LPD (Large Pixel Detector)
The LPD has been developed by the Rutherford Appleton Laboratory in the UK for European XFEL. The detector sensitive area is square-shaped with 1024x1024 pixels of 500 µm size and consists of 256 exchangeable rectangular tiles (128x32 pixels). The area is divided into four quadrants that can be moved independently in the detector plane to form an adjustable central hole to let the direct beam through. A 500-µm thick Si sensor enables quantum efficiency over 80% in the 1–13 keV photon energy range and ca. 40% detection efficiency at 20 keV. The LPD has a high dynamic range of up to 105 photons at 12 keV, while providing single photon sensitivity in the lowest amplifier gain setting. The detector electronics supports 3 parallel gain stages (1x, 10x, 100x) and with frame rates of 4.5 MHz up to 512 full frames can be stored into the detector memory, which are transferred every 100 ms to the storage place. It thus operates in the burst mode of the European XFEL pulse train pattern. A fast frame “veto” capability is added to discard poor images based on the online diagnostics, which helps to improve the overall quality of image sets stored within the burst on the detector.
FXE sample environment
Liquid flat sheet (sample delivery)
Currently available are sapphire nozzles for 0.1, 0.2, 0.3, and 0.5 mm jet thicknesses. These operate at speeds up to about 5 m/s and flow rates of up to 500 mL/min. The set of pump and nozzle are suitable for fairly aggressive liquids. Please contact the instrument scientists to enquire about special solvents, other than water, acetonitrile, and certain alcohols. The sample container can be heated or cooled to adjust the temperature of the solvent to better than 0.2 K.
A high-speed thin flat sheet jet (10–70 m/s) is available with adjustable thicknesses in the 1–100 µm thickness range. This jet is presently limited to the delivery of water-based samples under ambient conditions.
Sample stage and environment
The mounting plane (breadboard) is located 230 mm below the x-ray beam. A set of rotation and translation stages, described in more detail below, enables sample alignment and scanning. The beam direction is positive z (y vertical).