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Journal Articles

Electronic stopping power dependence of ion-track size in UO$$_{2}$$ irradiated with heavy ions in the energy range of $$sim$$1MeV/u

Ishikawa, Norito; Sonoda, Takeshi*; Sawabe, Takashi*; Sugai, Hiroyuki*; Sataka, Masao*

Nuclear Instruments and Methods in Physics Research B, 314, p.180 - 184, 2013/11

 Times Cited Count:20 Percentile:82.27(Instruments & Instrumentation)

In order to investigate electronic stopping power dependence of ion-track size in UO$$_{2}$$, ion-tracks in UO$$_{2}$$ irradiated with various ions with the specific energy in the order of 1 MeV/u have been observed by a transmission electron microscope. The ion-tracksize shows monotonic increase as a function of the electronic stopping power. Theion-track size obtained for UO$$_{2}$$ is smaller than that obtained for CeO$$_{2}$$, although these two compounds have same crystallographic structure and similar thermal properties. The ion-track sizes for irradiations with ions having relatively low energy of about1 MeV/u are smaller than those expected from the thermal spike models based on melting temperature criterion. The possible interpretations for the unusually smallion-tracks observed for UO$$_{2}$$ are discussed.

Journal Articles

Electrical property modifications of In-doped ZnO Films by ion irradiation

Matsunami, Noriaki*; Fukushima, Junichi*; Sataka, Masao; Okayasu, Satoru; Sugai, Hiroyuki; Kakiuchida, Hiroshi*

Nuclear Instruments and Methods in Physics Research B, 268(19), p.3071 - 3075, 2010/10

 Times Cited Count:13 Percentile:64.87(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Vicinage effect on secondary-electron emission in the forward direction from amorphous carbon foils induced by swift C$$_{2}$$$$^{+}$$ ions

Takahashi, Yasuyuki; Narumi, Kazumasa; Chiba, Atsuya; Saito, Yuichi; Yamada, Keisuke; Ishikawa, Norito; Sugai, Hiroyuki; Maeda, Yoshihito

EPL; A Letters Journal Exploring the Frontiers of Physics, 88(6), p.63001_1 - 63001_6, 2009/12

 Times Cited Count:7 Percentile:45.41(Physics, Multidisciplinary)

C$$_{2}$$$$^{+}$$ and C$$_{1}$$$$^{+}$$ ions with 62.5-250 keV/u were incident on self-supporting amorphous carbon foils of 1.4-150 $$mu$$g/cm$$^{2}$$ (70-7500 ${AA}$). The secondary electrons emitted in the forward direction from a carbon foil were detected by a microchannel-plate detector placed at the exit side of the target. The vicinage effect on the secondary-electron yield was evaluated with the ratio of the secondary-electron yield R$$_{2}$$ = $$gamma$$$$_{2}$$/2$$gamma$$$$_{1}$$, where $$gamma$$$$_{2}$$ and $$gamma$$$$_{1}$$ are the yields induced by the C$$_{2}$$$$^{+}$$ and C$$_{1}$$$$^{+}$$ ion with the same velocity, respectively. For the first time the disappearance of the vicinage effect on the secondary-electron yield from amorphous carbon foils bombarded with 62.5 keV/u C$$_{2}$$$$^{+}$$ ions was observed for thick foils of 61-150 $$mu$$g/cm$$^{2}$$. The internuclear distance between the fragment ions at the exit of the target was evaluated by calculating trajectories of the fragment ions considering the Coulomb explosion. For a 62.5 keV/u C$$_{2}$$$$^{+}$$ ion, we have determined the threshold internuclear distance where the vicinage effect disappears exits between 6 ${AA}$ and 23 ${AA}$. It is expected that the vicinage effect on the energy loss (production process) in this velocity region disappears at the internuclear distance of a few ${AA}$. This result means that the transport or transmission process is important for the appearance of the vicinage effect. Moreover, the threshold internuclear distance depends on the velocity of the ion and increases as the velocity increases. The average charge of the ion increases with increase of the velocity of the ion. These mean that there is a possibility that a charge state plays an important role in the origin of the vicinage effect. In order to account for the experimental results, we discussed two models taking account of two kinds of potentials induced in response to the charge of the fragment ion in the transport process.

