飞秒激光与等离子体相互作用过程中超热电子能谱的测量

Measurement of hot electron energy spectrum in femtosecond laser-plasma

报道了在3TW飞秒激光器上完成的激光 等离子体相互作用过程中产生的超热电子的能谱测量结果。能谱测量显示:在较低的能段,超热电子能谱先是呈现一个局部的平台,然后迅速衰减,呈现非类麦克斯韦分布,这是由于几种加热机制共同作用,其中占主导地位的是反射激光对电子的加速;在较高的能段,超热电子能谱呈类麦克斯韦分布,拟合的温度远远高于已知的温度定标律给出的温度,其原因在于超热电子分布的高能尾部本身的抬高和激光的自聚焦及成道。

This paper reports the results of the measurement of hot electron energy spectrum during the interaction of femtosecond laser-plasmas. First, there is a depression of hot electron fluence at the energy of around 40 keV. Second, there is a local plateau of electron fluence at energies of 100-350 keV, which is produced by the several acceleration mechanisms, and a rapid reduction of electron at energy greater than 350 keV. In the range of 1-5.4 MeV, the number of hot electrons decays approximately by an exponential function. Fitted with Maxwellian distribution, the temperature of hot electrons is much lager than those from the known temperature scaling, which is due to run-up of the energy spectrum at its tail and the self-focusing or channeling of laser.