PILATUS 2M A Detector for Small Angle X-ray Scattering

For the (coherent) small-angle X-ray scattering (SAXS) beamline X12SA of the Swiss Light Source at the Paul Scherrer Institut, a novel X-ray detector is built, the PILATUS 2M. Contributions in module fabrication, detector assembly, characterization and calibration are covered within the framework of this thesis. Furthermore, data analysis of a particular SAXS experiment demonstrating the performance of the beamline and the detector are accomplished. PILATUS is a silicon hybrid pixel detector system for synchrotron applications. Its core unit is a module consisting of 16 readout chips which are flip-chip bump bonded to a 320 μm thick silicon sensor. The readout electronics of a single pixel of 172× 172 μm2 size comprise an amplifier, comparator and a digital counter featuring single-photon counting. A module contains 487× 195 pixels which can be read out in within 2.85 ms. In the frame of detector calibration and characterization the intrinsic threshold dispersion of a PILATUS module is reduced to a minimum value of 36 eV root mean square (RMS). The minimum selectable threshold is 2 keV with all pixels of the module reliably counting photons above the electronic noise. Furthermore, a minimum overall energy resolution of 863 eV full width at half maximum (FWHM) and a minimum dead time of 101 ns are measured. The PILATUS 2M is a large area detector consisting of an array of 8 × 3 PILATUS modules. A total of 1475×1679 = 2, 476, 525 pixels cover an active area of 254×289 mm2. The maximum frame rate of the full detector is 31.4 Hz. The PILATUS 2M is custom built for SAXS experiments. One-dimensional tomographic reconstruction of SAXS images is demonstrated on the example of alumina dip-coated polyamide 6 monofilaments. The sample is scanned with a focussed synchrotron beam with a spot size at sample level of 5 × 20 μm2 (FWHM). The reconstructed sequence of SAXS images reflects the local nanostructure variation along the sample radius.