*; et al.

Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12

The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.

Journal Articles

Characteristics of electron spin resonance signal of quartz from sediments and adjacent bedrocks

Tokuyasu, Kayoko; Yasue, Kenichi; Komatsu, Tetsuya; Tamura, Itoko; Horiuchi, Yasuharu

QST-M-2; QST Takasaki Annual Report 2015, P. 189, 2017/03

Understanding the stage of mountain building is crucial to the stability assessment of geological environments in geological disposal system. In this context, we have carried out the research and development of provenance analysis techniques to elucidate the mountain-building stage. Here we present the results focusing on the R&D using the Electron Spin Resonance (ESR) signals from quartz in sediments and their basement rocks.

Journal Articles

Reduced-shifted conjugate-gradient method for a Green's function; Efficient numerical approach in a nano-structured superconductor

Nagai, Yuki; Shinohara, Yasushi*; Futamura, Yasunori*; Sakurai, Tetsuya*

Journal of the Physical Society of Japan, 86(1), p.014708_1 - 014708_9, 2017/01

 Times Cited Count:7 Percentile:59.82(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

SENJU; A New time-of-flight single-crystal neutron diffractometer at J-PARC

Ohara, Takashi; Kiyanagi, Ryoji; Oikawa, Kenichi; Kaneko, Koji; Kawasaki, Takuro; Tamura, Itaru; Nakao, Akiko*; Hanashima, Takayasu*; Munakata, Koji*; Moyoshi, Taketo*; et al.

Journal of Applied Crystallography, 49(1), p.120 - 127, 2016/02

 Times Cited Count:33 Percentile:94.36(Chemistry, Multidisciplinary)

Journal Articles

Stochastic estimation of nuclear level density in the nuclear shell model; An Application to parity-dependent level density in $$^{58}$$Ni

Shimizu, Noritaka*; Utsuno, Yutaka; Futamura, Yasunori*; Sakurai, Tetsuya*; Mizusaki, Takahiro*; Otsuka, Takaharu*

Physics Letters B, 753, p.13 - 17, 2016/02

AA2015-0661.pdf:0.39MB

 Times Cited Count:16 Percentile:81.37(Astronomy & Astrophysics)

Nuclear level density plays an important role in applications to nuclear energy and nuclear astrophysics, dominating neutron-capture cross sections. In this paper, we propose a new, practical and accurate method of estimating nuclear level density within the framework of the nuclear shell model, and show its feasibility and usefulness. This method is based on the idea that the level density is obtained by the number of eigenstates that is represented as a contour integral in the complex plane. We first confirm the feasibility of this method using a small system in which the exact eigenstates are available, and then calculate parity-dependent level density in $$^{58}$$Ni, which cannot be calculated with direct eigenstate counting. We succeed in reproducing the experimental result that the $$2^+$$ and $$2^-$$ level densities are almost identical in low-energy regions, which cannot be obtained with conventional methods of estimating level densities.

Journal Articles

Ion-track grafting of vinylbenzyl chloride into poly(ethylene-$$co$$-tetrafluoroethylene) films using different media

Nuryanthi, N.*; Yamaki, Tetsuya; Kitamura, Akane; Koshikawa, Hiroshi; Yoshimura, Kimio; Sawada, Shinichi; Hasegawa, Shin; Asano, Masaharu; Maekawa, Yasunari; Suzuki, Akihiro*; et al.

Transactions of the Materials Research Society of Japan, 40(4), p.359 - 362, 2015/12

The ion-track grafting of a vinylbenzyl chloride (VBC) into a poly(ethylene-co-tetrafluoroethylene) (ETFE) film is necessary for preparing nanostructured hydroxide-ion-conductive electrolyte membranes. A key for success here is to obtain as high graft levels as possible (for higher conductivity) in a smaller number of tracks (for improving the other membrane properties). To this end, therefore, the effect of the medium for the VBC grafting was investigated as part of our continuing effort to optimize the experimental conditions. A 25 $$mu$$m-thick ETFE film was irradiated in a vacuum chamber with 560 MeV $$^{129}$$Xe at different fluences, and then the grafting was performed by immersing the irradiated films in a 20vol% VBC monomer at 60$$^{circ}$$C. A medium was a mixture of water (H$$_{2}$$O) and isopropyl alcohol (iPrOH) at different volume ratios. The degree of grafting increased as the H$$_{2}$$O content became higher, and reached a maximum in pure H$$_{2}$$O. These results can be explained by considering the well-known Trommsdorff effect, in which poor solubility of the grafted polymer in polar media leads to an increased polymerization rate probably due to a lower termination rate.