Journal Articles

Diffusion experiment with the accelerated, shorot-lived radioactive beam of $$^{8}$$Li

Jeong, S.-C.*; Sugai, Hiroyuki; Yahagi, Masahito*

Nihon Butsuri Gakkai-Shi, 64(9), p.687 - 691, 2009/09

We have demonstrated a non-destructive and on-line radiotracer method for diffusion studies in lithium ionic conductors, by using, as a tracer, the short-lived alpha-emitting radioisotope of $$^{8}$$Li from TRIAC (Tokai Radioactive Ion Accelerator Complex). The method has been successfully applied to measure the lithium diffusion coefficients in a typical defect-mediated lithium ionic conductor of LiGa, well demonstrating that the method is very effective to measure the diffusion in the micrometer regime per second. Anomalous composition-dependence of Li diffusion coefficients in LiGa was observed. The anomaly was discussed qualitatively in terms of the formation of defect complex and the interaction between the constituent defects. The ordering of the Li vacancies in the Li-deficient LiGa was observed for the first time in terms of the Li diffusion by the present method, and its thermodynamic aspect was discussed.

Journal Articles

On-line diffusion tracing in Li ionic conductors by the short-lived radioactive beam of $$^{8}$$Li

Jeong, S.-C.*; Katayama, Ichiro*; Kawakami, Hirokane*; Watanabe, Yutaka*; Ishiyama, Hironobu*; Imai, Nobuaki*; Hirayama, Yoshikazu*; Miyatake, Hiroari; Sataka, Masao; Sugai, Hiroyuki; et al.

Japanese Journal of Applied Physics, 47(8), p.6413 - 6415, 2008/08

 Times Cited Count:5 Percentile:22.66(Physics, Applied)

A non-destructive and on-line diffusion tracing in Li ionic conductors has been demonstrated. As a tracer, pulsed beam of $$^{8}$$Li was implanted into LiGa. By analyzing the time dependent yield of the $$alpha$$-particles decaying from $$^{8}$$Li, diffusion coefficients were extracted with a high accuracy. The ordering of Li vacancies in the Li-deficient $$beta$$ phase of LiGa was observed for the first time in terms of the Li diffusion.

Journal Articles

Diffusion of $$^{8}$$Li short-lived radiotracer in Li ionic conductors of NaTl-type intermetallic compounds

Sugai, Hiroyuki; Sataka, Masao; Okayasu, Satoru; Ichikawa, Shinichi; Nishio, Katsuhisa; Mitsuoka, Shinichi; Nakanoya, Takamitsu; Osa, Akihiko; Sato, Tetsuya; Hashimoto, Takashi; et al.

Defect and Diffusion Forum, 273-276, p.667 - 672, 2008/00

Journal Articles

X-ray diffuse scattering from carbon-ion-irradiated diamond

Sugai, Hiroyuki; Maeta, Hiroshi*; Matsumoto, Norimasa*; Kato, Teruo; Haruna, Katsuji*; Sataka, Masao; Ono, Fumihisa*

Physica Status Solidi (C), 4(8), p.2963 - 2966, 2007/07

 Times Cited Count:0 Percentile:0.02(Engineering, Electrical & Electronic)

The synthetic semiconductor diamond is potentially one of the best materials for electronic devices in severe environments like high temperature and radiation. We have studied the electrical transport properties of boron-doped synthetic semiconductor diamond and characterized natural and synthetic single crystal diamonds by measurements of the X-ray integrated scattering intensity, lattice parameter and diffuse scattering. The synthetic diamond were irradiated with 100 MeV carbon-ion at Tandem accelerator in JAEA-Tokai. After the irradiation, measurements of lattice parameters X-ray diffuse scattering were made at room temperature. The lattice parameters increased with ion fluence. The scattering intensity of the irradiated synthetic diamond diffuses asymmetrically to form a streak along the [-1 0 0] direction parallel to the reciprocal lattice vector. The result suggests that interstitial atoms and vacancies aggregate to form dislocation loop on the (100) plane.

