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Rapp, L.*; Matsuoka, Takeshi*; Firestein, K. L.*; Sagae, Daisuke*; Habara, Hideaki*; Mukai, Keiichiro*; Tanaka, Kazuo*; Gamaly, E. G.*; Kodama, Ryosuke*; Seto, Yusuke*; et al.
Physical Review Research (Internet), 6(2), p.023101_1 - 023101_18, 2024/04
It is generally known that irradiating a solid surface with a laser pulse of ultra-relativistic intensity generates a plasma on the surface, which in turn creates an ultrahigh pressure inside. In this study, the crystal structure analysis of high-pressure phases generated inside silicon single-crystals irradiated by this laser was performed using the diffraction system at the Stress and Imaging apparatus of BL22XU, which is a JAEA-BL. The results obtained confirm the existence of high-pressure phases that silicon is said to possess: body-centered, rhombohedral, hexagonal, and tetragonal phases in the interior. We can get the results that the crystal structure of silicon polymorphs of being include body-centered, rhombohedral, hexagonal-diamond, tetragonal exists. In the future, we will accumulate data and apply them to control the internal structure, strength, and functionality of materials.
Daido, Hiroyuki*; Yamada, Tomonori
ILT-APR-34; ILT 2023 Nempo (Internet), p.1 - 5, 2023/07
The decommissioning of Fukushima and the contribution to reconstruction have become national issues. The authors participated in the "Analysis of fine particles generated by laser processing and development of nuclide identification method" (represented by Professor Shuichi Hasegawa of the University of Tokyo), which was adopted as one of the JAEA's publicly solicited projects for this purpose, from FY 2018 to FY 2021 as a subcontractor, The authors conducted research on the observation, evaluation and analysis of the interaction between lasers and various laser-irradiated targets. This report outlines the results of the research in which the authors took part. In the experiments, laser irradiation was carried out on test specimens set up in an irradiation chamber, and shadowgraphs were taken using a high-speed camera and a He-Ne laser. As an example of the experimental results, shadowgraphs of metal (stainless steel) and metal oxide (zirconia), irradiation traces after laser irradiation, and the relationship between laser irradiation power and jet mass are shown, and the interaction between the laser and the metal or metal oxide is discussed. The results will not only contribute to the decommissioning technology of the Fukushima Daiichi NPP, but also to laser processing technology and laser interaction research.
Daido, Hiroyuki*; Yamada, Tomonori; Saruta, Koichi; Miyabe, Masabumi; Ito, Chikara; Shibata, Takuya; Inoue, Kaoru*; Terabayashi, Ryohei*; Hasegawa, Shuichi*
Physica Scripta, 98(3), p.035112_1 - 035112_22, 2023/02
Times Cited Count：1 Percentile：22.15(Physics, Multidisciplinary)Characterization of kW class quasi-continuous wave (a pulse duration of 10 ms) laser interaction with metal targets and those with metal oxide targets are presented in respect to the laser induced breakdown and the successive laser induced melting and evaporation coupled with a mechanical response followed by ejection of various kinds of particles and fragments. An experiment was performed using fiber lasers coupled with a high-speed camera to observe dynamics of the interaction. Ejected fine particles were collected using a cascade impactor and a home-made collector and were observed with electron microscopes. Shapes of irradiation marks were observed with a digital optical microscope. We also measured total ejected mass from a target. The experimental results reveal that firstly the laser threshold intensity of the interaction with the metal target was lower and more stable than those with the metal oxide targets. Secondly, in the stainless steel targets, the dynamics of molten layer created by thermal conduction from the laser heated thin layer and successive particle ejection with less mechanical response by the adjacent solid layer are dominant processes, while in the metal oxide targets, the fracturing in the relatively deeper interaction region coupled with brittle material response having relatively large laser shot to shot fluctuation appears to play a significant role in addition to the laser induced melting.
Kumada, Takayuki
Purazuma, Kaku Yugo Gakkai-Shi, 96(4), p.176 - 180, 2020/04
We have developed time-resolved reflectivity measurement system using femtosecond laser pulses, which can measure structure of thin films generated by non-thermal effect.
Muramatsu, Toshiharu
JAEA-Research 2019-008, 111 Pages, 2019/11
JAEA-Research-2019-008.pdf:8.64MB
A general-purpose three-dimensional thermohydraulics numerical simulation code SPLICE (residual Stress control using Phenomenological modeling for Laser welding repair process In Computational Environment) was designed to deal with gas-liquid-solid consolidated incompressible viscous flows with a phase change process in various laser applications. Main features of the SPLICE code are as follows: (1) A multi-scale model is used to simulate complicated phenomena, such as welding to solidification of metal materials, thermal and mechanical interactions among gas, liquid and solid phases, etc., (2) SPLICE code is applicable for the evaluation of welding, cutting, piercing, coating, additive manufacturing, etc. and (3) A graphic user interface (GUI) is prepared for users to easy utilization of the SPLICE code. This report describes the details of the mathematics, physics, numerics, sample applications of the SPLICE code.
