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Journal Articles

Surface modification effects on hydrogen absorption property of a hydrogen storage alloy by short pulse laser irradiation

Abe, Hiroshi; Shimomura, Takuya; Tokuhira, Shinnosuke*; Shimada, Yukihiro*; Takenaka, Yusuke*; Furuyama, Yuta*; Nishimura, Akihiko; Uchida, Hirohisa*; Daido, Hiroyuki; Oshima, Takeshi

Proceedings of 7th International Congress on Laser Advanced Materials Processing (LAMP 2015) (Internet), 4 Pages, 2015/08

A short pulse laser (the nanosecond and femtosecond) was applied to hydrogen absorbing alloys surface layer, and a surface modification experiment was put into effective to aim at improvement of hydrogen adsorption functionally. It was investigated about correlation between an initial hydrogen absorption reaction rate of hydrogen alloys and a laser irradiation in this research. The laser irradiation condition was done with pulse width 100 fsec and energy 0.2 - 3.4 mJ/pulse. It blazed down on hydrogen absorbing alloys (LaNi$$_{4.6}$$Al$$_{0.4}$$) and changed local order in the surface. As a result, the initial hydrogen absorption reaction rate was 1.5 - 3.0 times as fast as a irradiated sample, and the result and laser irradiated sample found out that a hydrogen absorption function improves. A laser irradiation can conclude to be effective in surface modification of the hydrogen storage materials.

Journal Articles

Development of optical fiber Bragg grating sensors for structural health monitoring

Shimada, Yukihiro; Nishimura, Akihiko

Journal of Laser Micro/Nanoengineering, 8(1), p.110 - 114, 2013/01

 Times Cited Count:6 Percentile:37.43(Nanoscience & Nanotechnology)

A fiber Bragg grating (FBG) sensor with heat resistance was produced via a point microfabrication technique using a femtosecond pulse laser. The FBG sensor was reinforced by weaving with a carbon fiber tape. As a result, both high strength and a structure for mounting the sensor were readily incorporated. In a high-temperature tolerance evaluation of the FBG sensor, the temperature and strain were measured by the sensor at 600 $$^{circ}$$C. Therefore, the sensor is effective, and in addition, the problems associated with mounting the sensor on high-temperature piping have been eliminated.

Journal Articles

Instrumentation device and surface control technology for coolant piping system of nuclear power plants

Nishimura, Akihiko; Terada, Takaya; Shimada, Yukihiro; Yonemoto, Yukihiro*; Yamada, Tomonori

Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 5 Pages, 2012/07

Instrumentation devices using laser technologies were developed for maintenance of coolant piping system. For instrumentation devices, seismic monitoring by optical fiber sensors was able to detect vibration of piping system. X-ray absorption contrast by synchrotron radiation clarified convection motion inside a molten pool produced by laser welding. For surface control technologies, a new probing system was under development for heat exchanger tubes by laser cladding. And laser ablation could be used for surface cleaning. These technologies are expected for maintenance of the piping system of nuclear power plants.

Journal Articles

Developing maintenance technologies for FBR's heat exchanger units by advanced laser processing

Nishimura, Akihiko; Shimada, Yukihiro

Proceedings of 19th International Conference on Nuclear Engineering (ICONE-19) (CD-ROM), 7 Pages, 2011/10

Laser processing technologies were developed for the purpose of maintenance of FBR's heat exchanger units. Ultrashort laser processing fabricated fiber Bragg grating sensor for seismic monitoring. Fiber laser welding with a newly developed robot system repair cracks on inner wall of heat exchanger tubes. Safety operation of the heat exchanger units will be improved by the advanced laser processing technologies. These technologies are expected to be applied to the maintenance for the next generation FBR's.

Journal Articles

Development of inspection and repair technology for the micro cracks on heat exchanger tubes

Nishimura, Akihiko; Shobu, Takahisa; Oka, Kiyoshi; Yamaguchi, Toshihiko; Shimada, Yukihiro; Mihalache, O.; Tagawa, Akihiro; Yamashita, Takuya

Reza Kako Gakkai-Shi, 17(4), p.207 - 212, 2010/10

A prototype probe system with a hybrid optical fiber scope was designed for inspecting and re-pairing the micro cracks on heat exchanger tubes in fast breeder reactors (FBRs). It comprised a laser processing head combined with an eddy current testing unit. Ultrashort laser pulse ablation was used to remove work-hardened layers. And spot laser welding was used to repair the micro cracks. This system has both safe and economical options for the maintenance of FBRs because it extends the lifetime of the heat exchangers.

