[Show abstract][Hide abstract] ABSTRACT: Laser wakefield acceleration has the possibility to generate an ultrashort electron beam of the order of femtoseconds or less. Generation of ultrashort pulses is a key to exploring the dynamical behavior of matter on ever-shorter timescales. We found that the profile of the electron beam was manipulated by rotating the laser polarization. The electron beam is in the laser field, which oscillates the electron beam. From electron oscillations in the image of the electron energy distribution, the electron beam pulse width is estimated to be 1.7 fs (rms). The peak current is 10 kA.
No preview · Article · Jul 2015 · Journal of the Physical Society of Japan
[Show abstract][Hide abstract] ABSTRACT: We report recent progress on the J-KAREN laser upgrade to realize 1022 W/cm2 intensity at 0.1 Hz. Our current high-spatiotemporal-quality broadband pulses of over 20 J will be further amplified in the final amplifier.
[Show abstract][Hide abstract] ABSTRACT: A nonlinear oscillator with an abruptly inhomogeneous restoring force driven
by an uniform oscillating force exhibits stochastic properties under specific
resonance conditions. This behaviour elucidates the elementary mechanism of the
electron energization in the strong electromagnetic wave interaction with thin
Full-text · Article · Mar 2015 · Physics of Plasmas
[Show abstract][Hide abstract] ABSTRACT: High-order harmonic generation of high intensity ultra-short laser pulses by means of laser produced plasmas are discussed. Since with plasma targets there is no limitation on applicable laser intensity the generated harmonics can be substantially intense. Recent results of experiments and computer simulations on the high-order harmonic generation are briefly reviewed. Main attention is paid to the analysis of basic mechanisms of high-order harmonic generation from overdense and underdense plasma targets irradiated by relativistically intense laser pulses.
[Show abstract][Hide abstract] ABSTRACT: The ways toward modeling of astrophysical processes and extreme field regimes with super-power lasers are discussed. The main attention is paid to the problem of limited similarity in using the dimensionless parameters characterizing the processes in the laser and astrophysical plasmas. As the most typical examples, we address the magnetic reconnection and collisionless shock waves relevant to the problem of ultrarelativistic particle acceleration. In the extreme field limits we consider the regimes of dominant radiation reaction, changing the electromagnetic wave-matter interaction. In these regimes it, in particular, results in a new powerful source of ultra high-brightness gamma-rays and will make possible electron-positron pair creation in vacuum in a multiphoton processes. This will allow modeling under terrestrial laboratory conditions the processes in astrophysical objects and paves the way to experimental verifications using ultra intense lasers as they are currently developed within the ELI project.
Preview · Article · Jan 2015 · Plasma Physics Reports
[Show abstract][Hide abstract] ABSTRACT: A high-contrast high-intensity petawatt-class
Ti:sapphire chirped-pulse amplification laser has been developed
for research on high field science. A saturable absorber and a
low-gain optical parametric chirped-pulse amplification preamplifier
in the front-end have improved the temporal contrast in
the system to _2 × 1012 on the subnanosecond time scale at the
_70 TW power level. In addition to the high-contrast broadband
high-energy output from the final amplifier has been achieved with
a flat-top spatial profile with a filling factor of_70%. This is the result
of pump beam spatial profile homogenization with diffractive
optical elements. The system produces the uncompressed output
pulse energy of 29 J, indicating the capability for reaching a peak
power of _600 TW. We discuss in detail the design, performance,
and characterization of the laser including output power, pulse
duration, and spatiotemporal beam quality. We also describe the
on-going upgrade of the laser system and some applications for
the laser in relativistic dominated laser–matter interactions.
Full-text · Article · Jan 2015 · IEEE Journal of Selected Topics in Quantum Electronics
[Show abstract][Hide abstract] ABSTRACT: The radiation reaction radically influences the electron motion in an
electromagnetic standing wave formed by two super-intense counter-propagating
laser pulses. Depending on the laser intensity and wavelength, either classical
or quantum mode of radiation reaction prevail, or both are strong. When
radiation reaction dominates, electron motion evolves to limit cycles and
strange attractors. This creates a new framework for high energy physics
experiments on an interaction of energetic charged particle beams and colliding
super-intense laser pulses.
Full-text · Article · Dec 2014 · Physics Letters A
[Show abstract][Hide abstract] ABSTRACT: A new regime of relativistic high-order harmonic generation has been discovered (Pirozhkov 2012 Phys. Rev. Lett. 108 135004). Multi-terawatt relativistic-irradiance (>1018 W cm−2) femtosecond (∼30–50 fs) lasers focused to underdense (few × 1019 cm−3) plasma formed in gas jet targets produce comb-like spectra with hundreds of even and odd harmonic orders reaching the photon energy of 360 eV, including the ‘water window’ spectral range. Harmonics are generated either by linearly or circularly polarized pulses from the J-KAREN (KPSI, JAEA) and Astra Gemini (CLF, RAL, UK) lasers. The photon number scalability has been demonstrated with a 120 TW laser, producing 40 μJ sr−1 per harmonic at 120 eV. The experimental results are explained using particle-in-cell simulations and catastrophe theory. A new mechanism of harmonic generation by sharp, structurally stable, oscillating electron spikes at the joint of the boundaries of the wake and bow waves excited by a laser pulse is introduced. In this paper, detailed descriptions of the experiments, simulations and model are provided and new features are shown, including data obtained with a two-channel spectrograph, harmonic generation by circularly polarized laser pulses and angular distribution.
