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Kitaori, Aki*; Kanazawa, Naoya*; Kida, Takanori*; Narumi, Yasuo*; Hagiwara, Masayuki*; Kindo, Koichi*; Takeuchi, Tetsuya*; Nakamura, Ai*; Aoki, Dai*; Haga, Yoshinori; et al.
Journal of the Physical Society of Japan, 92(2), p.024702_1 - 024702_6, 2023/02
Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)Nemoto, Yoshiyuki; Kaji, Yoshiyuki; Kanazawa, Toru*; Nakashima, Kazuo*; Tojo, Masayuki*
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05
Oxidation behaviour of Zr cladding in SFP accident condition was evaluated by using a thermobalance in this work, and the obtained data were applied to construct oxidation model for SFP accident condition. For the validation of the constructed oxidation model, oxidation tests using a long cladding tube 500mm in length were conducted in conditions simulating SFP accidents, such as flow rate of the atmosphere in spent fuel rack, temperature gradient along the axis of cladding, and heating-up history. Thickness of oxide layer formed on the surface of cladding samples was evaluated by cross sectional observation, and compared with calculation results obtained by using the oxidation model. The detail of experimental results and validation of the oxidation model will be discussed.
Tojo, Masayuki*; Kanazawa, Toru*; Nakashima, Kazuo*; Iwamoto, Tatsuya*; Kobayashi, Kensuke*; Goto, Daisuke*; Nemoto, Yoshiyuki; Kaji, Yoshiyuki
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 13 Pages, 2019/05
In this study, fuel loading effects in BWR spent fuel rack accidents are widely investigated using three-dimensional analysis methods from both nuclear and thermal hydraulics viewpoints, including: (a) Decay heat of spent fuel after discharge, (b) The maximum temperature of spent fuel cladding in the spent fuel rack depending on heat transfer phenomena, and (c) Criticality of the spent fuel rack after collapsing of the fuel due to a severe accidents in the BWR spent fuel pool (SFP).
Nemoto, Yoshiyuki; Kaji, Yoshiyuki; Onizawa, Takashi*; Kanazawa, Toru*; Nakashima, Kazuo*; Tojo, Masayuki*
Proceedings of Annual Congress of the European Federation of Corrosion (EUROCORR 2018) (USB Flash Drive), 8 Pages, 2018/09
The authors proposed oxidation models based on oxidation data which previously obtained in high temperature oxidation tests on small sample of Zircalloy-2 (Zry2) cladding in dry air and in air/steam mixture environment. The oxidation models were implemented in computational fluid dynamics (CFD) code to analyse oxidation behavior of long cladding sample in hypothetical spent fuel pool (SFP) accident conditions. The oxidation tests were conducted using Zry2 cladding sample 500 mm in length. The oxide layer growth in dry air was well reproduced in the calculation using the oxidation model, meanwhile which in air/steam mixture was overestimated atmosphere composition change anticipated in the spent fuel rack during the accident, and its influence on the oxidation behaviour of the cladding were discussed in consideration of the oxidation model improvement.
Nemoto, Yoshiyuki; Kaji, Yoshiyuki; Ogawa, Chihiro; Kondo, Keietsu; Nakashima, Kazuo*; Kanazawa, Toru*; Tojo, Masayuki*
Journal of Nuclear Materials, 488, p.22 - 32, 2017/05
Times Cited Count:2 Percentile:19.91(Materials Science, Multidisciplinary)The authors previously conducted thermogravimetric analyses on zircaloy-2 in air. By using the thermogravimetric data, an oxidation model was constructed in this study so that it can be applied for the modeling of cladding degradation in spent fuel pool (SFP) severe accident condition. For its validation, oxidation tests of long cladding tube were conducted, and computational fluid dynamics analyses using the constructed oxidation model were proceeded to simulate the experiments. In the oxidation tests, high temperature thermal gradient along the cladding axis was applied and air flow rates in testing chamber were controlled to simulate hypothetical SFP accidents. The analytical outputs successfully reproduced the growth of oxide film and porous oxide layer on the claddings in oxidation tests, and validity of the oxidation model was proved. Influence of air flow rate for the oxidation behavior was thought negligible in the conditions investigated in this study.
