Demonstration of a 2-ps transient x-ray laser

A time-resolved measurement of the output from the Ni-like Ag transient-collisional-excitation x-ray laser is described. An ultrafast x-ray streak camera was used to diagnose the output of the $J=\stackrel{\ensuremath{\rightarrow}}{0}1$ $4d\ensuremath{-}4p$ lasing line at 13.9 nm. The full width at half maximum duration of the x-ray pulse is measured to be of $1.9\ifmmode\pm\else\textpm\fi{}0.7 \mathrm{ps}$ at optimum conditions of pump laser irradiation. This is the shortest x-ray laser duration directly demonstrated to date and illustrates the great potential of transient x-ray lasers as a high brightness, picosecond x-ray source for applications.