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Koga, J. K.; Bulanov, S. V.; Esirkepov, T. Z.; Kotaki, Hideyuki; Hayashi, Yukio; Kando, Masaki; Kiriyama, Hiromitsu; Mori, Michiaki
no journal, ,
Mikami, Katsuhiro; Hasegawa, Noboru; Okada, Hajime; Kondo, Shuji; Kawachi, Tetsuya
no journal, ,
An outdoor-use laser system to improve the performances of existing tunnel inspection techniques is studied. One of the typical concepts is that the blow by hammer in routine hammering test is replaced by the laser pulse irradiation. This new laser system is required to provide high average output power (5 J, 50 Hz, 
15 ns) with a compact geometry enough to mount on the inspection vehicle (4.2 m 
0.8 m). Dramatic speed-up of the inspection is expected by the combination of this new laser system and a laser scanning frequency measurement system.
Kotaki, Hideyuki; Hayashi, Yukio; Mori, Michiaki; Kando, Masaki; Koga, J. K.; Bulanov, S. V.
no journal, ,
Laser wakefield acceleration is regarded as a basis for the next-generation of charged particle accelerators. In experiments, it has been demonstrated that LWFA is capable of generating electron bunches with a very short duration of the order of ten femto-seconds. The oscillation of the electron beam by the transverse wakefield and the electric field of the laser pulse generates X-rays. The X-rays will be an useful tool for measurement of the ultrafast phenomena. The experiments have been performed with a Ti:sapphire laser system. The laser pulses with 160 mJ energy are focused onto a 3-mm-diameter helium gas-jet. The pulse width of the laser pulse is 40 fs. We observe two types of the electron oscillation. One of the oscillation is due to the transverse plasma wake. The other is due to the electric field if the laser pulse. The electron beam oscillation should be generated ultra-short X-rays. The X-rays will be an useful tool for measurement of the ultrafast phenomena.
Sagisaka, Akito
no journal, ,
High-intensity laser and thin-foil interactions produce high-energy particles, hard X-ray, high-order harmonics, and terahertz radiation. A proton beam driven by a high-intensity laser has received attention as a compact ion source for medical and other applications. We have performed high intensity laser-matter interaction experiments using a thin-foil target irradiated by Ti:sapphire laser (J-KAREN) at JAEA. The pulse duration is typically 40 fs (FWHM). The protons are observed with a track detector (CR-39) and RCF in the direction normal to the target. The maximum proton energy of 40 MeV is observed at the peak laser intensity of 110
W/cm
. The spectrometer is placed at the reflection direction for harmonics measurement. The UV harmonics are observed with the spectrometer in the reflected direction simultaneously.