AGIPD - The Adaptive Gain Integrating Pixel Detector for the European XFEL. Development and Status

The European XFEL [1] will provide fully coherent, 100 fs X-ray pulses, with up to 10(12) photons at 12keV. The high intensity per pulse will allow recording diffraction patterns of single particles or small crystals in a single shot. Consequently 2D-detectors have to cope with a large dynamic range: detection from single photon to >10(4) photons/pixel in the same image. An additional challenge is the European XFEL machine: an Electron bunch train with 10 Hz repetition rate, consisting of up to 2,700 bunches with a 220 ns spacing. Recorded images have to be stored inside the pixel during the bunch trains and readout in between. To meet these requirements, the European XFEL has launched 3 detector development projects. The AGIPD project is a collaboration between DESY, PSI and the Universities of Bonn and Hamburg. The goal is a 1024 x 1024 pixel detector, with 200 mu m pixel size and a central hole for the primary beam. The ASIC operates in charge integration mode: the output of each pixels preamplifier is proportional to the charge from the sensor generated by the Xrays. The input stage of the pixel cells uses dynamically adjustable gains. The output signal is stored in an analogue memory, which has to be a compromise between noise performance and the number of images. This is operated in random access mode, providing means to overwrite bad frames for optimal use of the 352 memory cells per pixel, which have to be readout and digitized in the 99.4 ms bunch gap. The detector will be built of 8 x 2 fully depleted monolithic silicon sensors with a 8 x 2 array of CMOS readout chips bump-bonded to these. Several prototypes of the readout ASIC have been produced. The results presented originate from the 16 x 16 pixel matrices AGIPD 0.2, which was bump-bonded to a pixel sensor, and AGIPD 0.3, which includes the intended control algorithm and a fast differential interface to the off-chip world.