arXiv subjects

Hai-Bo Sang

Publications and source records attributed to Hai-Bo Sang.

9 recordsLinked to original sources

arXiv2025

Entropy of Schwinger pair production in time-dependent Sauter pulse electric field

We investigate entropy of electron-positron pair production in time-dependent Sauter pulse electric field. Both cases of pair longitudinal momentum only and full momentum consideration are examined. We further examine three types of entropy, one is the usual entanglement entropy $S_{\text{E}}$, the other two extensions are thermal distribution entropy $S_{\text{Th}}$, and that with the chemical potential correction, $S_{\text{Th,CP}}$. For short pulse, $S_{\text{E}}$ is higher than $S_{\text{Th}}$ and vice versa for long pulse. The chemical potential causes the single-particle average thermal distribution entropy $\frac{S_{\text{Th,CP}}}{N}$ to exhibit non-monotonic behavior, similar to the single-particle average entanglement entropy $\frac{S_{\text{E}}}{N}$ in the short-pulse range. In the full momentum case, we calculate the thermal distribution entropy $S_{\text{Th, U}}$ via introducing the Unruh temperature as the local effective temperature. We find that both $S_{\text{Th, U}}$ and $S_{\text{E}}$ saturate asymptotically to the constant while the former has a larger asymptotic value. The results presented in this study reveals that the different entropies have some delicate relationships among them.

hep-ph↗

arXiv2024

Attosecond electron bunch generation by an intense laser propagation in conical channel with a curved wall

By using two-dimensional particle-in-cell simulations, attosecond electron bunches with high density, high energy and small divergence angle can be obtained by p-polarized laser irradiation in conical channel with curved wall. We find that some electrons in the wall are pulled into the channel by the transverse electric field and are directly accelerated. Meanwhile, they move steadily along the conical wall via laser pondermotive force. The results show that the focusing effect of the curved wall conical channel is stronger than that of the traditional flat wall conical channel, and the density of the attosecond electron bunches is increased by nearly 175% as well as the maximum energy is increased by 36%. We also find that the quality of the electron bunches is affected by the geometry of the concial channel wall. Interestingly it is found that the attosecond electron bunches obtained from the specific concial channel with the hyperbolic geometry of the curved wall can keep stable around the maximum electron energy within 10T0 even if they have left the channel.

physics.plasm-ph↗

arXiv2023

Stability range of parameters at fixed points for a class of complex dynamics

We study the parameters range for the fixed point of a class of complex dynamics with the rational fractional function as $R_{n,a,c}(z)=z^n+\frac{a}{z^n}+c$, where $n=1,2,3,4$ is specified, $a$ and $c$ are two complex parameters. The relationship between two parameters, $a$ and $c$, is obtained at the fixed point. Moreover the explicit expression of the parameter $a$ and $c$ in terms of $λ$ is derived, where $λ$ is the derivative function at fixed point. The parameter regimes for the stability of the fixed point are presented numerically for some typical different cases.

math.DS↗

arXiv2022

Generation of bright collimated vortex $γ$-ray via laser driven cone-fan target

We use numerical simulations to demonstrate that a source of bright collimated vortex $γ$-ray with large orbital angular momentum can be achieved by irradiating a circularly polarized laser with an intensity about $10^{22}\rm{W/{cm^2}}$ on a cone-fan target. In the studied setup, electron beam of energy of hundreds of MeV and vortex laser pulse are formed. And furthermore a high quality vortex $γ$-ray is yielded with small divergence of $5^{\circ}$ and high peak brilliance $\sim5\times10^{22}$ photons ${\rm\cdot s^{-1} \cdot mm^{-2} \cdot mrad^{-2}}$ $0.1\%\mathrm{BW}$ at $10\mathrm{MeV}$. A considerable fraction of angular momentum of laser is converted to electron beam and vortex $γ$-ray, which are roughly $27.8\%$ and $3\%$, respectively. And the conversion efficiency of energy from laser to electron beam and vortex $γ$-ray are around $41\%$ and $3.8\%$. Moreover, comparative simulations for different right radius of cone reveal that there exists an optimal size that makes the highest angular momentum of $γ$-ray photons to be around $2.8\times10^6\hbar$. The comparative simulations for different laser modes exhibit that it is more appropriate to choose the circularly polarized laser to generate vortex $γ$-ray than the Laguerre-Gaussian one.

physics.plasm-ph↗

arXiv2022

Angular distributions of nonlinear Thomson scattering in combining field with a general elliptically polarized laser and a background magnetic field

