KeV X-ray generation from picosecond KrF laser-produced plasmas

Summary form only given. The emission of X-rays in the photon energy range of 800-1400 eV from plasmas produced on solid targets by 0.85, 2, and 90 picosecond KrF laser pulses has been studied experimentally. One of the goals of this study was to optimize such a source of KeV X-rays for X-ray lithography. The pulse energies ranged from 1 to 50 mJ, which are typically the energies which can be extracted in a single short pulse from a commerical KrF discharge laser. The targets used ranged from iron to zinc in order to obtain emission from the neon-like ionization states in the keV energy range. In addition, titanium and tin targets were measured in order to study the scaling to lower and higher atomic number elements. The emission spectra, angular distribution, and X-ray conversion efficiencies into 2 /spl pi/ Srad have been measured in vacuum. Peak conversion efficiencies of laser light into keV X-ray emission of 10-13% were obtained for Fe, Co, Ni, Cu, and Zn targets for 90 ps, 50 mJ pulses.