X-ray pulse emission of alkali metal halide salts irradiated by femtosecond laser pulses

Abstract

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.