共查询到20条相似文献,搜索用时 781 毫秒
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A. A. Andreev I. A. Litvinenko K. Yu. Platonov 《Journal of Experimental and Theoretical Physics》1999,89(4):632-639
The possibility that fast electrons can escape in a direction close to the trajectory of a reflected ultrashort laser pulse
at extremely high laser radiation fluxes is examined analytically and numerically. Analytic estimates are made of the feasibility
of forming electron bursts in the plasma and of their subsequent motion. The self-consistent, collisionless motion of a plasma
acted on by specified incident and reflected ultrashort laser pulses is modeled in two dimensions by the particle-in-cell
method. It is shown that a substantial number of electrons located in the subcritical region are gathered into bunches by
the resultant forces and escape to the vacuum in a direction different from the normal to the target surface within a narrow
range of solid angles. This demonstrates the feasibility of laser acceleration of an electron burst during reflection of an
ultrashort laser pulse from a solid target.
Zh. éksp. Teor. Fiz. 116, 1184–1197 (October 1999) 相似文献
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Ultrabright γ-ray emission from the interaction of an intense laser pulse with a near-critical-density plasma
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Aynisa Tursun 《中国物理 B》2021,30(11):115202-115202
An efficient scheme for generating ultrabright γ-rays from the interaction of an intense laser pulse with a near-critical-density plasma is studied by using the two-dimensional particle-in-cell simulation including quantum electrodynamic effects. We investigate the effects of target shape on γ-ray generation efficiency using three configurations of the solid foils attached behind the near-critical-density plasma: a flat foil without a channel (target 1), a flat foil with a channel (target 2), and a convex foil with a channel (target 3). When an intense laser propagates in a near-critical-density plasma, a large number of electrons are trapped and accelerated to GeV energy, and emit γ-rays via nonlinear betatron oscillation in the first stage. In the second stage, the accelerated electrons collide with the laser pulse reflected from the foil and emit high-energy, high-density γ-rays via nonlinear Compton scattering. The simulation results show that compared with the other two targets, target 3 affords better focusing of the laser field and electrons, which decreases the divergence angle of γ-photons. Consequently, denser and brighter γ-rays are emitted when target 3 is used. Specifically, a dense γ-ray pulse with a peak brightness of 4.6×1026 photons/s/mm2/mrad2/0.1%BW (at 100 MeV) and 1.8×1023 photons/s/mm2/mrad2/0.1%BW (at 2 GeV) are obtained at a laser intensity of 8.5×1022 W/cm2 when the plasma density is equal to the critical plasma density nc. In addition, for target 3, the effects of plasma channel length, foil curvature radius, laser polarization, and laser intensity on the γ-ray emission are discussed, and optimal values based on a series of simulations are proposed. 相似文献
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A hot particle jet is induced as a laser pulse from a free oscillated Nd:YAG laser focused on a coal target. The particle jet successfully initiates combustion in a premixed combustible gas consisting of hydrogen, oxygen, and air. The experiment reveals that the ionization of the particle jet is enhanced during the laser pulse. This characteristic is attributed to the electron cascade process and the ionization of the particles or molecules of the target. The initial free electrons, which are ablated from the coal target, are accelerated by the laser pulse through the inverse Bremsstrahfung process and then collide with the neutrals in the jet, causing the latter to be ionized. 相似文献
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Schreiber J Bell F Grüner F Schramm U Geissler M Schnürer M Ter-Avetisyan S Hegelich BM Cobble J Brambrink E Fuchs J Audebert P Habs D 《Physical review letters》2006,97(4):045005
We present a general expression for the maximum ion energy observed in experiments with thin foils irradiated by high-intensity laser pulses. The analytical model is based on a radially confined surface charge set up by laser accelerated electrons on the target rear side. The only input parameters are the properties of the laser pulse and the target thickness. The predicted maximum ion energy and the optimal laser pulse duration are supported by dedicated experiments for a broad range of different ions. 相似文献
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I. N. Kosarev 《Technical Physics》2014,59(3):445-448
