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Journal Articles

Free-volume structure of fluoropolymer-based radiation-grafted electrolyte membranes investigated by positron annihilation lifetime spectroscopy

Sawada, Shinichi; Kawasuso, Atsuo; Maekawa, Masaki; Yabuuchi, Atsushi; Maekawa, Yasunari

Journal of Physics; Conference Series, 225, p.012048_1 - 012048_6, 2010/06

 Times Cited Count:6 Percentile:89.65

During the operation of polymer electrolyte fuel cell, supplied fuel gases sometimes permeate through the polymer electrolyte membrane (PEM), thereby affecting the cell performance. For developing the novel PEM with low gas permeability, it is required to obtain an insight into the micro-pore structures in the PEM, which is related to gas permeation phenomena. In this study, we investigated the miro pore structures in the crosslinked-polytetrafluoroethylene (PTFE) based radiation-grafted PEMs by using positron annihilation lifetime (PAL) spectroscopy. From the obtained PAL spectra, there were found to be the two types of o-Ps in the PEMs. Their lifetimes are 2.0-2.1 ns and 4.3-4.5 ns, which correspond to the pore sizes of 0.28-0.30 nm and 0.44-0.45 nm, respectively. The small-size pores should be in PTFE crystallites and grafted phases, while the larger-size ones are probably in PTFE amorphous regions.

Journal Articles

OH radical in water studied by quantum beats on positron annihilation; The Effect of water liquid structures

Lee, J.; Oka, Toshitaka; Hirade, Tetsuya

Journal of Physics; Conference Series, 225, p.012030_1 - 012030_5, 2010/06

 Times Cited Count:2 Percentile:69.52

The temperature dependence of quantum beats giving the hyperfine coupling constant of hydroxyl radical observed by positron annihilation Age-Momentum correlation measurement for ortho-Ps and hydroxyl radical. According to the measurements at 18$$^{circ}$$C, 25$$^{circ}$$C and 32$$^{circ}$$C, the hyperfine coupling constants were smaller at higher temperatures. Moreover, the slow and continuous change of water liquid structures were observed.

Journal Articles

Evaluation of stainless steel under tensile stress using positron microbeam

Maekawa, Masaki; Yabuuchi, Atsushi; Kawasuso, Atsuo

Journal of Physics; Conference Series, 225, p.012033_1 - 012033_4, 2010/06

 Times Cited Count:3 Percentile:78.3

We have developed a positron microbeam based on the commercial scanning electron microscope. The minimum beam diameter 1.9 micron on target was confirmed. Using this, vacancy-type defects in the small area can be detected. This means that the positron microbeam has a great advantage for the measurement under the extreme condition, such as high temperature, high tensile stress, high electric field, high pressure and so on, because it become easier to apply such condition when the sample size was smaller. We have applied the positron microbeam for the sample under tensile stress and high temperature.

Journal Articles

Characterization of helium bubbles in Si by a slow positron beam

Maekawa, Masaki; Kawasuso, Atsuo

Journal of Physics; Conference Series, 225, p.012032_1 - 012032_7, 2010/06

 Times Cited Count:10 Percentile:94.83

The helium bubble formed in silicon by the high-dose helium ion implantation was observed by the positron annihilation method. The peak intensities of annihilation $$gamma$$ rays (S parameter) and its annealing behaviors were measured. At as-implanted state, S parameter increased because of the implantation defects. After 300$$^{circ}$$C annealing, S parameter decreased by the helium bubble. After 900$$^{circ}$$C annealing, S parameter increased drastically due to the microvoids formed by the desorption of helium atoms. Positron annihilation method can detect the generation and disappearance process of the helium bubble by the ion implantation.

Journal Articles

Doppler broadening of annihilation radiation of some single-element materials from the second to the sixth periods

Kawasuso, Atsuo; Maekawa, Masaki; Betsuyaku, Kiyoshi*

Journal of Physics; Conference Series, 225, p.012027_1 - 012027_5, 2010/06

 Times Cited Count:5 Percentile:87.1

Electron-positron momentum distribution obtained through the Doppler broadening of annihilation radiation measurement is very useful for identifying defects in materials. For the detailed analysis of Doppler broadening spectrum, precise theoretical calculation is needed. It is pointed out that the pseudo-potential method has a problem in the calculation of electron wavefunction near core region. To avoid this difficulty, some all-electron manner should be employed. We thus calculated the Doppler broadening spectra based on the electronic state calculation by the projector-augmented wave method and compared them with experimental spectra.

