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Brilliant pulsed x-ray synchrotron radiation (SR) is useful for pump-probe experiment such as time-resolved x-ray diffraction, x-ray absorption fine structure, and x-ray spectroscopy. For laser pump-SR x-ray probe experiments, short pulsed lasers are generally synchronized to the SR master oscillator controlling the voltage for acceleration of electron bunches in an accelerator, and the interval between the laser and the SR pulses is changed around the time scale of target phenomenon. Ideal delay control produces any time delay as keeping the time-precision and pointing-stability of optical pulses at a sample position. We constructed the time delay control module using a continuous phase shifter of radio frequency signal and a frequency divider, which can produce the delayed trigger pulses to the laser without degradation of the time precision and the pointing stability. A picoseconds time-resolved x-ray diffraction experiment was demonstrated at SPring-8 storage ring for fast lattice response by femtosecond pulsed laser irradiation, and suggested the possibility of accurate sound velocity measurement. A delay control unit operating with subpicosecond precision has also been designed for femtosecond pump-probe experiments using a free electron laser at SPring-8 campus. [ABSTRACT FROM AUTHOR]

A time-to-space conversion scheme has been investigated to determine the time interval between laser and x-ray pulses. In future pump-probe experiments using ultrashort x-ray pulses, the precise register of the interval of arrival times of the laser and x-ray pulses can make obtained data with a non-negligible jitter be sorted, providing a precision higher than the jitter. This scheme was tested using the SPring-8 synchrotron radiation pulses with a duration of a few tens ps. A femtosecond pulsed laser beam was guided to a GaAs crystal surface with a shallow glancing angle, while an x-ray beam onto the surface from the opposite direction of the laser beam with the similar glancing angle, giving rise to enlarging asymmetric diffraction. The position where the both pulses meet on the surface was identified by observing the change in the diffraction intensity due to the transient expansion of lattice spacing. Since the position is a function of the interval of arrival times of the pulses, the relative arrival time has been determined with a precision of less than the SR pulse duration from the observed spatial distribution of the diffraction intensity. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present subnanosecond-resolved X-ray diffraction experiments at the SPring-8 high flux beamline BL40XU by use of time structure of synchrotron radiation. A phase-locked mechanical chopper (x-ray pulse selector), which is made by Forschungszentrum Jülich, has minimum opening time of 400 nanoseconds and generates single-bunch x-ray pulse trains with variable intervals of 1–2 millisecond (0.5–1 kHz) depending on the rotation speed and with the x-ray pulse duration of ∼ 30 picoseconds from the hybrid bunch mode (D-mode) of the SPring-8 ring operation. The interval of pulse trains is further expanded to more than 1 second by another slower shutter, if necessary. The pulse train is applicable to time-resolved diffraction experiments with both monochromatic and pink beams. An observed Laue data set from lysozyme crystal showed sufficient quality to refine the protein structure at 1.9 Å resolution. A 10-nanosecond pulse from a Nd:YAG laser initiating photoreaction in a crystal can be synchronized with the X-ray pulse. Installation of a mode-locked Ti:sapphire laser/regenerative amplifier system which has a pulse duration of ∼ 2 picoseconds for further pump-probe experiments is also planed. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]