Speaker
Description
Astrophysical X-ray polarimetry is a powerful technique for probing the physical conditions and emission mechanisms of cosmic X-ray sources. At energies below 50 keV, photoelectron track imaging is the leading method for measuring X-ray polarization. In this approach, the track of a photoelectron, produced when an X-ray photon is absorbed, is imaged to reconstruct its initial emission direction. Since photoelectrons are preferentially emitted along the direction of the X-ray’s linear polarization, this allows direct determination of the polarization state. These detectors are hybrid systems that integrate a gas cell for photon absorption, a gas amplification stage, and a pixelated readout for detailed track imaging. Gas detectors are preferred over semiconductor-based detectors, as photoelectron tracks in semiconductors are typically too short to resolve with standard pixel sizes. We present the development of a new generation of photoelectron track imaging detectors utilizing the Timepix3 pixel readout chip. This advanced technology enables three-dimensional track imaging and reconstruction by exploiting the relative timing between pixel hits, significantly improving the accuracy of polarization measurements. In addition, the sparse readout and low deadtime capabilities of Timepix3 allow the detector to operate under high count rate conditions, enabling potential integration with high-throughput X-ray optics. The gas amplification stage is implemented using a Micromegas structure. Two gas mixtures are used to span different energy ranges: dimethyl ether (DME) for 2–8 keV and argon-based mixtures for 6-35 keV.
