共查询到20条相似文献,搜索用时 0 毫秒
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Silva L.O. Mori W.B. Bingham R. Dawson J.M. Antonsen T.M. Jr. Mora P. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2000,28(4):1202-1208
A photon kinetic formalism is employed to describe the propagation of short laser pulses in tenuous plasmas. The photon kinetic theory contains all of the ingredients necessary to describe the relativistic nonlinear optics of short laser pulses in plasmas, and the shortest time scale is determined by the local evolution of the index of refraction. We use this feature to implement a photon in cell code, in which the typical time step is much bigger than is the laser field time scale. Additional information provided by the photon kinetic framework is illustrated by one-dimensional (1-D) and two-dimensional (2-D) simulations 相似文献
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The main characteristic of this interferometric system is such that the systems can be used for DCN laser (=195m, 190m) and also for HCN laser (=337m) by changing the work medium, regulating the temperature of tube wall and adjusting the optic path, without changing any optic element. 相似文献
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Single-shot wave-front measurements of high-intensity ultrashort laser pulses with a three-wave interferometer 总被引:1,自引:0,他引:1
A simple new three-wave interferometric technique is used to measure, for what is believed to be the first time, the wave front of femtosecond ultrahigh-peak-power pulses carrying a strong B integral (B = 5.26+/-0.15) in a single shot. Wave-front distortions of a terawatt-class laser system are measured with good accuracy (lambda/50) and discussed. These distortions can significantly reduce the focused peak intensity, emphasizing the necessity of implementing adaptive optics in ultrahigh-intensity chirped-pulse amplification lasers. 相似文献
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Clark EL Krushelnick K Zepf M Beg FN Tatarakis M Machacek A Santala MI Watts I Norreys PA Dangor AE 《Physical review letters》2000,85(8):1654-1657
Heavy ions with energies up to 430+/-40 MeV have been measured from laser-solid interactions at focused intensities of up to 5x10(19) W/cm(2). Observations of proton emission indicate significant structure in the energy spectrum as well as an angular emission profile which varies with energy. Two qualitatively different components of ion emission are observed: (i) a high-energy component which is likely generated by a combination of "Coulomb explosion" and acceleration by the space charge force from hot electrons which escape the plasma, and (ii) a lower-energy component which forms a ring likely created by magnetic fields in the ablated plasma. 相似文献
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Gordon D.F. Mori W.B. Antonsen T.M. Jr. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2000,28(4):1224-1232
A novel particle simulation code is described that self-consistently models certain classes of laser-plasma interactions without resolving the optical cycles of the laser. This is accomplished by separating the electromagnetic field into a laser component and a wake component. Although the wake component is treated as in a fully explicit particle-in-cell (PIC) code, the laser component is treated in the high-frequency limit, which allows the optical cycles to be averaged out. This leads to enormous reductions in computer time when the laser frequency is much greater than all other frequencies of interest. This work is an extension of the work of Mora and Antonsen, Jr. (1996 and 1997), who derived the time-averaged equations coupling the laser with the particles and developed a code to solve these equations in the quasi-static limit. The code presented is distinguished by the fact that it is useful when the plasma length is much less than the laser pulse length. Also, it is already parallelized and should be straightforward to extend to three dimensions 相似文献
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We propose a method to implement a Mach-Zehnder interferometry based upon a string of trapped ions with artificial nonlinear interactions. By manipulating the coupling strength between two involved internal states of the ions, we could achieve the beam splitting/recombination with NOON states. Using current techniques for manipulating trapped ions, we discuss the experimental feasibility of our scheme and analyze some undesired uncertainty under realistic experimental environment. 相似文献
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A. Frank J. Fuchs L. Lancia G. Lehmann J.-R. Marquès G. Mourou C. Riconda K.H. Spatschek T. Toncian L. Vassura S. Weber 《The European physical journal. Special topics》2014,223(6):1153-1156
The use of plasmas provides a way to overcome the damage threshold of classical solid-state based optical materials which is the main limitation encountered in producing extreme power laser pulses. In particular one can use plasmas to directly amplify ultra-short laser pulses to very high intensities. Multi-dimensional kinetic simulations and first proof-of-principle experiments show the feasibility of using plasma instabilities involving ion waves, such as stimulated Brillouin backscattering, in a controlled way to transfer energy from a long pump pulse to a short seed pulse and thereby increase the intensity of the latter. Plasma parametric amplification, and the use of plasma mirrors for focusing, is part of the newly developping domain of plasma optics, which eventually will pave the way to Exawatt lasers. 相似文献
