Time duration of the parametric x-ray radiation

Time evolution of the parametric X-Ray radiation, produced by a relativistic charged particle passing through a crystal, is studied. The most attention is given to the cases when the radiation lasts much longer (t_{PXR} ~0.1 ns) than the the time t_p of the particle flight through the crystal (t_p ~ 1 ps). It is shown that such long duration of the radiation makes possible the detailed experimental investigation of the complicated time structure of the parametric X-ray pulses, generated by electron bunches, which are available with modern acceleration facilities.