Electron dynamics in a thin target irradiated with femtosecond laser pulses at an intensity of 1020 W/cm2 is studied in the framework of the kinetic theory of laser plasma based on the construction of propagators (in classical limit) for electron and ion distribution functions in plasma. The calculations are performed for real densities and charges of plasma ions. Electrons are partly ejected from the target. The laser pulse energy is predominantly absorbed by electrons, and the electrons are accelerated to relatively high energies. 相似文献
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We present analytical studies of electron acceleration in the low-density preplasma of a thin solid target by an intense femtosecond laser pulse. Electrons in the preplasma are trapped and accelerated by the ponderomotive force as well as the wake field. Two-dimensional particle-in-cell simulations show that when the laser pulse is stopped by the target, electrons trapped in the laser pules can be extracted and move forward inertially. The energeticelectron bunch in the bubble is unaffected by the reflected pulse and passes through the target with small energy spread and emittance. There is an optimal preplasma density for the generation of the monoenergetic electron bunch if a laser pulse is given. The maximum electron energy is inverse proportion to the preplasma density. 相似文献
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Veltcheva M Borot A Thaury C Malvache A Lefebvre E Flacco A Lopez-Martens R Malka V 《Physical review letters》2012,108(7):075004
Experimental measurements of backward accelerated protons are presented. The beam is produced when an ultrashort (5 fs) laser pulse, delivered by a kHz laser system, with a high temporal contrast (10(8)), interacts with a thick solid target. Under these conditions, proton cutoff energy dependence with laser parameters, such as pulse energy, polarization (from p to s), and pulse duration (from 5 to 500 fs), is studied. Theoretical model and two-dimensional particle-in-cell simulations, in good agreement with a large set of experimental results, indicate that proton acceleration is directly driven by Brunel electrons, in contrast to conventional target normal sheath acceleration that relies on electron thermal pressure. 相似文献
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A. L. Galkin M. P. Kalashnikov V. A. Trofimov 《Bulletin of the Lebedev Physics Institute》2012,39(8):241-245
Based on the dynamics of the electron in the field of a laser pulse of relativistic intensity, the electron emission angles with respect to the laser pulse propagation axis are calculated. The angular distribution of accelerated electrons is analyzed together with their energy spectrum. It is shown that fast electrons forming the high-energy spectral region are emitted into a fixed angular cone. 相似文献
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在现有的一维粒子模拟程序的基础上发展了带光电离和碰撞电离及蒙特卡罗两体碰撞的模拟程序(1D PIC-MCC). 用此程序模拟研究了短脉冲激光与He气靶相互作用时电子和离子的加速过程. 研究表明当强激光与过临界密度的微米厚度的平面靶相互作用时,靶前表面物质将被激光脉冲前沿迅速离化;新生的电子被激光场有质动力加速成为高能电子,这些电子穿入到靶内,通过电子碰撞电离离化靶内物质;一部分高能电子穿透靶后,会在靶的后表面形成强的电荷分离场,该场迅速离化靶后表面物质,同时使得后表面离子得到加速. 部分穿透靶的超热电子将被电荷分离场重新拉回靶内,在靶的前后表面振荡. 一些振荡电子在此过程中得到电荷分离场加速,离开前表面,在前表面也形成电荷分离场,使前表面离子得到加速.
关键词:
激光等离子体
光电离和碰撞电离
电子加速
离子加速 相似文献
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When an intense laser pulse irradiates a solid-density foil target, electrons produced at the relativistic critical density can be accelerated to relativistic energy by the ponderomotive force. When a plasma fiber is attached to the back of the foil, the produced relativistic electrons are guided to propagate along the fiber for a long distance, because the high-current electron beam induces strong radial electric fields in the fiber. Transport and heating of intense laser-driven relativistic electrons in both wire and hollow plasma fibers are compared theoretically and numerically. We found that the coupling efficiency from the laser to the plasma fiber depends on the fiber structure. Because of the enhanced return currents in the wire fiber, the temperature in the wire fiber is higher than that in the hollow fiber. 相似文献
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P. Mora 《The European physical journal. Special topics》2009,175(1):97-104
The acceleration of electrons in laser plasma interaction has been observed since the seventies, when it was initially considered
as a deleterious effect, as, in the inertial fusion context, the so-called suprathermal electrons preheat the target. However,
it has been quickly observed that a large benefit could be taken from these electrons. Two main directions are now followed.