Kiriyama, Hiromitsu; Shimomura, Takuya; Mori, Michiaki; Nakai, Yoshiki*; Tanoue, Manabu; Kondo, Shuji; Kanazawa, Shuhei; Pirozhkov, A. S.; Esirkepov, T. Z.; Hayashi, Yukio; et al.
Applied Sciences (Internet), 3(1), p.214 - 250, 2013/03
Times Cited Count:15 Percentile:50(Chemistry, Multidisciplinary)This paper reviews techniques for improving the temporal contrast and spatial beam quality in an ultra-intense laser system that is based on chirped-pulse amplification (CPA). We describe the design, performance, and characterization of our laser system, which has the potential for achieving a peak power of 600 TW. We also describe applications of the laser system in the relativistically dominant regime of laser-matter interactions and discuss a compact, high efficiency diode-pumped laser system.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki*; Shimomura, Takuya; Sasao, Hajime*; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Kondo, Shuji; Kanazawa, Shuhei; et al.
Reza Kenkyu, 38(9), p.669 - 675, 2010/09
This paper reviews the temporal contrast and spatial beam quality improvement techniques in a high intensity Ti:sapphire laser system that is based on chirped-pulse amplification (CPA). We describe a low gain optical parametric chirped-pulse amplification (OPCPA) preamplifier that uses high energy, clean pulse seeding and is shown to significantly improve the contrast to better than 10-10 relative to the peak of the main femtosecond pulse. We also report the use of a diffractive optical element for beam homogenization of a 100 J level Nd:glass green pump laser, achieving a flat-topped spatial profile with a filling factor near 80 %.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya; Sasao, Hajime; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Okada, Hajime; Kondo, Shuji; et al.
JAEA-Conf 2010-002, p.18 - 21, 2010/06
We have developed a femtosecond high intensity laser system, which combines both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric chirped-pulse amplification (OPCPA) techniques, that produces more than 30 J broadband output energy, indicating the potential for achieving peak powers in excess of 500 TW. With a cleaned high-energy seeded OPCPA preamplifier as a front-end in the system, for the final compressed pulse (without pumping the booster amplifier) we found that the temporal contrast in this system exceeds 10 on the sub-nanosecond timescale, and is near 10 on the nanosecond timescale before the main femtosecond pulse. Using diffractive optical elements for beam homogenization of 100-J level high-energy Nd:glass green pump laser in a Ti:sapphire final amplifier, we have successfully generated broadband high-energy output with near-perfect top-hat intensity distributions.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya; Sasao, Hajime; Tanoue, Manabu*; Kanazawa, Shuhei; Wakai, Daisuke*; Sasao, Fumitaka*; Okada, Hajime; et al.
Optics Letters, 35(10), p.1497 - 1499, 2010/05
Times Cited Count:85 Percentile:95.22(Optics)OPCPA (Optical parametric chirped-pulse amplification) operation with low gain by seeding with high energy, clean pulses is shown to significantly improve the contrast to better than - in a high intensity Ti:sapphire laser system that is based on chirped pulse amplification. In addition to the high contrast broadband high energy output from the final amplifier is achieved with a flat-topped spatial profile of filling factor near 77%. This is the result of pump beam spatial profile homogenization with diffractive optical elements. Final pulse energies exceed 30-Joules indicating capability for reaching peak powers in excess of 500-TW.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya; Sasao, Hajime; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Okada, Hajime; Kondo, Shuji; et al.
Applied Optics, 49(11), p.2105 - 2115, 2010/04
Times Cited Count:39 Percentile:83.8(Optics)We have developed a femtosecond high intensity laser system, which combines both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric chirped-pulse amplification (OPCPA) techniques, that produces more than 30-J broadband output energy, indicating the potential for achieving peak powers in excess of 500-TW. With a cleaned high-energy seeded OPCPA preamplifier as a front-end in the system, for the compressed pulse without pumping the final amplifier we found that the temporal contrast in this system exceeds 10 on the sub-nanosecond timescales, and is near 10 on the nanosecond timescale prior to the peak of the main femtosecond pulse. Using diffractive optical elements for beam homogenization of 100-J level high-energy Nd:glass green pump laser in a Ti:sapphire final amplifier, we have successfully generated broadband high-energy output with a near-perfect top-hat-like intensity distribution.