Journal Articles

Design of monitoring system of high temperature piping system by heat resistant fiber Bragg grating

Shimada, Yukihiro; Nishimura, Akihiko; Yoshikawa, Masanari*; Kobayashi, Takao*

Journal of Laser Micro/Nanoengineering, 5(1), p.99 - 102, 2010/02

 Times Cited Count:7 Percentile:38.85(Nanoscience & Nanotechnology)

Ultrafast laser processing was applied to fabricate fiber Bragg gratings with specific wavelength characteristics. The high-temperature properties were examined. Reflection was not changed greatly when it was exposed to temperature of up to 600 $$^{circ}$$C for 1 hour. A time-domain detector of FBG was produced for vibration measurement. FBG of three wavelength was processed in one optical fiber, and the possibility of the multipoint measurement was shown. It was proposed that the heat-resistant FBG sensors combined with wavelength tunable laser will become powerful tool in surveillance for coolant piping system in nuclear power plants.

Journal Articles

Development of a health monitoring system using a thermal-resistant fiber Bragg grating for fast reactor power plants; Performance evaluation of a thermal-resistant FBG for strain measurement

Saruta, Koichi; Tsukimori, Kazuyuki; Shimada, Yukihiro; Nishimura, Akihiko; Kobayashi, Takao*

Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.219 - 222, 2009/08

A thermal-resistant fiber Bragg grating (FBG) fabricated by femtosecond laser processing was examined to evaluate the performance as a strain sensor, compared with a conventional FBG sensor. Each FBG was affixed on a stainless-steel beam along with a strain gauge to measure the Bragg wavelength shift as a function of strain. We used the intensity of the reflection spectra from the FBGs as a weighting factor to determine the Bragg wavelengths. Although the strain sensitivity for the thermal-resistant FBG was found to be 0.34 pm/$$mu$$$$varepsilon$$, a measurement accuracy of $$pm$$3$$mu$$$$varepsilon$$ was able to be achieved by employing the Bragg wavelength determination algorithm, which was comparable to a measurement accuracy of $$pm$$2$$mu$$$$varepsilon$$ for the conventional FBG sensor.

Journal Articles

Development of inspection and repairing technology for FBR heat exchanger tubes, 2; Preparation of operation software and performance check

Nishimura, Akihiko; Oka, Kiyoshi; Yamaguchi, Toshihiko; Akatsu, Tomohiro*; Seki, Takeshi*; Mihalache, O.; Shimada, Yukihiro; Tagawa, Akihiro; Yamashita, Takuya

Nihon Hozen Gakkai Dai-6-Kai Gakujutsu Koenkai Yoshishu, p.250 - 253, 2009/08

In order to maintain FBR heat exchanger tubes, a new probe system was designed. A coupling unit and operational software are key components in the second year. The coupling unit to combine a high energy laser beam and optical fiberscope images was developed. The operational software successfully controlled an eddy current testing device and a laser processing head.

Journal Articles

Cu K$$alpha$$ pulse generation in an X-ray tube with a plasma cathode induced by a femtosecond laser pulse

Yamada, Hidetaka; Murakami, Hiroshi; Shimada, Yukihiro

Radiation Physics and Chemistry, 78(6), p.375 - 379, 2009/06

 Times Cited Count:1 Percentile:10.95(Chemistry, Physical)

no abstracts in English

Journal Articles

Development of time-resolved X-ray fluorescence spectroscopy system using an X-ray tube driven by ultrafast pulsed laser

Yamada, Hidetaka; Murakami, Hiroshi; Shimada, Yukihiro

Hyomen Kagaku, 29(7), p.413 - 417, 2008/07

A femtosecond-laser-driven X-ray source and an X-ray focusing system have been developed for the time-resolved X-ray fluorescence spectroscopy. The X-ray source, in which a plasma cathode induced by a 10$$^{13}$$-W/cm$$^2$$ laser pulse serves as an electron source of an X-ray tube, provides 10$$^9$$ Cu K$$_alpha$$ photons in 4$$pi$$sr per pulse. The X-ray pulse duration is measured to be about two hundred nanoseconds. Emission analysis of the plasma cathode indicates that the temporal characteristics of the X-ray pulse are determined by the dynamics of the plasma particles under the electrostatic shielding against the applied voltage in the X-ray tube. As for the X-ray focusing system, a focal spot size by a polycapillary lens is measured and the enhancement of X-ray fluorescence intensity due to the lens is demonstrated.

