共查询到20条相似文献,搜索用时 15 毫秒
1.
Muhammad Ali Bake Aimierding Aimidula Arkin Zakir Nuriman Abdukerim Abduleziz Ablat 《Frontiers of Physics》2018,13(4):135202
This study investigates the generation of high energy photons and positrons using focused ultrahigh intensity femtosecond laser pulses on a relativistic electron beam with a set of two-dimensional particle-in-cell simulations. We consider circularly and linearly polarized, single and spatially separated double laser pulses. We model both 500 MeV and 1 GeV electron beams. Higher positron production is obtained using circularly polarized laser pulses. Using double pulses, the focusing effect of the ponderomotive force confines the electrons to a small volume, generating additional energetic photons and positrons. The positron spectral distributions are effectively modified by these variations. When the electron beam energy is doubled, the number of positrons increased, while the cutoff energy remained nearly constant. 相似文献
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Closed magnetic field plasma confinement geometries produced by plasma currents induced by rotating intense relativistic electron beams are discussed conceptually. Experimental evidence for the formation of such layers is presented. 相似文献
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An externally applied longitudinal magnetic field was found to enhance the particle trapping in the laser wakefield acceleration. When a static magnetic field of a few tens of tesla is applied in parallel with the propagation direction of a driving laser pulse, it is shown from two-dimensional particle-in-cell simulations that total charge of the trapped beam and its maximum energy increase. The analysis of electron trajectories strongly suggests that the enhanced trapping originates from the suppression of the transverse motion by the magnetic field. The enhanced trapping by the magnetic field was observed consistently for various values of the plasma density, the amplitude of the laser pulse and pulse spot size. 相似文献
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An analyzer is created for time-resolved measurements of the electron pitch-angles in high-current microsecond relativistic electron beams in a strong magnetic field. The electron pitch-angles in a 500-keV relativistic electron beam with a current density of ∼1 kA/cm2 and a 1-μs flat-top current profile are measured. The diode proposed previously by the authors allows one to produce a high-current electron beam in which pitchangles vary only slightly with time and over the beam cross section. 相似文献
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N. I. Zaitsev E. V. Ilyakov I. S. Kulagin A. S. Shevchenko 《Radiophysics and Quantum Electronics》2006,49(2):120-125
The paper presents the results of studying the analyzer of helical electron beams experimentally. The analyzer is based on
separation of electron velocity fractions in the adiabatically growing magnetic field. Optimization of the analyzer design
to minimize the amount of electrons reflected from the analyzer elements made it possible to practically eliminate the systematic
error in measurements of the velocity spread and pitch-factor.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 2, pp. 134–140, February 2006. 相似文献
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Hosokai T Kinoshita K Zhidkov A Maekawa A Yamazaki A Uesaka M 《Physical review letters》2006,97(7):075004
Significant enhancement of emittance and an increase of the total charge of femtosecond electron beams produced by a 12 TW, 40 fs laser pulse, tightly focused in a He gas jet, are observed after applying a static magnetic field, B> or =0.2 T, directed along the axis of laser pulse propagation. The effect appears when plasma produced by a laser prepulse becomes magnetized in the vicinity of the focus point: the electron Larmor frequency exceeds the collisional frequency, while periphery of the plasma remains unmagnetized. The entailed change in the shape of the plasma suppresses the diffraction of the main laser pulse that results in a much higher charge of electrons self-injected during the longitudinal wave breaking of the laser wake as well as the excellent stability of the beams. 相似文献
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The interaction of a high-energy relativistic laser pulse with an underdense plasma is studied by means of 3-dimensional particle in cell simulations and theoretical analysis. For powers above the threshold for channeling, the laser pulse propagates as a single mode in an electron-free channel during a time of the order of 1?picosecond. The steep laser front gives rise to the excitation of a surface wave along the sharp boundaries of the ion channel. The surface wave first traps electrons at the channel wall and preaccelerates them to relativistic energies. These particles then have enough energy to be further accelerated in a second stage through an interplay between the acceleration due to the betatron resonance and the acceleration caused by the longitudinal part of the surface wave electric field. It is necessary to introduce this two-stage process to explain the large number of high-energy electrons observed in the simulations. 相似文献
