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Journal Articles

Analysis of J-HBC stripper foil for the J-PARC RCS

Yoshimoto, Masahiro; Nakanoya, Takamitsu; Yamazaki, Yoshio; Saha, P. K.; Kinsho, Michikazu; Yamamoto, Shunya*; Okazaki, Hiroyuki*; Taguchi, Tomitsugu*; Yamada, Naoto*; Yamagata, Ryohei*

JPS Conference Proceedings (Internet), 33, p.011019_1 - 011019_7, 2021/03

The multi-turn charge-exchange H$$^{-}$$ beam injection scheme with stripper foils is one of the key techniques to achieve a MW-class high power proton beam. The J-PARC RCS adopts Hybrid type Boron-doped Carbon (HBC) stripper foil, which was developed in KEK to improve the lifetime. Indeed, the RCS user operation confirmed that HBC foil has the great advantage of a longer lifetime against high beam irradiation. To examine characteristics of the HBC foils, various beam studies were performed, such as the stripping efficiency measurement and long-term observation with an H$$^{-}$$ beam in the J-PARC RCS, foil analysis using RBS, EDR and PIXE methods, and SEM and TEM observation after the ion beam irradiation in Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) on National Institutes for Quantum and Radiological Science and Technology (QST). Recently, the deposition apparatus for the HBC foils from the KEK Tsukuba-site was relocated to the JAEA Tokai-site, and we started fabrication of new HBC foil in 2017. (The new one fabricated in JAEA we call J-HBC foil.) And, we continue investigations in TIARA with the J-HBC foils. Furthermore, in-depth researches by changing the process parameters of the foil deposition are carried on. Recent results suggest that the amount of the boron doped in the foil is more important parameter than the ratio of the discharge amount of carbon from cathode and anode electrodes. In this presentation, we will report the details of recent analysis of the J-HBC foil.

Journal Articles

Matrix-material dependence on the elongation of embedded gold nanoparticles induced by 4 MeV C$$_{60}$$ and 200 MeV Xe ion irradiation

Li, R.*; Narumi, Kazumasa*; Chiba, Atsuya*; Hirano, Yu*; Tsuya, Daiju*; Yamamoto, Shunya*; Saito, Yuichi*; Okubo, Nariaki; Ishikawa, Norito; Pang, C.*; et al.

Nanotechnology, 31(26), p.265606_1 - 265606_9, 2020/06

 Times Cited Count:1 Percentile:24.67(Nanoscience & Nanotechnology)

We report the elongation of embedded Au nanoparticles (NPs) in three different matrices under irradiations of 4 MeV C$$_{60}$$ ions and 200 MeV Xe ions. Large elongation of Au NPs was observed for crystalline indium tin oxide (ITO) under both 4 MeV C$$_{60}$$ and 200 MeV Xe irradiation. The ITO layer preserved the crystallinity even after large elongation was induced. This is the first report of the elongation of metal NPs in a crystalline matrix.

Journal Articles

Changes in electronic structure of carbon supports for Pt catalysts induced by vacancy formation due to Ar$$^{+}$$ irradiation

Okazaki, Hiroyuki*; Kakitani, Kenta*; Kimata, Tetsuya*; Idesaki, Akira*; Koshikawa, Hiroshi*; Matsumura, Daiju; Yamamoto, Shunya*; Yamaki, Tetsuya*

Journal of Chemical Physics, 152(12), p.124708_1 - 124708_5, 2020/03

 Times Cited Count:1 Percentile:0.01(Chemistry, Physical)

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

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

X-ray absorption study of platinum nanoparticles on an ion-irradiated carbon support

Kakitani, Kenta*; Kimata, Tetsuya*; Yamaki, Tetsuya*; Yamamoto, Shunya*; Matsumura, Daiju; Taguchi, Tomitsugu*; Terai, Takayuki*

Radiation Physics and Chemistry, 153, p.152 - 155, 2018/12

 Times Cited Count:1 Percentile:17.98(Chemistry, Physical)

Journal Articles

Synthesis of heterostructured SiC and C-SiC nanotubes by ion irradiation-induced changes in crystallinity

