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采用电子谱仪测量了飞秒激光-金属薄膜靶相互作用中靶前和靶后产生的超热电子能谱.结果显示:靶前超热电子能谱的峰出现在约430keV处,靶后超热电子能谱的峰出现在约175keV处;靶前超热电子的有效温度分别为218keV和425keV,靶后超热电子能谱出现“软化”现象,其有效温度分别为96keV和347keV.靶前和靶后超热电子能谱明显不同是由于超热电子输运穿越过密等离子体和冷材料的靶,并在靶后建立Debye鞘,鞘电场使靶后超热电子能谱峰向低能端移动,鞘电场和自生磁场导致靶后超热电子能谱产生“软化”,估算出的鞘电场小于激光电场.
The electron spectra of the femtosecond laser-metal thin films were measured before and after the target-target fusion by using an electron spectrometer. The results showed that the peak of the hot electron before the target appeared at about 430 keV, The peak of the hot electron spectrum appeared at about 175 keV. The effective temperatures of the target super hot electrons were 218 keV and 425 keV, respectively. The superheated electron spectra of the targets showed “softening” phenomenon with effective temperatures of 96 keV and 347 keV respectively The distinct difference from the target hypershotheric electron energy spectrum is the result of superheated electron transport across the target of over-dense plasma and cold material, and the establishment of a Debye sheath behind the target. The sheath electric field causes the post-target hyperthermophilic electron peak to lower energy Moving, sheathing and autogenic magnetic fields result in “softening” of the target hypershothelectron spectra, and the estimated sheath electric field is less than the laser electric field.