超强飞秒激光与固体靶产生的超热电子加热机制
Mechanism studies on hot electron generation by ultra-intense femtosecond laser interacting with solid target
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摘要: 在SILEX-1激光器上测量了超强飞秒激光与Ta靶相互作用产生的出射超热电子能谱及角分布，研究了出射超热电子加热机制。激光脉宽为 30 fs，激光功率密度为8.5×1018 W/cm2。靶前法线方向超热电子温度为550 keV。从实验结果可知：共振吸收是靶前法线方向超热电子主要加热机制，这与靶前存在大密度标长预等离子体的实验条件吻合。靶厚为6～50 μm时，靶后超热电子沿法线方向出射；靶厚为2 mm时，该发射峰消失。Abstract: The energy spectrum and the angular distribution of the hot electrons generated by an ultra-intense femtosecond laser interacting with a solid target are studied. The intensity of the femtosecond laser is 8.5×1018 W·cm-2 and the pulse duration is 30 fs in experiment. The temperature of the hot electrons at the normal of the target is 550 keV. Resonance absorption is the main mechanism that leads to the laser acceleration of the hot electrons at the normal of the target. And it accords with large plasma density scale length generated by pre-pulse which preceded the main pulse. The emission direction of the hot electron is normal to the rear surface for 30 μm target, and the emission peak disappears for 2 mm target.
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Key words:
- femtosecond laser /
- hot electron /
- energy spectrum /
- angular distribution /
- resonance absorption
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