Numerical studies on the ultrashort pulseK-α emission sources based on femtosecond laser–target interactions

Abstract

K-α emission is an intense short-pulse line source well suited for X-ray diagnostic techniques with subpicosecond and micrometer resolution. Numerical simulations are performed here in a search for laser–target interaction regimes where both high efficiency of laser energy transformation to X-ray emission and ultrashort X-ray pulses are achieved. We use the one-dimensional PIC code for the description of the laser interaction with the plasma layer at the target surface. Fast electron transport into the target is treated by our newly developed Monte Carlo code with temporal resolution that is described here in detail. Our simulations reveal extremely short ∼200 fs FWHM brightK-α X-ray pulses emitted from targets heated by 120-fs pulses of a table-top laser. Laser energy conversion efficiency toK-α line emission as high as 6 × 10−5is noticed. Integration of the emitted energy over the focal spot is carried out to improve the simulation accord with published experimental data. Negligible impact of self-induced electric fields onK-α emission is found for conducting target materials at moderate laser intensities [lsim ]1017W/cm2.