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.
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).
The results of Monte-Carlo simulations of electron-positron-photon cascades initiated by slow electrons in circularly polarized fields of ultrahigh strength are presented and discussed. Our results ...confirm previous qualitative estimations A. M. Fedotov et al., Phys. Rev. Lett. 105, 080402 (2010) of the formation of cascades. This sort of cascade has revealed a new property of restoration of energy and dynamical quantum parameter due to acceleration of electrons and positrons by the field. This may become a dominating feature of laser-matter interactions at ultrahigh intensities. Our approach incorporates radiation friction acting on individual electrons and positrons.
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 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.
Ion acceleration in laser-produced dense plasmas is a key topic of many recent investigations thanks to its potential applications. Indeed, at forthcoming laser intensities (I 1023 W cm−2) ...interaction of laser pulses with plasmas can be accompanied by copious gamma-ray emission. Here we demonstrate the mutual influence of gamma-ray emission and ion acceleration during relativistic hole boring in high-density plasmas with ultra-intense laser pulses. If the gamma-ray emission is abundant, laser pulse reflection and hole-boring velocity are lower and gamma-ray radiation pattern is narrower than in the case of low emission. Conservation of energy and momentum allows one to elucidate the effects of the gamma-ray emission which are more pronounced at higher hole-boring velocities.
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.
We present the results of the theoretical analysis and numerical simulations of the Weibel instability in two counterstreaming hot relativistic plasma flows, for instance the flows of electron-proton ...plasmas with rest-mass densities , Lorentz factors , and proper temperatures . The instability growth rate and the filament size at the linear stage are found analytically and are in qualitative agreement with the results of three-dimensional particle-in-cell simulations. In the simulations, incoherent synchrotron emission and pair photoproduction in electromagnetic fields are taken into account. If the plasma flows are dense, fast, and hot enough, the overall energy of the synchrotron photons can be much higher than the energy of the generated electromagnetic fields. Furthermore, a sizable number of positrons can be produced due to the pair photoproduction in the generated magnetic field. We propose a rough criterion to judge copious pair production and considerable synchrotron losses. By means of this criterion, we conclude that the incoherent synchrotron emission and the pair production during the Weibel instability can have implications for the collapsar model of gamma-ray bursts.
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