Journal Articles

Charge state evolution of 2MeV/u sulfur ion passing through thin carbon foil

Imai, Makoto*; Sataka, Masao; Kawatsura, Kiyoshi*; Takahiro, Katsumi*; Komaki, Kenichiro*; Shibata, Hiromi*; Sugai, Hiroyuki; Nishio, Katsuhisa

Nuclear Instruments and Methods in Physics Research B, 256(1), p.11 - 15, 2007/03

 Times Cited Count:6 Percentile:45.59(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Diffusion of tritium in intermetallic compound $$beta$$-LiAl; Relation to the defect structure

Sugai, Hiroyuki

Solid State Ionics, 177(39-40), p.3507 - 3512, 2007/01

 Times Cited Count:3 Percentile:17.80(Chemistry, Physical)

The diffusion coefficients and its activation energy (103.7$$pm$$9.5 kJ/mol) for tritium in intermetallic compound $$beta$$-LiAl are determined at temperatures from 699 to 886 K. Though the present result for the diffusion coefficient is almost the same as that reported earlier, the activation energy turns out nearly twice of that (64.9$$pm$$3.8 kJ/mol) reported earlier. On the basis of the crystal structure and defect structure, the large activation energy of this study suggest that tritium diffuses interstitially and is impeded by an attractive interaction with lithium atoms in lithium sublattices.

Journal Articles

Diffusion of tritium in intermetallic compound $$beta$$-LiAl; Relation to the defect structure

Sugai, Hiroyuki

Solid State Ionics, 177(39-40), p.3507 - 3512, 2007/01

The diffusion coefficient and its activation energy (116.3 $$pm$$ 11.7 kJ/mol) of tritium in an intermetallic compound $$beta$$-LiAl are determined at temperatures from 700 to 848 K. Though the present result for the diffusion coefficient is almost the same as that reported previously, the present result for the activation energy turns out nearly twice of that (64.9 $$pm$$ 3.8 kJ/mol). The present result for the activation energy is consistent with the systematics that an increase of lithium concentration in Al-Li systems increases the activation energy, but the previous result is not. Furthermore, a consideration of the crystal structure and defect structure suggests that tritium diffuses and is impeded by the attractive interaction with lithium atom at lithium sublattices.

Journal Articles

Irradiation effects with 100 MeV Xe ions on optical properties of Al-doped ZnO films

Fukuoka, Osamu*; Matsunami, Noriaki*; Tazawa, Masato*; Shimura, Tetsuo*; Sataka, Masao; Sugai, Hiroyuki; Okayasu, Satoru

Nuclear Instruments and Methods in Physics Research B, 250(1-2), p.295 - 299, 2006/09

 Times Cited Count:24 Percentile:82.87(Instruments & Instrumentation)

We have investigated the effects on electrical and optical properties of Al-doped ZnO (AZO) semiconductor films induced by high-energy heavy ion. The AZO films with c-axis on SiO$$_{2}$$ glass substrate were prepared by a RF-sputter-deposition method at 400 $$^{circ}$$C. Rutherford backscattering spectroscopy shows that the Al/Zn composition and the film thickness are 4 % and 0.3 $$mu$$m. No appreciable change was observed in optical transparency. We find that the conductivity monotonically increases from 1.5$$times$$10$$^{2}$$ to 8$$times$$10$$^{2}$$ S/cm with increasing the fluence up to 4$$times$$10$$^{13}$$/cm$$^{2}$$, as already been observed for 100 keV Ne irradiation. The fluence of 100 keV Ne at which the conductivity takes its maximum is 3$$times$$10$$^{16}$$/cm$$^{2}$$ (7 dpa). The dpa of 100 MeV Xe at 4$$times$$10$$^{13}$$/cm$$^{2}$$ is estimated as 0.008. Hence, the conductivity increase by 100 MeV Xe ion is ascribed to the electronic excitation effects.