Full-text · Article · Sep 2014 · New Journal of Physics
[Show abstract][Hide abstract] ABSTRACT: Nonlinear cascade scattering of intense, tightly focused laser pulses by relativistic electrons is studied numerically in the classical approximation including radiation damping for the quantum parameter h omega(x ray) / epsilon < 1 and an arbitrary radiation parameter.. The electron's energy loss, along with its being scattered to the side by the ponderomotive force, makes scattering in the vicinity of a high laser field nearly impossible at high electron energies. The use of a second, copropagating laser pulse as a booster is shown to partially solve this problem.
Full-text · Article · May 2014 · Physical Review Special Topics - Accelerators and Beams
[Show abstract][Hide abstract] ABSTRACT: Experimental demonstration of multi-charged heavy ion acceleration from the interaction between the ultra-intense short pulse laser system and the metal target is presented. Al ions are accelerated up to 12 MeV/u (324 MeV total energy). To our knowledge, this is far the highest energy ever reported for the case of acceleration of the heavy ions produced by the <10 J laser energy of 200 TW class Ti:sapphire laser system. Adding to that, thanks to the extraordinary high intensity laser field of ∼10(21) W cm(-2), the accelerated ions are almost fully stripped, having high charge to mass ratio (Q/M).
Full-text · Article · Feb 2014 · The Review of scientific instruments
[Show abstract][Hide abstract] ABSTRACT: When the laser intensity becomes higher than 1022
W/cm2, the motion of an electron becomes relativistic, and
emits large amounts of radiation. This radiation energy loss transferred
to the kinetic energy loss of the electron, is treated as an external
force, the "radiation reaction force". We show the new equation of
motion including this radiation reaction and the simulation method, as
well as results of single electron system or dual electrons system with
Liénard-Wiechert field interaction.
No preview · Article · Nov 2013 · The European Physical Journal Conferences
[Show abstract][Hide abstract] ABSTRACT: From the development of the electron theory by H. A. Lorentz in 1906, many
authors have tried to reformulate this model. P. A. M. Dirac derived the
relativistic-classical electron model in 1938, which is now called the
Lorentz-Abraham-Dirac model. But this model has the big difficulty of the
run-away solution. Recently, this equation has become important for
ultra-intense laser-electron (plasma) interactions. For simulations in this
research field, it is desirable to stabilize this model of the radiation
reaction. In this paper, we will discuss this ability for radiation reaction
with the inclusion of vacuum polarization.
Full-text · Article · Oct 2013 · Progress of Theoretical and Experimental Physics
[Show abstract][Hide abstract] ABSTRACT: When a finite contrast petawatt laser pulse irradiates a micron-thick foil, a
prepulse (including amplified spontaneous emission) creates a preplasma, where
an ultrashort relativistically strong portion of the laser pulse (the main
pulse) acquires higher intensity due to relativistic self-focusing and
undergoes fast depletion transferring energy to fast electrons. If the
preplasma thickness is optimal, the main pulse can reach the target generating
fast ions more efficiently than an ideal, infinite contrast, laser pulse. A
simple analytical model of a target with preplasma formation is developed and
the radiation pressure dominant acceleration of ions in this target is
predicted. The preplasma formation by a nanosecond prepulse is analyzed with
dissipative hydrodynamic simulations. The main pulse interaction with the
preplasma is studied with multi-parametric particle-in-cell simulations. The
optimal conditions for hundreds of MeV ion acceleration are found with
accompanying effects important for diagnostics, including high-order harmonics
Full-text · Article · Oct 2013 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
[Show abstract][Hide abstract] ABSTRACT: Non-linear cascade scattering of intense, tightly focused laser pulses by
relativistic electrons is studied numerically in the classical approximation
including the radiation damping for the quantum parameter hwx-ray/E<1 and an
arbitrary radiation parameter Kai. The electron energy loss, along with its
side scattering by the ponderomotive force, makes the scattering in the
vicinity of high laser field nearly impossible at high electron energies. The
use of a second, co-propagating laser pulse as a booster is shown to solve this
[Show abstract][Hide abstract] ABSTRACT: Radiation pressure is an effective mechanism of momentum transfer to ions in laser plasmas. The energy of ions accelerated by the radiation pressure can be greatly enhanced due to a transverse expansion of a thin target. The ion velocity cannot exceed the pulse group velocity. The beams of accelerated ions are unstable against various instabilities, which results in the target modulations and broadening of the ion energy spectrum.
[Show abstract][Hide abstract] ABSTRACT: We measured high-resolution spectra of high-order harmonics generated in the interaction of relativistic-irradiance (>1018 W/cm2) multi-terawatt femtosecond lasers with gas jets. The spectra exhibit very fine structures on the sub-eV scale, indicating temporal coherence of a few tens of femtoseconds.
[Show abstract][Hide abstract] ABSTRACT: Relativistic mirrors generated in laser-plasma interactions can enable the detection of photon-photon scattering. They can up-shift and tightly focus optical laser pulses to the x-ray regime. We find that photon-photon scattering events can be observed.