- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Dephasingless Laser Wakefield Acceleration
摘要： Laser wakefield accelerators (LWFAs) produce extremely high gradients enabling compact accelerators and radiation sources but face design limitations, such as dephasing, occurring when trapped electrons outrun the accelerating phase of the wakefield. Here we combine spherical aberration with a novel cylindrically symmetric echelon optic to spatiotemporally structure an ultrashort, high-intensity laser pulse that can overcome dephasing by propagating at any velocity over any distance. The ponderomotive force of the spatiotemporally shaped pulse can drive a wakefield with a phase velocity equal to the speed of light in vacuum, preventing trapped electrons from outrunning the wake. Simulations in the linear regime and scaling laws in the bubble regime illustrate that this dephasingless LWFA can accelerate electrons to high energies in much shorter distances than a traditional LWFA—a single 4.5 m stage can accelerate electrons to TeV energies without the need for guiding structures.
关键词： ponderomotive force,phase velocity,Laser wakefield accelerators,spatiotemporal pulse shaping,dephasing
更新于2025-09-23 15:21:01
-
Tilted Snowplow Ponderomotive Electron Acceleration With Spatio-Temporally Shaped Ultrafast Laser Pulses
摘要： We propose a novel scheme for using the ponderomotive force of a tilted ultrafast laser pulse to accelerate electrons in free space. The tilt of the intensity envelope results from the angular dispersion of the pulse’s spectrum and slows down the interaction of the pulse with free electrons. The slower effective pulse velocity allows time for the electrons to accelerate from rest while remaining on the wave. We present both non-relativistic and relativistic analytic single-particle models in the adiabatic ponderomotive approximation, describing the process for an ideal infinite tilted pulse as well as a finite width beam. The analysis predicts the threshold intensity as a function of the pulse front tilt angle and shows that in the ideal case the output energy of the electrons is four times that of the ponderomotive potential at the capture threshold. Full-field simulations using the 2D OSIRIS 4.0 particle-in-cell code confirm the basic scheme. This tilted pulse acceleration scheme shows promise as a lab-scale method of accelerating electrons to the MeV level with good energy and angular resolution, to be used for ultrafast electron diffraction or injection into a second stage accelerator.
关键词： ponderomotive force,spatio-temporal pulse shaping,ultrafast lasers,laser electron accelerators,relativistic kinematics
更新于2025-09-23 15:19:57
-
Terahertz radiation from multi ion plasma irradiated by two cross focused Gaussian laser beams
摘要： Terahertz (THz) radiation generation by nonlinear coupling of two color Gaussian laser beams in a plasma with multi-ion species is numerically investigated by taking into account the nonlinearity due to ponderomotive force and space-charge field. By calculating the modification of electron density distribution of such plasma, coupled differential equations governing the evolution of two laser beams’ spot size and the outcome THz wave amplitude are established. The influence of the ionic species density and charge composition on the cross focusing of laser beams as well as generation of THz radiation is studied. The results mainly demonstrated that nonlinear effects in a multiply ionized plasma are excited stronger in comparison to the singly ionized one. It was found that the presence of ion species of higher charge enhances the cross focusing of beams and, consequently, THz field amplitude. The generated THz emission also strongly depends on the density of ionic species. The results showed that the minimum output of THz radiation is related to the higher density of singly charged ionic species. Moreover, it was found that the maximum value of THz amplitude takes place within a specific range of laser intensities.
关键词： multi-ion plasma,ponderomotive force,space-charge field,Terahertz radiation,Gaussian laser beams
更新于2025-09-19 17:13:59
-
Generation of Low-Frequency Radiation Under the Laser Pulse Effect on a Plasma in a Magnetic Field
摘要： We reveal the possibility of a low-frequency radiation generation at a normal incidence of the laser pulse on a dense plasma in a constant magnetic ?eld. The generation occurs due to the motion of electrons under the magnetic ?eld e?ect and a ponderomotive force slowly varying with time localized in the skin layer where the laser radiation penetrates. The characteristic radiation frequencies are determined by the inverse duration of the laser pulse. We ?nd the ?eld strength of the radiation generated and its dependences on the Larmor frequency of electrons and the plasma and laser pulse parameters.
关键词： magnetic ?eld,terahertz radiation,ponderomotive force,femtosecond pulse,nonlinear current
更新于2025-09-12 10:27:22
-
Multipactor Analysis in Circular Waveguides Excited by TM <sub/>01</sub> Mode
摘要： A series of detailed numerical simulations are used to investigate the properties of multipactor breakdown in circular waveguides propagating the TM01 mode. A Monte Carlo model is constructed to track the motion of the electrons, study the multipactor scenarios, and predict the multipactor thresholds. The theoretical and numerical analyses indicate that the product of the frequency and the gap (f· D) affects both the intensity of the ponderomotive force and its spatial distribution, which results from the nonuniformity of the radio frequency (RF) field and significantly influences the electrons’ trajectories and multipactor trends. The decrease in f· Dresults in a remarkable enhancement in the magnitude of the ponderomotive force, while the maximal intensity gradually moves toward the half radius R/2 area. Low values of f·Dcorrespond to high ponderomotive potential, which sustains the short-range electrons and triggers the single-sided multipactor. In contrast, high values of f· D correspond to low ponderomotive potential, contributing to long-range electrons and exciting the double-sided multipactor. Fitting to the susceptibility diagram produces the border line and a modified f · D threshold of (f · D)th ≈ 338.4 GHz mm, which separates the susceptibility diagram into single-sided, double-sided, and mixed-sided zones. The initial electron energy influences their trajectories at high f · D and low RF power. This effect tends to dominate the multipactor behavior in the mixed-sided region.
关键词： ponderomotive force,multipactor,TM01 mode,Circular waveguide
更新于2025-09-12 10:27:22
-
Proton acceleration due to laser plasma interactions from mass-limited spherical targets
摘要： The proton acceleration processes involved in the interaction of an ultrashort circularly polarized laser with a near-critical density spherical target are investigated in this paper using three dimensional particles in cell simulations. Both the target size and the target density are varied to understand their influence on the accelerated beam of protons. The target is efficiently heated by relativistic transparency, and a complicated interplay is observed between the participating interaction processes. The electron heating and recirculations help in the formation of shocks which exert a further push to the protons accelerated by the electrostatic sheath formed due to the ponderomotive force. A maximum peak proton energy of about 40 MeV is observed, which is the result of the cumulative effects of various acceleration mechanisms. Electron jets are observed in the forward laser direction for the larger target size, which suppresses the energy of the proton beams.
关键词： spherical targets,laser plasma interactions,electrostatic sheath,electron heating,proton acceleration,relativistic transparency,ponderomotive force,shock formation
更新于2025-09-12 10:27:22
-
Nonlinear mixing of lasers and terahertz generation on CNT embedded metal surface
摘要： A scheme of terahertz generation, employing carbon nanotubes (CNTs) embedded metal surface is proposed. The surface is irradiated by two laser beams at angle of incidence θ. The lasers exert a ponderomotive force on CNT electrons at the beat frequency ω=ω1-ω2 and produce a nonlinear current, turning the nanotubes into an array of antennae emitting beat frequency THz radiation. The THz ?eld is resonantly enhanced at the plasmon resonance, =ω ω β/2 p , where ωp is the plasma frequency of the CNT electrons and β is a parameter that characterizes the metallic susceptibility of the CNTs. The collisions are a limiting factor and cause heating of CNTs.
关键词： Terahertz generation,Carbon nanotubes,Ponderomotive force,Nonlinear mixing
更新于2025-09-11 14:15:04