Development of a Mixed-Mode Pixel Array Detector for macromolecular crystallography

A Mixed-Mode Pixel Array Detector (MMPAD) has been conceived for protein crystallography applications. The most notable feature of the detector is the combination of analog and digital approaches used in the pixel to generate very large dynamic range, low dead time, and fast readout of the types of spot intensity measurements needed in X-ray images from large macromolecules. Prototype structures for the pixel have been fabricated and evaluated and indicate that an intensity range of 10⁷ to 1 can be measured with a precision of 0.25%, while still maintaining a high DQE for X-rays in the 6-18 keV range. The mixed-mode structure is compatible with a fast I/O system and allows the possibility of full-frame readout in the ms range. We present details of pixel behavior, design of support electronics, hybridization results and plans for fabrication of large arrays.