Taguchi, Tomitsugu; Yamamoto, Shunya; Kodama, Katsuaki; Asaoka, Hidehito

Carbon, 95, p.279 - 285, 2015/12

 Times Cited Count:9 Percentile:36.8(Chemistry, Physical)

Amorphous SiC nanotubes are successfully synthesized by 340 keV Si$$^{+}$$ ions irradiation of polycrystalline SiC nanotubes for the first time. A polycrystalline/amorphous heterostructure SiC nanotube, in which polycrystalline SiC and amorphous SiC coexist in the same nanotube, is also synthesized by ions irradiation with a mask in front of polycrystalline SiC nanotube. According to electron energy loss spectroscopy evaluation, the plasmon energies of SiC nanotube change rapidly at the interface between polycrystalline and amorphous regions. The volume swelling by amorphization evaluated from the differences of plasmon energies is approximately 5.0%. This result reveals that the further relaxed amorphous SiC nanotubes with higher density can be produced. The graphitic shells in carbon layer of C-SiC nanotube gradually bend to the radial direction of nanotube by the ion irradiation. Since the graphite (002) spots in the selected area electron diffraction pattern are clearly observed even after the ion irradiation, the carbon layer in C-SiC nanotube has certain crystallinity. Moreover, the new multi-walled carbon nanotube with the graphitic shells completely parallel to the radial direction of nanotube is also produced inside the amorphous SiC tubular layer in the case of C-SiC nanotube with large caliber.

Journal Articles

Size and dopant-concentration dependence of photoluminescence properties of ion-implanted phosphorus- and boron-codoped Si nanocrystals

Nakamura, Toshihiro*; Adachi, Sadao*; Fujii, Minoru*; Sugimoto, Hiroshi*; Miura, Kenta*; Yamamoto, Shunya

Physical Review B, 91(16), p.165424_1 - 165424_8, 2015/04

 Times Cited Count:13 Percentile:57.42(Materials Science, Multidisciplinary)

Semiconductor nanocrystals have unique electrical and optical properties, because of the quantum confinement effect, and the doping of impurities into nanocrystals. In this study, we investigated the photoluminescence (PL) properties of phosphorus- (P) and boron- (B) co-doped Si nanocrystals (Si NCs), which was synthesized using an ion implantation technique. The Si-NC size (average diameter: 3.5, 4.4, 5.2 nm) and the P and B ion doses (0.1-4.5$$times$$10$$^{16}$$ cm$$^{-2}$$)values were systematically varied. We find that the PL peak energy shifts to lower values with increasing the average diameters of Si NCs and PB ion dose. The results of PL measurements indicate that the PL spectra are due to the band-to-band transition at the reduced Si-NC band gap caused by the formation of impurity and the radiative transitions between defect- and/or impurity-related localized states. It was found that the PL properties can be controlled by varying the Si-NC size as well as the dopant concentration.

Journal Articles

Charge-to-spin conversion and spin diffusion in Bi/Ag bilayers observed by spin-polarized positron beam

Zhang, H. J.; Yamamoto, Shunya; Gu, B.; Li, H.; Maekawa, Masaki; Fukaya, Yuki; Kawasuso, Atsuo

Physical Review Letters, 114(16), p.166602_1 - 166602_5, 2015/04

 Times Cited Count:38 Percentile:89.02(Physics, Multidisciplinary)

Charge-to-spin conversion induced by the Rashba-Edelstein effect was directly observed for the first time in samples with no magnetic layer. A spin-polarized positron beam was used to probe the spin polarization of the outermost surface electrons of Bi/Ag/Al$$_2$$O$$_3$$ and Ag/Bi/Al$$_2$$O$$_3$$ when charge currents were only associated with the Ag layers. An opposite surface spin polarization was found between Bi/Ag/Al$$_2$$O$$_3$$ and Ag/Bi/Al$$_2$$O$$_3$$ samples with the application of a charge current in the same direction. The surface spin polarizations of both systems decreased exponentially with the outermost layer thickness, suggesting the occurrence of spin diffusion from the Bi/Ag interface to the outermost surfaces. This work provides a new technique to measure spin diffusion length.