Yogo, Akifumi; Sato, Katsutoshi; Nishikino, Masaharu; Mori, Michiaki; Teshima, Teruki*; Numasaki, Hodaka*; Murakami, Masao*; Demizu, Yusuke*; Akagi, Takashi*; Nagayama, Shinichi*; et al.
Applied Physics Letters, 94(18), p.181502_1 - 181502_3, 2009/05
Times Cited Count:109 Percentile:94.78(Physics, Applied)Tanaka, Yoshikazu*; Inami, Toshiya; Lovesey, S. W.*; Knight, K. S.*; Yakhou, F.*; Mannix, D.*; Kokubun, Jun*; Kanazawa, Masayuki*; Ishida, Kotaro*; Nanao, Susumu*; et al.
Physical Review B, 69(2), p.024417_1 - 024417_11, 2004/01
Times Cited Count:36 Percentile:79.64(Materials Science, Multidisciplinary)Direct evidence of the spatial ordering of Dy 4 quadrupole and hexadecapole moments in DyBC is demonstrated by resonant X-ray diffraction enhanced by an electric quadrupole event (2 resonance) at the Dy L absorption edge. The diffraction data show that the structural phase transition at = 24.7 K is accompanied by a reduction in the symmetry of the Dy site to 2/, from 4/, and the spatial ordering of the time-even Dy multipoles with A character. Below the crystal structure is described by the space group 4/ and Dy ions occupy sites (4). The distortion at T involves the lattice occupied by B and C ions, and it amounts to a buckling of B-C planes that are normal to the two-fold rotation axis of 2/. An immediately plausible model of low-energy Dy states correlates data on the specific heat, our X-ray diffraction signals, and magnetic ordering below 15.3 K which has been observed in magnetic neutron diffraction.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya; Tanoue, Manabu*; Okada, Hajime; Kondo, Shuji; Kanazawa, Shuhei; Sagisaka, Akito; Daito, Izuru; et al.
no journal, ,
We demonstrated laser peak intensity above 10W/cm and temporal contrast exceeding 10 at a 10 Hz repetition rate with a 60 TW, 30 fs laser (J-KAREN laser). Here we report the upgrade of the J-KAREN laser to the petawatt peak power level. This is accomplished by adding a Ti:sapphire booster amplifier downstream of the final amplifier chain of the 60 TW J-KAREN laser system. Stretched pulses of energy 3 J from the previous J-KAREN laser are up-collimated and introduced into the final booster amplifier. The booster amplifier consists of a large-aperture Ti:sapphire crystal pumped by a frequency-doubled Nd:silicate glass laser with pulse energy 60 J. Diffractive optical elements are used for pump beam homogenization to maintain a uniform spatial profile and reliable, damage-free operation. The system produces an uncompressed output pulse energy exceeding 30 J with a near homogeneous flat-top spatial distribution, indicating potential peak power of 500 TW.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya; Tanoue, Manabu*; Okada, Hajime; Kondo, Shuji; Kanazawa, Shuhei; Sagisaka, Akito; Daito, Izuru; et al.
no journal, ,
We have demonstrated over 30 J broadband output energy based on optical parametric chirped-pulse amplification (OPCPA) and Ti:sapphire chirped-pulse amplification (CPA), indicating potential for peak power of 500 TW with extremely high temporal contrast.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya; Sasao, Hajime; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Okada, Hajime; Kondo, Shuji; et al.
