超短激光与金薄膜靶相互作用产生的质子能谱

在能量11 mJ、波长744 nm、脉宽120 fs、功率密度61016 W/cm2的超短脉冲装置上，开展了超短脉冲激光与2.1 m和5.0 m金薄膜靶相互作用产生质子束的实验研究。利用Thomson谱仪测量了产生的质子能谱，发现利用2.1 m金薄膜靶时，质子能谱由于质子源数量不足而在74 keV附近出现单能峰，5.0 m的金薄膜靶产生的质子计数和能谱均比2.1 m的金薄膜靶产生的低，主要原因是超热电子穿过薄膜靶时出现的能量损失和几何倾斜降低了电子回流所致。

Energy spectra of protons driven by ultra-short laser interaction with thin gold foils

Proton acceleration experiments were performed by using an ultra-short laser to irradiate gold foils of 5 m and 2.1 m in thickness. The ultra-short laser pulse had the pulse duration of 120 fs and energy of 11 mJ. The peak focal intensity remained around 61016 W/cm2. A Thomson ion spectrometer with CR39 plastic nuclear track detectors were used to observe spectra of the accelerated protons. The spectrum of the 2.1 m foil featured a single peak around 74 keV due to the inefficiency of protons. The maximum energies and efficiencies of accelerated protons increased with decreasing the target thickness. The results were explained by the energy loss of electron transmission and a geometrical effect on hot electron recirculation.