arXiv subjects

Bai-Song Xie

Publications and source records attributed to Bai-Song Xie.

At least 37 records · Page 2Linked to original sources

arXiv2024

The enhancement of pair production in oscillated overlapped fields

The influence of potential well width on electron-positron pair production has been examined through theoretical and numerical approaches by employing the computational quantum field theory. Quantum interference effects in pair production is investigated in the two overlapped potential wells with varied widths and frequencies. Several dominant processes, involving the absorption of an integer number of photons, significantly impact on pair production. Notably, specific multiphoton absorption processes exhibit distinct changes as the potential well width expands, with the absorption of four photons process displaying noteworthy effects. Additionally, the influence of the smaller frequency to the yield of the pair production can not be ignored and the most optimized frequencies in our overlapped fields has been studied and exhibited.

hep-ph↗

arXiv2024

Asymmetric pulse effects on pair production in chirped electric fields

We investigate the effects of the asymmetric pulse shapes on electron-positron pair production in three distinct fields: chirp-free, small frequency chirp, and large frequency chirp fields via the real-time Dirac-Heisenberg-Wigner formalism. Our findings reveal the disappearance of interference effects with shorter falling pulse length, and the peak is concentrated on the left side of the momentum spectrum. As the falling pulse length extends, an incomplete multi-ring structure appears in the momentum spectrum. The number density of particles are very sensitive to the asymmetry of the pulse. With a long falling pulse, the number density can be significantly enhanced by over four orders of magnitude when certain frequency chirps are utilized. These results highlight the impact of the effective dynamically assisted mechanism and the frequency chirp on pair creation.

hep-ph↗

arXiv2023

Enhanced pair production in multi-pulse trains electric fields with oscillation

For different alternating-sign multi-pulse trains electric fields with oscillation, the effects of the electric field pulse number and the relative phase of the combined electric field on pair production are investigated by solving quantum Vlasov equation. It is found that the number density of created particles in the combined electric fields is increased by more than one order of magnitude compared to the results without oscillating structure for both zero transverse momentum and full momentum space. In the case of zero transverse momentum, the created particles longitudinal momentum spectrum are monochromatic for large pulse numbers and some suitable relative phases. The number density depends nonlinearly on the relative phase that enables the optimal relative phase parameters for the number density. Moreover, for the full momentum space, the created particles number density and momentum spectrum under different multi-pulse trains electric fields are given and discussed. We also find that the number density as a function of pulse number satisfies the power law with index 5.342 for the strong but slowly varying electric field with large pulse numbers.

hep-ph↗

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↗

arXiv2022

Simulation study of a bright attosecond $γ$-ray source generation by irradiating an intense laser on a cone target

The interaction between an ultrastrong laser and a cone-like target is an efficient approach to generate high power radiations like attosecond pulses and terahertz waves. The object is to study the $γ$-ray generation under this configuration with the help of 2D particle-in-cell simulations. It is deciphered that electrons experience three stages including injection, acceleration and scattering to emit high energy photons via nonlinear compton scattering (NCS). These spatial-separated attosecond $γ$-ray pulses own high peak brilliance ($>10^{22}$ photons/($\rm s\cdot\rm mm^2\cdot\rm mrad^2\cdot0.1\%BW$)) and high energy (6MeV) under the case of normalized laser intensity $a_0=30$ ($\mathrm{I=2\times10^{21}W/cm^2}$). Besides, the cone target turns out to be an order of magnitude more efficient in energy transfer compared with a planar one.

physics.plasm-ph↗

arXiv2021

Enhancement of electron-positron pairs in combined potential wells with linear chirp frequency

The effect of linear chirp frequency on the process of electron-positron pairs production from vacuum in the combined potential wells is investigated by computational quantum field theory. Numerical results of electron number and energy spectrum under different frequency modulation parameters are obtained. By comparing with the fixed frequency, it is found that frequency modulation has a significant enhancement effect on the number of electrons. Especially when the frequency is small, appropriate frequency modulation enhances multiphoton processes in pair creation, thus promoting the pair creation. However, the number of electrons created by high frequency oscillating combined potential wells decreases after frequency modulation due to the phenomenon of high frequency suppression. The contours of the number of electrons varying with frequency and frequency modulation parameters are given, which may provide theoretical reference for possible experiments.