Journal Articles

Characterization of Pt and Pd epitaxial films on sapphire substrates by RBS/channeling

Yamamoto, Shunya; Hakoda, Teruyuki; Yoshikawa, Masahito

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 129, 2015/03

no abstracts in English

Journal Articles

Development of a scintillator for single-ion detection

Yokoyama, Akihito; Kada, Wataru*; Sato, Takahiro; Koka, Masashi; Yamamoto, Shunya; Kamiya, Tomihiro; Yokota, Wataru

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 168, 2015/03

no abstracts in English

Journal Articles

Defect structure analysis of heterointerface between Pt and CeO$$_{rm x}$$ promoter on Pt electro-catalyst

Fugane, Keisuke*; Mori, Toshiyuki*; Yan, P.*; Masuda, Takuya*; Yamamoto, Shunya; Ye, F.*; Yoshikawa, Hideki*; Auchterlonie, G.*; Drennan, J.*

ACS Applied Materials & Interfaces, 7(4), p.2698 - 2707, 2015/02

 Times Cited Count:25 Percentile:69.58(Nanoscience & Nanotechnology)

no abstracts in English

Journal Articles

Structural and gasochromic properties of WO$$_{3}$$ films prepared by reactive sputtering deposition

Yamamoto, Shunya; Hakoda, Teruyuki; Miyashita, Atsumi; Yoshikawa, Masahito

Materials Research Express (Internet), 2(2), p.026401_1 - 026401_8, 2015/02

 Times Cited Count:2 Percentile:9.29(Materials Science, Multidisciplinary)

The effects of deposition temperature and film thickness on the structural and gasochromic properties of tungsten trioxide films used for the optical detection of diluted cyclohexane have been investigated. The tungsten trioxide films were prepared on SiO$$_{2}$$ substrates by magnetron sputtering, with the deposition temperature ranging from 300 to 550$$^{circ}$$C in an Ar and O$$_{2}$$ gas mixture. The gasochromic properties of the films, coated with a catalytic Pt layer, were examined by exposing them up to 5% cyclohexane in N$$_{2}$$ gas. We found that (001)-oriented monoclinic tungsten trioxide films, with a columnar structure, grew at deposition temperatures between 400 and 450$$^{circ}$$C. The gasochromic characterization of the tungsten trioxide films revealed that (001)-oriented tungsten trioxide films, with cauliflower-like surface morphology, were appropriate for the optical detection of cyclohexane.

Journal Articles

Development of a high-brightness and high-current electron gun for high-flux $$gamma$$-ray generation

Nishimori, Nobuyuki; Nagai, Ryoji; Matsuba, Shunya; Hajima, Ryoichi; Yamamoto, Masahiro*; Honda, Yosuke*; Miyajima, Tsukasa*; Uchiyama, Takashi*; Kuriki, Masao*

Nuclear Physics and $$gamma$$-ray sources for Nuclear Security and Nonproliferation, p.321 - 326, 2014/12

Journal Articles

Development of real-time position detection system for single-ion hit

Yokoyama, Akihito; Kada, Wataru*; Sato, Takahiro; Koka, Masashi; Yamamoto, Shunya; Kamiya, Tomihiro; Yokota, Wataru

Nuclear Instruments and Methods in Physics Research B, 332, p.334 - 336, 2014/08

 Times Cited Count:1 Percentile:11.75(Instruments & Instrumentation)

A system is developed for the real-time position detection of single-ions which hits a target with spatial accuracy about 1 $$mu$$m. The system combines highly luminescent, sensitive, scintillators with a high sensitivity luminescence detection system. The real-time detection system contains a Al$$_{2}$$O$$_{3}$$:Eu scintillator, Eu implanting into $$alpha$$-Al$$_{2}$$O$$_{3}$$. A single-crystal scintillator has been selected since position resolution of emission for powdery scintillator is limited by a grain size, several micrometers for ZnS for example. When the material is irradiated with an electron or ion beam, the Eu is activated and strong luminescence occurs. The detection system includes an image intensifier tube and an electron multiplier CCD camera. The results show that our system can be sufficiently sensitive to detect the hit of a single-ion in real time through simple improvement in emission intensity of the scintillator.

