[AIT logo]

Institut für Astronomie und Astrophysik

Abteilung Astronomie

Sand 1, D-72076 Tübingen, Germany
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Dissertation Alexander Bähr

Development of DEPFET sensors with advanced functionality for applications in X-ray astronomy

Athena is ESA’s next generation observatory for X-ray astronomy. One of its two focal-plane instruments is the WFI, a large area, pixelated silicon-detector for imaging spectroscopy that will provide an unmatched field of view and the capability to observe even brightest radiation sources with high throughput. The WFI’s sensor will be based on the combined sensor-amplifier structure DEPFET. This concept provides a high flexibility in terms of device readout and permits to add various functional features into each pixel of the detector. It is for instance, possible to implement a pixel wise electronic shutter and furthermore, provide every pixel with an additional storage area. In this thesis, these DEPFET concepts with enhanced functionality are evaluated with respect to a potential use as building block for Athena’s WFI. The focus was thereby on the application of a DEPFET based sensors as high count rate spectrometer and the influence and mitigation of readout artifacts on the spectral response of the sensor. To improve the understanding of the different concepts, a series of device simulations was carried out. Parts of these simulations were used as input for the layout of novel devices. To study the properties of the different DEPFET devices, a flexible measurement setup was designed, assembled and operated. With that setup, the properties of different DEPFETs were investigated. Especially time dependent readout artifacts were studied and models to describe these were developed. In the course of this thesis it was furthermore possible to confirm the basic functionality of the first devices providing an additional storage area. Based on the device simulations as well as measurements, spectral simulations were conducted. These show that a DEPFET is capable to do spectroscopy even at fastest timings. However, the spectral performance will deteriorate drastically due to readout artifacts. While the pixel-wise built-in shutter provides good spectral response it severely limits the throughput at fast timings due to the required deadtime. An additional storage area provides both, good spectral performance and high throughput even at fastest timings.
Key words: Röntgenastronomie, Bildsensor, DePFET

Online-Publikation: http://hdl.handle.net/10900/84631

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