quant-ph↗

arXiv2021

Enhanced dynamically assisted pair production in spatial inhomogeneous electric fields with the frequency chirping

Chirped dynamically assisted pair production in spatial inhomogeneous electric fields is studied by the Dirac-Heisenberg-Wigner formalism. The effects of the chirp parameter on the reduced momentum spectrum, the reduced total yield of the created pairs for either low or high frequency one-color field and two-color dynamically assisted combinational fields are investigated in detail. Also, the enhancement factor is obtained in the later two-color field case. It is found that for the low frequency field, no matter whether it is accompanied by the other high frequency field, its chirping has a little effect on the pair production. For the one-color high frequency field or/and two-color fields, the momentum spectrum exhibits incomplete interference and the interference effect becomes more and more remarkable as chirp increases. We also find that in the chirped dynamically assisted field, the reduced total yield is enhanced significantly when the chirps are acting on the two fields, compared with that the chirp is acting only for the low frequency strong field. Specifically, by the chirping, it is found the reduced pair number is increased by more than one order of magnitude in the field with a relative narrow spatial scale, while it is enhanced at least two times in other case of field with larger spatial scales or even in the quasi-homogeneous region. We also obtain some optimal chirp parameters and spatial scales for the total yield and enhancement factor in different scenarios of the studied external field. These results may provide a theoretical basis for possible experiments in the future.

hep-ph↗

arXiv2020

Asymmetric pulse effects on pair production in polarized electric fields

Using the Dirac-Heisenberg-Wigner (DHW) formalism, e?ects of asymmetric pulse shape on the generation of electron-positron pairs in three typical polarized fields, i.e., the linear, middle elliptical and circular ones, are investigated. Two kinds of asymmetries for the falling pulse length, one is compressed and the other is elongated, are studied. It is found that the interference e?ect disappears with the compression of the pulse length, and finally the peak value of the momentum spectrum is concentrated in the center of the momentum space. For the opposite situation by extending the falling pulse length, a multi-ring structure without interference appears in the momentum spectrum. Research results exhibit that the momentum spectrum is very sensitive to the asymmetry of the pulse as well as to the polarization of the fields. It is also found that the number density of electron-positron pairs under di?erent polarizations is sensitive to the asymmetry of electric field. For the compressed falling pulse, the number density can be enhanced significantly over 2 orders of magnitude. These results could be useful in planning high power or/and high-intensity laser experiments.

physics.atom-ph↗

arXiv2020

Two stage $γ$ ray emission via an ultrahigh intensity laser pulse interaction with a laser-wakefield accelerated electron beam

We investigate the generation of twin $γ$ ray beams in collision of an ultrahigh intensity laser pulse with a laser wakefield accelerated electron beam by using particle-in-cell simulation. We consider the composed target of a homogeneous underdense preplasma in front of an ultrathin solid foil. The electrons in the preplasma are trapped and accelerated by the wakefield. When the laser pulse is reflected by the thin solid foil, the wakefield accelerated electrons continue to move forward and passing through the foil almost without the influence of the reflected laser pulse and the foil. Consequently, two groups of $γ$ ray flashes, with tunable time delay and energy, are generated by the wakefield accelerated electron beam interacting with the reflected laser pulse from the foil as well as another counter propagating petawatt laser pulse in the behind the foil. The dependence of the $γ$ photon emission on the preplasma densities, driving laser polarization and the foil are studied.

physics.plasm-ph↗

arXiv2019

Effects of polarization and high harmonics of two-color fields on dynamically assisted pair production

