Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, 48109, USA.
Phys Rev Lett. 2011 Aug 5;107(6):065003. doi: 10.1103/PhysRevLett.107.065003. Epub 2011 Aug 3.
By using temporal pulse shaping of high-contrast, short pulse laser interactions with solid density targets at intensities of 2 × 10(21) W cm(-2) at a 45° incident angle, we show that it is possible to reproducibly generate quasimonoenergetic proton and ion energy spectra. The presence of a short pulse prepulse 33 ps prior to the main pulse produced proton spectra with an energy spread between 25% and 60% (ΔE/E) with energy of several MeV, with light ions becoming quasimonoenergetic for 50 nm targets. When the prepulse was removed, the energy spectra was broad. Numerical simulations suggest that expansion of the rear-side contaminant layer allowed for density conditions that prevented the protons from being screened from the sheath field, thus providing a low energy cutoff in the observed spectra normal to the target surface.
通过在 45°入射角下使用强度为 2×10(21) W cm(-2)的高对比度、短脉冲激光与固体密度靶相互作用的时间脉冲整形，我们证明了可以重复生成准单能质子和离子能谱。在主脉冲之前 33 ps 存在短脉冲预脉冲，产生的质子能谱具有 25%至 60%（ΔE/E）的能散度，能量为几兆电子伏特，对于 50nm 目标，轻离子变得准单能。当去除预脉冲时，能谱变宽。数值模拟表明，后表面污染物层的膨胀允许密度条件阻止质子被鞘层场屏蔽，从而在垂直于靶表面的观察到的光谱中提供了一个低能量截止。
