Various methods for X-ray pulse generation using a femtosecond laser and their potential for time-resolved X-ray analyses

Abstract

Three different methods for X-ray pulse generation with femtosecond laser pulses were outlined. The first method was with a photo-excitable X-ray tube irradiated by femtosecond laser pulses. The X-ray emission spectrum was composed of a broad component and some characteristic X-ray lines. The X-ray pulse width was calculated to be about 20 ps, based on an equation of the electron motion in the tube. The second method was by the irradiation of focused femtosecond laser pulses onto electrolyte aqueous solution jets, such as a cesium chloride aqueous solution. The X-ray emission spectra showed solute-dependent characteristic X-ray lines and broad bremsstrahlung backgrounds up to 40 keV. Under double-pulse excitation onto a distilled water jet, the X-ray intensity was about 103-times higher than the case excited by single pulse. The third method was by the irradiation of focused femtosecond laser pulses onto cassette tapes. The characteristic X-ray lines of Fe Kα and Kβ were clearly observed in addition to a broad bremsstrahlung background. By using this X-ray pulse source, an X-ray diffractometer was developed. An X-ray diffraction image of LiF (200) was clearly taken by an X-ray image intensifier and a cooled CCD camera.