In the first direction, one tries to accelerate electrons to high energy, presently in the GeV range. The electrons may originate
from a pre-accelerated beam, or directly from a gas target instantaneously transformed in a plasma by the ultra-intense laser
pulse. In the second direction, one tries to transfer the energy of the electrons to fast ions, especially protons, presently
in the few tens of MeV range. Thin targets are used for this transformation, the electrons being accelerated at the front
of the target, while the ions may originate from the front part or the back part of the target, or from inside the target,
depending on the parameters of the experiment. While the maximum energy was the initial goal of the pioneer experiments, there
are now strong experimental efforts to improve the quality of the beams, in terms of luminosity, emittance, and energy spectrum.
In the recent years, quasi-monoenergetic beams were obtained both for electrons and for ions. 相似文献
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Yonghong Yan Yuchi Wu Kegong Dong Bo Zhang Zongqing Zhao Zeen Yao Yuqiu Gu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(1):1-5
Positron generation by an ultra-short ultra-intense laser in an indirect manner has been studied with two-dimensional particle-in-cell (PIC) and Monte Carlo (MC) simulations. In this generation scheme, positrons are produced with energetic electrons accelerated by an ultra-shot laser pulse propagating through an underdense plasma. The dependence of the positron beam properties on the plasma length and secondary target (converter) thickness was investigated in detail. The simulation results reveal that the positron yield is strongly correlated with the total energy of laser-accelerated electrons; both the temperature and divergence of the positron beam are sensitive to the plasma length; and the positron beam has a pulse duration comparable to the incident electron beam. In addition, it is indicated that even with the optimal converter thickness, only a small fraction (11.4%) of positrons can escape out and most of the detected positrons originate from the back edge of the converter. 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
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S. V. Bulanov T. Zh. Esirkepov F. Califano Y. Kato T. V. Liseikina K. Mima N. M. Naumova K. Nishihara F. Pegoraro H. Ruhl Y. Sentoku Y. Ueshima 《JETP Letters》2000,71(10):407-411
A method is proposed for generating collimated beams of fast ions in laser-plasma interactions. Two-dimensional and three-dimensional particle-in-cell simulations show that the ponderomotive force expels electrons from the plasma region irradiated by a laser pulse. The ions with unneutralized electric charge that remain in this region are accelerated by Coulomb repulsive forces. The ions are focused by tailoring the target and also as a result of pinching in the magnetic field produced by the electric current of fast ions. 相似文献
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The interaction of femtosecond laser pulses with solid targets was studied through experiments and particle-in-cell (PIC) simulations. It is proved that the vacuum heating and the inverse bremsstralung process are the main mechanisms of the laser pulse absorption under such conditions. The distribution of hot electrons and that of X-ray are found to have double-temperature structure, which is confirmed by PIC simulations. While the lower temperature is attributed to the resonant absorption, the higher one, however, is caused by the laser-induced electric field in the target normal direction. The time-integrated spectra ofthe reflected laser pulse shows that the mechanism of electron acceleration is determined by the plasma density profile. 相似文献
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Seungwoo Lee Han Sup Uhm Tae Yeon Kang Min Sup Hur Hyyong Suk 《Current Applied Physics》2019,19(4):464-469
We propose a new idea to enhance and control the betatron radiation by using a modulating laser pulse in laser wakefield acceleration. In this scheme, a high-power laser pulse is used for self-trapping and acceleration of the plasma electrons and the accelerated electron beam is modulated by a separately-propagating laser pulse for large amplitude betatron oscillations and microbunching. In this way, the relatively low power modulating laser pulse can enhance the X-ray photon flux and energy significantly. We performed two-dimensional particle-in-cell simulations to demonstrate the idea and the results show that a sub-TW laser pulse is enough for electron beam modulation and it can generate easily-controllable fs X-ray pulses with a wide range of photon energies from soft X-rays to hard X-rays. 相似文献