共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Kurata-Nishimura T. Kobayashi T. Motobayashi J. Kawai 《Applied Surface Science》2009,255(24):9729-9733
Direct observations of ablation plasma dynamics in electric field is presented. A time-resolved spatial profile of the ablation plasma induced by femtosecond laser ablation (fsLA) with high fluence is visualized using a planar-laser-induced fluorescence (P-LIF) method. The external electric field is produced by installing a mesh electrode at 6 mm from a Samarium solid target. The Sm ion plasma created by the fsLA showed collective motion regardless of the external electric field, until they reached close to the electrode. When the accelerating and decelerating field was applied, the ions almost disappeared behind the electrode from the field of view. The observations are understood utilizing a SIMION simulation with a conceivable potential gradient caused by Debye shield effect, which is that the ablation plasma keeps the same potential as the target voltage and follows electric potential gradient near the mesh electrode. It is also revealed that this effect degrades time-of-flight resolution at high fluence irradiation. This work gives a new direction for further developments of a fsLA time-of-flight spectrometer. 相似文献
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Thomas Träxler Wolfram Just Herwig Sauermann 《Zeitschrift für Physik B Condensed Matter》1995,99(2):285-295
Spatially homogeneous solutions of the Landau-Lifshitz-Gilbert equation are analysed. The different cases of conservative as well as dissipative motion are considered separately. For the linearly polarized driven Hamiltonian system we apply a global perturbation theory to uncover the main resonances as well as the phase space structure. The case of circularly polarized driven dissipative motion is studied in detail. We present the complete bifurcation diagram including bifurcations up to codimension three. 相似文献
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Thomas Träxler Wolfram Just Herwig Sauermann 《Zeitschrift für Physik B Condensed Matter》1995,99(1):285-295
Spatially homogeneous solutions of the Landau-Lifshitz-Gilbert equation are analysed. The different cases of conservative
as well as dissipative motion are considered separately. For the linearly polarized driven Hamiltonian system we apply a global
perturbation theory to uncover the main resonances as well as the phase space structure. The case of circularly polarized
driven dissipative motion is studied in detail. We present the complete bifurcation diagram including bifurcations up to codimension
three. 相似文献
5.
Electron and proton acceleration in three-dimensional electric and magnetic fields is studied through test particle simulations. The fields are obtained by a three-dimensional magnetohydrodynamic simulation of magnetic reconnection in slab geometry. The nonlinear evolution of the system is characterized by the growth of many unstable modes and the initial current sheet is fragmented with formation of small scale structures. We inject at random points inside the evolving current sheet a Maxwellian distribution of particles. In a relatively short time (less than a millisecond) the particles develop a power-law tail. The acceleration is extremely efficient and the electrons absorb a large percentage of the available energy in a small fraction of the characteristic time of the MHD simulation, suggesting that resistive MHD codes are unable to represent the full extent of particle acceleration. 相似文献
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K. V. Safronov D. A. Vikhlyaev A. G. Vladimirov D. S. Gavrilov S. A. Gorokhov A. G. Kakshin E. A. Loboda V. A. Lykov E. S. Mokicheva A. V. Potapov V. A. Pronin V. N. Saprykin P. A. Tolstoukhov O. V. Chefonov M. N. Chizhkov 《JETP Letters》2008,88(11):716-719
Experimental results are presented for proton acceleration from the back of a target irradiated by laser pulses with intensities up to 2 × 1019 W/cm2 generated by the SOKOL-P facility. The proton acceleration efficiency increases with decreasing of the target thickness. However, thin targets are destroyed by the amplified spontaneous emission (ASE) prepulse before the main pulse arrival. An additional optical switch based on a Pockels cell has been used in the amplification section to carry out the experiments with ultrathin foils. As a result, the energy contrast with respect to the ASE prepulse has been increased up to 4 × 106. Owing to high contrast, the experiments on studying proton acceleration from foils with thicknesses less than 100 nm have been carried out. 相似文献
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V. Petržílka 《Czechoslovak Journal of Physics》1991,41(9):807-811
Using Klíma-Bogoliubov-Zubarev method, the acceleration of charged particles (electrons) in moving intensity minima of interference laser fields is investigated. The electromagnetic field intensity threshold for a prospective slipping-through of the particle through the potential barrier is found both analytically and numerically. Millimetre and submillimetre electromagnetic waves should be emitted because of forced electron oscillations in potential wells.This work has been initiated by gratefully acknowledged discussions with Professor H. Hora during the author's stay at the University of N. S. W., Sydney. The author thanks this University for the kind hospitality. 相似文献
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Sheng ZM Mima K Sentoku Y Jovanović MS Taguchi T Zhang J Meyer-Ter-Vehn J 《Physical review letters》2002,88(5):055004
We propose a mechanism that leads to efficient acceleration of electrons in plasma by two counterpropagating laser pulses. It is triggered by stochastic motion of electrons when the laser fields exceed some threshold amplitudes, as found in single-electron dynamics. It is further confirmed in particle-in-cell simulations. In vacuum or tenuous plasma, electron acceleration in the case with two colliding laser pulses can be much more efficient than with one laser pulse only. In plasma at moderate densities, such as a few percent of the critical density, the amplitude of the Raman-backscattered wave is high enough to serve as the second counterpropagating pulse to trigger the electron stochastic motion. As a result, even with one intense laser pulse only, electrons can be heated up to a temperature much higher than the corresponding laser ponderomotive potential. 相似文献
11.