Electron-positron pair production in dynamically assisted two-color electric fields is investigated for various polarizations. Momentum spectrum and number density of the created pairs are examined carefully, in particular, the effects of polarization and high harmonics of two-color fields are exhibited. For only single strong field, the interference effects of momentum spectrum would vanish when polarization is high, however, for the dynamical assisted two-color fields, the interference effects would be more and more remarkable with polarization. The multiple peaks of momentum spectrum in elliptic or/and circular polarization are observed and explained. It is found that there exists a strong nonlinear dependence of the number density on the high harmonics of two-color fields, for example, the number density can be enhanced significantly over $7-8$ orders when appropriate high harmonics is present. Another interesting finding is that the polarization effect on number density is gradually weaken as the high harmonics increases, however, a weak nonlinearity relation appears again if the high harmonics exceeds a single-photon threshold.

quant-ph↗

arXiv2019

Effects of finite spatial extent on Schwinger pair production

Electron-positron pair production from vacuum in external electric fields with space and time dependencies is studied numerically using real time Dirac-Heisenberg-Wigner formalism. The influence of spatial focusing scale of the electric field on momentum distribution and the total yield of the particles is examined by considering standing wave mode of the electric field with different temporal configurations. With the decrease of spatial extent of the external field, signatures of the temporal field are weaken in the momentum spectrum. Moreover, in the extremely small spatial extent, novel features emerge due to the combined effects of both temporal and spatial variations. We also find that for dynamically assisted particle production, while the total particle yield drops significantly in small spatial extents, the assistance mechanism tends to increase in these highly inhomogeneous regimes, where the slow and fast pulses are affected differently by the overall spatial inhomogeneity.

hep-ph↗

arXiv2019

Thomson backscattering in combined two laser and magnetic field

The Thomson backscattering of an electron moving in combined fields is studied by a dynamically assisted mechanism. The combined fields are composed of two co-propagating laser fields and a magnetic field, where the first laser field is strong and low-frequency while the second is weak and high-frequency, relatively. The dependence of fundamental frequency of emission on the ratio of incident laser high-to-low frequency is presented and the spectrum of backscattering is obtained. It is found that, with a magnetic field, the peak of the spectrum and the corresponding radiation frequency are significantly larger in case of two-laser than that in case of only one laser. They are also improved obviously as the frequency of the weak laser field. Another finding is the nonlinear correlation between the emission intensity of the backscattering and the intensity of the weak laser field. These results provide a new possibility to adjust and control the spectrum by changing the ratios of frequency and intensity of the two laser fields.

physics.optics↗

arXiv2018

Thomson backscattering in combined uniform magnetic and envelope modulating circularly-polarized laser fields

The Thomson backscattering spectra in combined uniform magnetic and cosine-envelope circularly-polarized laser fields are studied in detail. With an introduction of the envelope modulation, the radiation spectra exhibit high complexity attributed to the strong nonlinear interactions. On the other hand, four fundamental laws related to the scale invariance of the radiation spectra are analytically revealed and numerically validated. They are the laws for the radiation energy as the $6$th power of the motion constant exactly, also as the approximate negative $6$th power with respect to the initial axial momentum and laser intensity in a certain of conditions, respectively, and finally an important self-similar law, i.e., when the circular laser frequency, the envelope modulation frequency, and the modified cyclotron frequency are simultaneously increased by a factor, the radiation energy will be increased by the second power of that factor without changing the shape of the spectrum. With the application of these laws, especially the last one, a much higher radiation energy can be obtained and the harmonic at which the maximum radiation occurs can be precisely tuned without changing its amplitude. These findings provide a possible way to advance radiation technology in many fields such as medicine, communications, astrophysics, and security.

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

Pair production in differently polarized electric fields with frequency chirps

Electron-positron pair production in strong electric fields, i.e., the Sauter-Schwinger effect, is studied using the real-time Dirac-Heisenberg-Wigner formalism. Hereby, the electric field is modeled to be a homogeneous, single-pulse field with subcritical peak field strength. Momentum spectra are calculated for four different polarizations - linear, elliptic, near-circular elliptic or circular - as well as a number of linear frequency chirps. With details depending on the chosen polarization the frequency chirps lead to strong interference effects and thus quite substantial changes in the momentum spectra. The resulting produced pairs' number densities depend non-linearly on the parameter characterizing the polarization and are very sensitive to variations of the chirp parameter. For some of the investigated frequency chirps this can provide an enhancement of the number density by three to four orders of magnitude.

hep-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↗