Resonant High-Intensity Picosecond X-Ray Generation; Thin Films Usage Advantages

Abstract

Femtosecond laser-induced plasma has proved to be the powerful source of short pulses of incoherent soft X-rays with energy from 50 ev up to few keV and even harder [1,2]. Extremely short X-ray pulse duration down to 1 ps makes it possible to use this radiation in time-resolved X-ray diagnostics of ultrafast processes (X-ray diffraction, spectroscopy, microscopy). It is of special interest to design X-ray microscope in so-called “water window” region to investigate living cells. One more advantage here is as shorter X-ray pulses are used less information recorded is deteriorated by damaging of an investigated cell by X-rays. To generate X-rays above 200 eV intensities of 1015– 1016 W·cm−2 and even higher have to be used. As it was shown previously [3] large amount of X-ray energy emitted from femtosecond plasma consisting of light atomic elements (B,C etc.) is radiated from resonance transitions of highly stripped ions. In the case of carbon target the most bright lines of H- and He-like C ions lie in the “water window” region. The main goals of our research are to find “optimal” conditions for generating powerful few-picosecond X-ray pulses in the vicinity of “water window” region by femtosecond laser pulses with rather low intensities 1015– 1017 W·cm−2 and to investigate whether it is possible to increase electron temperature of the plasma and to generate few keV X-rays by using thin targets.