A digital pixel address generator for pixel array detectors

An 8×8 analog pixel array detector prototype has been constructed for characterizing a larger 50×50 digital pixel array detector (DPAD) that will be used for protein crystallography. Each detector readout element in the array consists of a preamplifier and shaper, with adjustable reset and shaping times. The readout array is bump-bonded to a Si pixel array detector and provides 64 independent analog output channels for data processing. This paper describes the digital processing electronics which is used for mapping the prototype pixel detector characteristics. The event driven digital encoding circuitry processes each photon hit by grouping each pixel into a column of 8 pixels and then grouping each column into an array of 8 columns forming an 8×8 pixel array. The logic is inexpensive and easy to implement. Results from these measurements were used as an aid in the design of the DPAD detector and DPAD ASIC.