Design, Construction, and Test of the Gas Pixel Detectors for the IXPE Mission

TL;DR

This paper details the design, manufacturing, and testing of Gas Pixel Detectors for NASA's IXPE mission, emphasizing their performance metrics, operational stability, and suitability for X-ray polarization measurements.

Contribution

It presents a comprehensive characterization of the IXPE Gas Pixel Detectors, linking design choices to performance and operational considerations for space-based X-ray polarimetry.

Findings

Detectors achieved low noise and high trigger efficiency.

Uniform response and spectral performance meet mission requirements.

Instrumental effects analyzed for accurate polarization measurements.

Abstract

Due to be launched in late 2021, the Imaging X-Ray Polarimetry Explorer (IXPE) is a NASA Small Explorer mission designed to perform polarization measurements in the 2-8 keV band, complemented with imaging, spectroscopy and timing capabilities. At the heart of the focal plane is a set of three polarization-sensitive Gas Pixel Detectors (GPD), each based on a custom ASIC acting as a charge-collecting anode. In this paper we shall review the design, manufacturing, and test of the IXPE focal-plane detectors, with particular emphasis on the connection between the science drivers, the performance metrics and the operational aspects. We shall present a thorough characterization of the GPDs in terms of effective noise, trigger efficiency, dead time, uniformity of response, and spectral and polarimetric performance. In addition, we shall discuss in detail a number of instrumental effects that are relevant for high-level science analysis -- particularly as far as the response to unpolarized radiation and the stability in time are concerned.