This paper proposes an intense x-ray source based on the interactions of intense laser pulses with nanowire targets. The presented electron dynamics and energy scalings have been studied by three dimensional particle-in-cell simulations. The resonance of the electronic betatron oscillations with the incident laser field results in extremely high energy electrons. The scaling of radiation intensity is predicted to be ∼IL5/2, where IL is the laser intensity, using optimal parameters. In this case, the number of photons emitted, via synchrotron radiation, with energies above the keV level with 0.1 rad angular spread is greater than 108/fs for intensities IL>1020 W/cm2. This scaling law suggests that the photon flux production using nanowires of suitable lengths is much greater than in a underdense plasma.
This paper proposes a novel and effective method for generating GigaGauss level, solenoidal quasi-static magnetic fields in under-dense plasma using screw-shaped high intensity laser pulses. This method produces large solenoidal fields that move with the driving laser pulse and are collinear with the accelerated electrons. This is in contrast with already known techniques which rely on interactions with over-dense or solid targets and generates radial or toroidal magnetic field localized at the stationary target. The solenoidal field is quasi-stationary in the reference frame of the laser pulse and can be used for guiding electron beams. It can also provide synchrotron radiation beam emittance cooling for laser-plasma accelerated electron and positron beams, opening up novel opportunities for designs of the light sources, free electron lasers, and high energy colliders based on laser plasma acceleration.
The efficient transfer of angular orbital momentum from circularly polarized laser pulses into ions of solid density targets is investigated with different geometries using particle-in-cell simulations. The detailed electron and ion dynamics presented focus upon the energy and momentum conversion efficiency. It is found that the momentum transfer is more efficient for spiral targets and the maximum value is obtained when the spiral step is equal to twice the laser wavelength. This study reveals that the angular momentum distribution of ions strongly depends up on the initial target shape and density.
Current laser technology allows the production of extremely high laser intensities and brings ever closer experimental probing of quantum electro-dynamic effects e.g. radiation reaction and electron-positron pair creation via the multiphoton Breit-Wheeler process. The exponential dependence of the latter process on laser intensity means that the process appears suddenly above some threshold, which is still not well defined in the case of laser-plasma interactions. The threshold intensity for the generation of a significant number of positrons is shown to be in the order 10 22 W cm −2 , when optimal target properties, as presented in this paper, are considered. With the help of a modified particle-in-cell code, the detailed angular-energy distribution of positrons is presented, which is in good agreement with our simple analytical model.
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