X-Ray Pump Probe (XPP)
X-Ray Pump Probe (XPP)
The XPP instrument 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.Anwendungsbeispiele:
- light-induced phase transitions
- ferroelectric switching dynamics
- material-specific thermal transport dynamics
depends on experiment - please discuss with Instrument Scientist
|2 - 14 keV
|1/5000 - 1/4000
|Focus size (hor. x vert.)
|350 µm x 350 µm
|+49 30 8062 14695
|15 - 400 K
|Sample holder compatibility
|maximum sample size:
• 12 x 12 mm2 for standard low-temperature sample holder,
• 20 x 20mm2 for electrical measurement setup,
• up to 40 x 40mm2 can be mounted with special sample holders for room temperature measurements.
|Laser for optical excitation:
• wavelength 1028 nm
• second and third harmonic generation is available
• pulse energy 20 – 400 µJ
• repetition rate 1 – 1000 kHz, 1 – 625 kHz synchronized to the storage ring
• time-resolved measurements: time-resolution >100 ps in hybrid mode and single bunch operation, >16 ps in low-alpha operation
• PicoQuant PicoHarp 300 (HydraHarp 400 in preparation) single photon counting modules for various photon counters with 1 ps time-resolution
For details and current status of the experimental station contact the Instrument Scientist.
The XPP endstation is designed for time-resolved pump -- X-ray probe experiments. We use optical laser excitation or electrical excitation schemes and study the structural non-equilibrium response of a sample. Therefore 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 is 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 are able to obtain 4 ns time resolution in time-correlated photon counting mode and are able to measure simulateneously delays up to 33 μs during one sample scan. Static experiments can be performed using a CyberStar detector.
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.