PILATUS 1M Detector Research Articles

Vacuum-compatible photon-counting hybrid pixel detector for wide-angle x-ray scattering, x-ray diffraction, and x-ray reflectometry in the tender x-ray range.

A vacuum-compatible photon-counting hybrid pixel detector has been installed in the ultra-high vacuum reflectometer of the four-crystal monochromator beamline of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II in Berlin, Germany. The setup is based on the PILATUS3 100K module. The detector can be used in the entire photon energy range accessible at the beamline from 1.75 keV to 10 keV. Complementing the already installed vacuum-compatible PILATUS 1M detector used for small-angle x-ray scattering (SAXS) and grazing incidence SAXS, it is possible to access larger scattering angles. The water-cooled module is located on the goniometer arm and can be positioned from -90° to 90° with respect to the incoming beam at a distance of about 200 mm from the sample. To perform absolute scattering experiments, the linearity, homogeneity, and angular dependence of the quantum efficiency, including their relative uncertainties, have been investigated. In addition, the first results of the performance in wide-angle x-ray scattering, x-ray diffraction, and x-ray reflectometry are presented.

The new NCPSS BL19U2 beamline at the SSRF for small-angle X-ray scattering from biological macromolecules in solution.

The beamline BL19U2 is located in the Shanghai Synchrotron Radiation Facility (SSRF) and is its first beamline dedicated to biological material small-angle X-ray scattering (BioSAXS). The electrons come from an undulator which can provide high brilliance for the BL19U2 end stations. A double flat silicon crystal (111) monochromator is used in BL19U2, with a tunable monochromatic photon energy ranging from 7 to 15 keV. To meet the rapidly growing demands of crystallographers, biochemists and structural biologists, the BioSAXS beamline allows manual and automatic sample loading/unloading. A Pilatus 1M detector (Dectris) is employed for data collection, characterized by a high dynamic range and a short readout time. The highly automated data processing pipeline SASFLOW was integrated into BL19U2, with help from the BioSAXS group of the European Molecular Biology Laboratory (EMBL, Hamburg), which provides a user-friendly interface for data processing. The BL19U2 beamline was officially opened to users in March 2015. To date, feedback from users has been positive and the number of experimental proposals at BL19U2 is increasing. A description of the new BioSAXS beamline and the setup characteristics is given, together with examples of data obtained.

Latest Hybrid Pixel Detectors for increased q/t-resolution in SAXS

The PILATUS was the first Hybrid Pixel Detector available for SAXS. It has transformed data collection by its photon-counting technology, which enables noise-free X-ray detection with high dynamic range and excellent stability at high frame rates. These properties are essential for superior data quality in all scattering experiments, especially for optimal background correction when studying low-concentration samples. Besides optimal data quality at each sampling point, highest resolution is desired in most SAXS experiments both in q-range and in time. The newly developed EIGER pixel detector more than doubles the q-resolution that can be achieved when compared with PILATUS3 for the same sample-to-detector distance. EIGER features a pixel size of only 75 µm (in comparison: PILATUS3 has 172 µm). To characterize the spatial resolution of these detectors, point-spread functions were measured at the PTB laboratory at BESSY II, which show that the resolution is directly proportional to the pixel size with minimal cross talk between neighboring pixels. The EIGER 1M detector allows data acquisition at up to 3'000 frames per second. This enables unprecedented temporal resolution in time-resolved SAXS measurements and increases the speed of novel imaging techniques such as scanning SAXS/WAXS and coherent diffractive imaging applications, allowing images to be recorded faster or with higher spatial resolution. The design of the EIGER detector makes it vacuum compatible. Operation at low X-ray energies and correspondingly large scattering angles is another way of increasing q-resolution and also gives access to the lowest q data near the beam stop. In-vacuum detectors enable measurements with ultra-soft x-rays and thus high q-resolution. Moreover they optimize the data quality in scattering experiments by removing absorption and scatter caused from air and windows. An in-vacuum PILATUS 1M detector has been installed at the BESSY-2 FCM beamline and is applied for SAXS/GI-SAXS measurements at energies from 1.75 to 10 keV. For simultaneous SAXS/WAXS applications covering an even wider q-range, in-vacuum detectors with L-shaped detection surface are under development. These will detect the WAXS signal, while a clearance in the detector permits the direct beam to pass on to a SAXS detector placed at larger distance. These latest detector developments will be presented along with corresponding experimental results.

