AbstractsAstronomy & Space Science

Development of a stacked detector system and its application as an X-ray polarimeter

by Daniel Maier

Institution: Universität Tübingen
Year: 2015
Record ID: 1100825
Full text PDF: http://hdl.handle.net/10900/59850


Astronomical observations in the X-ray range must be performed outside of earth’s atmosphere and are nowadays mainly done by the use of X-ray satellites. The optics which defines the field of view of the satellite and the sensor which detects the X-ray radiation are two essential parts of an X-ray satellite. The use of a focusing optics which concentrates the radiation to a small sensor achieves a high spatial resolution and a low detector background and results therefore in a high sensitivity to detect weak X-ray sources. The recent development of multi-layer-coated X-ray optics allows to focus radiation up to the hard X-ray range and requires new detector concepts. A stacked detector setup consisting of a low energy detector (LED) and a high energy detector (HED) that is placed behind the LED to cover such a wide energy range has been developed in this work. The main advantage of a stacked detector system is its effective detec- tion of broad band X-ray radiation (0.1keV to 80keV) that is focused by the optics. The main goal of this work is the construction of a stacked detector system and the investigation of its properties with analysis software that was especially developed for this purpose. In this context, the mutual influence between both detector systems is of special interest and shall be studied experimentally. The LED is realized by a silicon based active pixel matrix with a maximal readout speed of 410 frames per second. The HED consists of cadmium telluride Schottky diodes with a self-triggered integrated readout electronics. The performance of both detectors was first studied individually to become ac- quainted with their individual characteristics. The construction of the LED subsystem is especially worth mentioning because it is to a large fraction an in-house develop- ment of the IAAT (Institute for Astronomy and Astrophysics Tübingen). Besides the detector control electronics, the signal digitization, the signal preprocessing, and the data transfer were newly developed and tested during the construction of the LED setup. To a large fraction, this was done in the framework of this work. The combined operation of the LED and the HED in the stacked configuration results in a minor mutual heating between both detectors, the appearance of fluores- cence lines (emitted by the HED and detected by the LED), and the flux reduction of the HED for energies below ~25keV. A signal crosstalk between both systems was not observed. The presented work shows that these negative mutual influences of both detector systems can not only be compensated with an appropriate data analysis but that also typical detector artifacts, e.g. escape peaks, can be suppressed. Furthermore, the combined operation of the stacked system allows for additional quantities to be measured which is presented in the example of a Compton camera and a Compton polarimeter. In this context, the expected efficiency of the setup to operate as a Compton camera and its sensitivity as a Compton polarimeter are…