Journal Articles

Electrical conductivity increase of Al-doped ZnO films induced by high-energy-heavy ions

Sugai, Hiroyuki; Matsunami, Noriaki*; Fukuoka, Osamu*; Sataka, Masao; Kato, Teruo; Okayasu, Satoru; Shimura, Tetsuo*; Tazawa, Masato*

Nuclear Instruments and Methods in Physics Research B, 250(1-2), p.291 - 294, 2006/09

 Times Cited Count:15 Percentile:70.33(Instruments & Instrumentation)

We have investigated the effects on electrical properties of Al-doped ZnO (AZO) semiconductor films induced by high-energy heavy ion. The AZO films with c-axis on SiO$$_{2}$$ glass substrate were prepared by a RF-sputter-deposition method at 400 $$^{circ}$$C. Rutherford backscattering spectroscopy shows that the Al/Zn composition and the film thickness are 4 % and 0.3 $$mu$$m. We find that the conductivity monotonically increases from 1.5$$times$$10$$^{2}$$ to 8$$times$$10$$^{2}$$ S/cm with increasing the fluence up to 4$$times$$10$$^{13}$$/cm$$^{2}$$, as already been observed for 100 keV Ne irradiation. The fluence of 100 keV Ne at which the conductivity takes its maximum is 3$$times$$10$$^{16}$$/cm$$^{2}$$ (7 dpa). The dpa of 100 MeV Xe at 4$$times$$10$$^{13}$$/cm$$^{2}$$ is estimated as 0.008. Hence, the conductivity increase by 100 MeV Xe ion is ascribed to the electronic excitation effects.

Journal Articles

The Characterization of synthetic and natural single crystal diamonds by X-ray diffraction

Maeta, Hiroshi*; Matsumoto, Norimasa*; Haruna, Katsuji*; Saotome, Takao*; Ono, Fumihisa*; Sugai, Hiroyuki; Otsuka, Hideo; Ohashi, Kazutoshi*

Physica B; Condensed Matter, 376-377, p.283 - 287, 2006/04

 Times Cited Count:3 Percentile:17.92(Physics, Condensed Matter)

Natural and synthetic single crystal diamonds (type Ia, Ib, IIa and IIb) have been characterized by measurements of the X-ray integrated scattering intensity, lattice parameter and diffuse scattering. We found that the lattice parameter is smallest for natural diamond and largest for the B-doped diamond. We measured the diffuse scattering for (400) Bragg reflection for the four types of crystals. The scattering intensity of the natural crystals diffuses asymmetrically to form a streak along the [100] direction parallel to the reciprocal lattice vector. These results suggest the existence of the nitrogen atom platelets on (100) plane in the natural diamond. We also found the diffuse streaks along the [$$bar{1}$$00] direction for (400) Bragg reflection for the B-doped crystal, suggesting that boron atoms are likely to form precipitates on the (100) plane.

Journal Articles

Measurement of self-diffusion coefficients in Li ionic conductors by using the short-lived radiotracer of $$^8$$Li

Jeong, S.-C.*; Katayama, Ichiro*; Kawakami, Hirokane*; Watanabe, Yutaka*; Ishiyama, Hironobu*; Imai, Nobuaki*; Hirayama, Yoshikazu*; Miyatake, Hiroari; Sataka, Masao; Okayasu, Satoru; et al.

Journal of Phase Equilibria and Diffusion, 26(5), p.472 - 476, 2005/09

Authors developed a radiotracer method for diffusion studies in solids. The experimental test was performed by the measurement of the diffusion coefficients of Li in a sample of the compound $$beta$$LiAl using an $$alpha$$-emitting radiotracer of $$^8$$Li(T$$_{1/2}$$ = 0.84 s). It was found that the time-dependent yields of the alpha particles from the diffusing 8Li that was initially implanted in the sample could be used as a measure of the diffusivity of the tracer in a nondestructive way. The method was applied to measure the self-diffusion coefficients of Li in $$beta$$LiGa, and for investigating how the Li diffusion in the Li ionic conductors is affected by the concentration of atomic defects.

