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arXiv · 2608.00273

A Focal-plane X-ray Polarimeter with Spectral and Timing Capabilities for Future Missions

Hemanth Manikantan·Carlo Lefevre·Lorenzo Petrucci·Paolo Soffitta·Fabio Muleri·Enrico Costa·Alda Rubini·Vladislavs Plesanovs·Markus Gruber·Jochen Kaminski·Klaus Desch·Alessandro Di Marco·Sergio Fabiani·Riccardo Ferrazzoli·Saba Imtiaz·Dawoon E. Kim·Alessandro Lacerenza·John Rankin·Ajay Ratheesh
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Abstract

The NASA-ASI mission Imaging X-ray Polarimeter Explorer (IXPE) firmly established X-ray polarimetry as a core observation pillar of high-energy astrophysics, alongside imaging, timing, and spectroscopy. While IXPE made groundbreaking discoveries in the 2$-$8 keV range on both point and extended X-ray sources, the Gas Pixel Detectors onboard IXPE demand substantial improvements to be ready for the next generation of imaging X-ray polarimeters. Here, we present the development of a detector prototype that can deliver the next generation of sensitive imaging X-ray polarimetry across the energy band of 2--30 keV. We use Ar/DME based gas volume to absorb X-rays by the photoelectric effect and a pixelated CMOS readout ASIC, Timepix3, with excellent timing capabilities to image the resulting photoelectron track in three dimensions. The Timepix3 is integrated with a multiplication stage called InGrid that enables single-primary-electron detection from the gas volume. The photoelectron track reconstructed in three dimensions increases the polarimetric sensitivity towards the lowest operable energies, and the deadtime-free operation of the ASIC facilitates the usage as a focal plane instrument on high-throughput X-ray mirrors. With this prototype, we demonstrate a low-medium-energy X-ray polarimeter with excellent timing and moderate spectral capabilities.

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Hemanth Manikantan, Carlo Lefevre, Lorenzo Petrucci, Paolo Soffitta, Fabio Muleri, Enrico Costa, Alda Rubini, Vladislavs Plesanovs, Markus Gruber, Jochen Kaminski, Klaus Desch, Alessandro Di Marco, Sergio Fabiani, Riccardo Ferrazzoli, Saba Imtiaz, Dawoon E. Kim, Alessandro Lacerenza, John Rankin, Ajay Ratheesh. 2026-07-31. A Focal-plane X-ray Polarimeter with Spectral and Timing Capabilities for Future Missions. https://arxiv.org/abs/2608.00273

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