超薄靶激光质子加速实验研究

在超短超强飞秒SILEX-Ⅰ激光装置上,开展了薄膜靶激光质子加速的实验研究。实验发现激光预脉冲、靶厚度对质子加速有很大的影响。在激光强度3×1018~3×1019W/cm2条件下,采用前表面厚度为3μm铜、后表面镀4μm厚CH靶,质子的最大能量达到3.15 MeV。而对190 nm厚CH膜靶,质子的最大能量为0.54 MeV。初步研究了激光偏振对质子加速的影响,相同激光功率条件下,圆偏振激光加速产生的质子最大能量略低于P偏振打靶。这些结果与靶后鞘层加速机制相一致。

Experimental study of laser-driven proton acceleration with ultrathin targets

The generation of proton beams from thin-foil targets on SILEX-Ⅰ is studied. It shows that prepulse has a profound effect on the maximum proton energy. The thinner the target is, the more sensitive it is to the prepulse. Under the laser intensity of 10¹⁸ to 3×10¹⁹ W/cm², the maximum proton energy is 0.54 MeV with 190 nm CH target and 3.15 MeV with 3 μm Cu target (back surface plated with 4 μm CH) respectively. Besides, the effect of laser polarization on proton acceleration is also studied. The maximum proton energy accelerated by a circularly polarized laser pulse is a little lower than that by a P-polarized laser pulse with the same laser power density. The mechanism is consistent with target normal sheath acceleration.