The alkali metal halide salts (KBr, NaBr, KI, NaI and CsI) were used to generate X-rays by femtosecond laser irradiation. Due to a wide band-gap, these materials are transparent and allow generation of X-rays inside the target rather than on its surface. The femtosecond amplified laser system “Pharos” with the wavelength $$\lambda $$ = 1028 nm, 4 kHz repetition rate and typical pulse energy 250 µJ (maximum 1.5 mJ) was used for the experiment. Using this system, we were able to reach laser peak power density of $$2.7\times 10^{15}$$ W/cm $$^2$$ . We have registered X-ray radiation spectra in a range of 3–30 keV with typical flux values of $$1\times 10^7$$ ph/s for potassium $$K_\alpha $$ line. We were able to confirm that there were enough electrons with the energy higher than 33 keV.

中文翻译：

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飞秒激光脉冲照射碱金属卤化物盐的 X 射线脉冲发射

碱金属卤化物盐（KBr、NaBr、KI、NaI 和 CsI）用于通过飞秒激光照射产生 X 射线。由于带隙较宽，这些材料是透明的，允许在目标内部而不是在其表面产生 X 射线。实验使用飞秒放大激光系统“Pharos”，波长$$\lambda $$ = 1028 nm，重复频率为4 kHz，典型脉冲能量为250 µJ（最大1.5 mJ）。使用该系统，我们能够达到 $2.7\times 10^{15}$$ W/cm $$^2$$ 的激光峰值功率密度。我们已经记录了 3-30 keV 范围内的 X 射线辐射光谱，钾 $$K_\alpha $$ 线的典型通量值为 $$1\times 10^7$$ph/s。我们能够确认有足够的能量高于 33 keV 的电子。