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Yamagiwa, Mitsuru; Bulanov, S. V.*; Esirkepov, T. Z.*; Koga, J. K.; Kando, Masaki; Ueshima, Yutaka; Saito, Kanji; Wakabayashi, Daisuke*
Laser Physics, 16(2), p.252 - 258, 2006/02
Times Cited Count：2 Percentile：13.03(Optics)no abstracts in English
Kando, Masaki; Masuda, Shinichi; Zhidkov, A.*; Yamazaki, Atsushi; Kotaki, Hideyuki; Kondo, Shuji; Homma, Takayuki*; Kanazawa, Shuhei; Nakajima, Kazuhisa; Hayashi, Yukio; et al.
Physical Review E, 71(1), p.015403_1 - 015403_4, 2005/01
Times Cited Count：33 Percentile：77.37(Physics, Fluids & Plasmas)no abstracts in English
Kotaki, Hideyuki
JAERI-Research 2002-031, 88 Pages, 2002/12
JAERI-Research-2002-031.pdf:3.33MB
We investigate a nonlinear phenomena in laser-plasma interaction, a wakefield excited by intense laser pulses, and a possibility of generating an electron beam by an intense laser pulse. Ionization of gas with a self-focusing causes a broad continuous spectrum with blueshift. The normal blueshift depends on the laser intensity and the plasma density. We have found the spectrum shifts to fixed wavelength independent of the laser power and gas pressure. We call the phenomenon "anomalous blueshift". An intense laser pulse excites a wakefield in plasma. The wakefield excited by 2TW, 50fs laser pulses in a gas-jet plasma is measured with a time-resolved frequency domain interferometer (FDI). This is the first time-resolved measurement of the wakefield of 20GeV/m in a gas-jet plasma. The FDI and the anomalous blueshift will be modified to an optical injection system as an electron beam injector. In a simulation we obtain a high quality intense electron beam. The result illuminates the possibility of a high energy and a high quality electron beam acceleration.
Chen, P.*; Tajima, Toshiki; Takahashi, Yoshiyuki*
Physical Review Letters, 89(16), p.161101_1 - 161101_4, 2002/10
Times Cited Count：101 Percentile：92.42(Physics, Multidisciplinary)A cosmic acceleration mechanism is introduced which is based on the wakefields excited by the Alfven shocks in a relativistically flowing plasma,where the energy gain per distance of a test particle is Lorentz invariant. We show that there exists a threshold condition for transparency below which the accelerating particle is collision-free and suffers little energy loss in the plasma medium. The stochastic encounters of the random accelerating-decelerating phases results in a power-law energy spectrum: 1/E
. The environment suitable for such plasma wakefield acceleration can be cosmically abundant. As an example, we discuss the possible production of super-GZK ultra high energy cosmic rays ( UHECR ) through this mechanism in the atmosphere of gamma ray bursts. We show that the acceleration gradient can be as high as 10
eV/cm. The estimated event rate in our model agrees with that from UHECR observations.
Dewa, Hidenori*; H.Ahn*; Harano, Hideki*; Kando, Masaki*; Kinoshita, Kenichi*; Kondo, Shuji; Kotaki, Hideyuki; Nakajima, Kazuhisa*; Nakanishi, Hiroshi*; Ogata, Atsushi*; et al.
Nuclear Instruments and Methods in Physics Research A, 410(3), p.357 - 363, 1998/00
Times Cited Count：40 Percentile：92.83(Instruments & Instrumentation)no abstracts in English
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.
