X-ray pulse compression using strained crystals

The use of strained crystals to time-compress chirped x-ray FEL pulses is proposed. The chirped beam diffracts from a crystal in which the strain varies with depth. Low-Z crystals are favored to reduce absorption over the required path lengths and small Bragg angles are favored to increase the diffraction efficiency of the strained crystal. The best compression ratios found for a 230 fs, 0.5% chirped beam at a wavelength of 1.54 Å are achieved with graphite and diamond crystals. The calculations indicate for graphite that the pulse may be compressed in time by a factor of up to 10 with an efficiency such that this produces 6.8 times as many photons as a comparable time-slicing method.