ИСТИНА

Interaction of femtosecond laser pulses of intensity above 10^15 W/cm^2 with solid target is accompanied with high-temperature dense plasma formation. The plasma is a source of K-line X-ray radiation with ultra-short duration and narrow energy spectrum in a range of 0,05-8 keV (the radiation of elements with atomic numbers up to 29, i.e., Cu). X-ray lines can be used in various tasks including the X-ray diffraction analysis - investigation the dynamics of ultrafast phase transitions and control of the crystal lattice; plasma diagnostics (including fusion plasma) with high temporal resolution. If the source contains two X-ray lines which correspond to the different energies it can be used in densitometry tasks. We propose to use CuSO4 crystal to develop double-energy X-ray source. The crystal contains atoms of sulfur and copper with K-line energy 2.3 keV and 8 keV correspondingly. In this paper, we discuss experiments on the generation of X-rays when the microchannel is formed in CuSO4 crystal by a sequence of intense (~1015 W/cm2) femtosecond laser pulses. Choose of the experimental conditions is based on our previous experiments where we have found that under microchannel production in a target by a sequence of intense (~10^16 W/cm^2) femtosecond laser pulses, yield of the X-ray radiation increases. We show in this paper that X ray spectrum from CuSO4 contains two K-lines (of sulfur and copper). We discuss the possibility of creation of mono-energetic source based on polyatomic target (for instance, CuSO4 crystal) by filtration of X-rays and varying laser intensity. The problem of X-ray yield optimization is also discussed, actually the influence of focusing accuracy on X-line contrast (ratio of line amplitude to the amplitude of brehmsstralung radiation). In addition we show the results of comparative experiments on K-line X-ray generation under laser interaction with copper target.