Journal Articles

Unique Fermi surface and emergence of charge density wave in EuGa$$_4$$ and EuAl$$_4$$

Nakamura, Ai*; Hiranaka, Yuichi*; Hedo, Masato*; Nakama, Takao*; Miura, Yasunao*; Tsutsumi, Hiroki*; Mori, Akinobu*; Ishida, Kazuhiro*; Mitamura, Katsuya*; Hirose, Yusuke*; et al.

JPS Conference Proceedings (Internet), 3, p.011012_1 - 011012_6, 2014/06

Journal Articles

Fermi surface and magnetic properties of antiferromagnet EuBi$$_3$$

Nakamura, Ai*; Hiranaka, Yuichi*; Hedo, Masato*; Nakama, Takao*; Tatetsu, Yasutomi*; Maehira, Takahiro*; Miura, Yasunao*; Mori, Akinobu*; Tsutsumi, Hiroki*; Hirose, Yusuke*; et al.

Journal of the Physical Society of Japan, 82(12), p.124708_1 - 124708_6, 2013/12

 Times Cited Count:18 Percentile:72.91(Physics, Multidisciplinary)

Journal Articles

Microscopic evaluation of the absolute fluence distribution of a large-area uniform ion beam using the track-etching technique

Kitamura, Akane; Yamaki, Tetsuya; Yuri, Yosuke; Sawada, Shinichi; Yuyama, Takahiro

Nuclear Instruments and Methods in Physics Research B, 314, p.47 - 50, 2013/11

 Times Cited Count:1 Percentile:12.7(Instruments & Instrumentation)

Journal Articles

Magnetic and Fermi surface properties of EuGa$$_4$$

Nakamura, Ai*; Hiranaka, Yuichi*; Hedo, Masato*; Nakama, Takao*; Miura, Yasunao*; Tsutsumi, Hiroki*; Mori, Akinobu*; Ishida, Kazuhiro*; Mitamura, Katsuya*; Hirose, Yusuke*; et al.

Journal of the Physical Society of Japan, 82(10), p.104703_1 - 104703_10, 2013/10

 Times Cited Count:29 Percentile:82(Physics, Multidisciplinary)

Journal Articles

Numerical construction of a low-energy effective Hamiltonian in a self-consistent Bogoliubov-de Gennes approach of superconductivity

Nagai, Yuki; Shinohara, Yasushi*; Futamura, Yasunori*; Ota, Yukihiro*; Sakurai, Tetsuya*

Journal of the Physical Society of Japan, 82(9), p.094701_1 - 094701_10, 2013/09

 Times Cited Count:17 Percentile:71.77(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Full-coherent free electron laser seeded by 13th- and 15th-order harmonics of near-infrared femtosecond laser pulses

Sato, Takahiro*; Iwasaki, Atsushi*; Owada, Shigeki*; Yamanouchi, Kaoru*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Togashi, Tadashi*; Fukami, Kenji*; et al.

Journal of Physics B; Atomic, Molecular and Optical Physics, 46(16), p.164006_1 - 164006_6, 2013/08

 Times Cited Count:3 Percentile:21.46(Optics)

By introducing 13th- (61.7 nm) and 15th-order harmonics (53.4 nm) of femtosecond laser pulses at 800 nm into an undulator of SCSS (SPring-8 Compact SASE Source) test accelerator at RIKEN, these harmonic pulses were amplified by a factor of more than 10$$^{2}$$ with a high contrast ratio through the interaction between accelerated electron bunches and the harmonic pulses. From numerical simulations of the amplification processes of high-order harmonic pulses in the undulator, optimum conditions of the electron bunch duration interacting with the high-order harmonic pulses were investigated for generating full-coherent and intense pulses in the extreme ultraviolet wavelength region.

105 (Records 1-20 displayed on this page)