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Kotaki, Hideyuki; Kawase, Keigo*; Hayashi, Yukio; Mori, Michiaki; Kando, Masaki; Koga, J. K.; Bulanov, S. V.
Journal of the Physical Society of Japan, 84(7), p.074501_1 - 074501_5, 2015/07
Times Cited Count：7 Percentile：47.73(Physics, Multidisciplinary)Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Faenov, A. Y.*; Pikuz, T. A.*; Kawachi, Tetsuya; Sagisaka, Akito; Koga, J. K.; Mori, Michiaki; Kawase, Keigo*; et al.
RAL-TR-2015-025, P. 22, 2015/00
Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T. A.*; Kawachi, Tetsuya; Sagisaka, Akito; et al.
New Journal of Physics (Internet), 16(9), p.093003_1 - 093003_30, 2014/09
Times Cited Count：31 Percentile：80.46(Physics, Multidisciplinary)
/SiO multilayerTateno, Ryo*; Okada, Hajime; Otobe, Tomohito; Kawase, Keigo*; Koga, J. K.; Kosuge, Atsushi; Nagashima, Keisuke; Sugiyama, Akira; Kashiwagi, Kunihiro*
Journal of Applied Physics, 112(12), p.123103_1 - 123103_3, 2012/12
Times Cited Count：3 Percentile：13.07(Physics, Applied)Elucidation of the mechanisms of laser damage is indispensable in realizing high resistance mirrors for the next generation of ultra-short pulse high intensity lasers. In this study, the surface and a section of the laser-damaged area of a laser mirror were observed with a laser microscope and a transmission electron microscope (cross-sectional TEM), respectively. A grain boundary of HfO microcrystal was observed in the damaged area. This observation, and an evaluation of the mirror's damage resistance showed that the formation of crystals in the multilayer mirror is one of the major determinants of damage resistance.
Kando, Masaki; Pirozhkov, A. S.; Nakamura, Tatsufumi; Hayashi, Yukio; Kotaki, Hideyuki; Kawase, Keigo*; Esirkepov, T. Z.; Fukuda, Yuji; Kiriyama, Hiromitsu; Okada, Hajime; et al.
AIP Conference Proceedings 1465, p.159 - 166, 2012/07
Times Cited Count：0 Percentile：0.00(Physics, Applied)Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; Kawachi, Tetsuya; Sagisaka, Akito; et al.
AIP Conference Proceedings 1465, p.167 - 171, 2012/07
Times Cited Count：1 Percentile：45.62(Physics, Applied)Esirkepov, T. Z.; Pirozhkov, A. S.; Kando, Masaki; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A.*; Pikuz, T.; Kawachi, Tetsuya; Sagisaka, Akito; et al.
AIP Conference Proceedings 1465, p.172 - 180, 2012/07
Times Cited Count：0 Percentile：0.00(Physics, Applied)The bow wave induced mechanism of high-order harmonics generation was discovered using simulations and catastrophe theory. This mechanism feasibility was successfully demonstrated in 3D and 2D PIC simulations. The mechanism and the simulations explained high-order harmonics in the XUV spectral region seen in recent experiments with terawatt lasers. Development of new XUV light and X-ray source based on the high-order harmonics generation mechanism is proposed.
Pikuz, T.; Faenov, A.*; Skobelev, I.*; Fortov, V. E.*; Boldarev, A.*; Gasilov, V.*; Chen, L. M.*; Zhang, L.*; Yan, W.*; Yuan, D.*; et al.
AIP Conference Proceedings 1465, p.181 - 201, 2012/07
Times Cited Count：0 Percentile：0.00(Physics, Applied)Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; Kawachi, Tetsuya; Sagisaka, Akito; et al.
Physical Review Letters, 108(13), p.135004_1 - 135004_5, 2012/03
Times Cited Count：72 Percentile：90.57(Physics, Multidisciplinary)We demonstrate a new high-order harmonic generation mechanism reaching the "water window" spectral region in experiments with multi-terawatt femtosecond lasers irradiating gas jets. A few hundred harmonic orders are resolved, giving 
J/sr pulses. Harmonics are collectively emitted by an oscillating electron spike formed at the joint of the boundaries of a cavity and bow wave created by a relativistically self-focusing laser in underdense plasma. The spike sharpness and stability are explained by catastrophe theory. The mechanism is corroborated by particle-in-cell simulations.
contrast femtosecond-pulse laser irradiation of argon clustersColgan, J.*; Abdallah, J. Jr.*; Faenov, A. Ya.*; Pikuz, T. A.*; Skobelev, I. Yu.*; Fukuda, Yuji; Hayashi, Yukio; Pirozhkov, A. S.; Kawase, Keigo*; Shimomura, Takuya; et al.
High Energy Density Physics, 7(2), p.77 - 83, 2011/06
Times Cited Count：21 Percentile：64.15(Physics, Fluids & Plasmas)A study is made of the ultra-short laser pulse irradiation of Ar cluster targets. Experiments have been performed with large cluster sizes and using very high laser contrasts, which have allowed clear and unambiguous observation of exotic inner-shell transitions in near-neutral Ar ions. The interaction of the main laser pulse with the unperturbed target is a necessary requirement for observing these lines. Our measurements are supported by kinetics calculations in which a very detailed atomic model is used. The calculations predict all of the spectral features found experimentally, and support the notion that the X-ray emission arises from many ion stages of the Ar plasma, from near-neutral through He-like ions, and from a range of plasma temperatures and densities.
Kotaki, Hideyuki; Kando, Masaki; Daito, Izuru; Kameshima, Takashi*; Kawase, Keigo*; Chen, L. M.*; Fukuda, Yuji; Koga, J. K.; Kiriyama, Hiromitsu; Kondo, Shuji; et al.
