Electron acceleration at grazing incidence of a subpicosecond intense laser pulse onto a plane solid target (original) (raw)
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Electron acceleration by few-cycle laser pulses with single-wavelength spot size
Physical review. E, Statistical, nonlinear, and soft matter physics, 2003
Generation of relativistic electrons from the interaction of a laser pulse with a high density plasma foil, accompanied by an underdense preplasma in front of it, has been studied with two-dimensional particle-in-cell (PIC) simulations for pulse durations comparable to a single cycle and for single-wavelength spot size. The electrons are accelerated predominantly in forward direction for a preplasma longer than the pulse length. Otherwise, both forward and backward electron accelerations occur. The primary mechanism responsible for electron acceleration is identified. Simulations show that the energy of the accelerated electrons has a maximum versus the pulse duration for relativistic laser intensities. The most effective electron acceleration takes place when the preplasma scale length is comparable to the pulse duration. Electron distribution functions have been found from PIC simulations. Their tails are well approximated by Maxwellian distributions with a hot temperature in the ...
Journal of Plasma Physics, 2006
Motivated by recent experimental observations of fast electron jets emitted along the target surface in intense laser-solid interactions with a large incident angle of the laser pulse, we simulate electron emissions by two-dimensional particlein-cell simulations. When there is no preplasma in advance of the main laser pulse, electrons are emitted dominantly along the target surface. However, when there is preplasma, electron emission changes to the target normal. This difference originates from the different absorption mechanisms and different Coulomb electrostatic fields and self-generated magnetic fields induced in front of the target for the two cases.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2014
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 generation.
Physics of Plasmas, 2010
The effect of preplasma on fast electron generation and transport has been studied using an intense-laser pulse ͑I =2ϫ 10 18 W / cm 2 ͒ at the Osaka University. An external long pulse laser beam ͑E Ͻ 1.5 J͒ was used to create various levels of preplasmas in front of a planar target for a systematic study. K␣ x-ray emission from a fluorescence layer ͑copper͒ was absolutely counted and its spatial distribution was monitored. Experimental data show K␣ x-ray signal reduction ͑up to 60%͒ with an increase in the preplasma level. In addition, a ring structure of K␣ x rays was observed with a large preplasma. The underlying physics of the ring structure production was studied by integrating the modeling using a radiation hydrodynamics code and a hybrid particle-in-cell code. Modeling shows that the ring structure is due to the thermoelectric magnetic field excited by the long pulse laser irradiation and an electrostatic field due to the fast electrons in the preplasma.
Plasma Physics Reports, 2015
The electron acceleration mechanism associated with the generation of a plasma wave due to selfmodulation instability of laser radiation in a subcritical plasma produced by a laser prepulse coming 10 ns before the arrival of the main intense femtosecond pulse is considered. Three-dimensional particle-in-cell simulations of the interaction of laser radiation with two-dimensionally inhomogeneous subcritical plasma have shown that, for a sufficiently strong plasma inhomogeneity and a sharp front of the laser pulse, efficient plasma wave excitation, electron trapping, and generation of collimated electron beams with energies on the order of 0.2-0.5 МeV can occur. The simulation results agree with experiments on the generation of collimated beams of accelerated electrons from metal targets irradiated by intense femtosecond laser pulses.
Journal of Applied Physics, 2018
The role of ballistic electrons generated during ultrashort pulse laser (USPL) absorption in metallic targets was investigated in a wide range of laser intensities using our developed simulation package FEMTO-2D. The simulation package is based on the numerical solution of the two-temperature model with the assumption of local thermal equilibrium for electron and lattice subsystems within the simulation cell at any time step. Electron thermodynamic parameters were calculated through the processes of material transition from the cold solid state into the dense plasma state during and after the pulse based on the collision theory. The appropriate model for temperature dependent thermodynamic parameters allows defining the heat transport during an early stage of the USPL-matter interaction directly, without relying on the effective absorption depth model. The study investigated, for the first time, using integrated computer simulation the role of ballistic electrons in energy transfer and heat conduction during USPL deposition. The simulation predictions of the electron heat transport dynamics during and shortly after the laser pulse were benchmarked for the gold target against available experimental data and were able to confirm the dominant role of the ballistic electrons in the initial heat propagation within 100-120 nm of the target at laser intensities below 10 13 W/cm 2 .
Acceleration of electrons in the interaction of a subterawatt laser pulse with a nonuniform plasma
Quantum Electronics, 2019
We consider the effect of nonlinear self-focusing and self-modulation processes on the acceleration of electrons in the interaction of a subterawatt femtosecond laser pulse with a gas jet plasma. A three-dimensional particle-in-cell (3D PIC) simulation of the interaction of laser radiation with a low-density nonuniform plasma shows that laser pulse self-focusing that arises when the critical power of relativistic self-focusing determined by the local concentration of plasma electrons exceeds the pulse power results in efficient generation of a plasma wave. Due to a decrease in the phase velocity of the wake plasma wave generated via self-modulation of the laser pulse, electrons are trapped into the accelerating phase of the plasma wave and are accelerated to energies of ~ 10 MeV. It is demonstrated that under the conditions for limiting the electrons' acceleration region by the length of their dephasing, quasi-monoenergetic electron bunches with a characteristic energy of ~ 9 MeV can be produced. The effective temperature of the accelerated electrons and their angular distribution, obtained by 3D PIC simulation, are in good agreement with those determined in the experiment.
Fast electron heating of a solid target in ultrahigh-intensity laser pulse interaction
Physical Review E, 2004
We report one of the first measurements of induced heating due to the transport of a fast electron beam generated by an ultrashort pulse laser interaction with solid targets. Rear-side optical reflectivity and emissivity have been used as diagnostics for the size and temperature of the heated zone. A narrow spot has been observed of the order of the laser focus size. Values up to ϳ10 eV at the target back surface were inferred from the experimental data and compared with the predictions of a hybrid collisional-electromagnetic transport simulation.
Physical Review Letters, 1998
Novel features of plasma generation by 1 ps, 1 mm, ϳ10 19 W cm 22 laser pulses on thick plastic targets are presented: (i) The electron distribution in the ablated plasma has a minimum along the target normal which persists long after the laser pulse ͑.1 ns͒; (ii) a narrow plasma jet is formed at the rear surface after a few picoseconds, in line with the laser focus. This is consistent with a beam of fast electrons traveling through the target, collimated by a magnetic field in the target.