Journal Articles

Plasmonic cyclohexane-sensing by sputter-deposited Au nanoparticle array on SiO$$_{2}$$

Kawaguchi, Kazuhiro*; Yamamoto, Shunya; Yoshikawa, Masahito; Takahiro, Katsumi*

Thin Solid Films, 562, p.648 - 652, 2014/07

 Times Cited Count:4 Percentile:22.6(Materials Science, Multidisciplinary)

Liquid organic-hydrides such as cyclohexane which can release-absorbing hydrogen in reversible have been proposed approvable carriers to store and transport hydrogen. However, organic-hydrides are known as highly flammable in air. To realize practical use of this hydrogen production process, the monitoring of leakage of organic-hydride gas is strongly required. In the present work, we have examined the plasmonic sensing ability of Au nanoparticle (NP) arrays for dilute cyclohexane. Au NP arrays were prepared on SiO$$_{2}$$ by a sputter deposition technique. The change in an extinction spectrum of Au NP arrays before and after exposure of cyclohexane vapor enabled us to detect it. The Au NP array prepared with 4.4 $$times$$ 10$$^{16}$$ Au atoms/cm$$^{2}$$ deposited at 300$$^{circ}$$C was and demonstrated a high sensitivity for cyclohexane at RT. The experimentally detectable concentration of cyclohexane was as low as 0.5 vol%, much lower than its explosion limit (1.3 vol%).

Journal Articles

Generation of a 500-keV electron beam with milliampere current from a photoemission DC gun

Nishimori, Nobuyuki; Nagai, Ryoji; Matsuba, Shunya; Hajima, Ryoichi; Yamamoto, Masahiro*; Miyajima, Tsukasa*; Honda, Yosuke*; Uchiyama, Takashi*; Iijima, Hokuto*; Kuriki, Masao*; et al.

Proceedings of 10th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.174 - 178, 2014/06

no abstracts in English

Journal Articles

Experimental investigation of an optimum configuration for a high-voltage photoemission gun for operation at $$geq$$ 500 kV

Nishimori, Nobuyuki; Nagai, Ryoji; Matsuba, Shunya; Hajima, Ryoichi; Yamamoto, Masahiro*; Honda, Yosuke*; Miyajima, Tsukasa*; Iijima, Hokuto*; Kuriki, Masao*; Kuwahara, Makoto*

Physical Review Special Topics; Accelerators and Beams, 17(5), p.053401_1 - 053401_17, 2014/05

 Times Cited Count:18 Percentile:78.97(Physics, Nuclear)

Journal Articles

Current-induced spin polarization on metal surfaces probed by spin-polarized positron beam

Zhang, H.; Yamamoto, Shunya; Fukaya, Yuki; Maekawa, Masaki; Li, H.; Kawasuso, Atsuo; Seki, Takeshi*; Saito, Eiji*; Takanashi, Koki*

Scientific Reports (Internet), 4, p.4844_1 - 4844_5, 2014/04

 Times Cited Count:34 Percentile:83.52(Multidisciplinary Sciences)

Journal Articles

Production of nano-sized platinum-particle films using low energy electron beams

Hakoda, Teruyuki; Yamamoto, Shunya; Aritani, Hirofumi*; Yoshikawa, Masahito

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 127, 2014/03

Reduction of noble metal ions and subsequent production of noble metal particles in a solution has been performed as a radiation-induced precipitation (RIP) method using high energy ionizing radiation. Electron beams with energies below 300 keV have shorter penetration range and can irradiate at higher dose rates. Application of such low energy EBs to the RIP method has a possibility of producing film matters consisting of noble metal particles on the surface of the solution. In the present study, this possibility was examined using a few ten keV EBs for PtCl$$_{6}$$$$^{2-}$$ ion solutions. Black-colored film matters were produced on the surface of the sample solution after EB irradiation. Lower concentrations of ethanol such as 0.5v% accelerated the formation of Pt films on the sample solution. The films had network structure consisting of connected Pt particles with sizes of 2-5 nm.

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