no journal, ,
We have developed a femtosecond high intensity laser system, which combines both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric chirped-pulse amplification (OPCPA) techniques, that produces more than 30 J broadband output energy, indicating the potential for achieving peak powers in excess of 500 TW. With a cleaned high-energy seeded OPCPA preamplifier as a front-end in the system, for the final compressed pulse we found that the temporal contrast in this system exceeds 10 on the sub-nanosecond timescale before the main femtosecond pulse. Using diffractive optical elements for beam homogenization of 100-J level high-energy Nd:glass green pump laser in a Ti:sapphire final amplifier, we have successfully generated broadband high-energy output with near-perfect top-hat intensity distributions.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya; Sasao, Hajime; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Okada, Hajime; Kondo, Shuji; et al.
no journal, ,
We have developed a femtosecond high intensity laser system, which combines both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric chirped-pulse amplification (OPCPA) techniques, that produces more than 30 J broadband output energy, indicating the potential for achieving peak powers in excess of 500 TW. With a cleaned high-energy seeded OPCPA preamplifier as a front-end in the system, for the final compressed pulse we found that the temporal contrast in this system exceeds 10 on the sub-nanosecond timescale before the main femtosecond pulse. Using diffractive optical elements for beam homogenization of 100-J level high-energy Nd:glass green pump laser in a Ti:sapphire final amplifier, we have successfully generated broadband high-energy output with near-perfect top-hat intensity distributions.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki*; Shimomura, Takuya; Sasao, Hajime; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Okada, Hajime; Kanazawa, Shuhei; et al.
no journal, ,
We report the demonstration of over 30-J of uncompressed broadband energy, indicating the potential peak power in excess of 500-TW with high temporal-contrast around 10 and a flat-toped spatial-profile with an 80 percent filling factor.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki*; Shimomura, Takuya; Sasao, Hajime*; Tanaka, Momoko; Ochi, Yoshihiro; Tanoue, Manabu*; Okada, Hajime; Kanazawa, Shuhei; et al.
no journal, ,
OPCPA (Optical parametric chirped-pulse amplification) operation with low gain by seeding with high energy, clean pulses is shown to significantly improve the contrast to better than 10-10 in a high intensity Ti:sapphire laser system that is based on chirped pulse amplification. In addition to the high contrast broadband high energy output from the final amplifier is achieved with a flat-topped spatial profile of filling factor near 77 %. This is the result of pump beam spatial profile homogenization with diffractive optical elements. Final pulse energies exceed 30 Joules indicating capability for reaching peak powers in excess of 500-TW.
Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki*; Shimomura, Takuya; Sasao, Hajime*; Tanoue, Manabu*; Okada, Hajime; Kanazawa, Shuhei; Daito, Izuru; Sasao, Fumitaka; et al.
no journal, ,
We have developed a femtosecond high intensity laser system, which combines both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric chirped-pulse amplification (OPCPA) techniques, that produces more than 30 J broadband output energy, indicating the potential for achieving peak powers in excess of 500 TW. With a cleaned high-energy seeded OPCPA preamplifier as a front-end in the system, for the final compressed pulse we found that the temporal contrast in this system exceeds 10 on the sub-nanosecond timescale before the main femtosecond pulse. Using diffractive optical elements for beam homogenization of 100-J level high-energy Nd:glass green pump laser in a Ti:sapphire final amplifier, we have successfully generated broadband high-energy output with near-perfect top-hat intensity distributions.
Kiriyama, Hiromitsu; Mori, Michiaki; Shimomura, Takuya; Nakai, Yoshiki*; Tanoue, Manabu*; Sasao, Hajime*; Kondo, Shuji; Kanazawa, Shuhei; Ochi, Yoshihiro; Tanaka, Momoko; et al.
no journal, ,
We report on a femtosecond high-intensity OPCPA/Ti:sapphire hybrid laser system that produces more than 30 J broadband output energy, indicating the potential for achieving petawatt-class peak powers. High temporal-contrast of 10 to 10 has been obtained with a near-perfect flat-topped spatial-profile of filling factor 80%. We also present a compact, high-intensity OPCPA/Yb:YAG hybrid laser system that generates 100 mJ output energy with a temporal contrast of better than 10 and good spatial beam quality.