fs激光在靶背表面产生的质子束成丝
Filamented proton beams from the rear surface of target irradiated by fs laser
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摘要: 介绍了利用3TW/60fs钛宝石超短超强激光与20μm铜薄膜靶相互作用的实验。实验观测到质子束的角分布随激光功率密度有所变化。在较高的功率密度（～1×1018 W/cm2）时，观测到环状的质子束分布，发散角较大。在较低的激光功率密度（～2×1017 W/cm2）时，质子束发散角减小，质子束出现成丝现象。质子束的角分布实际上反映了从靶前输运到靶背的超热电子电流横向分布。在输运过程中，由于Weibel不稳定性会使超热电子电流出现空心化并最后破裂成丝。Abstract: Proton emission patterns from the rear surface of targets irradiated by 60fs laser pulse at different intensity have been studied. The filaments of protons emission from 20μm Cu target were observed in the shots with lower laser intensity (about 2×1017W/cm2). As the laser intensity increased up to about 1×1018W/cm2 for the same target thickness, the filaments of proton beam disappeared and a hollow proton beam emerged. The patterns of proton beams revealed the traverse distribution of hot electrons reached the rear surface of target after a long distance transportation from the front surface of target. In this process, Weibel instability will drive electron beam into hollow structure and break into filaments in the end.
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Key words:
- ultra-short and ultra-intense laser /
- proton emission /
- filament /
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