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 $J=\overrightarrow{0}1$ $4d-4p$ lasing line at 13.9 nm. The full width at half maximum duration of the x-ray pulse is measured to be of $1.9\pm 0.7\hspace{0.5em}\mathrm{ps}$ 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.