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arXiv physics/0411133physics.plasm-ph
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强laser -等离子体相互作用对谐波发射光谱的调制

Modulation of harmonic emission spectra from intense laser-plasma interaction

Tim James Morrow Boyd, Ricardo Ondarza-Rovira

摘要:

我们报告的结果从一系列的PIC模拟进行调查的相互作用的强激光与过密等离子体,特别是在这些相互作用中产生的谐波发射光谱方面。瓦茨等人(2002)最近对这一范围内的辐射进行了观测,结果表明,20次谐波以上的辐射延伸到37次谐波,转换效率为10^-6,该光谱显示出两个和四个谐波之间的明显调制(如果是可变的)。该光谱特征被证明对入射强度高度敏感,在较高强度下具有更明显的调制。这些作者还报告了一组模型PIC模拟的结果,这些模拟显示了在整个谐波范围内调制的发射光谱,但具有更宽的调制带宽。在将要提出的结果中,我们报告的发射光谱的功能在很宽的参数范围内,其依赖于等离子体密度分布的详细结构。虽然我们确实看到了调制光谱的证据,但这似乎不仅对入射强度敏感,而且对等离子体密度分布敏感。此外,等离子体发射的存在进一步使谐波发射光谱复杂化。我们的研究结果使我们得出这样的结论,试图解释调制的发射光谱中的一个特定的理论模型,并从这个推断的临界表面的动态可能是误导。

英文摘要:

We report results from a series of PIC simulations carried out to investigate the interaction of intense laser light with overdense plasma and in particular, aspects of the harmonic emission spectrum generated in these interactions. Recent observations of emission in this range by Watts et al. (2002) show emission above the 20th harmonic extending to the 37th with conversion efficiencies of order 10^-6 with this spectrum showing distinct, if variable, modulation of between two and four harmonics. This spectral feature proved highly sensitive to the incident intensity, with more pronounced modulation at higher intensities. These authors also reported results from a set of model PIC simulations which showed a modulated emission spectrum across the entire harmonic range, but with a wider modulation bandwidth. In the results to be presented we report on features of the emission spectrum across a wide parameter range and its dependence on the detailed structure of the plasma density profile. While we do see evidence of a modulated spectrum, this appears to be sensitive not only to the incident intensity but to the plasma density profile. In addition plasma emission present further complicates the harmonic emission spectrum. Our results lead us to conclude that attempts to interpret modulation in emission spectra in terms of one particular theoretical model and from this to infer the dynamics of the critical surface may be misguided.

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