Characterization of an in-vacuum PILATUS 1M detector.

A dedicated in-vacuum X-ray detector based on the hybrid pixel PILATUS 1M detector has been installed at the four-crystal monochromator beamline of the PTB at the electron storage ring BESSY II in Berlin, Germany. Owing to its windowless operation, the detector can be used in the entire photon energy range of the beamline from 10 keV down to 1.75 keV for small-angle X-ray scattering (SAXS) experiments and anomalous SAXS at absorption edges of light elements. The radiometric and geometric properties of the detector such as quantum efficiency, pixel pitch and module alignment have been determined with low uncertainties. The first grazing-incidence SAXS results demonstrate the superior resolution in momentum transfer achievable at low photon energies.

Protein crystallography with a novel large-area pixel detector

The PILATUS 1M detector, developed at the Paul Scherrer Institut, is a single-photon-counting hybrid pixel detector designed for macromolecular crystallography. With more than 1 million pixels covering an area of 243 × 210 mm, it is the largest such device constructed to date. The detector features a narrow point spread function, very fast readout and a complete absence of electronic noise. Unfortunately, this prototype detector has numerous defective pixels and sporadic errors in counting that complicate its operation. With appropriate experimental design, it was largely possible to work around these problems and successfully demonstrate the application of this technology to structure determination. Conventional coarse ϕ-sliced data were collected on thaumatin and a refined electron density map was produced that showed the features expected of a map at 1.6 Å resolution. The results were compared with the performance of a reference charge-coupled device detector: the pixel detector is superior in speed, but showed higherR-factors because of the counting errors. Complete fine ϕ-sliced data sets recorded in the continuous-rotation mode showed the predicted advantages of this data collection strategy and demonstrated the expected reduction ofR-factors at high resolution. A new readout chip has been tested and shown to be free from the defects of its predecessor; a PILATUS 6M detector incorporating this new technology is under construction.

The PILATUS 1M detector

The PILATUS 1M detector is a hybrid pixel array detector with over one million pixels that operate in single photon counting mode. The detector, designed for macromolecular crystallography, is the largest pixel array detector currently in use at a synchrotron. It is a modular system consisting of 18 multichip modules covering an area of 21 cm x 24 cm. The design of the components as well as the manufacturing of the detector including the bump-bonding was performed at the Paul Scherrer Institute (PSI). The use of a single photon counting detector for protein crystallography requires detailed studies of the charge collection properties of the silicon sensor. The 18 modules are read out in parallel, leading to a full frame readout-time of 6.7 ms. This allows crystallographic data to be acquired in fine-varphi-slicing mode with continuous rotation of the sample. The detector was tested in several experiments at the protein crystallography beamline X06SA at the Swiss Light Source at PSI. Data were collected both in conventional oscillation mode using the shutter, as well as in a fine-varphi-slicing mode. After applying all the necessary corrections to data from a thaumatin crystal, the processing of the conventional data led to satisfactory merging R-factors of the order of 8.5%. This allows, for the first time, determination of a refined electron density map of a macromolecular biological crystal using a silicon pixel detector.

Protein crystallography with the PILATUS 1M detector

Protein crystallography with the PILATUS 1M detector

Distortion calibration of the PILATUS 1M detector

The PILATUS 1M detector is a large area tiled X-ray detector for protein crystallography. One million 217 × 217 μ m 2 pixels cover an area of 24.3 × 20.0 cm 2 with 300 μ m thick silicon sensors. The readout electronics enable single photon counting and a readout time of 6.7 ms. Images from this detector are spatially distorted by the influence of three factors. First, the absorption properties of the silicon leads to parallax broadening by a fraction of a pixel, depending on the angle of incidence and the photon energy. A simulation was compared to experimental data. Second, the modular architecture causes a mechanical displacement of the modules from their assumed positions. The modules are positioned on average to a precision of ∼ 300 μ m . Third, to reduce the dead area the modules are tilted by 6 ∘ and are overlapped. This introduces large distortions of several pixels which depend on the sample to detector distance. An algorithm for distortion correction of CCD detector data was adapted to correct the data of the PILATUS 1M detector. The results of the metrology as well as the parallax shift were incorporated in these corrections. Images from a Ta-mask were used to test the corrections and quantify the remaining spatial distortion. The mask images were also used to refine the individual module positions. In order to verify the distortion corrections crystallographic standards were used. The result is that images of the detector can be spatially corrected to a precision of 74 μ m or about 0.34 pixel.