A study of picosecond laser–solid interactions up to 1019 W cm−2

The interaction of a 1053 nm picosecond laser pulse with a solid target has been studied for focused intensities of up to 1019 W cm−2. The maximum ion energy cutoff Emax (which is related to the hot electron temperature) is in the range 1.0–12.0 MeV and is shown to scale as Emax≈I1/3. The hot electron temperatures were in the range 70–400 keV for intensities up to 5×1018 W cm−2 with an indication of a high absorption of laser energy. Measurements of x-ray/γ-ray bremsstrahlung emission suggest the existence of at least two electron temperatures. Collimation of the plasma flow has been observed by optical probing techniques.