Creation of angular momentum in a relativistic electron-positron plasma is explored. It is shown that a chain of angular momentum carrying vortices is a robust asymptotic state sustained by the generalized nonlinear Schrodinger equation characteristic to the system. The results may suggest a possible electromagnetic origin of angular momenta when it is applied to the MeV epoch of the early Universe.
The effect of carrier envelope phase (CEP) on the spatio-temporal distribution of the electron-positron pairs created by untraintense counterpropagating femtosecond laser pulses is studied. When the laser pulses are linearly polarized, the temporal distribution of the pairs is found to be sensitive to CEP. On the hand, it is found to be largely insensitive to CEP for circularly polarized pulses.
Relativistic positron beams are required for fundamental research in nonlinear strong field QED, plasma physics, and laboratory astrophysics. Positrons are difficult to create and manipulate due to their short lifetime, and their energy gain is limited by the accelerator size in conventional facilities. Alternative compact accelerator concepts in plasmas are becoming more and more mature for electrons, but positron generation and acceleration remain an outstanding challenge. Here we propose a new setup where we can generate, inject and accelerate them in a single stage during the propagation o…
Creation of electrons and positrons from light alone is a basic prediction of quantum electrodynamics, but yet to be observed. Here we show that it is possible to create ${>}10^8$ positrons by dual laser irradiation of a structured plasma target, at intensities of $2 \times 10^{22} \mathrm{W}\mathrm{cm}^{-2}$. In contrast to previous work, the pair creation is primarily driven by the linear Breit-Wheeler process ($γγ\to e^+ e^-$), not the nonlinear process assumed to be dominant at high intensity, because of the high density of $γ$ rays emitted inside the target. The favorable scaling with las…
The radiation pressure of next generation ultra-high intensity ($>10^{23}$ W/cm$^{2}$) lasers could efficiently accelerate ions to GeV energies. However, nonlinear quantum-electrodynamic effects play an important role in the interaction of these laser pulses with matter. Here we show that these effects may lead to the production of an extremely dense ($\sim10^{24}$ cm$^{-3}$) pair-plasma which absorbs the laser pulse consequently reducing the accelerated ion energy and energy conversion efficiency by up to 30-50\% \& 50-65\%, respectively. Thus we identify the regimes of laser-matter interacti…
Electron-positron pair creation in collisions of a modulated laser pulse with a high-energy photon (nonlinear Breit-Wheeler process) is studied by means of strong-field quantum electrodynamics. It is shown that the driving pulse modulations lead to appearance of comb structures in the energy spectra of produced positrons (electrons). It is demonstrated that these combs result from a coherent enhancement of probability amplitudes of pair creation from different modulations of the laser pulse. Thus, resembling the Young-double slit experiment for anti-matter (matter) waves.
Phase control of multi-photon electron-positron pair creation from vacuum
Institute of Astronomy and Physics, Inner Mongolia University（内蒙古大学天文与物理学院）；School of Science, China University of Mining and Technology（中国矿业大学理学院）；Laboratory of Zhongyuan Light, School of Physics, Zhengzhou University（郑州大学物理学院中原光实验室）；School of Management Science and Engineering, Anhui University of Finance and Economics（安徽财经大学管理科学与工程学院）；State Key Laboratory for Tunnel Engineering, China University of Mining and Technology（中国矿业大学隧道工程国家重点实验室）
The dynamics of an electron bunch irradiated by two focused colliding super-intense laser pulses and the resulting gamma and electron-positron production are studied. Due to attractors of electron dynamics in a standing wave created by colliding pulses the photon emission and pair production, in general, are more efficient with linearly polarized pulses than with circularly polarized ones. The dependence of the key parameters on the laser intensity and wavelength allows to identify the conditions for the cascade development and gamma-electron-positron plasma creation.
