AGIPD is a hybrid pixel detector developed by DESY, PSI, the University of Bonn and the University of Hamburg. The detector is targeted for use at the European XFEL, a source with unique properties: a bunch train of 2700 pulses with> 10 12 photons of 12 keY each, only 100 fs long and with a 220 ns spacing, is repeated at a 10 Hz rate. This puts up very demanding requirements: dynamic range has to cover the detection of single photons and extend up to > 10 4 photons/pixel in the same image, and as many images, as possible have to be recorded in the pixel to be read out between pulse trains. The high photon flux impinging on the detector also calls for a very radiation hard design of sensor and ASIC. The detector will consist of 16 Sensor modules arranged around a central hole for the direct beam. Each made of a single sensor bump bonded to 2 X 8 readout chips of 64 X 64 pixels in a grid of 200/-lm pitch. Each pixel of these ASICs contains a charge sensitive preamplifier featuring adaptive gain switching, changing sensitivity in three ranges, and a buffer to provide correlated double sampling (in the highest sensitivity mode). Most of the pixel area, albeit, is used for an analogue memory to record 352frames. It is operated in random-access mode: data containing bad frames can be overwritten and the memory can be used in the most efficient way. The readout between two bunch trains is arranged via 4 ports: Data from pixels of one row is read in parallel and serialised by 4 multiplexers at the end of the pixel columns and driven off-chip as differential signals. The operation of the ASIC is controlled via a three-line serial interface, using a command based protocol. It is also used to configure the chip's operational parameters and internal timings.
PROF. DR. MICHAEL POTTHOFFii "Τὸν δὲ νοῦ καί ἐπιστήμης ἐραστὴν ἀνάγκη τὰς τῆς ἔμφρονος φύσεως αἰτίας πρώ-τας μεταδιώκειν." Πλάτωνος, Τίμαιος, Κεφ. 16 "The lover of reason and knowledge must first seek for the causes which belong to the rational order."Plato, Timaeus, Ch. 16 iii To my parents. . . iv AbstractSilicon detectors in Photon Science and Particle Physics require silicon sensors with very demanding specifications. New accelerators like the European X-ray Free Electron Laser (EuXFEL) and the High Luminosity upgrade of the Large Hadron Collider (HL-LHC), pose new challenges for silicon sensors, especially with respect to radiation hardness. High radiation doses and fluences damage the silicon crystal and the SiO 2 layers at the surface, thus changing the sensor properties and limiting their life time. Non-Ionizing Energy Loss (NIEL) of incident particles causes silicon crystal damage. Ionizing Energy Loss (IEL) of incident particles increases the densities of oxide charge and interface traps in the SiO 2 and at the Si-SiO 2 interface.In this thesis the surface radiation damage of the Si-SiO 2 system on high-ohmic Si has been investigated using circular MOSFETs biased in accumulation and inversion at an electric field in the SiO 2 of about 500 kV/cm. The MOSFETs have been irradiated by X-rays from an X-ray tube to a dose of about 17 kGy(SiO 2 ) in different irradiation steps. Before and after each irradiation step, the gate voltage has been cycled from inversion to accumulation conditions and back. From the dependence of the drain-source current on gate voltage the threshold voltage of the MOSFET and the hole and electron mobility at the Si-SiO 2 interface were determined. In addition, from the measured drain-source current the change of the oxide charge density during irradiation has been determined. The interface trap density and the oxide charge has been determined separately using the subthreshold current technique based on the Brews charge sheet model which has been applied for first time on MOSFETs built on high-ohmic Si. The results show a significant field-direction dependence of the surface radiation parameters. The extracted parameters and the acquired knowledge can be used to improve simulations of the surface radiation damage of silicon sensors.
Abstract-The European XFEL [1] will provide fully coherent, 100 fs X-ray pulses, with up to 10 12 photons at 12 keV. 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 × 1024 pixel detector, with 200 µm 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 × 2 fully depleted monolithic silicon sensors with a 8 × 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 × 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.
AGIPD is a charge integrating, hybrid pixel readout ASIC, which is under development for the European XFEL [1, 2]. A dynamic gain switching logic at the output of the preamplifier (preamp) is used to provide single photon resolution as well as covering a dynamic range of at least 10 4 · 12.4 keV photons [3, 4]. Moreover, at each point of the dynamic range the electronics noise should be lower than the Poisson fluctuations, which is especially challenging at the points of gain switching. This paper reports on the progress of the chip design on the way to the first full-scale chip AGIPD1.0, focusing on the optimization of the dynamic range and the implementation of protection circuits at the preamplifier input to avoid pixel destruction due to high intense spots.
One of the detector's important parts is the radiation tolerant front end ASIC fulfilling the European-XFEL requirements: high dynamic range -from sensitivity to single 12.5keV-photons up to 10 4 photons. It is implemented using the dynamic gain switching technique with three possible gains of the charge sensitive preamplifier. Each pixel can store up to 352 images in memory operated in random-access mode at ≥4.5 MHz frame rate. An external vetoing may be applied to overwrite unwanted frames.
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