Quantum reflection above the classical radiation-reaction barrier in the quantum electro-dynamics regime

Abstract

The colliding between an ultra-intense laser pulse with a high energy electron beam is not only an important source for high-brightness gamma-rays but also a powerful approach to exploit new physics in the exotic strong-field QED regime. In the cross-colliding geometry, when radiationreaction (RR) force is interpreted by the classical Landau-Lifshitz equation, we found that there is a distinctive barrier that allows penetration of electrons at energies beyond the barrier and blocks those of lower energies. While in the QED perspective, electrons can be well reflected (transmit) in the regime where complete transmission (reflection) is allowed classically. The reflection (transmission) is guaranteed by the quantum nature of radiation but forbidden by classical description. This effect is accompanied by the blurring of the angular distribution for scattered electrons and becomes significant for laser intensities at 2 × 10 23 W/cm 2 and electron energies of ∼ 10 2 MeV; thus could be measured in the up-coming 10-100PW laser facilities. By detecting the reflection rate of the energetic electron beam after colliding and resolve the angular distribution, the results are capable of identifying the boundaries between classical and QED approaches in the strong field regime and testifying the various models describing the fundamental process.Understanding the electron dynamics in relativistic laser fields has been a core interest in strong-field physics and brooded numerous key applications such as fast ignition fusion, acceleration of charged particles and producing bright X/gamma-ray sources. These advantages become strong motivations for developing the 10-100PW high-power laser systems, including SEL, ELI, XCELS, Apollon, Vulcan, SULF [1-6] etc. Light intensity is likely to approach 10 23−24 W/cm 2 in the foreseeable future and promote light-matter interaction to the unprecedented radiation-dominated regime [7] or even the QED regime [8][9][10]. In the new regimes, a rising interest of fundamental importance is the unique electron dynamics at extreme laser fields, in which electrons are accelerated and radiate photons of considerable energies such that recoil force is not negligible. This phenomenon is usually referred as radiation-reaction (RR).Theoretical attempts were made to account for classical RR such as Lorentz-Abraham-Dirac equation [11] and Landau-Lifshitz (LL) equation [12], both of which were derived from the assumption of continuous classical radiation. The latter is widely accepted because it resolves the nonphysical run-away solution [13]. Classical treatment is successive in describing accumulative RR effects. In the QED regime, stochastic radiation and high energy photon (Nos.

Spin-dependent radiative deflection in the quantum radiation-reaction regime

“…The bunch get polarized along y because the electrons with positive s y tend to be scattered upwards while those with negative s y downwards. Experimental measurement of this anti-symmetric phenomenon provides a new degree of freedom to study the quantum RR effect in addition to spin-free phenomena [7,10,[31][32][33]. Effects of the electron beam energy spread and angular divergence are illustrated in figure 4(c).…”

“…For instance, electrons emit high-energy gamma-photons via non-linear Compton scattering and consequently feel recoil, which is usually referred to as radiation-reaction (RR) force [3,4]. In the case where the photon energy is comparable to the electron energy, quantum behavior appears such that the radiation turns to be stochastic [5][6][7][8][9][10]. The electron motion therefore is governed by the quantum radiation-reaction effect in the strong field quantum electro-dynamics (QED) picture.…”

Radiation reaction as an energy enhancement mechanism for laser-irradiated electrons in a strong plasma magnetic field

“…At these facilities, even experimental observation of the instantaneous RF became possible 12,13 in the random energy loss of a laser-accelerated relativistic electron bunch when scattered by a high-power laser pulse. Similar setups were investigated in a series of theoretical studies 14–26 , indicating the acceleration of electrons as an important field of application for high-intensity laser facilities 27–30 .…”

Quasimonochromatic Bright Gamma-ray Generation from Synchronized Compton Scattering via Azimuthal Spatial-Temporal Coupling

“…This is necessary for the case of 𝑎 0 = 25. For electron energy of 𝛾 = 𝑂 (10 3 ) and field strength of 𝑎 = 𝑂(1), we have the quantum parameter [49] 𝜒 = 𝑂(10 −2 ) that indicates the nonlinear quantum effects are weak [50][51][52]. Therefore classical calculations are sufficient to deal with the radiation spectrum.…”