A novel approach for positron injection and acceleration in laser driven plasma wakefield is proposed. A theoretical model is developed and confirmed through PIC simulation. One ring-shaped beam and one co-axially propagating Gaussian beam drive wakefields in a preformed plasma volume filled with both electrons and positrons. The laser's ponderomotive force as well as the charge separation force in the front bucket of the first bubble are utilized to provide the transverse momenta of injected positrons and those positrons can be trapped by the focusing field and then accelerated by the wakefie…
QED-effects are known to occur in a strong laser pulse interaction with a counter-propagating electron beam, among these effects being electron-positron pair creation. We discuss the range of laser pulse intensities of J > 5*10^22 W/cm2 combined with electron beam energies of tens of GeV. In this regime multiple pairs may be generated from a single beam electron, some of the newborn particles being capable of further pair production. Radiation back-reaction prevents avalanche development and limits pair creation. The system of integro-differential kinetic equations for electrons, positrons and…
Electron-positron pairs are produced through the Breit-Wheeler process when energetic photons traverse electromagnetic fields of sufficient strength. Here we consider a possible experimental geometry for observation of pair creation in the highly nonlinear regime, in which bremsstrahlung of an ultrarelativistic electron beam in a high-$Z$ target is used to produce $γ$ rays that collide with a counterpropagating laser pulse. We show how the target thickness may be chosen to optimize the yield of Breit-Wheeler positrons, and verify our analytical predictions with simulations of the cascade in th…
The creation of an electron space charge in a dipole magnetic trap and the subsequent injection of positrons has been experimentally demonstrated. Positrons (5eV) were magnetically guided from their source and injected into the trapping field generated by a permanent magnet (0.6T at the poles) using a cross field E $\times$ B drift, requiring tailored electrostatic and magnetic fields. The electron cloud is created by thermionic emission from a tungsten filament. The maximum space charge potential of the electron cloud reaches -42V, which is consistent with an average electron density of ($4 \…
We have studied the linear dispersion relation for Langmuir waves in plasmas of very high density, based on the Dirac-Heisenberg-Wigner formalism. The vacuum contribution to the physical observables leads to ultra-violet divergences, that are removed by a charge renormalization. The remaining vacuum contribution is small, and is in agreement with previously derived expressions for the time-dependent vacuum polarization. The main new feature of the theory is a damping mechanism similar to Landau damping, but where the plasmon energy give rise to creation of electron-positron pairs. The dependen…
We present a short review of recent progress in studying QED effects of interaction of ultra-relativistic laser pulses with vacuum and $e^-e^+$ plasma. The development of laser technologies promises very rapid growth of laser intensities in close future already. Two exawatt class facilities (ELI and XCELS, Russia) in Europe are already in the planning stage. Realization of these projects will make available a laser of intensity $\sim 10^{26}$W/cm$^2$ or even higher. Therefore, discussion of nonlinear optical effects in vacuum are becoming urgent for experimentalists and are currently gaining m…
Direct production of electron--positron pairs in two photon collisions, the Breit--Wheeler process, is one of the basic processes in the Universe. However, it has never been observed in laboratory because of absence of the intense gamma-ray sources. Laser induced synchrotron sources emission may open for the first time a way to observe this process. A feasibility of an experimental set--up using a MeV photon source is studied in this paper. We compare several $γ$--ray sources, estimate the expected number of electron--positron pairs and competing processes by using numerical simulations includ…
The possibility to observe vacuum electron-positron pair creation due to a powerful optical laser pulse is discussed. We employ a quantum kinetic formulation of the problem with a source term describing the vacuum pair production in a homogeneous electric field with arbitrary time dependence (dynamical Schwinger mechanism). For a periodic field weak in comparison with the critical value E_{cr}=m^2/|e|, the electron-positron plasma density changes approximately periodically with twice the field frequency. Under these conditions, the mean value $<n>$ for the density per period in the volume lamb…
We study the process of energy conversion from overcritical electric field into electron-positron-photon plasma. We solve numerically Vlasov-Boltzmann equations for pairs and photons assuming the system to be homogeneous and anisotropic. All the 2-particle QED interactions between pairs and photons are described by collision terms. We evidence several epochs of this energy conversion, each of them associated to a specific physical process. Firstly pair creation occurs, secondly back reaction results in plasma oscillations. Thirdly photons are produced by electron-positron annihilation. Finally…
