The legacy of IXPE: directions towards a new generation of 3D photo-electric x-ray polarimetry missions

IXPE has been a highly successful mission, opening a new window in X-ray astronomy. IXPE observations have highlighted the importance of polarimetry along with spectroscopy in determining the geometry and physics behind many high-energy emissions from black hole X-ray binaries (BHXRBs), Pulsar Wind Nebulae (PWN), Active Galactic Nuclei (AGN) etc. However, IXPE is just the first step towards future wide band (0.1 to 100 keV) X-ray polarimetry. The future of this field demands larger effective areas, better energy resolution, and broader energy bands. IXPE is barely capable to address key scientific cases such as reflection features in X-ray binaries, molecular clouds around the Galactic Center, radio-quiet AGNs, non-thermal emission regions in supernova remnants etc. To take advantage of the recent advances in X-ray optics, gaseous detectors with different thickness, pressures and gas mixtures would be required. Using next-generation ASICs, like Timepix3, it is possible to have parallel fast readout, providing simultaneous time and charge information for each pixel, enabling 3D imaging of photoelectron tracks. In this article, we explore such a possibility using GridPix detectors.