用无色散X射线谱仪分别在靶前后测量了飞秒激光辐照铜箔产生的Kα X射线，获得了能量转换效率。入射激光脉冲宽度33 fs，能量在50 mJ～5 J，强度1017～1019 W/cm2。靶后发射的Kα X射线强度随入射激光能量的增加而增加，其单色性较靶前好。采用100 μm厚靶，其能量转换率为2.2×10-5。

The Kα X-ray emission from femtosecond laser-material interactions has been measured with a dispersionless Kα X-ray spectrometer in front of and behind the Cu foil targets. The conversion efficiency from laser energy to Kα photons was obtained. Laser pulse width was typically 33 fs and intensity was kept within the range of 1017 W/cm2 to 1019 W/cm2 by changing laser energy from 50 mJ to 5 J. The experimental results show that the intensity of the Kα X-ray increases with the laser energy， and the X-ray background behind the target is better than that in front of the target. With a 100 μm-thick foil, the conversion efficiency is 2.2×10-5.