Pixel Detectors For Diffraction Experiments At The Swiss Light Source

Abstract

The PILATUS detector (Pixel Apparatus for the SLS) is a large, quantum‐limited area X‐ray detector for protein crystallography which is currently under construction. Its basic units are modules with 16 CMOS chips bump‐bonded to a large, continuously sensitive silicon sensor with 157×366 pixels of 217×217 μm2, leading to an active area of 34×80 mm2. With a counting circuit in each pixel, X‐rays are detected in single photon counting mode, leading to excellent, noise‐free data. The main properties of the detector are an energy range of 6 to 30 keV, no back‐ground due to leakage current or readout‐noise, fast read‐out time of 6.7 ms, a rate/pixel >104/s and a PSF of one pixel. PILATUS detectors are installed at the SLS X06SA protein crystallography beamline, and at both the surface diffraction (SD) station and the radiography and tomography (XTM) station of beamline X04SA. The detectors are operated at room temperature and thus are very easy to use. Experiments benefit from the ability to detect very weak diffraction spots with high precision. At the SD station and at the XTM station, which is equipped with a Bragg magnifier, diffraction, radiography and tomography experiments showed promising results. At beamline X06SA, a three‐module array (1120×157 pixels) with a readout time of 6.7 ms was tested. This system was used to collect fine phi‐sliced protein crystal data in continuous sample rotation mode in which the crystal was continuously rotated with a slow angular velocity of 0.04 °/s without any shutter operation. Exposure time per frame ranged from 100 ms to a few seconds, depending on the crystal. These initial experiments show the potential of this method.