The long-standing scientific quest of real-time tracing electronic motion and dynamics in all states of matter has been remarkably benefited by the development of intense pulsed laser sources with a temporal resolution in the attosecond (1 attosecond (asec) = 10^-18 sec) time scale. In the last 15 years we have systematically developed the means for the generation of high photon flux extreme ultraviolet (XUV) pulses with 1fs to sub-fs pulse duration, making use of the process of higher order harmonic generation (HOHG). Utilizing multi-cycle laser pulses delivered by high peak Ti:S laser systems, in combination with Polarization Gating techniques , XUV pulse intensities up to 10^14 W/cm2 have been reached in the spectral region 10-24 eV. These pulses have been exploited in I) the temporal characterization of attosecond pulses [2-4]; II) the first proof of principle XUV-pump-XUV-probe experiments for the study of 1fs scale electron dynamics in atoms/molecules [5, 6], and III) quantitative studies of linear and non-linear ionization processes in XUV regime [7,8].
The latest technological advance towards an XUV high photon flux attosecond pulsed source is the newly constructed ≈ 18 m long (HHG) 20 GWatt XUV beam line . The beam line beam line provides the highest ever XUV pulse energy (≈ 230 µJ per pulse) in the spectral region 20-30eV. The corresponding photon flux of 0.6 X 10^14 photons/pulse is competitive with FEL photon fluxes in this spectral region. Using these pulses a focused intensity of ~7 X 10^15 W/cm^2 has been achieved (a value that by using high reflectivity XUV optics can be increased to 10^17 W/cm^2) and multiply charged Argon atoms (Ar^4+) have been produced by multi-XUV-photon ionization processes.
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