An interpolating 2D pixel readout structure for synchrotron X-ray diffraction in protein crystallography

The high rates available now at synchrotron beam lines ask for detectors allowing online measurements with good spatial resolution and a precise intensity measurement. For this purpose gaseous detectors operating in the single photon counting mode are well suited, An interpolating 2D pixel readout structure will be presented. It has been tested as backplane of a MSGC or a CAT-detector (recently developed by the group of M. Lemonnier at LURE), and it operates on the principle of resistive charge partition, allowing asynchronous readout. A resolution of 200 mu m is reached. Under similar conditions the energy resolution from the signals of the readout structure presented is nearly the same as that of standard readout. In combination with a CAT an energy resolution of 20% is reached. A prototype of 64 channels with a sensitive area of 14 mm x 14 mm was tested at the synchrotron at LURE (Orsay). Diffraction patterns from a collagenase protein crystal were measured and rocking curves were obtained with an angular resolution of 1.5 x 10(-5o).