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The collective acceleration of hydrogen and helium ions by relativistic electron rings has been successful, using a very fast ring compression, and has clearly been demonstrated by the inertia of the loaded rings and by nuclear track recording. 相似文献
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Håkan Danared 《Hyperfine Interactions》1998,115(1-4):61-65
Molecular-dynamics simulations of relaxation processes in electron beams at high magnetic fields are presented. The result
of the longitudinal–longitudinal relaxation and the rate of the transverse–longitudinal relaxation are calculated for magnetic
fields between 0.006 and 0.1 T for electron beam parameters typical of those in low-energy electron coolers. Comparisons with
theoretical and experimental values are made.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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A. V. Korzhimanov A. V. Kim 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(2):287-292
A simple model taking into account the effect of electron temperature is derived to define the plasma-field structures which
may arise during relativistically intense laser interaction with overdense plasmas. We show that there exist multilayer solutions
with electron cavitation, allowing for both relativistic and ponderomotive nonlinearities. The influence of finite electron
temperature on such structures is studied. Examples of these plasma-field structures for the cases of an infinite plasma and
a plasma layer are presented. 相似文献
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W. Wang P.X. Wang Y.K. Ho Q. Kong Y. Gu S.J. Wang 《Applied physics. B, Lasers and optics》2007,88(2):273-279
Using three-dimensional test particle simulations, we investigated electrons accelerated by a focused flat-top laser beam
at different intensities and flatness levels of the beam profile before focusing in vacuum. The results show that the presence
of sidelobes around the main focal spot of the focused flat-top laser beam influences the optimum (as far as electron acceleration
is concerned) initial momentum (and incident angle) of electrons for acceleration. The difference of initial conditions between
laser beams with and without sidelobes becomes evident when the laser field is strong enough (a0>10, corresponding to intensities I>1×1020 W/cm2 for the laser wavelength λ=1 μm, where a0 is a dimensionless parameter measuring laser intensity). The difference becomes more pronounced at increasing a0. Because of the presence of sidelobes, there exist three typical CAS (capture and acceleration scenario) channels when a0≥30 (corresponding to I>1×1021 W/cm2 for λ=1 μm). The energy spread of the outgoing electrons is also discussed in detail.
PACS 41.75.Jv; 42.60.Jf; 42.25.Fx 相似文献
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Based on analysis of the effective potential, a possibility is found to realize a single type of radial evolution of high-density
relativistic electron beams. This operating mode is characterized by periodic oscillations of the beam radius within a certain
range. Conditions are found for radial beam stabilization under this beam transport regime. 相似文献
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Electron acceleration in the inverse free electron laser (IFEL) with a helical wiggler in the presence of ion-channel guiding and axial magnetic field is investigated in this article. The effects of tapering wiggler amplitude and axial magnetic field are calculated for the electron acceleration. In free electron lasers, electron beams lose energy through radiation while in IFEL electron beams gain energy from the laser. The equation of electron motion and the equation of energy exchange between a single electron and electromagnetic waves are derived and then solved numerically using the fourth order Runge-Kutta method. The tapering effects of a wiggler magnetic field on electron acceleration are investigated and the results show that the electron acceleration increases in the case of a tapered wiggler magnetic field with a proper taper constant. 相似文献
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We present a new mechanism of energy gain of electrons accelerated by a laser pulse.It is shown thatwhen the intensity of an ultrafast intense laser pulse decreases rapidly along the direction of propagation,electrons leaving the pulse experience an action of ponderomotivc deceleration at the descending part ofa lower-intensity laser field than acceleration at the ascending part of a high-intensity field, thus gain netenergy from the pulse and move directly forward. By means of such a mechanism, a megaelectronvoltelectron beam with a bunch length shorter than 100 fs could be realized with an ultrafast(≤30 fs),intense (>10~(19)W/cm~2)laser pulse. 相似文献