Nishimura, Akihiko; Takenaka, Yusuke*; Furusawa, Akinori; Torimoto, Kazuhiro; Ueda, Masashi; Fukuda, Naoaki*; Hirao, Kazuyuki*
E-Journal of Advanced Maintenance (Internet), 9(2), p.52 - 59, 2017/08
no abstracts in English
Muramatsu, Toshiharu
KANRIN, 68, p.14 - 18, 2016/09
no abstracts in English
Muramatsu, Toshiharu
RIST News, (60), p.22 - 27, 2016/01
no abstracts in English
Nishimura, Akihiko; Takenaka, Yusuke*; Furuyama, Takehiro*; Shimomura, Takuya; Terada, Takaya; Daido, Hiroyuki
Journal of Laser Micro/Nanoengineering, 9(3), p.221 - 224, 2014/11
Times Cited Count：0 Percentile：0.00(Nanoscience & Nanotechnology)Heat resistant FBG sensors were developed by femtosecond laser processing to apply them to high temperature operated piping system of nuclear power plants. The FBG sensor was installed on the surface of a steel blade and a vibration test was conducted to detect the resonant vibration frequency of the vibrating blade. The FBG sensor had the heatproof performance at 600
C. A frequency stabilized sensing system using a tunable laser was tested for structural health monitoring in daily operation of nuclear power plants. The FBG sensor was installed on the surface of a steel blade for vibration induced strain measurements. Welding, brazing, soldering and noble metal powder adhesive were discussed for molding the FBG sensors.
Nishimura, Akihiko; Terada, Takaya; Takenaka, Yusuke*; Furuyama, Takehiro*; Shimomura, Takuya
Proceedings of 22nd International Conference on Nuclear Engineering (ICONE-22) (DVD-ROM), 6 Pages, 2014/07
Since 2007, JAEA has been developing laser based technologies of structural health monitoring. The FBG sensor made by femtosecond laser processing will be the best candidate. To make the best use of the heat resistant characteristic, the FBG sensor was embedded in metal mold by laser cladding. A groove was processed to the surface of a SUS metal plate. We used a QCW laser to weld a filler wire on the plate. A series of weld beads perfectly formed a sealing clad on the groove. Though the FBG sensor was buried tightly, no degradation on the reflection spectrum was detected after the processing. The FBG sensor could detect the vibration of the plate caused by impact shocks and audio vibration. The reflection peak of the FBG sensor under laser cladding condition was shifted to be 6 nm. We demonstrated that the corresponded temperature derive from the reflection peak shift reached 600 degrees in heat shock experiments. The installation procedure of a FBG sensor using a portable laser cladding machine was described.
Fukumoto, Ichiro; Omura, Etsuji*
Seimitsu Kogakkai-Shi, 67(6), p.916 - 921, 2001/06
no abstracts in English
Nishimura, Akihiko; Usami, Tsutomu*; Deki, Kyoichi*; Shimobeppu, Y.*; Hayasaka, N.*; Arisawa, Takashi
Technical Digest on 4th Pacific Rim Conference on Lasers and Electro-Optics (CLEO/Pacific Rim 2001), p.II_280 - II_281, 2001/00
no abstracts in English
猿田 晃一; 直江 崇; 勅使河原 誠; 二川 正敏; 梁 輝
Erkan Nejdet*
JP, 2021-188317 Patent licensing information
【課題】加工により発生するヒュームの大気中への拡散防止およご前記ヒュームを回収可能な加工装置を提供すること。 【解決手段】 加工対象物10の局所部16を溶融するために、前記局所部16を加熱する加熱ヘッド122を備えた加熱装置120と、前記局所部16と前記加熱ヘッド122とを繋ぐ加熱エリア20の外側にミストカバー層40を形成するミスト層形成装置140と、液体からミスト41を生成して前記ミスト層形成装置140に供給するミスト生成装置130と、前記加熱ヘッド122により加熱されて溶融する前記局所部16を前記加工対象物10の加工場所12に沿って移動させる加工位置移動機構30と、を備え、前記ミスト層形成装置140から噴霧された前記ミスト41により、前記加熱エリア20の外周を覆う前記ミストカバー層40を形成した、ことを特徴とする加工装置。
Miyabe, Masabumi; Iwata, Yoshihiro; Terabayashi, Ryohei*; Hasegawa, Shuichi*
no journal, ,
Various laser processing techniques such as laser cutting and laser decontamination are being considered for use in decommissioning. We are developing emission and absorption spectroscopy techniques to detect contamination in the work environment during laser processing and to evaluate the decontamination efficiency of materials in a rapid and non-contact manner. Atomic species ejected from the surface of a material irradiated by an intense laser beam absorb the optical energy of the irradiating laser via inverse bremsstrahlung process and rapidly grow into laser plasma. Therefore, the characteristics of the resulting laser plasma are strongly affected by the pulse length of the ablation laser. In previous studies. However, little was known about the emission and absorption spectra of laser irradiation of about 10 ms, which is often used in laser processing. Therefore, in this study, we measured the emission spectra of various materials such as zirconia using a QCW fiber laser with a pulse length of about 10 ms. The resultant emission spectra are very similar to the characteristics previously reported for long-pulse lasers, and basic spectral characteristics were clarified, such as the greater contribution of molecular emission compared to atomic emission, and the stronger the emission intensity for elements that are more likely to undergo combustion reactions in air. This provided basic data for spectroscopic measurements for laser processing.
