Direct spectroscopic observation of multicharged MeV ions in plasma, heated by intense femtosecond laser radiation

Summary form only given, as follows. Experimental and theoretical investigations of multicharged ions acceleration by an intense femtosecond laser radiation in wide (10/sup 17/-4-10/sup 18/W/cm/sup 2/) laser flux density range is presented. With the help of focusing spectrometers with spatial resolution (FSSR-1,2D) we have observed evidence of the emission of energetic He- and H-like ions in fluorine of more than 1 MeV produced via the optical field ionization (OFI) from solid target irradiated by intense I=(1-4)/spl middot/10/sup 18/ W/cm/sup 2/ (UHI-10 laser facility, 60 fs, /spl lambda/=800 nm), obliquely incident p-polarized pulse laser. The measured blue wing of He/sub /spl alpha//, He/sub /spl beta// and Ly/sub /spl alpha// lines of fluorine shows a Doppler-shifted spectrum due to the self-similar ion expansion dominated by superthermal electrons with the temperature T/sub h//spl sim/100-400 keV. Using a collisional particle-in-cell simulation, which incorporates the nonlocal-thermodynamic-equilibrium ionization including OFI, we obtained the plasma temperature, line shapes, hot electron spectra and maximal energy of accelerated ions, which agree well with those determined from experimental hot electrons and ions spectra. The red wing of ion spectra gives the temperature of bulk plasma electrons. By using simultaneously 3 FSSR spectrometers we also obtained X-ray spectra with 3D spatial distribution for He/sub /spl alpha//-K/sub /spl alpha// lines of Al, Ca and Cu targets. Such spectra clearly show that the size of emission zone of Ka radiation on the target surface in 2-5 times large, than the size of emission zone of Ka lines and their satellites. At the same time the size of all lines emission in the direction of laser-plasma expansion were equal. Interpretation of such an effect is presented.