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Volume 24, Issue 2
Displaying 1-17 of 17 articles from this issue
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Tomoo FUJIOKA1996 Volume 24 Issue 2 Pages 153
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSDownload PDF (129K) -
Akira TSUNEMI, Hideo TASHIRO1996 Volume 24 Issue 2 Pages 154-164
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSThis paper reviews laser surface cleaning of solid materials from paint or radioactive contaminations by means of irradiation of lasers. The recent developments of high power pulsed lasers have enabled us to remove and clean steel and concrete surfaces by laser ablation with a reasonable rate as efficient and environment-conscious technique. Through comparison of excimer, YAG and CO2 lasers, the prospect of TEA CO2 lasers is emphasized.View full abstractDownload PDF (1500K) -
Ian A. WATSON, Alvin YOU, See W. OON, Duncan E. S. STEWART-TULL1996 Volume 24 Issue 2 Pages 165-173
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSCO2 and Nd: YAG lasers were used to clean carboniferous and blonde sandstone which were contaminated with pollution, microbial growth and bryophyte. The effect of translation velocity was investigated to find the optimum value for cleaning. Analysis of the stone, after laser treatment and 15 month's exposure to the Glaswegian climate, indicated that no growth, recontamination or effects of pollution had occurred for some settings of the laser parameters. Energy dispersive x-ray spectroscopy was used to quantify the efficacy of laser remediation by analysing the chemical composition of the stone's surface in the treated and untreated regions after laser treatment. The aluminium content of the sample was found to give the most sensi-tive measure of the CO2 laser cleaning efficiency.View full abstractDownload PDF (1464K) -
Bunji SHIGEMATSU, Tsutomu SAITO1996 Volume 24 Issue 2 Pages 174-181
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSWe have developed an underwater survey system using a scanning sensor and a GPS (Global Positioning System) sensor instrument that is capable of providing high resolution data in low-visibility water. A laser is used as a light source which limits highly directional pulsed beams with high intensity. Topology is surveyed by detecting the propagation time of pulsed laser beams which are reflected at the bottom of the sea. The laser system is installed in a ship and the beam are introduced to a remotely-operated-vehicle (ROV) through an optical fiber. The extremely high propagation velocity of the beam in the water compared with that of an ultrasonic beam and the scanning survey system enable us to measure a large area within a short time. A deeper system has been designed and will have a 50 m depth capability.View full abstractDownload PDF (1003K) -
Hirofumi KAMATA, Takeo MIMORI, Masaaki TACHIIWA, Kenji SUGIMOTO1996 Volume 24 Issue 2 Pages 182-190
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSUnlike the deep radio-activation of biological shield concrete of nuclear power reactors, the concrete surfaces at JRTF (JAERI's Reprocessing Test Facility) are contaminated by radioactive material including α-nuclide up to depth of about 10mm from the top surface. Two methods of decontamination of such concrete are described here. In the first method, laser irradiation at high energy density and low scanning speed is made to cause instantaneous melting of the elements of the concrete (mainly oxides of silicon, aluminum, and calcium) by intense heat, resulting in the formation of a glass layer, which is then removed easily and collected by appropriate means. In the second method, using lower energy density and higher scanning speeds, instantaneous evaporation of the water in the concrete is induced and rapid build-up pressure occurs without surface melting. This phenomenon causes spalling of the contaminated surface layer. Debris are collected by appropriate means.View full abstractDownload PDF (1424K) -
Kenji SUGIMOTO, Toshihiro AIHARA, Hirofumi KAMATA, Suguru KANAOKA1996 Volume 24 Issue 2 Pages 191-199
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSMarble is cut with laser, the crystal water may be scattered due to heating, or the several millimeters extent around the cutting edge provided the white line-shapes. Therefore, the laser cutting could not be applied. This study deals with proposing a new pulse waves cutting and being absorbed a water beforehand into the marble. And the evaporation of the water around the cutting section consumes the heat during the laser cutting. This method allows the excess heat to be eliminated. As a result, we succeeded in preventing the formation of white lines at the cutting edge of the marble and the edge quality is greatly improved. Using this method, a large wall mosaic having a height of 3.5m and length of 30m was completed in the entrance of a new sky-scraper in Kasumigaseki, Tokyo. And this mosaic was assembled the copper plates on which patina was formed and the marble inlays.View full abstractDownload PDF (1973K) -
Yoshihiro YOKOYAMA, Kenji SUGIMOTO1996 Volume 24 Issue 2 Pages 200-208