Miyabe, Masabumi
no journal, ,
We have studied the applicability of spectroscopic technique for obtaining process information needed for laser decommissioning and other various laser processing techniques. When a material is irradiated with intense laser pulses, atomic species eject from the surface which absorbing the light energy via inverse Bremsstrahlung process and laser plasma grows rapidly. Thus various properties of the generated laser plasma strongly depend on the duration of the laser irradiation. Although previous studies have reported differences in emission characteristics between Nd:YAG lasers with about 10 ns-pulse and long-pulse lasers with about 100 ns-pulse, little is known about the emission and/or absorption characteristics of the plasma produced through the irradiation of longer than 10 ms duration, which is common in current laser processing. In this study, we investigated the emission characteristics of the laser plasma produced in atmospheric air using a QCW (Quasi Continuous Wave) fiber laser. As a result, it was found that the emission intensity of oxide molecules is enhanced. Also, only for zirconia and gadolinia targets, strong emission lines of atomic species were observed. From the images recorded during laser ablation process, it was observed that the sputtered materials were burned while floating in the air and this might contribute to strong emission signal of atomic species. This study demonstrated the possibility of applying emission spectroscopy to laser processing to evaluate elemental composition of the processed materials.
Oka, Kiyoshi*; Nishimura, Akihiko
no journal, ,
no abstracts in English
Kosuge, Atsushi
no journal, ,
Carbon fiber reinforced plastic is a resin-based composite material reinforced with carbon fiber, which is a high-performance fiber having features such as light weight, high strength, and high rigidity. CFRTP using a thermoplastic resin has a short molding time and is excellent in economy, and the thermoplastic resin melts when heat is applied, so that it can be recycled. On the other hand, CFRP and CFRTP are known as difficult-to-process materials that are difficult to process, and in laser processing, a heat-affected region is generated in which the resin evaporates and carbon fibers are exposed when irradiated with a laser. Since there is a concern that this heat-affected zone will reduce the strength of CFRP and CFRTP, it has become an important issue in recent years to find processing conditions that keep this heat-affected zone small. Search for conditions.
Kumada, Takayuki; Akagi, Hiroshi; Itakura, Ryuji; Otobe, Tomohito; Nishikino, Masaharu; Yokoyama, Atsushi
no journal, ,
Dynamics of femtosecond laser ablation of transparent polymers was examined using time-resolved reflectivity. When a pump pulse with fluence above ablation thresholds of 0.8-2.0 J/cm
was irradiated to these polymers, we observed oscillation of the reflectivity, which was caused by the interference between the reflected probe pulses from the sample surface and thin layer due to non-thermal photomechanical effect of spallation. As the fluence of the pump pulse increased, the separation velocity of the thin layer increased from 6 km/s to the asymptotic value of 11 km/s. We consider that the velocities are determined by shock-wave velocities of the photo-excited layer.
Kumada, Takayuki; Akagi, Hiroshi; Itakura, Ryuji; Otobe, Tomohito; Yokoyama, Atsushi
no journal, ,
It has been proposed that not only thermal but also non-thermal effect plays an important role on femtosecond laser ablation. In this study, we develop a high-sensitivity time-resolved reflectivity measurement system to study the non-thermal effect on the femtosecond laser ablation of polymers.
ray irradiation effects of a multi functional laser processing head for fuel debris removalMuramatsu, Toshiharu; Nakamura, Masaki; Abe, Hiroshi*
no journal, ,
no abstracts in English
