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A reliable analytical expression for the potential of plasma waves with phase velocities near the speed of light is derived.The presented spheroid cavity model is more consistent than the previous spherical and ellipsoidal models and it explains the mono-energetic electron trajectory more accurately,especially at the relativistic region.The maximum energy of electrons is calculated and it is shown that the maximum energy of the spheroid model is less than that of the spherical model.The electron energy spectrum is also calculated and it is found that the energy distribution ratio of electrons △E/E for the spheroid model under the conditions reported here is half that of the spherical model and it is in good agreement with the experimental value in the same conditions.As a result,the quasi-mono-energetic electron output beam interacting with the laser plasma can be more appropriately described with this model. 相似文献
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Using the ellipsoidal cavity model, the quasi-monoenergetic electron output beam in laser-plasma interaction is described. By the cavity regime the quality of electron beam is improved in comparison with those generated from other methods such as periodic plasma wave field, spheroidal cavity regime and plasma channel guided acceleration. Trajectory of electron motion is described as hyperbolic, parabolic or elliptic paths. We find that the self-generated electron bunch has a smaller energy width and more effective gain in energy spectrum. Initial condition for the ellipsoidal cavity is determined by laser-plasma parameters. The electron trajectory is influenced by its position, energy and cavity electrostatic potential. 相似文献
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P. Zobdeh R. Sadighi‐Bonabi H. Afarideh E. Yazdani R. Rezaei Nasirabad 《等离子体物理论文集》2008,48(8):555-560
In this work we evaluate the interaction of high intense laser beam with a steepened density profile. During laser interaction with underdense plasma by freely expanding plasma regime, modification of density profile is possible. In this paper we have investigated the ultra short laser pulse interaction with nonisothermal and collisionless plasma. We consider self–focusing as an effective nonlinear phenomenon that tends to increase when the laser power is more than critical rate. By leading the expanded plasma to a preferred location near to critical density, laser reflection is obtained, so the density profile will be locally steepened. The electromagnetic fields are evaluated in this new profile. We show the amplitude and period of electrical field oscillation are increased by reducing the steepened scale length. Also our numerical results identify that by reducing the steepened scale length, the electrical field is increased to wave breaking threshold limit. This high gradient electrical field causes the effective beam loading during the wave breaking phenomenon. The wave breaking can be the initial point for other acceleration regime as cavity or channel guiding regime. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Extension of high-order harmonics and generation of an isolated attosecond pulse in the chirped laser field 
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下载免费PDF全文 This paper theoretically investigates the high-order harmonic generation cutoff extension using intense few-cycle linearly chirped laser pulses. It shows that the cutoff of the harmonic can be extended remarkably by optimising the chirping parameters. The time-frequency characteristics of high-order harmonics with different chirping parameters are analysed by means of wavelet transform of the dipole acceleration. It also gives out the classical three-step model pictures of electron. By superposing a properly selected range of the harmonic spectrum, it obtains an isolated 65as pulse. 相似文献