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSConventional tiles are a traditional materials that dates from ancient Egypt, and are used to cover floors, walls and roofs, etc. Until recently, the dimension of economical tiles were limited to a 300mm square. However, in 1985 the authers, et al., developed a method of manufacturing extra-large tiles having a dimension of 6 × 1000 × 3000 mm3. This was achieved by combining approximately 50% of inorganic fiber (wollastonite fiber) in the raw material of the tile. Upsizing of the tiles is effective in preventing contamination as the tile seams are reduced. Applications of these large tiles include scientific experiment tables, kitchen walls, bathroom walls, exterior walls and floors, etc. However, when cutting the large tiles with a diamond cutter, the corners often chip at the final point, and thus cutting of complicated shapes or complicated curves is difficult. The vibration that occurs during cutting is also a great factor in cracks. A laser processing machine was introduced as a cutting method, and in combination with an NC controller, we tested cutting of free-shaped large tiles. However, molten dross of a diameter of 0.5 to 1.0mm formed when cutting the large tile, and a highly precise cutting was not possible. The seam dimension cannot be guaranteed when the tiles are laid with the dross adhered. Thus, we used CO2 gas Laser having a maximum power of 3000W, and obtained the optimum cutting conditions for large tiles. Our conclusion on our study regarding the cutting conditions for ceremics are discussed below.View full abstractDownload PDF (2929K) -
R. M. A. AZZAM1996 Volume 24 Issue 2 Pages 209-219
Published: February 29, 1996
Released on J-STAGE: July 30, 2010
JOURNAL FREE ACCESSEllipsometry provides the means for both in-situ and ex-situ nondestructive characterization of optical coatings based on the change of polarization that accompanies light reflection at oblique incidence. For optical coatings deposited on transparent substrates, reflection and transmission ellipsometry can be performed simultaneously to increase the information throughput of the optical monitor. In-situ monitoring with fast ellipsometers is suited for process control. The refractive indices of deposited layers, layer thicknesses, and void fractions in a coating can be determined. This paper briefly reviews the principles, instrumentation, and some applications of ellipsometry.View full abstractDownload PDF (1244K) -
Angela DUPARRÉ, Axel KIESEL, Stefan GLIECH1996 Volume 24 Issue 2 Pages 220-228
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSExperimental studies are described of the problem of scattering and roughness modification after deposition of optical thin films as used for application in laser components. BK7 substrates with different surface finish have been coated with MgF2, LaF3, Si02 and Nb2O5 films as representatives of low index/ high index columnar structured and structureless films, respectively. Total integrated scattering (TIS) and angle resolved scattering (ARS) measurements at 632.8 nm and 325 nm as well as atomic force microscopy (AFM) investigations demonstrate that coating can result not only in roughness and scattering enhancement but also in its reduction.View full abstractDownload PDF (1557K) -
Hideki TAKEDA, Yuichi TERAMURA, Fumihiko KANNARI1996 Volume 24 Issue 2 Pages 229-234
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSPassive Q-switching operation of a flashlamp-pumped Ti: sapphire laser utilizing an intracavity telescope filled with a liquid Brillouin medium, C2Cl3F3, is described. A narrow linewidth seed pulse is generated with an auxiliary resonator consisting of a grazing incidence grating to reduce the stimulated Brillouin scattering threshold. The magnificationof a telescope and an auxiliary resonator length were designed so that a large TEM00 mode volume is obtained in the gain medium. When the Q-switch timing was optimized by inserting a loss in the auxiliary resonator, an output energy of nearly 40 mJ in a-20-ns pulse was obtained.View full abstractDownload PDF (675K) -
Shinki NAKAMURA, Katsumi MIDORIKAWA, Minoru OBARA, Koichi TOYODA1996 Volume 24 Issue 2 Pages 235-243
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSWe have measured the characteristics of a flashlamp pumped Ti: sapphire laser in which a double step simmer circuit and a solid state florescent converter (KTF-2 filter glass) were used in order to extend the life time of the laser equipment. The pulse width of the main discharge current was measured to be 6 μs for a 200-μs prepulse. We measured the laser energy as a function of shot number. The results have shown that the life time of the flashlamps was 105 shots, and that the double step simmer circuit did not only increase the life timeof the flashlamps but also improved the pumping efficiency. The characteristic influence of the KTF-2 filter glass was a red shift of the spectra emitted by the flashlamps, which avoids damage of the laser crystal and improves its absorption efficiency.View full abstractDownload PDF (1037K) -
Minoru UEHARA, Hirotaka KANAZAWA1996 Volume 24 Issue 2 Pages 244-252
