X-ray pixel detector for crystallography

For X-ray diffraction experiments, the required dynamic range 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 charge-coupled device camera, a dedicated hybrid pixel detector is under development. We have designed a new counting chip with pixel size of 330 μm. The expected counting rate per pixel is 107 ph/s, and a continuous readout with time stamping will allow a dynamic range for up to 4×109 (16-bit counter in each pixel and 16-bit counter per pixel in the readout boards). This chip has been submitted for fabrication and is under test. First results of this chip will be presented. As a first step, a small detector (4×1.6 cm2) is being built, using a DELPHI(LEP/CERN) silicon array of diodes, which have good efficiency for collecting X-rays between 5 and 25 keV. After the electrical tests, the performance of this X-ray detector will be measured in the ESRF-D2AM beam line (Grenoble, France), scheduled for December 2000. If this prototype performs as expected, a large array (25×25 cm2) of such detectors could be built