Abstract
We have carried out time resolved stroboscopic diffraction experiments on standing surface acoustic waves (SAWs) of Rayleigh type on a LiNbO3 substrate. A novel timing system has been developed and commissioned at the storage ring Petra III of Desy, allowing for phase locked stroboscopic diffraction experiments applicable to a broad range of timescales and experimental conditions. The combination of atomic structural resolution with temporal resolution on the picosecond time scale allows for the observation of the atomistic displacements for each time (or phase) point within the SAW period. A seamless transition between dynamical and kinematic scattering regimes as a function of the instantaneous surface amplitude induced by the standing SAW is observed. The interpretation and control of the experiment, in particular disentangling the diffraction effects (kinematic to dynamical diffraction regime) from possible non-linear surface effects is unambiguously enabled by the precise control of phase between the standing SAW and the synchrotron bunches. The example illustrates the great flexibility and universality of the presented timing system, opening up new opportunities for a broad range of time resolved experiments.
Highlights
Surface acoustic waves (SAWs) are an enabling technology for electromechanical frequency filters, micro-fluidic devices[1,2] as well as sensor applications.[3]
A precise control of phase φ between the acoustic wave and the synchrotron bunches allows for the observation of a seamless transition between dynamical and kinematic scattering regimes induced by the surface acoustic waves (SAWs)
It was shown that the strain field induced by standing SAWs leads to a seamless transition from dynamical to kinematic diffraction regimes for a highly ordered LiNbO3 crystal lattice on the 100 ps timescale
Summary
Surface acoustic waves (SAWs) are an enabling technology for electromechanical frequency filters, micro-fluidic devices[1,2] as well as sensor applications.[3]. The bunchclock provides three independent and basically arbitrary integral dividers of the microwave frequency which can be used to synchronize pulsed excitation mechanisms (e.g. pulsed lasers) or to gate modern pixel detectors[6,7] to the bunch frequency fb with phase stability. Research Systems) to the 10 MHz reference, see Fig. 2(a) This allows for time resolved diffraction experiments without the need for a reduction of the effective X-ray frequency and flux by gated detectors[6] or high speed choppers.[8] The effective time delay t between SAW pump- and X-ray probe pulses can be set as a phase φ between the synchrotron pulses at fb and the SAW signal at f S AW directly on the frequency generator, time delay t and phase φ are related via t.
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