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSA transverse flow radio frequency discharge excited carbon monoxide laser has been developed for a high output power and high conversion efficiency operation at room temperature. In experiments performed, a maximum output power of 1.0 kW at a conversion efficiency of 13.3% has been achieved with an entrance gas temperature of 278 K, using gas mixture of He, N2, CO and 02, without Xe addition. Long term output power stabilization was successfully obtained to trap the CO2 with molecular sieves. Also, modulated pulse operation has led to realize fast response and good reproducibility.View full abstractDownload PDF (1239K) -
-The Effect of Diffuser Configuration-Tsunehisa SATAKE, Tomoyuki CHIMURA, Takehito YAG, Mitsuo NAKAJIMA, Kun ...1996 Volume 24 Issue 2 Pages 253-260
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSThis paper describes an experimental study on the gasdynamic and aero-optical performance of a free-vortex aerodynamic laser window. The emphasis was placed on the effect of diffuser configuration. The pressure of a simulated laser cavity strongly depended on the position of diffuser blocks, especially on that of cavity side one. Although, the transversely averaged density and temporal fluctuation of the window jet gradually increased along the flow direction, the fluctuation level was 4kHz at worst.View full abstractDownload PDF (971K) -
Osamu HIROTA, Masao OSAKI, Masahide SASAKI, Masashi BAN1996 Volume 24 Issue 2 Pages 261-269
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSQuantum interference is one of the most interesting phenomena in the field of quantum communications. So it is important to investigate properties of quantum interference for several quantum processes. This paper clarifies some properties as a quantum channel of the Jaynes-Cummings model (JCM) which is one of attractive models to generate quantum interference. When input states are assumed to be pure state, output states are approximately treated as a pure state. It is called Gea-Banacloche effect. This effect is not available in the small photon number region. It is, however, shown that the quantum interference can be observed in the measurement of the quadrature amplitudes at the special condition even if the output state is a mixed state. As a result, we conclude that it has still potentialty on possibility of the application of quantum interference effect.View full abstractDownload PDF (1056K) -
Hitoshi SATO, Mamoru ODAGAWA, Christophe PRAT, Kazuo MAENO, Hiroki HON ...1996 Volume 24 Issue 2 Pages 270-277
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSThe behavior of bubbles in cryogenic liquids may differ from those in water or other normal temperature liquids, because the subcooled degree and their thermophysical properties are greatly different from normal ones. Experimental reports of laser-induced cryogenic bubbles, however, have been quite insufficient. This paper describes an investigation of the behavior of pulse-laser-induced vapor bubble in liquid nitrogen. The bubble is produced by pulsed irradiation of a ruby laser. The dynamics of laser-induced bubble is visualized by high-speed photography of an image-converter camera. The pressure signals from the bubble motion in the liquid nitrogen have been measured. For comparison with the experimental results, numerical study has also been performed on the dynamics of a single spherical bubble in liquid nitrogen with including the phase change effects.View full abstractDownload PDF (1224K) -
Yoshiki OKADA, Kazuo TAKEUCHI1996 Volume 24 Issue 2 Pages 278-292
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSThis work presented a methodology in evaluating the energy unit from the energy required for photodissociation and the energy efficiency of the reactor in infrared laser isotope separation. The photon energy for producing 1 mol of the product was obtained from the absorption constant and the dissociation probability. The value of that photon energy in the case of infrared multiphoton dissociation of UF6 for a typical enrichment condition of uranium (3% enrichment and 0.2% depletion) has been estimated to be about seven times as large as the U-F bond energy. The energy efficiency of the photodissociation reactor was dependent on the axial distribution of the fluence. Estimation of the efficiency of a uranium isotope separation reactor has shown that an irradiation geometry where two beams with the same fluence irradiate in directions counter to each other gave a higher value of efficiency than did an irradiation geometry with one combined beam. The value of the reactor efficiency obtained in the former irradiation geometry for uranium enrichment (3% enrichment and 0.2% depletion) was 0.63.View full abstractDownload PDF (1482K) -
Hidetsugu YOSHIDA, Masahiro NAKATSUKA1996 Volume 24 Issue 2 Pages 293-298
Published: February 29, 1996
Released on J-STAGE: February 26, 2010
JOURNAL FREE ACCESSThe Russian coaxially pumped Nd: glass amplifier head is introduced. The amplifier has a compact head and a glass rod is easily exchanged which is illuminated by high intensity radiation from the Xe flashlamp. In normal operation, an output energy of 37 J and an absolute efficiency of 2.4% have been obtained at 1.58 kJ pumping. The laser head has provided the homogeneous gain distribution and small signal gain equal to 3.6-4.2 at the pumping energy of 1.35 kJ.View full abstractDownload PDF (737K)
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