Hollow-atom Al X-ray spectra excited by PW laser pulses in foil and CH-buried targets

Pikuz, S. Jr.*; Wagenaars, E.*; Culfa, O.*; Dance, R.*; Rossall, A.*; Tallents, G.*; Faenov, A.*; Kmpfer, T.*; Schulze, K.*; Uschmann, I.*; et al.

no journal, , 

Aluminum K-shell spectra from solid targets were measured during an experiment at Vulcan Petawatt facility. Laser pulses of very high contrast and 150 J of energy allowed interaction studies between the very high intensive laser field and solid state. Intense emission of exotic spectral lines related to the transitions in Al hollow atoms were observed from Al targets. Specifically for 1.5 micron thin foil target the hollow atom yield dominated the resonance line emission. It is suggested that the hollow atoms were predominantly excited by the impact of keV X-ray photons generated on the front surface of the target. On the contrary, the spectra of aluminum foils buried in several microns of CH demonstrated lower K-shell emission and contained much weaker yield of hollow-atom lines. In this case the laser did not interact directly with aluminum matter, so most probably hollow atoms excited by fast electrons penetrating the target.