Journal Articles

Development of a spin-polarized positron source

Kawasuso, Atsuo; Fukaya, Yuki; Maekawa, Masaki; Yabuuchi, Atsushi

Journal of Physics; Conference Series, 225, p.012028_1 - 012028_4, 2010/06

 Times Cited Count:3 Percentile:78.3

Positrons emitted from beta-plus emitters are longitudinally spin polarized. To use spin-polarized positrons in the future materials science, we develop a spin-polarized positron beam. The spin-polarization increases with the Q-value of beta-plus emitter. We thus develop a $$^{68}$$Ge-$$^{68}$$Ga positron source. We irradiate high energy protons to the $$^{69}$$Ga stable isotope and obtain $$^{68}$$Ge-$$^{68}$$Ga through the nuclear reaction. We report the optimum condition of proton irradiation and design of the source capsule.

Journal Articles

Surface plasmon excitation at metal surfaces studied by reflection high-energy positron diffraction

Fukaya, Yuki; Kawasuso, Atsuo; Ichimiya, Ayahiko

Journal of Physics; Conference Series, 225, p.012009_1 - 012009_5, 2010/06

 Times Cited Count:0 Percentile:0.14

no abstracts in English

Journal Articles

Structure and phase transition of low-dimensional metals on Si(111) surfaces studied by reflection high-energy positron diffraction

Fukaya, Yuki; Hashimoto, Mie; Kawasuso, Atsuo; Ichimiya, Ayahiko

Journal of Physics; Conference Series, 225, p.012008_1 - 012008_8, 2010/06

 Times Cited Count:1 Percentile:53.11

no abstracts in English

Journal Articles

Development of elemental analysis by muonic X-ray measurement in J-PARC

Ninomiya, Kazuhiko; Nagatomo, Takashi*; Kubo, Kenya*; Strasser, P.*; Kawamura, Naritoshi*; Shimomura, Koichiro*; Miyake, Yasuhiro*; Saito, Tsutomu*; Higemoto, Wataru

Journal of Physics; Conference Series, 225, p.012040_1 - 012040_4, 2010/06

 Times Cited Count:13 Percentile:96.57

Muon irradiation and muonic X-ray detection can be applied to non-destructive elemental analysis. In this study, in order to develop the elemental analysis by muonic X-ray measurement we constructed a new X-ray measuring system in J-PARC muon facility. We performed muon irradiation for Tempo-koban (Japanese old coin) for test experiment of elemental analysis.

Journal Articles

The EPICS-based remote control system for muon beam line devices J-PARC MUSE

Ito, Takashi; Nakahara, Kazutaka*; Kawase, Masato; Fujimori, Hiroshi*; Kobayashi, Yasuo*; Higemoto, Wataru; Miyake, Yasuhiro*

Journal of Physics; Conference Series, 225, p.012022_1 - 012022_5, 2010/06

 Times Cited Count:1 Percentile:53.11

The Experimental Physics and Industrial Control System (EPICS) provides software infrastructure and framework for building distributed control systems (DCS) to operate beam line devices. The DCS based on EPICS has been adopted by many accelerator facilities in the world, where reliability, maintainability, and scalability of the system have been demonstrated. This system is also used to operate the high energy proton accelerator in the Japan Proton Accelerator Research Complex (J-PARC). We here report on the EPICS-based remote control system developed for operating the decay muon beam line in J-PARC. Major functions of beam line devices, three bending magnets, eighteen quadrupole magnets, and four slits, are accessible via Ethernet from a graphical user interface composed of the Motif Editor and Display Manager (MEDM).

Journal Articles

$$mu^+$$ diffusion in cubic $$f$$-electron compounds observed by high transverse field $$mu^+$$SR

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki*; Nishida, Nobuhiko*; Heffner, R. H.; Aoki, Yuji*; Suzuki, Hiroyuki*; Onimaru, Takahiro*; Tanida, Hiroshi*; Takagi, Shigeru*

Journal of Physics; Conference Series, 225, p.012021_1 - 012021_6, 2010/06

 Times Cited Count:1 Percentile:53.11

The diffusion of positive muon $$mu^+$$ in condensed matter has been investigated for many years by using $$mu^+$$ spin rotation/relaxation ($$mu^+$$SR) technique. The $$mu^+$$SR studies have provided deep insight into quantum diffusion at low temperatures as well as hopping process at high temperatures, which are closely related to hydrogen dynamics in the dilute limit. We here report transverse field (TF) $$mu^+$$SR studies of the $$mu^+$$ diffusion in cubic $$f$$-electron compounds PrPb$$_3$$ and SmAg$$_2$$In. The $$mu^+$$ site splits into two magnetically labeled sites when high TF is applied to single-crystalline specimens along the [001] direction. The $$mu^+$$SR lines show drastic variation according to the $$mu^+$$ motion between the magnetically labeled sites. From detailed analysis of the $$mu^+$$SR lines, we deduced $$mu^+$$ hopping parameters for both compounds.