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We study the dynamics of single electron in an inhomogeneous cylindrical plasma channel during the direct acceleration by linearly polarized chirped laser pulse. By adjusting the parameters of the chirped laser pulse and the plasma channel, we obtain the energy gain, trajectory, dephasing rate and unstable threshold of electron oscillation in the channel. The influences of the chirped factor and inhomogeneous plasma density distribution on the electron dynamics are discussed in depth. We find that the nonlinearly chirped laser pulse and the inhomogeneous plasma channel have strong coupled influence on the electron dynamics. The electron energy gain can be enhanced, the instability threshold of the electron oscillation can be lowered, and the acceleration length can be shortened by chirped laser, while the inhomogeneity of the plasma channel can reduce the amplitude of the chirped laser. 相似文献
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在弱相对论条件下，给出了超短强激光脉冲在稀薄等离体中传播的孤子解及其所激发的尾波场孤子解。 相似文献
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用一维相对论粒子模拟研究了相对论超短强激光脉冲在等离子体中传播时激发的尾波场,初步获得了近共振区尾波场的峰值幅度随激光脉冲宽度变化的特点,发现在近共振区等离子体波激发出现增强。通过准静态近似下尾波激发的一维非线性方程数值求解,并与粒子模拟结果比较,得到了该非线性方程的适用范围：当激光脉冲宽度小于等离子体波波长的4倍时,该方程所得结果与粒子模拟结果一致;而当激光脉冲宽度大于该数值时,该方程不再适用。 相似文献
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论述了啁啾脉冲放大技术中运用单光栅展宽器结构将少光脉冲在时域进行啁啾展宽的原理及特性，导出了该展宽器所提供色散量的具体表达式及其展宽后激光脉冲宽度的计算，然后通过数值计算分析了其展宽因子及展宽比随各参量的之间的变化关系；本文在此基础上进一步获得了实验的测量结果。 相似文献
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本文理论上研究了初态为基态与第一激发态等权叠加的一维氦离子在空间非均匀啁啾双色场驱动下氦离子的高次谐波发射及孤立阿秒脉冲的产生. 研究表明, 一维氦离子在空间非均匀啁啾双色场驱动下发射的高次谐波相对于均匀场情况截止位置得到明显扩展, 得到了光滑的超连续谱,并应用半经典三步模型解释了高次谐波发射的物理机理. 通过小波变换的方法对连续谱进行了时频分析, 并且与电子的经典运动轨迹进行了对比分析, 结果显示在空间非均匀场中长量子轨道消失, 短量子轨道加强. 讨论了空间非均匀啁啾双色场中时间延迟对谐波和孤立阿秒脉冲产生的影响, 发现适当调整时间延迟值可以得到较大延展的光滑的超连续谐波谱, 本方案中时间延迟为t0=1.6πup/ω1时得到了最大延展, 通过对谐波中600次到680次(80次)谐波合成得到32 as的孤立脉冲. 相似文献
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针对SILEX钛宝石激光器参数,采用PIC数值模拟程序VORPAL对激光尾波场加速进行了模拟,得到了电子轨迹及能量数据,进而通过理论计算得到了空泡机制下X射线辐射特性。结果表明,空泡机制下高能电子在空泡中做betatron振荡且多数电子被加速到170 MeV左右;加速能量较低的电子（约100 MeV）, 其辐射谱为临界能量约3 keV的类同步辐射谱,发散角约为8 mrad,而能量较高的电子（约170 MeV）对应的光子临界能量约为10 keV。 相似文献
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若驱动激光的相干时间小于不稳定性增长时间,则有可能直接控制参量不稳定性。研究了有限带宽的啁啾展宽脉冲对等离子体冕区参量不稳定性及超热电子的抑制效果,给出解析分析及用PIC程序数值模拟结果,考察了电子－离子碰撞对超热电子的影响。 相似文献
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脉冲时域相干合成技术主要通过对功率放大后的高重频脉冲序列进行时序合成,从而降低激光的重复频率,有效地提升输出脉冲的峰值功率与能量,避免放大过程中高峰值功率引起的非线性效应。该技术与空域相干合成相结合,能够突破单纤激光的性能极限,实现高能量、高平均功率和高峰值功率的超短脉冲激光输出,具有广阔的应用前景。介绍了超短脉冲光纤激光时域相干合成的基本原理和关键技术,综述了时域相干合成系统的发展历程及其关键技术的研究现状,重点介绍了近年来脉冲分割放大与脉冲相干堆积技术的研究进展,并对时域相干合成的不同技术路线进行了分析与比较,最后对其未来的发展方向进行了梳理,为相关领域的研究提供参考。
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Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992,optical parametric chirped pulse amplification(OPCPA)became the most promising method for the amplification of broadband optical pulses.In the meantime,we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers.The output power and pulse duration of these systems have ranged from a few gigawatts to hundreds of terawatts with a potential of tens of petawatts power level.Meanwhile,the output pulse duration based on optical parametric amplification has entered the range of fewoptical-cycle field.In this paper,we overview the basic principles,trends in development,and current state of the ultrashort and laser systems based on OPCPA,respectively. 相似文献
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