SwissFEL Instrument Bernina
The X-ray beamline design emphasizes experimental stability with state-of-the-art X-ray optical elements and single pulse diagnostics which should ensure stable FEL beam pointing and femtosecond timing over days.
A flexible diffractometer platform allows to apply different resonant and non-resonant diffraction techniques in combination with even heavy load sample environments like low temperature cryostats or magnets.
A large range from THz to UV light pulses pulses converted from a 20 mJ Ti:Sapphire laser system can be used to specifically excite specimens in pump/probe experiments.
The instrument is operated by the Bernina Group.
Status: The Bernina Instrument welcomes first users and is being further commissioned and developed.
|Bernina endstation and X-ray parameters|
|Photon energy range||4.5 keV – 8 keV (12.4 keV planned)|
|Beam profile||Focused 5x5 µm2 (fwhm, measured) to unfocused 1000x1000 µm2 (fwhm, photon energy dependent)|
|Bandwidth||Monochromatic (Si(111) commissioned, InSb(111), Si(311) available) and pink beam (0.5% of fundamental)|
|Environment||He or ambient atmosphere, platform for user-supplied chambers, N2 and He based cryo stream coolers down to ~80 K (tested)|
|Sample systems||Solids: single crystals, powders, amorphous systems|
|Detectors and Spectrometer||-1.5 M Jungfrau detector |
-16 M Jungfrau detector (planned)
-Diodes or single element (0.5 M) Jungfrau detectors for multi- purpose applications
|Bernina optical pump laser|
|Primary pump source||800 nm, 35 fs FWHM, 10 mJ (Ti:Sapphire)|
|Secondary pump sources||240 nm - 14 micron (OPA with additional nonlinear conversion options). At present pulse energies at the sample location for 240-400 nm have been measured in the range of 10-30 µJ. We expect pulse energies of 150-500 µJ between 400 nm and 780 nm; 150-500 µJ between 1 µm and 2.5 µm; 15-30 µJ between 2.5 µm and 14 µm. Pulse durations are expected to be approximately 50 fs fwhm and up to 250 fs for the 2.5 µm to 14 µm range depending on the wavelength. Nearly single cycle THz (~ 1THz center frequency). Preliminary commissioning measurements have measured fields of > 300 kV/cm for nearly-single-cycle pulses with a center frequency near 1 THz. Other center frequencies in the range of 1-2.5 THz are possible but not yet tested.|
Current Highlights and News
Ultrafast long-range coherent dynamics in electronic structure excited by THz pulses and studied using free electron laser based resonant X-ray diffraction.
Organic–inorganic ‘hybrid’ perovskites have recently gained attention as a low-cost alternative to silicon solar cells. However, many properties of these materials are still poorly understood. In particular, how imperfections in the crystals, which can be both static or dynamic, affect energy transport remains unclear.
The summer shutdown was used to install more missing hardware. With the new components the Bernina instrument will be already very close to the full design capabilities when the exciting time of user experiments will begin in 2019.