Karlsruhe 2024 – scientific programme

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T: Fachverband Teilchenphysik

T 93: Detectors 9 (gas detectors)

T 93.2: Talk

Thursday, March 7, 2024, 16:15–16:30, Geb. 30.23: 2/17

Development of a GridPix-based X-ray Polarimeter — Klaus Desch, •Markus Gruber, Jochen Kaminski, and Vladislavs Plesanovs — Physikalisches Institut Uni Bonn, Nussallee 12, 53115 Bonn

In astrophysics with X-ray telescopes and material science at synchrotron light sources the measurement of X-ray polarisation can be a valuable tool. It can be directly measured by tracking photoelectrons created in photoelectric interactions. This is possible because their emission angle depends on the direction of the electric field vector of the photons. Within a gaseous detector these electrons have a sufficiently long mean free path such that tracking is possible - if the granularity of the readout is high enough to resolve the tracks and scattering. Also resolving the charge and time distribution of secondary ionisations is needed to differentiate the start and the end of the track. For this a GridPix - a combination of a Timepix(3) ASIC with 55 µm pixel pitch and a photolithographically postprocessed gas amplification stage (integrated grid) can be used. Perfect alignment of the holes in the grid to the pixels enables the possibility to detect avalanches of individual primary electrons.

In this talk, I will present new results on the performance of a GridPix-based X-ray polarimeter. Based on data taken at PETRA III and at a polarised X-ray source at INAF-IAPS the dependence on different detector parameters like gas choice and geometry will be discussed and compared to simulations. Additionally challenges and possible improvements of such a detector will be presented.

Keywords: GridPix; X-ray; Polarimetry; MPGD; Timepix3