Journal Articles

Transient-Grating FROG for measurement of sub-10-fs to few-ps amplified pulses

Pirozhkov, A. S.; Mori, Michiaki; Ogura, Koichi; Nishimura, Akihiko; Murakami, Hiroshi; Shimada, Yukihiro; Sagisaka, Akito; Orimo, Satoshi; Kimura, Toyoaki; Daido, Hiroyuki

Advanced Solid-State Photonics; OSA Technical Digest Series (CD-ROM), p.MC8_1 - MC8_3, 2008/01

Oral presentation

Remote sensing of sound velocity by pulse-laser induced stimulated brillouin scattering

Shimada, Yukihiro; Nishimura, Akihiko

no journal, , 

no abstracts in English

Oral presentation

Hard-X-ray generation in a femtosecond-laser-driven X-ray diode

Yamada, Hidetaka; Murakami, Hiroshi; Shimada, Yukihiro

no journal, , 

no abstracts in English

Oral presentation

Generation of hard X-ray pulse in a femtosecondlaser-driven X-ray tube and its application to time-resolved spectral measurements

Yamada, Hidetaka; Murakami, Hiroshi; Shimada, Yukihiro

no journal, , 

no abstracts in English

Oral presentation

Development of time-resolved X-ray fluorescence measurement system with ultrafastlaser-driven X-ray diode

Yamada, Hidetaka; Murakami, Hiroshi; Shimada, Yukihiro

no journal, , 

no abstracts in English

Oral presentation

Current status of non-destructive checking techniques on Fast Breeder Reactor and its improvement

Yamashita, Takuya; Nishimura, Akihiko; Tsuchida, Noboru; Yamaguchi, Toshihiko; Oka, Kiyoshi; Fujiki, Kazunari*; Shimada, Yukihiro

no journal, , 

The preservation techniques of safety research on "Monju" and the next generation Fast Breeder Reactors have been exhibited. The exhibition consists of (1) EMAT, (2) ECT, (3) Laser Processing Head. Both (1) and (2) are the checking techniques for the cracks on nuclear power plants, while (3) is the repairing technique for the heat exchanger. In 2009, these three techniques will have been integrated to be a new probing system. The hybrid optical fiber has been involved in (3), which the project "photo-Medical Valley in JAEA-KANSAI are now developing as a fiber surgery device.

Oral presentation

Remote sensing of sound velocity by pulse-laser induced stimulated light scattering

Shimada, Yukihiro; Nishimura, Akihiko

no journal, , 

We developed the pulsed laser induced light scattering method. This method is performed in generation of a sound wave, and a detection process by non-contact. This technique has the feature measurement of the frequency dynamics range of a broad sound wave excelled in possible. We performed the principle actual proof using the liquid sample, and as a result of comparing a sonic measurement numerical value with the supersonic method of a contact type, we were well in agreement.

Oral presentation

Vibration and deformation monitoring for high temperature structures by heat-resistant FBG

Shimada, Yukihiro; Masuzumi, Takashi; Nishimura, Akihiko; Doi, Motoo*; Tsukimori, Kazuyuki

no journal, , 

We performed irreversible lattice processing into the quartz board using the technique of non-heat processing which used femtosecond laser. The heat-resistant evaluation was performed for the purpose of development of heat-resistant FBG for always supervising heat transfer system vibration and modification of a high temperature structure. As a result, the intensity ratio of diffraction light did not change but after rising temperature up to 950 $$^{circ}$$C showed that the system of heat-resistant FBG was effective as a local vibration of high temperature piping, and the distorted detection technique.

Oral presentation

Manufacture of heat-resistant FBG by femto-second laser processing for high temperature structure surveillance

Shimada, Yukihiro; Nishimura, Akihiko; Masuzumi, Takashi; Tsukimori, Kazuyuki

no journal, , 

The FBG (Fiber Bragg Grating) sensor already put in practical use as a method of carrying out the monitoring of modification of a structure and the vibration has a fault in which the durability under high temperature environment is inferior. In order to conquer this fault, we performed the micro fabrication in the silica optical fiber by femtosecond laser, and created a heat-resistant periodic refractive-index structure.

Oral presentation

Development of heat-resistant FBG sensor for high temperature structures monitoring

Masuzumi, Takashi; Tsukimori, Kazuyuki; Shimada, Yukihiro; Nishimura, Akihiko

no journal, , 

Strain sensors, which can be used for integrity monitoring of plant components and piping during the operation period continuously, are effective from the point of view of proactive maintenance. FBG (Fiber Bragg Grating) sensor is one of the expective sensors and is used in various plants and civil engineering and construction fields except for high temperature service. In order to apply to the component and piping of fast reactor, heat resistance is an indispensable feature of the sensor. In this study, we tried to improve heat resistance of FBG by using femtosecond laser in the process. The heat resistance at the FBGs was examined experimentally and the results compared with those of ordinary FBGs.

48 (Records 1-20 displayed on this page)