Observations of picosecond X-ray pulses

An upper limit on the duration of X-ray pulses emitted by a laser-produced plasma has been obtained using a picosecond optical-sampling system. When irradiating an iron target with 1-J 40-ps pulses from a Nd:glass laser, X-ray pulses were as short as 50 ps with a 0.5- percent conversion efficiency. The technique utilized direct excitation of a plastic scintillator and measurement of the scintillation light rise time. Time resolution was ≤50 ps.