Nonlinear Thomson scattering of an electron motion in a combining field constituted by an elliptically polarized laser and a background magnetic field is investigated. The dependence of the electron trajectories, the fundamental frequency, the maximum radiation power in spatial distribution and corresponding spatial angle on ellipticity are obtained. In addition, we find that the angular distributions of scattering spectra with respect to the azimuthal angle exhibits the symmetry no matter what the order of harmonics, the laser intensity, the magnetic resonance parameter and the initial axial momentum are. Meanwhile, the polar angle distribution of the spectra approaches more and more the laser propagation direction with the laser intensity, the magnetic resonance parameter and the initial axial momentum. The maximum radiated power increases and the corresponding polar angle decreases. The optimal angle for the maximum radiated power per unit of solid, the corresponding photon number and the photons brightness can be obtained, which implies that the high quality XUV or/and x-ray can be generated by the studied scheme when the suitable parameters are chosen.

physics.optics↗

arXiv2018

The high density $γ$-ray emission and dense positron production via multi-lasers driven circular target

A diamond-like carbon circular target is proposed to improve the $γ$-ray emission and pair production with lasers intensity of $8\times 10^{22} ~\mathrm{W/cm^2}$ by using two-dimensional particle-in-cell simulations with quantum electrodynamics. It is found that the circular target can significantly enhance the density of $γ$-photons than plane target when two colliding circularly polarized lasers irradiate the target. By multi-lasers irradiate the circular target, the optical trap of lasers can prevent the high energy electrons accelerated by laser radiation pressure from escaping. Hence, high density as $5164 n_c$ $γ$-photons is obtained through nonlinear Compton back-scattering. Meanwhile, $2.7 \times 10^{11}$ positrons with average energy of $230 ~\mathrm{MeV}$ is achieved via multi-photon Breit-Wheeler process. Such ultrabright $γ$-ray source and dense positrons source can be useful to many applications. The optimal target radius and laser mismatching deviation parameters are also discussed in detail.

physics.plasm-ph↗

arXiv2018

Angular Distributions of Thomson Scattering in Combined Laser and Magnetic fields

Angular distributions of Thomson scattering are researched in the combined fields with a circularly polarization of laser field and a strong uniform magnetic field. The trajectories of the electron and the dependence of it on the initial phase are also given. It is found that the angular distributions with respect to the azimuthal angle show twofold symmetry whatever the laser intensity, the order of harmonics, the resonance parameter, and the initial axial momentum are. On the other hand, the radiation with respect to the polar angle is mainly distributed in two regions which are roughly symmetric of the laser propagation. In addition, the larger the laser intensity, the resonance parameters, the initial axial momentum are, the closer radiation is to the laser propagation direction. Besides, a new possibility of X-ray production is indicated. That is to say, with appropriate choice of laser and electron parameters, the high frequency part of the Thomson scattering radiation can reach the frequency range of X-ray (10^17 Hz - 10^18 Hz).

physics.plasm-ph↗

arXiv2017

Enhanced laser radiation pressure acceleration of protons with a gold cone-capillary

A scheme with gold cone-capillary is proposed to improve the protons acceleration and involved problems are investigated by using the two-dimensional particle-in-cell simulations. It is demonstrated that the cone-capillary can efficiently guide and collimate the protons to a longer distance and lead to a better beam quality with a dense density $\geq10n_c$, monoenergetic peak energy $E_k \sim 1.51~\mathrm{GeV}$, spatial emittance $\sim0.0088~\mathrm{mm}~\mathrm{mrad}$ with divergence angle $θ\sim 1.0^{\circ}$ and diameter $\sim 0.5\mathrm{μm}$. The enhancement is mainly attributed to the focusing effect by the transverse electric field generated by the cone as well as the capillary, which can prevent greatly the protons from expanding in the transverse direction. Comparable to without the capillary, the protons energy spectra have a stable monoenergetic peak and divergence angle near to $1.0^{\circ}$ in longer time. Besides, the efficiency of acceleration depending on the capillary length is explored, and the optimal capillary length is also achieved. Such a target may be benefit to many applications such as ions fast ignition in inertial fusion, proton therapy in medicine and so on.

physics.plasm-ph↗

arXiv2016

Scale invariance and scaling law of Thomson backscatter spectra by electron moving in laser-magnetic resonance regime

The Thomson scattering spectra by an electron moving in the laser-magnetic resonance acceleration regime are computed numerically and analytically. The dependence of fundamental frequency on the laser intensity and magnetic resonance parameter is examined carefully. By calculating the emission of a single electron in a circularly polarized plane-wave laser field and constant external magnetic field, the scale invariance of the radiation spectra is evident in terms of harmonic orders. The scaling law of backscattered spectra are exhibited remarkably for the laser intensity as well for the initial axial momentum of the electron when the cyclotron frequency of the electron approaches the laser frequency. The results indicate that the magnetic resonance parameter plays an important role on the strength of emission. And the rich features of scattering spectra found may be applicable to the radiation source tunability.

physics.plasm-ph↗