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Kodama R Tanaka KA Sentoku Y Matsushita T Takahashi K Fujita H Kitagawa Y Kato Y Yamanaka T Mima K 《Physical review letters》2000,84(4):674-677
Long-scale jetlike x-ray emission was observed in a 100-TW laser-plasma interaction. The jet was well collimated with a divergence of 30-40 mrad and continued from the target surface into underdense regions for a distance over 4 mm in the specular direction of the laser light. A two-dimensional particle-in-cell simulation shows an electron acceleration with the specularly reflected laser light and collimation of the electron stream by a self-generated magnetic field, resulting in the electron jet to the direction of the specularly reflected light. 相似文献
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Najmudin Z. Dangor A.E. Modena A. Salvati M.R. Clayton C.E. Danson C.N. Gordon D. Joshi C.J. Marsh K.A. Malka V. Muggli P. Neely D. Walsh F.N. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2000,28(4):1057-1070
The interaction of an intense short pulse laser (>5×10 18 Wcm-2) with underdense plasma was extensively studied. The beam is found to be highly susceptible to the forward Raman scattering instability. At sufficiently high growth rates, this can lead to wavebreaking with the resultant production of a high flux of accelerated electrons (>1011 for E>2 MeV). Some electrons are found to be accelerated well above the dephasing energy, up to 94 MeV. Self-scattered images intimate the presence of high-intensity channels that extend more than 3.5 mm or 12 Rayleigh lengths. These filaments do not follow the axis of laser propagation, but are seen to be emitted within an f4 cone centered around this axis. Spectra of the self-scattered light show that the main contribution of the scattering is not from light captured within these filaments. But there is evidence for self-phase modulation from effects such as ionization and relativistic self-focusing. However, no clear correlation is observed between channel length and the number or energies of accelerated electrons. Evidence for high intensities within the channels is given by small-angle Thomson scattering of the plasma wave generated therein, with this method, the intensity is found to be of the order of 1018 Wcm-2 greater than 12 Rayleigh lengths from focus 相似文献
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第四讲 超强激光脉冲与等离子体相互作用中高能离子的产生 总被引:2,自引:0,他引:2
近几年来,由于高功率激光技术的不断发展,利用超强激光脉冲与等离子体相互作用产生高能离子束的研究得到了极大推动.实验和理论模拟均发现,在超强激光脉冲与等离子体相互作用过程中,可以产生高亮度、小尺寸、方向性好的高能质子束和高能重离子束.这种基于超强激光的高能离子源在先进离子束成像技术、惯性约束聚变混合“快点火”、新型台面离子加速器以及医疗等方面都有很诱人的应用前景.文章主要介绍了超强激光与固体靶相互作用中高能离子束(尤其是质子束)的加速机制、高能离子束特性、常用测量方法及其潜在应用,并对最新的研究进展进行了简单介绍. 相似文献
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We report results from particle-in-cell simulations of the interaction of intense laser light with overdense plasma designed to examine the effects of plasma waves generated by pulses of fast electrons on high-order harmonic emission from the plasma. We show that the emission spectrum is modulated at the plasma frequency and identify combinations of parameters and circumstances favorable for modulation. In particular, the observed modulation is shown to depend not only on the chosen plasma electron density and intensity of the incident light but on the density profile and pulse shape. 相似文献
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A qualitative model is given, which predicts nonlinear broadening of the spectrum of laser light anomalously reflected by a plasma. The predicted nonlinear broadening compares favourably with recent experimental results. 相似文献
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The dependences of the second harmonic (SH) intensity output by the dispersion interferometer (DI) upon the relative phase of the SH and fundamental waves θ0 (called phase characteristics) are studied both experimentally and theoretically. It has been found that high irradiance (when self-action effects are not negligible) makes the phase characteristics differ from the cosine type which is usual for linear interferometry. In the case of high power pulsed radiation, a strong dependence of the SH pulse shape on θ0 was observed. The evolution of the SH pulse shape in the DI output registered as θ0 varies is checked against the numeric simulation data. By measuring the nonlinear phase characteristics of the DI, the main influence of the slow (response time of ≈ 1 ns) cubic nonlinearity on the frequency doubling of nanosecond pulses is determined for the employed KTP crystals. 相似文献
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The characterization of the plasma state is of great interest in industrial applications based on plasma enhanced chemical vapour deposition (CVD) processes. We have performed experiments on a capacitively coupled radio frequency discharges in air and SF6. The use of gases containing electronegative components, such as oxygen or fluorine, leads to quite peculiar discharges, due to the presence of negative ions which affects the transport properties of such a plasma. Plasma parameters have been measured by means of movable electrostatic Langmuir probes. The implementation of a suitable numerical model of gas-phase chemistry and transport phenomena allow us to predict the amount of negative ions. In particular we show that the ion to electron density ratio strongly depends on the diffusion process and on ion recombination rates. Thus measuring it leads to a better understanding of ion diffusion and in particular of the ambipolar electric field. 相似文献