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 detecto rs allowing online measurements with good spatial resolution and a pre cise intensity measurement. For this purpose gaseous detectors operati ng in the single photon counting mode are well suited, An interpolatin g 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 resisti ve charge partition, allowing asynchronous readout. A resolution of 20 0 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 resoluti on 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). Diffr action patterns from a collagenase protein crystal were measured and r ocking curves were obtained with an angular resolution of 1.5 x 10(-5o ).