We present a self-consistent theory of strongly nonlinear plasma wakefield (bubble or blowout regime of the wakefield) based on the energy conservation approach. Such wakefields are excited in ...plasmas by intense laser or particle beam drivers and are characterized by the expulsion of plasma electrons from the propagation axis of the driver. As a result, a spherical cavity devoid of electrons (called a "bubble") and surrounded by a thin sheath made of expelled electrons is formed behind the driver. In contrast to the previous theoretical model W. Lu et al., Phys. Rev. Lett. 96, 165002 (2006)PRLTAO0031-900710.1103/PhysRevLett.96.165002, the presented theory satisfies the energy conservation law, does not require any external fitting parameters, and describes the bubble structure and the electromagnetic field it contains with much higher accuracy in a wide range of parameters. The obtained results are verified by 3D particle-in-cell simulations.
A radiation-reaction trapping (RRT) of electrons is revealed in the near-QED regime of laser-plasma interaction. Electrons quivering in laser pulse experience radiation reaction (RR) recoil force by ...radiating photons. When the laser field reaches the threshold, the RR force becomes significant enough to compensate for the expelling laser ponderomotive force. Then electrons are trapped inside the laser pulse instead of being scattered off transversely and form a dense plasma bunch. The mechanism is demonstrated both by full three-dimensional particle-in-cell simulations using the QED photonic approach and numerical test-particle modeling based on the classical Landau-Lifshitz formula of RR force. Furthermore, the proposed analysis shows that the threshold of laser field amplitude for RRT is approximately the cubic root of laser wavelength over classical electron radius. Because of the pinching effect of the trapped electron bunch, the required laser intensity for RRT can be further reduced.
The vast majority of QED results are obtained in relatively weak fields and so in the framework of perturbation theory. However, forthcoming laser facilities providing extremely high fields can be ...used to enter not-yet-studied regimes. Here, a scheme is proposed that might be used to reach a supercritical regime of radiation reaction or even the fully non-perturbative regime of quantum electrodynamics. The scheme considers the collision of a 100 GeV-class electron beam with a counterpropagating ultraintense electromagnetic pulse. To reach these supercritical regimes, it is unavoidable to use a pulse with ultrashort duration. Using two-dimensional particle-in-cell simulations, it is therefore shown how one can convert a next-generation optical laser to an ultraintense (I ≈ 2.9 × 10
Wcm
) attosecond (duration ≈ 150 as) pulse. It is shown that if the perturbation theory persists in extreme fields, the spectrum of secondary particles can be found semi-analytically. In contrast, a comparison with experimental data may allow differentiating the contribution of high-order radiative corrections if the perturbation theory breaks.
We study hollow plasma channels with smooth boundaries for laser-driven electron acceleration in the bubble regime. Contrary to the uniform plasma case, the laser forms no optical shock and no ...etching at the front. This increases the effective bubble phase velocity and energy gain. The longitudinal field has a plateau that allows for monoenergetic acceleration. We observe as low as 10⁻³ rms relative witness beam energy uncertainty in each cross section and 0.3% total energy spread. By varying the plasma density profile inside a deep channel, the bubble fields can be adjusted to balance the laser depletion and dephasing lengths. Bubble scaling laws for the deep channel are derived. Ultrashort pancakelike laser pulses lead to the highest energies of accelerated electrons per Joule of laser pulse energy.
Abstract
We study electron acceleration in a plasma wakefield under the influence of the radiation-reaction force caused by the transverse betatron oscillations of the electron in the wakefield. Both ...the classical and the strong quantum-electrodynamic (QED) limits of the continuous radiation reaction are considered. For the constant accelerating force, we show that the amplitude of the oscillations of the QED parameter
χ
in the radiation-dominated regime reaches an equilibrium value determined only by the magnitude of the accelerating field, while the averaged over betatron oscillations radiation reaction force saturates at a value smaller than the accelerating force and thus is incapable of stopping acceleration. We find the parameters of the electron bunch and the plasma accelerator for which reaching such a regime is possible. We also study effects of the dephasing and the corresponding change of the accelerating force over the course of acceleration and conclude that the radiation-dominated regime is realized both in cases of single-stage acceleration with slow dephasing (usually corresponding to bunch-driven plasma accelerators) and multi-stage acceleration with fast dephasing (corresponding to the use of laser-driven accelerators).
Recently, much attention has been attracted to the problem of limitations on the attainable intensity of high power lasers A. M. Fedotov et al., Phys. Rev. Lett. 105, 080402 (2010). The laser energy ...can be absorbed by electron-positron pair plasma produced from a seed by a strong laser field via the development of the electromagnetic cascades. The numerical model for a self-consistent study of electron-positron pair plasma dynamics is developed. Strong absorption of the laser energy in self-generated overdense electron-positron pair plasma is demonstrated. It is shown that the absorption becomes important for a not extremely high laser intensity I ∼ 10(24) W/cm(2) achievable in the near future.
Laser-driven vacuum breakdown waves Samsonov, A S; Nerush, E N; Kostyukov, I Yu
Scientific reports,
07/2019, Letnik:
9, Številka:
1
Journal Article
Recenzirano
Odprti dostop
It is demonstrated by three-dimensional quantum electrodynamics - particle-in-cell (QED-PIC) simulations that vacuum breakdown wave in the form of QED cascade front can propagate in an extremely ...intense plane electromagnetic wave. The result disproves the statement that the self-sustained cascading is not possible in a plane wave configuration. In the simulations the cascade is initiated during laser-foil interaction in the light sail regime. As a result, a constantly growing electron-positron plasma cushion is formed between the foil and laser radiation. The cushion plasma efficiently absorbs the laser energy and decouples the radiation from the moving foil thereby interrupting the ion acceleration. The models describing propagation of the cascade front and electrodynamics of the cushion plasma are presented and their predictions are in a qualitative agreement with the results of numerical simulations.
Photon emission by an ultrarelativistic charged particle in extremely strong magnetic field is analyzed, with vacuum polarization and photon recoil taken into account. Vacuum polarization is treated ...phenomenologically via refractive index. The photon emission occurs in the synergic (cooperative) synchrotron-Cherenkov process J Schwinger et al 1976 Annals of Physics 96 303 which is similar to the synchrotron emission rather than to the Cherenkov one. For electrons, the effect of vacuum polarization on the emission spectrum is not evident at least below the probable onset of non-perturbative quantum electrodynamics (QED). However, the effect of vacuum polarization on the emission spectrum can be observable for muons already at γB/BS ≈ 30, with γ the muon Lorentz factor, B the magnetic field strength and BS the critical QED field. Nevertheless, vacuum polarization leads to only 10% enhancement of the maximum of the radiation spectrum.
The radiation reaction (beamstrahlung) effect on particle dynamics during interaction of oppositely charged beams is studied. It is shown that the beam focusing can be strongly enhanced due to ...beamstrahlung. An approximate analytical solution of the motion equations including the radiation reaction force is derived. The disruption parameter is calculated for classical and quantum regime of beamstrahlung. The analytical model is verified by QED-PIC simulations. The model for head-on collision of long beams undergoing a number of betatron oscillation during interaction is also developed. It is demonstrated that the beamstrahlung-enhanced disruption effect can play an important role in future lepton colliders with high-current particle beams.
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