arXiv subjects

L. G. Zhang

Publications and source records attributed to L. G. Zhang.

4 recordsLinked to original sources

arXiv2020

Generalizing the Sokolov-Ternov effect for radiative polarization in intense laser fields

A consistent description of the radiative polarization for relativistic electrons in intense laser fields is derived by generalizing the Sokolov-Ternov effect in general field structure. The new form together with the spin-dependent radiation-reaction force provides a complete set of dynamical equations for electron momentum and spin in strong fields. When applied to varying intense fields, e.g. the laser fields, the generalized Sokolov-Ternov effect allows electrons to gain or lose polarization in any directions other than along the magnetic field in the rest frame of the electron. The generalized theory is applied to the collision process between initially polarized/unpolarized high energy electrons with linearly polarized ultra-intense laser pulse, showing results that eliminate the dependence on specific choices of a quantization axis and spin initialization existing in spin-projection models.

physics.plasm-ph↗

arXiv2019

Radiative deflection by spin effect in the quantum radiation-reaction regime

The colliding between ultra-relativistic electrons and an ultra-intense laser pulse is a powerful approach to testify the physics in strong-field QED regime. By considering spin-dependent radiation-reaction during laser-electron collision we find anti-symmetric deflection of electrons with different spin states. We revealed that such deflection is induced by the non-zero work done by radiation-reaction force along field polarization-direction in a half-period of phase, which is larger for spin-anti-paralleled electrons and smaller for spin-paralleled electrons. The spin-projection on the magnetic field of an electron gets inversed in adjacent half-periods due to oscillating magnetic field and therefore the deflection due to spin-dependent radiation is accumulated rather than vanishing. The new mechanism provides an extra dimension to observe quantum radiation-reaction effect in the strong-field QED regime by measuring the anti-symmetric distribution.

physics.plasm-ph↗

arXiv2018

Quantum Reflection above the Classical Radiation-reaction Barrier in the QED Regime

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 radiation-reaction (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 $2\times10^{23}\ \mathrm{W/cm^2}$ and electron energies of $\sim 10^2\ \mathrm{MeV}$; 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.

physics.plasm-ph↗

arXiv2014

High quality electron bunch generation with CO2-laser plasma accelerator

CO2 laser-driven electron acceleration is demonstrated with particle-in-cell simulation in low-density plasma. An intense CO2 laser pulse with long wavelength excites wakefield. The bubble behind it has a broad space to sustain a large amount of electrons before reaching its charge saturation limit. A transversely propagating inject pulse is used to induce and control the ambient electron injection. The accelerated electron bunch with total charge up to 10 nC and the average charge per energy interval of more than 0.6 nC/MeV are obtained. Plasma-based electron acceleration driven by intense CO2 laser provides a new potential way to generate high-charge electron bunch with low energy spread, which has broad applications, especially for X-ray generation by table-top FEL and bremsstrahlung.

physics.plasm-ph↗