X-Ray Pump Probe (XPP)
The XPP instrument is installed at the hard x-ray beamline KMC-3, which is equipped with an x-ray mirror assembly and a double monochromator, which can be removed from the x-ray beam path to allow for experiments with a monochromatic or a white x-ray beam. The energy range extends from 2 keV to 14 keV.
The XPP is dedicated to time-resolved hard X-ray diffraction experiments, which study thin film samples under a broad range of ambient conditions like low temperatures or under applied electric or magnetic fields. We use optical laser excitation and electrical excitation schemes to study the structural non-equilibrium response of the samples. To do so, we routinely use a gated area detector that is synchronized to the single bunch of the BESSY filling pattern, that is, we record data only when a short burst of X-ray photons arrive at the sample. With this scheme we are essentially only limited by the length of the X-ray pulses, which are around 80 ps in standard hybrid mode and 15 ps in low-alpha operation mode. Using a home-built fast scintillation detector (Scionix) with a commercial photomultiplier tube (Hamamatsu), we can obtain 4 ns time resolution in time-correlated photon counting mode and are able to measure simultaneously delays up to 33 μs during one sample scan. Static experiments can be performed using a CyberStar detector.
Selected Applications:
- light-induced phase transitions
- ferroelectric switching dynamics
- material-specific thermal transport dynamics
The X-ray Pump Probe (XPP) station at the KMC-3 beamline.
Methods
Time-resolved diffraction
Remote access
depends on experiment - please discuss with Instrument Scientist
For the optical sample excitation, we use a synchronized laser system (Light Conversion Pharos) that is synchronized with a Menlo RRE-Syncro module to the bunch timing of BESSY. With an electronic delay unit we can remotely shift the arrival time of the laser pulses with respect to the X-ray pulses up to 1 ms, which is limited by the repetition rate of the laser with a time resolution of roughly 1 ps.
A special setup for the investigation of ferroelectric switching dynamics is available upon request. We use a Keithley 3390 Arbitrary Function Generator, either in stand-alone mode or synchronized to the BESSY ring, to apply electric field pulse sequences to the sample with a tungsten needle. A voltage amplifier is available that allows to multiply the output of the function generator by a factor of 5.
We offer a high-vacuum environment (10-6 mbar) for the sample. The sample is mounted on a 4 circle goniometer (3 circle goniometer in vacuum) and the detectors mounted outside on the 2Θ arm. The sample temperature can be varied between 10 and 400 K using a closed-cycle cryostat.