X-ray pixel detector for crystallography

For X-rays diffraction experiments, the required dynamic is a challenge. The signal ranges usually over more than six orders of magnitude. To meet this requirement and to reduce the readout time with respect to the commonly used CCD camera a dedicated hybrid pixel detector is under fabrication. We have designed a new counting chip with pixel sizes of 330 mu m. The expected counting rate per pixel is 10/sup 7/ ph/s and a continuous readout with time stamping-will allow for up to 4*10/sup 9/ dynamics range (16-bit counter in each pixel and 16-bit counter per pixel in the readout boards). This chip has been submitted for fabrication and it is under test. We will show first results. As a first step a small detector (4* 1.6 cm/sup 2/) is being built, using a DELPHI (LEP/CERN) Si array of diodes which have good efficiency for collecting X-rays between 5 and 25 keV. After the electrical tests, the performances of this X-ray detector will be measured in the ESRF-D2AM beam line (Grenoble, France), scheduled in next December. If this prototype shows expected performances, a large array (25*25 cm/sup 2/) of such detectors could be built. (2 refs).