Journal Articles

Radiation defects in heavy ion-irradiated nickel at low temperature by X-ray diffuse scattering

Maeta, Hiroshi*; Matsumoto, Norimasa; Kato, Teruo; Sugai, Hiroyuki; Otsuka, Hideo*; Sataka, Masao

Nuclear Instruments and Methods in Physics Research B, 232(1-4), p.312 - 316, 2005/05

 Times Cited Count:1 Percentile:14.38(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Charge state distribution and its equilibration of 2 MeV/u sulfur ions passing through carbon foils

Imai, Makoto*; Sataka, Masao; Kawatsura, Kiyoshi*; Takahiro, Katsumi*; Komaki, Kenichiro*; Shibata, Hiromi*; Sugai, Hiroyuki; Nishio, Katsuhisa

Nuclear Instruments and Methods in Physics Research B, 230(1-4), p.63 - 67, 2005/04

 Times Cited Count:8 Percentile:52.75(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Measurement of diffusion coefficients in solids by the short-lived radioactive beam of $$^{8}$$Li

Jeong, S.-C.*; Katayama, Ichiro*; Kawakami, Hirokane*; Watanabe, Yutaka*; Ishiyama, Hironobu*; Miyatake, Hiroari*; Sataka, Masao; Okayasu, Satoru; Sugai, Hiroyuki; Ichikawa, Shinichi; et al.

Nuclear Instruments and Methods in Physics Research B, 230(1-4), p.596 - 600, 2005/04

 Times Cited Count:6 Percentile:45.49(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Evidence for a hard gap and Wigner lattice in heavily boron-doped synthetic diamond

Sudo, Tomoko*; Ohashi, Kazutoshi*; Sato, Toshimaro*; Ota, Eiji*; Okayasu, Satoru; Sugai, Hiroyuki

Physical Review B, 71(4), p.045211_1 - 045211_7, 2005/01

 Times Cited Count:1 Percentile:7.18(Materials Science, Multidisciplinary)

We have measured low frequency generation-recombination noise (g-r moise) spectra of a heavily boro-doped diamond crystal over the temperature range 20-300 K. The experimental results show that there are two peaks in the g-r noise spectrum at 120 K and 67 K, respectively. The 120 K peak corresponds to experimental evidence for the existence of hard gap having width of 10.4 meV. We interpret the 67 K peak as evidence for Wigner lattice formation whose gap width is 5.8 meV.

Journal Articles

Simulation study on the measurements of diffusion coefficients in solid materials by short-lived radiotracer beams

Jeong, S.-C.*; Katayama, Ichiro*; Kawakami, Hirokane*; Ishiyama, Hironobu*; Miyatake, Hiroari*; Sataka, Masao; Iwase, Akihiro*; Okayasu, Satoru; Sugai, Hiroyuki; Ichikawa, Shinichi; et al.

Japanese Journal of Applied Physics, Part 1, 42(7A), p.4576 - 4583, 2003/07

 Times Cited Count:14 Percentile:50.29(Physics, Applied)

no abstracts in English

Journal Articles

Simulation study on the measurements of diffusion coefficients in solid materials by short-lived radiotracer beams

Jeong, S.-C.*; Katayama, Ichiro*; Kawakami, Hirokane*; Ishiyama, Hironobu*; Miyatake, Hiroari*; Sataka, Masao; Iwase, Akihiro; Okayasu, Satoru; Sugai, Hiroyuki; Ichikawa, Shinichi; et al.

Japanese Journal of Applied Physics, Part 1, 42(7A), p.4576 - 4583, 2003/07

no abstracts in English

57 (Records 1-20 displayed on this page)