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| Home > Publications database > Development of a compact hard X-ray split-and-delay line for studying ultrafast dynamics at free electron laser sources |
| Book/Dissertation / PhD Thesis | PUBDB-2019-03551 |
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2019
Verlag Deutsches Elektronen-Synchrotron
Hamburg
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Please use a persistent id in citations: doi:10.3204/PUBDB-2019-03551
Report No.: DESY-THESIS-2019-023
Abstract: The study of condensed matter dynamics on ultrafast timescales is one of the key topics in modern material science research. Hard X-ray free-electron laser sources with extreme peak brightness and ultra short pulses provide excellent conditions for studying ultrafast dynamics in the time domain by employing such techniques as X-ray pump-probe spectroscopy or X-ray photon correlation spectroscopy. However, the intrinsic time structure of FEL sources limits the investigated timescales to 0.2 microseconds or slower. One way of overcoming this limitation is split-and-delay technology. This work presents a new concept for a compact hard X-ray split-and-delay device, enabling such experiments at X-ray FEL sources. The device is designed to split a single X-ray pulse into two fractions introducing time delays from -5 to 815 ps. Accessing such timescales allows to push studies of ultrafast dynamics beyond the intrinsic temporal limit of the X-ray source. The split-and-delay unit is based on Bragg optics and modern technologies for mechanics. Having a compact portable design with dimensions of 60x60x30 cm and a weight of about 60 kg allows to install the device in basically any experimental hutch of a FEL source. The split-and-delay line utilizes a combination of various silicon Bragg optics, arranged in various configurations, enabling the operation in the energy range from 7 to 16 keV. The quality of the beam splitting optics is checked by X-ray topography measurements. A novel method for the split-and-delay line alignment and time delay calibration using a infrared laser setup is developed and successfully used. The infrared setup allows a temporal pre-alignment with a precision better than 22 ps without the need for X-rays. The performance of the split-and-delay setup is checked by measuring the throughput and the delay times with the use of Si(111), Si(220) and Si(422) optics at 7 keV and 9 keV photon energies. Delay times are measured, ranging from 130 ps to 716 ps. The average uncertainty of measured delay times is 16.2 ps. The results show, that ultrafast pump-probe or XPCS experiments can be carried out with the compact split-and-delay line.
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