Japanese Journal of Applied Physics, 50(6), p.066401_1 - 066401_3, 2011/06
Times Cited Count：1 Percentile：4.62(Physics, Applied)Kawase, Keigo; Kando, Masaki; Hayakawa, Takehito; Daito, Izuru; Kondo, Shuji; Homma, Takayuki; Kameshima, Takashi*; Kotaki, Hideyuki; Chen, L. M.*; Fukuda, Yuji; et al.
Nuclear Instruments and Methods in Physics Research A, 637(1, Suppl.), p.S141 - S144, 2011/05
Times Cited Count：7 Percentile：47.24(Instruments & Instrumentation)We report the present status of the sub-MeV X-ray generation via Compton backscattering by using 150-MeV electron beam and the Nd:YAG laser. In particular, we show the result of the X-ray generation experiment and of the laser pulse compression for increasing the X-ray flux.
Hayashi, Yukio; Pirozhkov, A. S.; Kando, Masaki; Fukuda, Yuji; Faenov, A.*; Kawase, Keigo*; Pikuz, T.*; Nakamura, Tatsufumi; Kiriyama, Hiromitsu; Okada, Hajime; et al.
Optics Letters, 36(9), p.1614 - 1616, 2011/05
Times Cited Count：22 Percentile：69.99(Optics)The interaction between a 25 TW laser and Xe clusters at a peak intensity of 1
10
W/cm
has been investigated. Xe K-shell X-rays, whose energies are approximately 30 keV, were clearly observed with a hard X-ray charge-coupled device (X-ray CCD) at 3.4 MPa. Moreover, we studied the yield of the Xe K-shell X-rays by changing the pulse duration of the laser at a constant laser energy, and found that the pulse duration of 40 fs is better than that of 300 fs for generating Xe K-shell X-rays.
Fukuda, Yuji; Faenov, A.*; Tampo, Motonobu; Pikuz, T.*; Nakamura, Tatsufumi; Kando, Masaki; Hayashi, Yukio; Yogo, Akifumi; Sakaki, Hironao; Kameshima, Takashi*; et al.
Progress in Ultrafast Intense Laser Science VII, p.225 - 240, 2011/05
http://www.springer.com/physics/atomic,+molecular,+optical+%26+plasma+physics/book/978-3-642-18326-3We present substantial enhancement of the accelerated ion energies up to 10-20 MeV per nucleon by utilizing the unique properties of the cluster-gas target irradiated with 40-fs laser pulses of only 150 mJ energy, corresponding to approximately tenfold increase in the ion energies compared to previous experiments using thin foil targets. A particle-in-cell simulation infers that the high energy ions are generated at the rear side of the target due to the formation of a strong dipole vortex structure in sub-critical density plasmas. The demonstrated method can be important in the development of efficient laser ion accelerators for hadron therapy and other applications.
Kotaki, Hideyuki; Hayashi, Yukio; Kawase, Keigo; Mori, Michiaki; Kando, Masaki; Homma, Takayuki; Koga, J. K.; Daido, Hiroyuki; Bulanov, S. V.
Plasma Physics and Controlled Fusion, 53(1), p.014009_1 - 014009_7, 2011/01
Times Cited Count：5 Percentile：22.38(Physics, Fluids & Plasmas)
emissions from micron-sized Kr cluster target irradiated with intense femtosecond laser pulsesHayashi, Yukio; Fukuda, Yuji; Faenov, A. Y.*; Kando, Masaki; Kawase, Keigo; Pikuz, T. A.*; Homma, Takayuki; Daido, Hiroyuki; Bulanov, S. V.
Japanese Journal of Applied Physics, 49(12), p.126401_1 - 126401_3, 2010/12
Times Cited Count：12 Percentile：44.84(Physics, Applied)Kawase, Keigo; Kando, Masaki; Hayakawa, Takehito; Daito, Izuru; Kondo, Shuji; Homma, Takayuki; Kameshima, Takashi*; Kotaki, Hideyuki; Chen, L. M.*; Fukuda, Yuji; et al.
JAEA-Conf 2010-002, p.95 - 98, 2010/06
At the previous symposium in Advanced Photon Research, we proposed and demonstrated the laser pulse compression via stimulated Brillouin scattering (SBS) for increasing the flux of the Compton backscattered X rays. After that, we improved the SBS pulse compression system by introducing the image relay in the laser transport line. As a result, we achieve the stably compressed laser pulse with a duration of 2.1 ns and with an energy of 0.84 J. By installing this system into the Compton backscattered X-ray source, the X-ray flux will be increased 3.2 times for the present system at the KPSI-JAEA.
Kotaki, Hideyuki; Hayashi, Yukio; Kawase, Keigo; Mori, Michiaki; Kando, Masaki; Homma, Takayuki; Bulanov, S. V.
JAEA-Conf 2010-002, p.99 - 102, 2010/06
Faenov, A. Y.; Pikuz, T.*; Fukuda, Yuji; Kando, Masaki; Kotaki, Hideyuki; Homma, Takayuki; Kawase, Keigo; Skobelev, I.*; Gasilov, S.*; Kawachi, Tetsuya; et al.
Japanese Journal of Applied Physics, 49(6), p.06GK03_1 - 06GK03_5, 2010/06
Times Cited Count：8 Percentile：33.56(Physics, Applied)Kotaki, Hideyuki; Hayashi, Yukio; Kawase, Keigo; Mori, Michiaki; Kando, Masaki; Homma, Takayuki; Koga, J. K.; Bulanov, S. V.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.3608 - 3610, 2010/05