The SPB/SFX instrument will operate an instrument laser hutch, served by the aforementioned PP-laser-system. The variety of samples expected to be investigated at SPB/SFX exhibit very different absorption and reflectivity spectra, and an optical laser needs to generate an appropriate wavelength to excite or align such samples. Those wide wavelength regions, which will be demanded by users of SPB/SFX, are covered (ultimately) by an optical parametric amplifier (OPA). Second harmonic generation (SHG), third harmonic generation (THG) and fourth harmonic generation (FHG) will be provided for experiments that require higher fluence than an OPA system can provide. The fundamental wavelength of 800 nm is tunable from 740–840 nm. It is expected that SHG (370–420 nm) will fit to many sample cases for excitation.
Sample delivery
In order to fully exploit the potential of X-ray FEL sources, diffraction experiments are usually performed at single pulse energies far above damage limits while utilizing the ultrashort duration to obtain still images even from exploding samples. This operation mode requires sample delivery concepts to replenish fresh sample for every shot.
At the SPB/SFX instrument, the upstream and downstream sample chambers are equipped with multiple ports to mount different kinds of gas-focused, liquid jet and/or aerosol injectors for fast sample replenishment of biological samples at high repetition rates. However, for experiments at 10 Hz, a fast, fixed-target scanner can be used which holds samples previously prepared and characterized offline. Such solid state sample systems could also be utilized at non-destructive intensities (i.e., multiple images from one single sample).
In case different, special sample delivery equipment for a particular experiment is to be used users are encouraged to cross check with the instrument scientists about how to best incorporate a specific user setup.
Detectors
The SPB/SFX instrument will (ultimately) feature two AGIPD photon detectors, a 1 Mpx variant in the upstream interaction region and a 4 Mpx variant downstream, with a pixel size of 200 x 200 µm2. The AGIPD provides a dynamic range of >104 photons/px at a photon energy of 12 keV, an electronic noise of >350 e- r.m.s., and is capable to collect data at the full intra-train repetition rate of the European XFEL (4.5 MHz) and store up to 352 frames per train.
The two AGIPD detectors at the SPB/SFX instrument have different mechanical designs. The upstream 1 Mpx detector can be placed between distances of 0.13 m and ~6 m distance to the upstream interaction region while the downstream 4 Mpx detector features sample-detector distances between 0.12 m and 0.52 m. For further details about the mechanical design of both detectors, users are encouraged to contact the instrument scientists directly.