Y. Q. Zhang J. B. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,64(2-3):549-555
We investigate the dynamics of quantum discord in a system consisting of two Tavis-Cummings models, each of which contains two atoms driven by a classical field. We compare the dynamics of quantum discord for the system with that of entanglement and show that quantum discord vanishes only asymptotically although entanglement disappears suddenly during the time evolution. Furthermore, we examine the influence of the initial states and the classical field on the discord dynamics and find that the value of quantum discord can be improved by adjusting the classical driving field. Finally, the quantum discord of two atoms in dissipative cavity is also discussed. 相似文献
12.
3/2 dimensional Hamiltonian equations, accounting for arbitrary polarized plane wave laser radiation and arbitrary electric and magnetic fields in the directions both along and across to the direction of the laser beam propagation, are derived for superluminal phase velocity of the laser radiation. An impact of superluminal laser radiation phase velocity on the transition to stochastic electron motion is studied. 相似文献
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Mackinnon AJ Borghesi M Hatchett S Key MH Patel PK Campbell H Schiavi A Snavely R Wilks SC Willi O 《Physical review letters》2001,86(9):1769-1772
The influence of the plasma density scale length on the production of MeV protons from thin foil targets irradiated at I lambda(2) = 5 x 10(19) W cm(-2) has been studied. With an unperturbed foil, protons with energy >20 MeV were formed in an exponential energy spectrum with a temperature of 2.5+/-0.3 MeV. When a plasma with a scale length of 100 microm was preformed on the back of the foil, the maximum proton energy was reduced to <5 MeV and the beam was essentially destroyed. The experimental results are consistent with an electrostatic accelerating mechanism that requires an ultrashort scale length at the back of the target. 相似文献
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Fuchs J Cecchetti CA Borghesi M Grismayer T d'Humières E Antici P Atzeni S Mora P Pipahl A Romagnani L Schiavi A Sentoku Y Toncian T Audebert P Willi O 《Physical review letters》2007,99(1):015002
Proton beams laser accelerated from thin foils are studied for various plasma gradients on the foil rear surface. The beam maximum energy and spectral slope reduce with the gradient scale length, in good agreement with numerical simulations. The results also show that the jxB mechanism determines the temperature of the electrons driving the ion expansion. Future ion-driven fast ignition of fusion targets will use multikilojoule petawatt laser pulses, the leading part of which will induce target preheat. Estimates based on the data show that this modifies by less than 10% the ion beam parameters. 相似文献
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T. Döppner S. Teuber Th. Diederich Th. Fennel P. Radcliffe J. Tiggesbäumker K. H. Meiwes-Broer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):157-160
Lead clusters are exposed to strong femtosecond light
pulses. The dependence of the recoil energy on the charge state
of the atomic ion is now investigated using a new detection
setup, i.e., a Thomson
analyser. First results show that in contrast to laser-induced
overdense plasmas at surfaces the recoil energy distribution
appears much narrower. Comparing free lead clusters with lead
clusters embedded in large helium droplets, the charging
dynamics show distinct differences on the femtosecond time
scale. In the embedded case the maximum ionization enhancement
is reached earlier. 相似文献
19.
LO-phonon instability in semiconductors in the simultaneous presence of laser and dc electric fields
《Physics letters. A》1986,114(7):389-391
We investigate the conditions for LO-phonon amplification in semiconductors excited by both a strong electromagnetic field and a dc electric field. It is found that under certain conditions the phonon excitation rate may become greater than the rate of relaxation and the LO-phonon system may reach instability. 相似文献
20.
I. M. Podgorny Yu. V. Balabin E. V. Vashenyuk A. I. Podgorny 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(6):738-740
Investigations based on neutron monitor data show that two components of relativistic cosmic rays are generated by a solar
flare. The so-called prompt component comes from a flare with flight times and is characterized by an exponential spectrum
with a parameter of E
0 ≈ 0.5 Gev. Numerical simulation of the conditions in the flare current sheet of the Bastille flare demonstrated that such
a spectrum is formed at a magnetic reconnection velocity of ∼107 cm s−1. The delayed component has a power law spectrum and is apparently formed during the diffusion of protons in the plasma of
the interplanetary magnetic field. 相似文献