A modular table-top setup for ultrafast X-ray diffraction
We present a table-top setup for femtosecond time-resolved X-ray diffraction based on a Cu Kα (8.05 keV) laser driven plasma X-ray source. Due to its modular design it provides high accessibility to its individual components (e.g. X-ray optics and sample environment). The Kα-yield of the source is optimized using a pre-pulse scheme. A magnifying multilayer X-ray mirror with Montel-Helios geometry is used to collect the emitted radiation, resulting in a quasi-collimated flux of more than 105 Cu Kα photons/pulse impinging on the sample under investigation at a repetition rate of 10 Hz. A gas ionization chamber detector is placed right after the X-ray mirror and used for normalization of the diffraction signals enabling the measurement of relative signal changes of less than 1% even at the given low repetition rate. Time-resolved diffraction experiments on laser-excited epitaxial Bi films serve as an example to demonstrate the capabilities of the set-up. The set-up can also be used for Debye-Scherrer type measurements on poly-crystalline samples.