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Journal Articles

Direct observation of the pulse width of an ultrashort electron beam

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:5 Percentile:50.33(Physics, Multidisciplinary)

Journal Articles

High order harmonics from relativistic electron spikes

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

Journal Articles

High order harmonics from relativistic electron spikes

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:22 Percentile:20.08(Physics, Multidisciplinary)

Journal Articles

Negative effect of crystallization on the mechanism of laser damage in a HfO$$_{2}$$/SiO$$_{2}$$ multilayer

Tateno, 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:2 Percentile:89.21(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$$_{2}$$ 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.

Journal Articles

Relativistic high harmonic generation in gas jet targets

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:48.59

Journal Articles

The Spectra of the multicharged argon hollow ions; Observation, modeling and using for diagnostics of the early stage of the heating of clusters by a supper high contrast femtosecond laser pulses

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:100

Journal Articles

High-order harmonics from bow wave caustics driven by a high-intensity laser

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:100

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.

Journal Articles

X-ray emission from relativistically moving electron density cusps

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:100

Journal Articles

Soft-X-ray harmonic comb from relativistic electron spikes

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:59 Percentile:8.18(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 $$mu$$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.

Journal Articles

Observation and modeling of high resolution spectral features of the inner-shell X-ray emission produced by 10$$^{-10}$$ contrast femtosecond-pulse laser irradiation of argon clusters

Colgan, 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:26.89(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.

Journal Articles

Effect of the laser contrast ratio within picosecond timescales on generating a high-quality electron beam by laser-plasma interaction

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:94.28(Physics, Applied)

Journal Articles

Development of a sub-MeV X-ray source via Compton backscattering

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:43.84(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.

Journal Articles

Efficient generation of Xe K-shell X rays by high-contrast interaction with submicrometer clusters

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:21 Percentile:24.69(Optics)

The interaction between a 25 TW laser and Xe clusters at a peak intensity of 1$$times$$10$$^{19}$$ W/cm$$^2$$ 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.

Journal Articles

Ion acceleration in subcritical density plasma via interaction of intense laser pulse with cluster-gas target

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

We 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.

Journal Articles

Manipulation and electron-oscillation-measurement of laser accelerated electron beams

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:72.15(Physics, Fluids & Plasmas)

Journal Articles

Intense and reproducible K$$_{alpha}$$ emissions from micron-sized Kr cluster target irradiated with intense femtosecond laser pulses

Hayashi, 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:10 Percentile:55.15(Physics, Applied)

Journal Articles

Control of the laser accelerated electron beam

Kotaki, Hideyuki; Hayashi, Yukio; Kawase, Keigo; Mori, Michiaki; Kando, Masaki; Homma, Takayuki; Bulanov, S. V.

JAEA-Conf 2010-002, p.99 - 102, 2010/06

Journal Articles

Improvement of SBS laser pulse compression system for the Compton backscattered X-ray source

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.

Journal Articles

Metrology of wide field of view nano-thickness foils' homogeneity by conventional and phase contrast soft X-ray imaging

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:61.62(Physics, Applied)

Journal Articles

Control and pulsewidth-measurement of laser accelerated electron beams

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

119 (Records 1-20 displayed on this page)