Journal Articles

Free volume in Zr-based bulk glassy alloys studied by positron annihilation techniques

Ishii, Akito*; Iwase, Akihiro*; Yokoyama, Yoshihiko*; Konno, Toyohiko*; Kawasuso, Atsuo; Yabuuchi, Atsushi; Maekawa, Masaki; Hori, Fuminobu*

Journal of Physics; Conference Series, 225, p.012020_1 - 012020_6, 2010/06

 Times Cited Count:5 Percentile:87.1

To reveal the relationship between mechanical properties and microscopic structure of Zr-based amorphous metals, we performed positron annihilation measurements on specimens with different Zr contents. Although the positron lifetimes were nearly the same for all the specimens, the Doppler broadening of annihilation radiation spectra were significantly different for the specimens at and above the eutectic point. This indicates that both the structure and composition of free volumes depend on the Zr-content.

Journal Articles

Magnetism in Ce$$_2$$Rh(In,Sn)$$_8$$ heavy-fermion compound

Oishi, Kazuki*; Suzuki, Takao*; Heffner, R.*; Ito, Takashi; Higemoto, Wataru; Bauer, E.*

Journal of Physics; Conference Series, 225, p.012042_1 - 012042_4, 2010/06

 Times Cited Count:1 Percentile:53.11

Journal Articles

$$mu$$SR study of CeRhIn$$_5$$ under applied pressure

Heffner, R.*; Goko, Tatsuo*; Andreica, D.*; Oishi, Kazuki*; Higemoto, Wataru; Ito, Takashi; Amato, A.*; Spehling, J.*; Klauss, H. H.*; Bauer, E. D.*; et al.

Journal of Physics; Conference Series, 225, p.012011_1 - 012011_6, 2010/06

 Times Cited Count:1 Percentile:53.11

Journal Articles

J-PARC muon facility, MUSE

Miyake, Yasuhiro*; Shimomura, Koichiro*; Kawamura, Naritoshi*; Strasser, P.*; Makimura, Shunsuke*; Koda, Akihiro*; Fujimori, Hiroshi*; Nakahara, Kazutaka*; Takeshita, Soshi*; Kobayashi, Yasuo*; et al.

Journal of Physics; Conference Series, 225, p.012036_1 - 012036_7, 2010/06

 Times Cited Count:7 Percentile:91.45

Journal Articles

J-PARC decay muon channel construction status

Strasser, P.*; Shimomura, Koichiro*; Koda, Akihiro*; Kawamura, Naritoshi*; Fujimori, Hiroshi*; Makimura, Shunsuke*; Kobayashi, Yasuo*; Nakahara, Kazutaka*; Kato, Mineo*; Takeshita, Soshi*; et al.

Journal of Physics; Conference Series, 225, p.012050_1 - 012050_8, 2010/06

 Times Cited Count:11 Percentile:95.51

Journal Articles

JAEA-ASRC muon research at J-PARC MUSE

Higemoto, Wataru; Ito, Takashi; Ninomiya, Kazuhiko; Heffner, R.*; Shimomura, Koichiro*; Nishiyama, Kusuo*; Miyake, Yasuhiro*

Journal of Physics; Conference Series, 225, p.012012_1 - 012012_4, 2010/06

 Times Cited Count:2 Percentile:69.52

The Japan Atomic Energy Agency (JAEA)-Advanced Science Research Center (ASRC) has developed experimental equipment at the J-PARC MLF muon science facility (MUSE) for muon spin rotation/relaxation experiments. We have extracted part of the muonbeam into a muon spectrometer constructed downstream from the Decay/Surface muon beam line. The current status of our project is discussed here.

Oral presentation

Development of positron probe microanalyzer using RI source and its applications

Fujinami, Masanori*; Jinno, Satoshi*; Oka, Toshitaka; Kawashima, Yuji*

no journal, , 

Oral presentation

Formation of isolated three-spin system Pr-$$mu^+$$-Pr in PrPb$$_3$$

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki*; Nishida, Nobuhiko*; Heffner, R. H.; Aoki, Yuji*; Amato, A.*; Onimaru, Takahiro*; Suzuki, Hiroyuki*

no journal, , 

An isolated few-spin system including a $$mu^+$$ spin $$S$$ is usually unlikely to be realized in metal. Contrary to the expectation, we actually found an isolated three-spin system $$^{141}$$Pr-$$mu^+$$-$$^{141}$$Pr in a rare-earth intermetallic compound PrPb$$_3$$. This system results in $$mu^+$$ spin precession with six frequencies at regular intervals. Such harmonic frequencies cannot be obtained only from dipolar interactions between $$S$$ and bare $$^{141}$$Pr nuclear spins $$I_{141}$$. Extremely anisotropic enhancement of the $$S$$-$$I_{141}$$ coupling is required. This enhancement can be explained by mechanism of the $$^{141}$$Pr hyperfine-enhanced nuclear magnetism and $$mu^+$$-induced perturbation on 4f-electronic state of two Pr ions next to the $$mu^+$$.

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